Bose Speaker Amps/radio face

[LancePearson]

The punchlist on my new to me 91 included replacing the rf amp on the rf speaker and replacing the scratched radio face on the Bose Gold radio which has good sound but the rf had a repeating sound which Dr. Don correctly said was a failed amp. His comment was that the components used by Bose included resistors, etc from Malayasia that were doped incorrectly and with the heat and time acid leached out and made them fail. His are doped correctly with lifetime warranty. The parts came early this week and I put the new rf amp in by removing the sill which includes the cover, removing the speaker assembly, unhooking the wires and then indoors removing the back plate and extracting and unhooking the amp that had failed. I had no trouble removing all this and re installing and it works perfectly now. I'll put the new radio face on this weekend when I pull the center console trim to check shift boots and do some minor sound proofing as well though it looks simple enough to do.

Here are some photos of the Bose Gold 1991 cassette/cd am/fm radio and the amp with the rf metal shielding off. On the back side opposite the rf shielding you can see the resistor or whatever it is which failed as the dark spot in the center which has liquid, presumably that acid, around it.

2210

2211

2212

2213

2214

[Schrade]

Got a pic of the Head Unit's face pulled there Mr. P?

I found an easier way to wire in a switchable AUX input to the Delco BG, rather than pulling the Data Control Module (instead of FM modulation interrupt).

Only question is if the 3.5mm plug will mount INTO the Head Unit faceplate, or get routed back in the console...

[Starman]

The problem with the capacitors is universal to our amps, all will fail in time regardless of use. I bought all the components to rebuild the amps myself for about $30 and then chickened out and sent them to Bose.

Bose refurbishes the speakers/amps for a pretty reasonable price. I did all four about 4-5 years ago. You send them the entire speaker/amp module and they remanufacture it and send it back with a lifetime warranty. Cost was $75 per at the time. Stereo sounds great now, clean with good power.

I did install a Pioneer DVD head unit and the adapter harness - this is not something for the faint of heart, but the end result was great and I now have bluetooth to the phone & iPod compatibility.

[LancePearson]

Got a pic of the Head Unit's face pulled there Mr. P?

I found an easier way to wire in a switchable AUX input to the Delco BG, rather than pulling the Data Control Module (instead of FM modulation interrupt).

Only question is if the 3.5mm plug will mount INTO the Head Unit faceplate, or get routed back in the console...

I haven't pulled the radio head yet. I need to pull the center tunnel and shift tunnel and console trim first to check shift boots, add some sound proofing then change the radio face place so have not done that yet. I'll unplug the battery this weekend and start removing the trims to reveal and do the three things since they all share the same need.

From what I've seen of the back of the radio head there are a couple of wiring harness connections behind the head which might be able to be tapped for such a thing. Presumably power in then outputs to the CDM below the glove box and to speakers from that. I haven't looked at the wiring diagrams at all. If you can tap in for a 1/8" plug seems like you could mount it in the trim piece below the radio itself as wire length wouldn't matter a whole lot there.

In my case I don't think I have to pull the radio head at all just to put a new face on it as without the trim it's all exposed.

How do you do what you said with the added aux? I'll add a photo of someone elses radio back if that will help.


Lance

[Z51JEFF]

Did he mention have the CDM box gone through?I had mine done when I did the speakers,not an easy job to deal with.

[Schrade]

You need a SWITCHABLE 3.5mm jack ($5), and 2-3 feet of wire.

The way the mod works that I saw posted (page bookmarked with snappics on another computer), is : (and I can't take credit; it's web-blogged (or Stickied) somewhere)

the optical disk / CD Player has a dedicated logic board IN THE HEAD UNIT, which connects by an internal harness to the main logic board, ALSO IN THE HEAD UNIT.

this internal harness carries L and R signals, a common, and a few others, one of which is a POWER interrupt, so that when you plug in a CD, it auto-plays.

The mod is thus:

cut the L and R signal wires on the internal harness. Splice onto the FROM CD PCB (printed circuit board) side L and R signal wires, and on the other end, ONTO the 3.5mm INPUT terminals.

Route 2 more leads from the 3.5mm OUTPUT, BACK to the L and R mainboard INPUTS, where you cut.

Put in a CD, and it plays as normal, THROUGH the 3.5mm plug.

BUT, plug a 3.5 jack iPod into the socket, and the L and R signal circuit FROM the CD is interrupted by the switch (switch activates by the plug), and the iPod - or x device, gets carried to the mainboard.

Where to mount the 3.5mm socket???

This is why I asked if you had a snappic of the BACK of the HEAD UNIT faceplate. If it has IT'S OWN logic board behind the faceplate, and many do, then you cannot drill and mount the 3.5mm socket in the face of the HEAD UNIT. It DOESN'T need THAT much space tho'.

Otherwise, the socket would probably get routed to the center console somewhere.

Only 'problem' is, is that a CD must be playing, in order for the MAINBOARD to look for a signal from the CD INPUT harness. BUT, the CD won't be heard, with the signal interrupted at the socket.

(the CD PCB-to-mainboard harness must also include a SWITCH, activated by CD insertion, jumpable, so that a CD DOESN'T necessarily have to be inserted. That part isn't solved yet)

Will try to get this phot-doc'ed soon here...

