For those who have BOSE Stereo issues ...

[Journey11]

Hi All,
I have recently worked on a stereo from a Cadillac Allante which is the same unit for the ZR-1 for all intents and purposes and more or less.
I have a schematic which I drew up as I have had a pcb for many months to draw it it up with. I also did a diagram of the backside components that match with the schematic so you can diagnose easier.
It took me many hrs over weeks to get this done so I ask for a nominal fee for them. They are 99.9% accurate ... in fact I just recently updated them as I found one mistake and missed 2 resistors in the scheme.
AS of today I'd say it's 99.9999% accurate ... I did the rear and front amps ... I found my mistakes as I was doing the front amp ... Gary James troubleshoot guide is pretty good but has some errors and or some confusion as to how this thing is built.
I have been able to source replacement IC's for the amp driver 134499 chip ... so far the op amp is still out of reach ... I have a bad amp with a bad opamp and will be trying to rebuild it with other discrete op amps.
I'm still hoping the op amp is good and another component is bad but hopes are fading so my attempt to rebuild it is the only option left. There aren't many of the 134499 ic's left on the planet.
The reason the rear amp I was working on went faulty is I recapped it and got one backwards and it blew something up. My experience with op amps is that this shouldn't have hurt it in any way. I'm totally OCD about getting things in the right way but now and again I miss something. If the op amp is blown I will attempt to find a way to get around this not being able to get replacement IC using separate discrete op amps in smaller packages.

So what ever you do when recapping an amp ... MAKE damned sure they are all in the right position for polarity !!!!
I recapped the other 3 speaker/amps and they all had issues. All are upand working again ... I will keep you updated on the fix for a bad op amp if I get it fixed.
Since it is unavailable to replace a fix must be found ...

This op amp is a custom jobby ... it has 5 op amps inside which is just not right. usually you have one or two or 4 in an IC NOT 5 !!! and the one that is lets say the 5th odd one out has internal connections for the negative input for that amp to Signal ground according to James ... which is where the confusion comes in.
5 op amps in the chip which equates to 15 pin connections and it all adds up when doing the math. 2 No Connects and 3 power pin connects.
The confusion lies in pins 16 and 17 which look like one is an input and the other is maybe an offset ? ... input AGAIN ? op #4 looks like is connected to LGND and has internal feedback to it's output ... how he figured this out without a datasheet I'll never know ... because THERE ARE NO DATASHEETS for any of these IC's ...

As far as damage to an op amp ... you can connect the power BACKWARDS and it will not damage it ... they have reverse power connect diodes for that.
I used to work in manufacturing and we used to have pick & place machines place the parts for reflow and every now and again someone would place a unit into a test bed and have a reversed polarized cap EXPLODE and the circuit would be just fine ... and we talking about fine digital stuff not analog op amps.
So far on the bad amp ... no O/P from pin 5 on the op amp ... not good sign. Just cannot imagine how an op amp could get damaged by a reversed power filter cap.


Ton's of experience with these things now so anyone needing help ... I'm here ...and when I mean experience ... I drew a schematic for the rear and front amps having the pcb's in front of me for weeks if not months both front and rear's ... I thought it might be prudent to do up a schematic diagram. These are for the 136898 pcb burns ... keep that in mind.
There are definitely other etches out there for different years ...
I also found that the EQ codes are very different from year to year and from ZR-1 to Cadillac versions.
For instance my Cadillac Allante codes are 151 for front and 152 for rear ... a ZR-1 code is like whatever Gary James said it was which doesn't even come close the Cadillac version ... so be wary.
As far as I'm concerned ... the EQ is not that relevant ... you can change that in a heartbeat using the main brain to a certain degree.


Another thing I noticed in Gary James TS manual is that my rear amps look like my front amps save for EQ and compression crap. Some of his diagram is not right ... especially after I drew the actual schematics. Looking at my signal flow paths ... don't line up with his diagrams ... at least for the Cadillac versions. But why would they change it for Caddy over the Vette ?
Only acoustics in the shape of the interior of he car would be the only reason ... which is super fine with me ... that is what I call REAL science.
Actually figuring out the freakin math of it ...