[LancePearson]

That's a little too complex for me at the moment. I took the trim off today and found the radio face. It was not as simple as I thought and I SCREWED IT UP ROYALLY. I did finally pull the radio back out a bit and free the face, remove the face then take it to the kitchen table and unscrewed the electronics on the back, carefully moved the buttons side by side, one by one in parallel, put the plastic spacer parts and light distribution parts on the new face then went back to the car to put that face on the radio head box. On the left there are two connectors with the tiny many pin female parts. They are not fixed but float and I could not figure out how to put the face with it's male pins on so that the pins would go into the floating female parts. I finally put duct tape in the opening to hold the floating housings in place and carefully put the pins in to the best of my knowledge and closed it up. However, it was not quite as secure as the one I took out which worked perfectly but was scratched. I can not reach in behind the radio even when the screws holding it in are out to unclip the connectors so I could try and do this in the kitchen as my hands are too big. I just ended up putting it back in and putting the attachment screws back in which was tricky to begin with expecting it would not work. when all trim was back on and the battery hooked back up again it did exactly that, played on one radio station and when I touched another button it did some erratic functions and the lights did not come on in the display at all so I seriously doubt I have the connectors connected, possibly have some bent as well which can be straightened. Right now I'm just sort of frustrated.

Right now I'm after dinner going to go pull the radio fuse, think about it for a few days and if I think I can, maybe try and get the radio out and send it to Dr. Don to redo the thing and then hire someone with small hands when it comes back to put it back in. There are times when being 6'4" with size fifteen shoes, big hands and height is not exactly a happy thing.

Right now you are reading the ravings of a frustrated, failed guy who cannot do this though the speaker amp was a cinch. Putting the electrics on the new face once I got it out I thought was as well but getting those pins in? It was impossible for me and for all I know I've now maybe screwed it up beyond saving. I'm not sure what I'm going to do about it right now

time to let it sit, think about the experience as I don't want to go back and remove all the trim after four hours of messing with it right now. Would not be patient enough.

To be polite: Bollocks!

[dan1495]

Lance,
Sorry to hear it did not go well. Your idea of taking a break and thinking about for a few days makes sense to me. Usually when I do that I will suddenly have an "aha" moment and everything becomes clear. I suspect that someone here will come up with a solution. I have not had the pleasure of tackling this job myself. Hang in there.

[Schrade]

Just got back from the 'Shack...

$2.49, and a pro sound installer would probably take $275 to install it in the Head Unit (or console).

https://lh3.googleusercontent.com/-URTGpqBFOFw/USbUrSaTkyI/AAAAAAAAA8o/gR4U-Qdd_bc/s1280/trigger_dev.jpg

You need a SWITCHABLE 3.5mm jack ($5), and 2-3 feet of wire.

The way the mod works that I saw posted (page bookmarked with snappics on another computer), is : (and I can't take credit; it's web-blogged (or Stickied) somewhere)

the optical disk / CD Player has a dedicated logic board IN THE HEAD UNIT, which connects by an internal harness to the main logic board, ALSO IN THE HEAD UNIT.

this internal harness carries L and R signals, a common, and a few others, one of which is a POWER interrupt, so that when you plug in a CD, it auto-plays.

The mod is thus:

cut the L and R signal wires on the internal harness. Splice onto the FROM CD PCB (printed circuit board) side L and R signal wires, and on the other end, ONTO the 3.5mm INPUT terminals.

Route 2 more leads from the 3.5mm OUTPUT, BACK to the L and R mainboard INPUTS, where you cut.

Put in a CD, and it plays as normal, THROUGH the 3.5mm plug.

BUT, plug a 3.5 jack iPod into the socket, and the L and R signal circuit FROM the CD is interrupted by the switch (switch activates by the plug), and the iPod - or x device, gets carried to the mainboard.

Where to mount the 3.5mm socket???

This is why I asked if you had a snappic of the BACK of the HEAD UNIT faceplate. If it has IT'S OWN logic board behind the faceplate, and many do, then you cannot drill and mount the 3.5mm socket in the face of the HEAD UNIT. It DOESN'T need THAT much space tho'.

Otherwise, the socket would probably get routed to the center console somewhere.

Only 'problem' is, is that a CD must be playing, in order for the MAINBOARD to look for a signal from the CD INPUT harness. BUT, the CD won't be heard, with the signal interrupted at the socket.

(the CD PCB-to-mainboard harness must also include a SWITCH, activated by CD insertion, jumpable, so that a CD DOESN'T necessarily have to be inserted. That part isn't solved yet)

Will try to get this phot-doc'ed soon here...

[mike100]

I found some compatible 1998 Nissan/Infinity Maxima/J30 Bose amps for $7 ea in the junkyard. Additionally, I have successfully repaired a pair of the original amps by swapping capacitors from used amps I acquired. The newer Nissan ones were much easier to deal with and are still running 2 years later.

I kept the front /rear part numbers sorted out since the Nissan applications have very similar sized speakers front to rear.

[Hib Halverson]

This might be helpful to you guys working on the Bose systems...two articles on the Zip Products tech. web site.

http://www.corvettemagazine.com/late-c4-corvette-sound-system-upgrade-part-1-installing-a-modern-receiver/

http://www.corvettemagazine.com/late-c4-corvette-sound-system-upgrade-part-2-the-bose-amplifierspeaker-assemblies/

[LancePearson]

Hib,
Thanks. I found another set of instructions on the speaker amps and did that first. Went perfectly and worked well. I had hoped to replace the radio face since the radio was working perfectly without removing the radio head. I ended up unscrewing the radio head fasteners and could pull it back some but not enough to get my hand behind it to unclip the connections from the back of the radio head. It's back in place poorly at the moment with the fuse out and the radio disabled, trim back on.

I will have to remove the trim again. Should be much easier this time since I won't have any wasted motion. The radio head has to come out so I can work on getting the many little but long head pins into their female floating connectors. I may have to disassemble a side of the unit to get access as they are not fixed in place so when you push against them the male pins do not go in. They do not appear to be tagged with long enough wires to hook them up outside the head to the face assembly then move the head assembly back into the front of the case to snap in either so it must be from the side or opening the case in some way. Can't get serious about that with the head in the car. At worst I can send it to be done by Dr. Don if I can get it out. I got two pairs of forcepts out and am resting up as this old geezer pulled a muscle in my rib cage in the process. Bollocks again. This weekend or next week will tackle it again. I absolutely don't want to go through replacing the bose with adapter harnesses and all the rest per zip as the stereo when working is more than adequate for my needs. I hate working inside dash boards as everything is tight and cramped and my hands are big. I wear a size 13 ring for example. I also don't trust installers having read some horror stories but I may have to go that way if I can't figure out how to get it out.

I swear, if I get the radio head out I might consider adding a splice of 5" of wire in and solder it to every single one of the leads on the radio head side to it's connectors so I can get my hand in there effectively to connect, disconnect which is what should be done to begin with.

Otherwise, I'll have to hire either Sleepy, Doc or Gumpy to do the work. Should have left the scratched up face in apparently.

Still mightily frustrated.

[secondchance]

I found some compatible 1998 Nissan/Infinity Maxima/J30 Bose amps for $7 ea in the junkyard. Additionally, I have successfully repaired a pair of the original amps by swapping capacitors from used amps I acquired. The newer Nissan ones were much easier to deal with and are still running 2 years later.

I kept the front /rear part numbers sorted out since the Nissan applications have very similar sized speakers front to rear.

How can you tell which is for the front vs. rear?
Front/rear speaker sizes in Nissan/Infiniti corresponds to smalll up front and larger in the rear like our Zs?

[LancePearson]

I found a used, fully functional, in good shape bose readio head for my 91 z just like I have on ebay and hopefully will get that. The photos show enough of the back wiring harness that I now wonder if there isn't enough wiring length to the connecters wire to free up movement but it's tucked up behind a clip on the back of the head case and I can just reach over the top, free them then pull the radio to me enough to then reach behind it and unclip the connections and pull the radio head. Right now I'm just letting it all sit in place with trim on until I acquire a replacement and fuse out and will then go in and then replace.

I fear I've screwed the one I have up but with another which I'm happy enough with I can then open the radio head of hte one I may have messed up with the new "face" and the pin issue later and see if I can get the pins in when it's on a table and I can open the metal case enough to affix them solidly first.

At least one solution is emerging. I managed to pull a muscle in my rib cage messing around with it yesterday so will have to let it sit a while anyway.

Sheesh, Bollocks, but maybe a path forward is emerging.

[secondchance]

Lance,

Would you mind taking a pic and posting when you take the face plate off of the head unit?
I have a headunit out of my 94 (black face plate) and would like to replace one burnt out bulb on the left side of the display. Would be easier if I nknew what I was getting into.
Also, if you can wait 'till our next WAZOO event at Mt. Vernon I'll be happy to replace the head unit (done that a few times in the last 21 years) and perhaps reassemble your old unit w/ a new face plate.

[LancePearson]

Lance,

Would you mind taking a pic and posting when you take the face plate off of the head unit?
I have a headunit out of my 94 (black face plate) and would like to replace one burnt out bulb on the left side of the display. Would be easier if I nknew what I was getting into.
Also, if you can wait 'till our next WAZOO event at Mt. Vernon I'll be happy to replace the head unit (done that a few times in the last 21 years) and perhaps reassemble your old unit w/ a new face plate.

The old unit with the new faceplate incorrectly on it is in the console now but not functioning as I don't have the pins in right. I probably screwed it up so decided to buy a good used bose head for a 91 and hopefully have that coming. When it gets here I'll pull the trim then unscrew the radio screws and reach over and hopefully free enough wire harness to pull the radio forward enough to reach behind and unclip the connectors and pull the unit out. When I do that I'll probably just put the new/used one in and hopefully that will be that but when I have the one I tried to put the face plate on out I'll put it on the table and open it up and photo it then. I think to get those two many little pin connectors which are not mounted but float on you have to remove some of the metal radio head case, attach them to the head then put the case back on and the face on the front of that. However, I won't know until I get it out which will be a couple weeks maybe. It may be salvagable since the pins can be straightened and if I line them up and mate them properly the rest should not be damaged but there are some bulbs under there I noticed and I'm afraid I might have damaged them. Regardless, it does not work from the control face where the buttons are when the pins aren't properly in place because that's how the action gets communicated to the head I believe.

I have seen one note that says I may have to take the hvac control unit just above it out to get access to the connections if they are stuck on the frame....but I don't think they were....will see. New used unit headed my way and should be here by 28th. Will tackle it then.

Thanks for the offer. Let's see how my current plan works and if I get it out I'll open it up and photo it and post it.

Lance

[mike100]

How can you tell which is for the front vs. rear?
Front/rear speaker sizes in Nissan/Infiniti corresponds to smalll up front and larger in the rear like our Zs?

I marked my amps when I pulled them out of the junkyard car. The speaker sizes were small front, large rear very much like the C4 ones. At first I was going to be a stickler and get the exact vette application amps, but after finding two completely equipped Bose Nissans with 8 fully functional amps, I grabbed those to try them out or maybe rob for parts.

Turns out they sounded just fine so I never bothered trying to get the exact Corvette units as the rears are tuned for a larger speaker anyhow. Additionally they are late 90's so they aren't as old. Not sure if they figured out to use a better capacitor by then or not, but when I found these amps for peanuts, I just grabbed a few extra.