[secondchance]

Very interesting! It makes perfect sense that Bose tweaked EQ depending on the interior of particular cars. Another reason to play with EQ and capping low frequency, may have been driven by size of speakers. For C4, it seems Bose couldn?t find any space for decent size speakers up front resulting in 3.5? speakers. I imagine Bose made sure to limit low frequency for the fronts.

[Matt B]

I've been working on car hifi for decades and have a pretty decent installation in my 95 Audi S6. Equalization and timing adjustments are KEY to a great sound system. Same holds true for speaker placement which, in terms of the C4, is everything but ideal.
I don't think that Bose already corrected the timing to equalize the 4 different distances between speakers and driver's head. But for sure they considered interior materials (there's a significant difference between leather and cloth seat, for instance), size and position of glass areas and also (hopefully) the sound emissions by engine, exhaust, etc.
That's why I think (but only think - not know) that swapping amps in favor of Cadillac or Lexus Amps will affect the quality of sound. But that doesn't necessarily mean that things go worse.
That's true since as you said and I spent ages in my Audi with measure equipment - first and foremost a calibrated microphone and a great piece of software to fine tune every factor of that multi channel system. You have to consider so much, where you cut the frequencies, how you set timing and phase, how the various chassis interfere with each other, and so on. It's the same challenge as programming a nicely working chip for an engine, I guess

[dredgeguy]

All good points listed above. I recall having a long discussion years ago with Dr. Don about using replacement amps from other car models that had the Bose Gold speakers. He said Bose created the Corvette speaker amps specifically for the Corvette interior. Using different amps would work but would have the wrong crossover points and would not sound as good. After 39 years of selling dredges with Caterpillar engines, my hearing is not what it used to be (just ask my wife) but my reconditioned stock system (with Dr. Don's Aux input for XM radio) sounds great to me. Perhaps somebody can do an interview with Dr. Don for a HOTB article?

[DRM500RUBYZR-1]

Hah!
I vividly recall thinking the AM/FM Stereo with 8 track and three speakers in my new 76 Grand Prix was the absolute epitome of perfection.

That was about the same time I thought the best beer was "imported" from west of the Mississippi.

Funny how life has changed....................


Marty

[Matt B]

Hahaha, well said . My 1970 Lincoln Mark III also features an 8-Track tape deck plus enhanced 4 speaker setup. I assume that was the "Wow!" of these days. I had it fixed by a professional, added some replacement speakers made to the original specifications and bought Conway Twitty "Hello Darling" on 8-Track. Goes without saying that it sounds awful. BUT: it's the way it sounded back in 1970 when people thought an 8-Track tape and 4 speakers are the pinnacle of car audio.

Therefore I really appreciate everyone who spends time in rebuilding stuff to the original specifications. Of course it always depends from one's personal approach - for my Audi it is to have the ultimate sound system, for my ZR it's to have the ultimately unmolested car. Whereas the Audi sounds better than reality I want to feel my ZR like it was 30 years ago, with all it's "quirks and features" as Doug DeMuro always says. (however please don't blame me in case I'll go for Haibeck chip one day )
So I'll follow this threat with high interest, it's a great exercise for who ever wants it time correct.

[WARP TEN]

Originally Posted by DRM500RUBYZR-1

Hah!
I vividly recall thinking the AM/FM Stereo with 8 track and three speakers in my new 76 Grand Prix was the absolute epitome of perfection.

That was about the same time I thought the best beer was "imported" from west of the Mississippi.

Funny how life has changed....................


Marty

Ain't that the truth. I had an 8-Track in my 1974 Pantera and of course an standard AM-FM in my '67 corvette. Thought they were fine. Of course now wth the current quality of my hearing, I suspect they would still sound fine for me! --Bob