If I were to do it again, I would suggest a solution like the ones shown in Hib's links. As a reward for all my work on amps, my car failed a CDM tuner and already had a malfunctioning CD player...so basically my whole system was junk, but I made the effort to repair it to have the oem look.

[secondchance]

I marked my amps when I pulled them out of the junkyard car. The speaker sizes were small front, large rear very much like the C4 ones. At first I was going to be a stickler and get the exact vette application amps, but after finding two completely equipped Bose Nissans with 8 fully functional amps, I grabbed those to try them out or maybe rob for parts.

Turns out they sounded just fine so I never bothered trying to get the exact Corvette units as the rears are tuned for a larger speaker anyhow. Additionally they are late 90's so they aren't as old. Not sure if they figured out to use a better capacitor by then or not, but when I found these amps for peanuts, I just grabbed a few extra.

If I were to do it again, I would suggest a solution like the ones shown in Hib's links. As a reward for all my work on amps, my car failed a CDM tuner and already had a malfunctioning CD player...so basically my whole system was junk, but I made the effort to repair it to have the oem look.

I too found out about Infiniti/Bose amp and purchased a used set last year. Funny how if they are out of a Corvette they ask for $90+/ea. and when out of a Nissan they ask for less then a half of Corvette price.
Back in 84 when Bose first teamed up with Delco, they made a big deal out of how speakers and amps were tuned specifically to work with a particular car interior. I agree their speaker/enclosure was tuned carefully and that's why we can get a decent mid-bass and volume out of 3" speakers up front. As for amps being tuned for a specific car or the location in the car - I am not so sure. I replaced an amp out of a coupe in a convertible and did not make any discernable difference. I won't be suprised if amps used in Infinities are the same ones used in C4s - just my thought.

[LancePearson]

Saturday morning...renewed energy, less frustration.

This morning I tackled it again and with what I learned overnight it turned out to be rather easy to get the radio out. While there with the trim all off I used a magnetic tipped pointer and found all the screws someone else had dropped before me, added some adhesive, urethane, foil coated .080" sound deadening where applicable though there is sound deadening on top of the tunnel below all that. This may just help minimize resonance of the trim from the gear train a little.

Brought the freed radio head unit into the kitchen and worked with good light on it on the table on a towel and removed the outter metal case frame and there were the connectors for me to easily connect up by holding them, oddly enough, with forceps. I did that, checked what I could and assembled the new face and clicked it in place and reattached the case. Radio unit whole with new face. Stuck it in without putting the trim on, connected battery and put the radio fuse back in the fuse box and it works perfectly functionally. However, none of the lights come on so I assume the first attempt must have blown some little fuse and I'll call .dr. Don Monday to ask him. Either way, I have a good one coming and know how to put it in. I just left the trim all off and the radio in place and disconnected the battery until I'm all done as there are some connections to other things currently undone.

If I have to I can certainly use it now like it is but I would prefer the lights as it gives you a cockpit feeling and helps when tuning and showing the clock which is in the radio. Every function from cd to am/fm, volume, base, fade, eject, switch to radio, etc. works and the sound is great. Dr. Don will probably tell me there is a fuse about a quarter inch long in the radio head I've blown and either I can get it from Radio Shack or he will send one. As these cars get older I don't mind having two good head units as nothing lasts forever and they don't make these bose gold for this Vette anymore to the best of my knowledge. I'd like to keep it like it is as the sound is fine for my ears. If I want fine sound I turn it off and run it up to 6500 rpms hitting it a little anyway.

At any rate, relative progress though "I'm not done yet." What I've learned makes it relatively easy to get in and out without removing anything around it but the trim for access then the radio. There was enough wire to pull the radio forward and reach the connections behind which are self explanatory..two sizes, only go in one way. I took some photos including of the face, etc. and will upload them later today and post. A work in progress but there is some progress and I feel much better about it.

Not done yet but moving right along.

[LancePearson]

Here are the photos of the center area of the tunnel and the dash with the radio head out, with some foil faced urethane adhered below in some places to minimize any plastic parts resonance from the sound in the gear box below and on the center trim piece back as well. There is a bit of a well which can be a sound chamber of sorts below the radio when it's in and above the zf tranmission so it has a tendancy to act like a resonator and this .080 material should help minimize that by absorbing sound a touch. Won't hurt anything and is something I could do.

there are photos of the radio without its face, the face back, the edge where the bulbs are, the radio with the new face on minus its metal case and then back just sitting loosely in place in the stack of "Modules" from DIC, HVAC controls, radio below all minus the external trim piece. I did remove the shift trim but just loosened it enough to get the tabs back to free the module trim and remove it. Not complicated once you've done it a couple times. helpful to have magnetic pointer in case you drop a screw btw.

Just page through the photos. I have other photos of the speaker amp I replaced but they are not here. It worked perfectly and this is the new face but I managed to not get the bulbs lit so have one more thing to check..a fuse probably got screwed inside the radio case but will call about that Monday. it plays perfectly and no longer has face scratches.

http://www.flickr.com/photos/zr1lp/8501409674/in/photostream/

[LancePearson]

I'm wondering...do I have to have the radio head case metal side brackets screwed into the opening so that a negative comes from the reception of the screws to complete the light circuit? I just have it sitting there, not screwed in at all. I wonder. I'll call Dr. Don Monday and see what he says. The photo showing the cd track 1 playing appears orange but that's from the flash of the camera not the two bulbs of the radio. It might depend on the ground pickup through the fastening screws to be connected to negative power to trigger the light functions.

I'm too lazy to do any more experimenting at the moment but I do wonder.

[Fully Vetted]

Good time to put in a shift light if you don't already have one.

[LancePearson]

shift light inside the a/c vent would work. Not a bad thought.

[Schrade]

I'm wondering...do I have to have the radio head case metal side brackets screwed into the opening so that a negative comes from the reception of the screws to complete the light circuit? I just have it sitting there, not screwed in at all. I wonder. I'll call Dr. Don Monday and see what he says. The photo showing the cd track 1 playing appears orange but that's from the flash of the camera not the two bulbs of the radio. It might depend on the ground pickup through the fastening screws to be connected to negative power to trigger the light functions.

I'm too lazy to do any more experimenting at the moment but I do wonder.

Schematic section 8A 151 does not show a ground integral with the Head Unit housing.

However, the more places that those unruly electrons can disperse to, the BETTER! Just like kids, when they get together in a tight spot, trouble abounds yUP!

[LancePearson]

Schematic section 8A 151 does not show a ground integral with the Head Unit housing.

However, the more places that those unruly electrons can disperse to, the BETTER! Just like kids, when they get together in a tight spot, trouble abounds yUP!

Shrade...does it show an in head fuse for the lights..I tried a contact from housing to screw holes...no change so that confirms what you said. All the green in head lights work function by function but the two incandescents dont...I suspect a fused circuit as the culprit. Darned radio works perfect with good sound otherwise and no face scratches from previous owner any more. I dont have the diagram.

[Schrade]

Shrade...does it show an in head fuse for the lights..I tried a contact from housing to screw holes...no change so that confirms what you said. All the green in head lights work function by function but the two incandescents dont...I suspect a fused circuit as the culprit. Darned radio works perfect with good sound otherwise and no face scratches from previous owner any more. I dont have the diagram.

No lights? But the LCD DOES light up?

I didn't see a fuse while inside the HU; Bob carstereohelp.com is going to get to me a schematic for the unit itself Monday - talked to him Fri night.

Looks like the solid Grey might be the culprit. It's in the smaller of the 2 HU harness connectors.

HU troubleshoot chart 'No Incandescent Display' says, "Park Lamps on" ? Dimmer NOT at 'minimum'; then refers to Interior Lights T/S chart.

https://lh3.googleusercontent.com/-LL5jjvujNaU/USmuX_f6soI/AAAAAAAAA-Q/6Nj9DQ26pBw/s1480/IMG_5114.JPG



'Dimmer' troubleshoot chart 8A-117 does NOT show isolation for HU incandescent lights!!!

Bent pin?

[LancePearson]

I double checked the dimmer switch setting this morning. When parking lights are on all the orange back lights on the radio light just like the rest of the dash and are dimmed or not with the dimmer. When the radio is on and you push a function button the small green lights come on as they should. It appears the incandescents that light the radio in orange are the lights which make things orange through the distribution plastic and are controlled by the dimmer and they are both on and working. Hard to imagine I damaged both incand. Small bulbs since I touched neither and I now know they are working because they light a lot when you turn the parking or headlights on.

I now think what happened is that when I switched the existing circuit board from the back of the old scratched face unit then incorrectly tried to put that unit back on the radio while it was in place and did not get the pins right that in pressing somehow I must have damaged some type of very tiny, low current draw light wired directly into the inside of that board on the back of the face unit itself which illustrates the displace space alone for the clock, the radio station, the cd track, etc. info which is displayed either through pushing too hard or some other mechanism.

Every other light, of which there are many displays, on the radio and every other function now works perfectly save that. The display displays and in daylight it works well enough to use but when light is low the letters displayed in the display are black and need the contrast of a low level backlight.

I won't take it apart again since I am not up to soldering on a solid state board and if the used/new unit coming works I'll drop it in then send this one back to Dr. Don and let him do it and return it to me. I know it's not popular to say this here but I like the radio and the sound that comes out of it in the car and won't mind having a ready backup just in case. It's been a learning experience anyway.

I did not take a photo of the inside of the board on the face unit when I had it apart, only the completed and assembled face unit from the back so I can't be sure but logic gets me here and I now see for 99% that the two incandescent 1/4" diameter bulbs appear to be working perfectly. Therefore, it's probably what I think . Thks for diagram.

[LancePearson]

on the Corvette Forum Alchemist posted these instructions and there are bulbs on the board for the face and that must be what is shot on mine. I'll repost it here and have saved it and will look into either getting the bulbs and soldering or sending to Dr. Don and let him do it. I'm not confident in my soldering ability and it is only the display bulbs on mine that aren't working. I'm not surprised I did something as it was not done right the first time.

Here is some interesting info that Bose automotive just sent me...the head is made by Delco to feed the other parts..

"....Thank you for your inquiry. I am sorry to hear that you are having problems with the Bose Music System in your 1991 Chevrolet Corvette. The speakers/amplifiers are manufactured by Bose Corporation and the radio/cd portion of the system is manufactured by Delco Electronics...."


Ok Guys! You asked for it...you got it. Here's the text from the tech tip on replacing that lit'l PITA Delco bulb! I just wish i could remember who originally posted this to give credit where credit is due!

Steps for Removal Of the Delco-Bose Radio for light bulb replacement

Before doing anything, take a good look at your unit at night and determine where the dark areas are. This will help you understand which bulbs require replacement once you get the radio apart.

Parts Required
Radio Shack
12 volt, Bi-Pin, 50 milliamp bulbs - P/N 272-1154 ($1.39 each) 1 per package

Pulling the Head Unit
With car sitting on a level surface, apply emergency brake and select neutral with shifter.

Turn ignition switch to off.

Pry shifter button out of shift knob by inserting a thin blade screwdrivers on each side of button.

Use a pair of straight nose snap ring pliers to remove spring clip on shifter knob.

Pull shifter knob off of shift lever.

Remove shifter trim plate by first removing two 7 mm screws inside console.

Pull corners of carpet up to reveal screws.

Remove the one 7 mm screw that is found inside cup holder.

Gently lift up trim plate until you can unplug shift indicator light. Rotate light socket to disengage from plate.

Unplug cigarette lighter socket by prying the two tabs and slide socket off of lighter receptacle.

Leave rear deck release wiring attached to button, and swing trim plate to the passenger seat.

Lower steering wheel by tilting to the lowest position.

Remove two cross head screws in A/C duct, and remove grill

Remove radio trim plate by first removing two screws at bottom of plate and one at top right. Be careful when removing trim plate because there is a spring clip on left side. Pull straight out to disengage clip.

Radio has 4 screws that hold it into dash. Remove all 4 screws, being careful not to drop any. They are hard to find once you drop them.

Remove radio from dash, by sliding out and at the same time prying the trim away to allow room for the radio attachment ears. If you are not careful, you will scratch the trim work.

When radio is out sufficiently, unplug the two electrical connectors. Don’t worry; they are keyed so you can’t mix them up when plugging back in.

Repairing the Backlight
Take radio to workbench, or table, and lay a soft cloth or cardboard down to protect both the radio and counter top.

Remove the top cover of radio. There are about 13 small screws located on the top, back and sides. With top off, remove the volume, balance, and tone knobs by pulling off. These knobs are specific to each function, so don’t mix them up. If you do, no big deal, you just have to sort it out.

Next, you want to remove the faceplate. This is done by gently prying the tabs that are located on the top and sides. The face will rotate out at the top first. Continue rotating until you can disengage the tabs on the bottom side. Pull the plate out far enough to disconnect the two connectors on the ribbon cables going to the back of the faceplate. Once the cables are disconnected, the plate can be completely removed from the radio.

There are 4 small socket head screws on the circuit board that hold the circuit board to the faceplate. Lay the face plate face down and remove the four screws. Gently lift the board away from the face plate. Be careful and don’t accidentally dump out all your face plate push buttons, cause then you won’t know which button goes where…unless you have a better memory than me. My savior was a picture of the radio in the MidAm Catalog. Need I say more?

Now, where were we? You will see 3 lights around the display, and four lights in the pushbutton area. The 3 lights around the display are identical to the ones you bought at Radio Shack. Unsolder the old ones and replace. The 4 in the pushbutton area are not an exact match in size, but they work, and are easy to solder into the board.

When all lights are replaced in the board, set it aside and look at the two light bulbs by the volume and balance controls. The top light is replaceable, and can be removed by grasping with your fingers and pulling out. Replacement bulbs are available at AutoZone or at the dealer. Don’t ask the dealer to look the part up on his computer, cause he won’t show it. Just show him the bulb. The bottom light is hard soldered and if you must replace it, use one of the bulbs you purchased at Radio Shack. Again, the bulbs won’t be an exact match, but they work just fine.

Re-assembly is pretty straightforward. Be careful, and when re-installing into the dash, slide the unit in far enough to hook the two connectors up, then try the lights prior to final assembly.

Don’t forget to slide the shift indicator slot over the shifter tab when lowering the console plate back into position.

(Edit to correct spellings and make article more readable ;) )

[LancePearson]

a diagram service sent me the system diagram schematics today so I'll pass it along. It does not go inside the boards but is a fairly clear presentation of the system as I see it.2228

[cvette98pacecar]

I haven't pulled the radio head yet. I need to pull the center tunnel and shift tunnel and console trim first to check shift boots, add some sound proofing then change the radio face place so have not done that yet. I'll unplug the battery this weekend and start removing the trims to reveal and do the three things since they all share the same need.

From what I've seen of the back of the radio head there are a couple of wiring harness connections behind the head which might be able to be tapped for such a thing. Presumably power in then outputs to the CDM below the glove box and to speakers from that. I haven't looked at the wiring diagrams at all. If you can tap in for a 1/8" plug seems like you could mount it in the trim piece below the radio itself as wire length wouldn't matter a whole lot there.

In my case I don't think I have to pull the radio head at all just to put a new face on it as without the trim it's all exposed.

How do you do what you said with the added aux? I'll add a photo of someone elses radio back if that will help.


Lance

Lance Don't waste your time or money with sound proofing. I did dynopad and dynomat throughout the entire cockpit and it made no difference in reducing road noise.

[LancePearson]

Robert, I agree in general. When I have opened the tunnel to deal with the radio there is some 1/2" or 3/8" thick stuff in there that is dry and not rotted and the car's interior noise level and heat level is fine especially when compared to my 76 where I ripped it all out and did what you did. However, on the highway just forward of the tunnel when I drove the car home from my Atlanta purchase in December all 515 miles I kept hearing this sort of whooshing sound almost behind the radio. I did not know what it was but since have learned the ZF is a noisy tranny and that simply folding a microfiber towel and placing it on the ashtray access door and forward and up 4" across the front of the bottom of the center trim piece over the radio/hvac/dic stack stops the noise entirely. When I opened it up for the radio, sure enough it's all thin plastic and below the radio there is a sort of 1.5" or so by the radio head deep cave there which I believe can act a bit like a resonance chamber...the tube on a pipe organ so to speak under the right circumstances. All I did was use the .080 urethane foam adhesive with foil face to coat most of those plastic surfaces and the inside of the trim to try and stop what I think is inherent, resonance in the plastic surfaces which aren't thick enough to stop it. I'll probably put some on the bottom of the radio to absorb sound a bit more as well when I do the final stick it back in. I did not close any openings so air can flow if it is a design feature which I doubt but just in case....We'll see when I get the radio all the way done. Just waiting for something to arrive now and then I'll button it up and try it. I sure agree it's not worth redoing the cockpit. The cockpit so far is much cooler than the 76 was before I did this with thicker urethane on the cage floor and tunnel the way it is already so I'm not worried about that either. We'll see in a little while. I'm probably being obsessive about the noise.

In the 76 I also switched the two seats when I had them out to redo the floor and carpets. I'll probably switch the two seats next winter on the 91 as well though I may recover the driver's side with new leather. next year's project. In a month or so it's time to start using it, time to resume serious kayaking and time to start thinking about my Flying scot sailboat too!

Thanks for the information...it confirms what I'd thought about the cockpit.

[Schrade]

a diagram service sent me the system diagram schematics today so I'll pass it along. It does not go inside the boards but is a fairly clear presentation of the system as I see it.2228

I got board schematics there Lance, for the mainboard, and for the tape/CD board from Bob carstereohelp.com.

Your lights don't go through the board. Only way to check the missing incandescant bulbs is to pull them, and check the bulb filament for continuity, then check the Incand input (the solid gray input on the smaller HU connector), TO the first bulb socket, then the second (I don't know if the bulbs are in series, or in parallel). ON SECOND THOUGHT; THE FSM NOTE TO THE RIGHT SAYS NOT TO MEASURE IMPEDANCE TO THE UNIT - I DON'T KNOW IF YOU CAN ISOLATE THE INCAND CIRCUIT THROUGH THE HU

(in the 2 schematics, board header ID's P701 and P702 correspond to CN101, and CN102, respectively, to our HU header ID's.

Never mind my notes there; that's for the AUX Input mod...

The gray input

https://lh3.googleusercontent.com/-LL5jjvujNaU/USmuX_f6soI/AAAAAAAAA-Q/6Nj9DQ26pBw/s1280/IMG_5114.JPG

https://lh3.googleusercontent.com/-wmp-uywLI-s/USvARWBqJcI/AAAAAAAAA_k/y_b7Q7W5l5w/s1280/Delco%252520Corvette%2525202.jpg

https://lh5.googleusercontent.com/-e-bUlzCeHkQ/USvAboU_LZI/AAAAAAAAA_w/gM0rxUO74yc/s1280/Delco%252520Corvette.jpg

[LancePearson]

Shrade, I don't have the unit in front of me but the total head unit by Delco consists of three boards/electronic controls including the cd and cassette mechanisms if memory serves...there is one horizontal on the floor of or somewhere innside the the metal case I think (memory here or it could all be the mechanism controlled by the side board.)..will see. There is a second vertical one on edge with its length the depth of the head unit when put into the dash behind the two incandescent bulbs on the left side as you look at it when the top and two sided metal case is removed. Then, on the separate approx 1/2" deep face unit is a third, or another, green circuit board which screws to the back of the face with all it's buttons and light distribution plastic "runners" in place. All you see when looking at the back is the soldered pins instead of what is on the other side. I haven't removed it again at this point but will in time. Between it, the buttons and the plastic face they all reside in are two pieces of clear plastic with white lines on them which I believe distribute the dash lights controlled by the dimmer to the entire face and when the lights come on for the car, parking or headlights, then the dimmer switch controls them and they show an orange light throughout my radio (the basic lighting schemel across my dash gauges). I think it is the two fairly powerful little incandescant bulbs on the vertical board on the left side which generates that light. Each of the buttons also has a green lcd or led that lights on demand as well. The lights show three types on the schematic: Incand, LED, LCD....and normally display screens are lcd types I think but I'm in over my head without it open and in front of me. Every single light function works fine save the backlighting for the 1/2" x 3-4" long display area which by definition has to be a more subtle light source and I believe does not come from the two incandescent bulbs on the left side of the h.u.

The metal case to which the completed face unit with it's green board screwed to it attaches clicking in with its separate board is the face mounted on the h.u. metal head box then. There are pieces of insulating material to keep that board from touching the metal case itself. I don't remember exactly what's under the face board itself but the one thing in the entire radio function not working at the moment is the display window backlighting which is more or less a constant though gets brighter if memory serves when the headlights are on as well. It can probably only be lit by a source on that face board just described. Without the headlights there is backlighting there normally and right now in mine it is not there. So, if it's the two Radio Shack 50 miliamp bulbs referred to in Alchemist's post I put up here then I'll see that when my new/used radio arrives and I substitute it in place. Then I'll take my current which will become a backup h.u. apart and see what is on the inside of the face's board. I'm no EE but what I've seen so far does not look like the board for the face unit. Maybe wrong and maybe I'll have to eventually send it to one of the radio tuners, dr. don or Bob, to let them do it but right now it's an interesting puzzle. I'll let you know when I get my new/used unit and put it in assuming it works correctly as purchased says it does.

We'll see. Not often I spend this much time on one thing. I just have the dash open in that area now as it's too cold to drive at the moment anyway. Sound is terrific when I do try it though.

[HAWAIIZR-1]

Lance,

Thanks for all your posting about Bose stereo woes as it made me finally get off my arse this weekend to pull the two front amps to ship out for repairs. They were buzzing and hissing with no sounds otherwise. Initially I thought it was my plug wires or alternator not really looking into it to actually listen, but after disconnecting them it was easily known to be the problem. I replaced my head unit years ago with an aftermarket unit (JVC Chameleon) and it still works great even with back speakers only. I guess it never really bothered me since I don't listen to the stereo and always enjoy the music from the modified LT5. Again, thanks for motivating me to get this done.

Craig

[LancePearson]

Hawaiizr-1,
You are welcome. The speaker amps are really very easy to remove and replace..probably one of the easiest things I've done to date with either of mine and you will like the new amp on the speaker unit with the Bose speaker setup. I'm not a huge base guy but clear sound and hi fidelity when I'm listening to a book on cd or cd on a long drive or the radio and it is more than sufficient for me for that. I like the original look and is why I'm going to all the trouble.

[LancePearson]

One last thing..there are small bulbs around that face c. board and if you bend them you can make them inoperable as lights for the backlighting of the display which is almost certainly what I've done in my first attempt. He, Dr. Don, and I discussed the radios a little and he told me he was the JVC national audio Engineer as a career and quit to do the radio repair business 13 years ago since national companies don't service what they sell very well. The head unit in our case was made by Delco and the CDM unit was made by Bose as were the speaker amp units and they jealously guard the circuitry diagrams. He said that the front speakers are designed to give good mid base and high sounds and the rear speakers to give good base and mid high sounds as a system. Bose simply got rid of the energy of producing sound we don't want to hear. The amps are 50 amps going into 1 ohm speakers which if you put it into the traditional sound producing design would be the equivilent of about 100 amps of power in each amp. He says that he has taken any number of our corvettes where the owner says the amps are fine, gone through the amp boards on them one by one and the sound improves dramatically like it's a whole new radio and the system is good. Dr. Bose is a genius he says but he hired people to buy capacitors and resisters who bought poorly made (not doped effectively is his term) and they started leeching acid the moment they were put in use and then heat and activity over time makes them all fail. He uses components that do not do that he says and when done you have an outstanding audio system. I keep reading here where they are not good systems but I suspect that is the reaction to the many components and dealing with the capacitors which fail, etc. Once set up properly he says they are one of the best systems around. I will probably send my unit back to him since it will become my backup unit shortly and he'll go through it and clean it all up, put the bulbs in, for a very minimal fee and redo the lights on the display as well and return it.

He advises never to use anything other than water and a very soft rag like a microfiber rag to wash the radio face as it is an lcd screen just like your laptop and you can use soaps and sprays and turn them cloudy in an instant. Treat it like your laptop and you'll do fine.

If you did not realize it there is a mute sound system built into it as well. it uses the speakers as microphones, identifies some background sounds which are not good for the human ear and sends out sounds that cancel them in the course of using the radio as well as the SCV, Speed Corrected Volume feature.

Lance just passing on what I'm learning from experts.

[HAWAIIZR-1]

Hawaiizr-1,
You are welcome. The speaker amps are really very easy to remove and replace..probably one of the easiest things I've done to date with either of mine and you will like the new amp on the speaker unit with the Bose speaker setup. I'm not a huge base guy but clear sound and hi fidelity when I'm listening to a book on cd or cd on a long drive or the radio and it is more than sufficient for me for that. I like the original look and is why I'm going to all the trouble.

Hi Lance,
I'm not surprised that some maintenance comes with owning this Bose system from an over 20 year old car. I think it is well worth it to rebuild so I did as I like the sound myself. I know if you want one of those really thumping systems it might be best to replace it all, but as you said I like Bose and the sound quality even for my home. I understand your wanting to keep it stock and nothing wrong with that with the original look. Thanks for sharing what you found out from Dr. Don about the history and information in detail for this system.

Craig

[LancePearson]

Part of why I like the Bose is that Dr. Bose and his systems use some cleverness rather than just the raw application of indiscriminate electrical power. I like rock and roll and jazz and often listen to books on cd discs on long drives or a local radio station though with the targa top off and in the back which it normally is I just listen to the motor and nature. I like the tuned application of the speaker enclosures and the fact that they aren't 12" in diameter to get the sound they get. Just, as you say, a matter of choice. Sound is like art, you like or dislike what you want and it varies widely for different people. Dr. Bose in the sound community is considered a genius for the approach he took but not everyone likes his approach.

My backup used new to me head unit is enroute and will be here late Thursday then I'll take a look at the one with the new face but no backlighting on the display and pack it up with a note and ship it to Dr. Don who will fix the backlighting issue and return it to me.

Have a great day...

[LancePearson]

I have a friend who is a serious audiophile...Kliptsch speakers, et al, and has his own sound meter and is a meticulous guy. While I'm quite content with my Bose in the Z, especially since I only use it when I'm under 50 mph and ride around with the Targa top out listening to the Borlas and the LT5 for the most part, here's what he and his audiophile buddies have to say: "If it has no highs and no lows, it must be Bose!" Made me laugh as these are the equivalent of wine snobs as applied to sound. it's true that Bose gets rid of some sound that they consider un necessary. It's also true that my friend worships at the holy grail of: "huge speakers and huge amps of 400 amps or more, minimum." Sort of different for me and to continue the wine analogy, not worth buying me $200 bottles of wine as my pallet is only good enough to manage the difference to about $40 a bottle.

He is very knowledgable and spends enormous amounts at home on speakers and headphones chasing "pure, full and rich sound."

I'm sorta content with what I have and then there's the beast and the borlas which is way better anyway.

Thought you'd enjoy the audiophile view...