Tach op amp needed for my '90 ZR-1

[Paul Workman]

Apparently, the op amp driver for my tach is fried...long story. Anyway, I'm appealing to anyone that might have either information as to where to get it, or even the part itself?

The chip is stamped with the numbers

9907A
CS8939J

I'm hoping there is somewhere I can cross-reference it to an OEM.

Note to self: Don't use alligator clips on resistor leads. Next time solder the the fkin connection (while calibrating the tach).

P.

[mike100]

My first thought is that the amplifier chip is going to be the same p/n as any Late C4 gauge cluster so there is always the option to scab parts off of a more common L98/LT1 gauge face.

[Paul Workman]

Originally Posted by mike100

My first thought is that the amplifier chip is going to be the same p/n as any Late C4 gauge cluster so there is always the option to scab parts off of a more common L98/LT1 gauge face.

I'm hoping for just that, Mike. I'm just hoping the "J" designation does not mean VIN having "J".

P.

[mike100]

OP-Amp gain is dependent on the outside circuitry so to retune for the 8k tach face on the LT4/LT5, I think just the resistors are different. The opamp itself is just a universal chip that drives a certain amount of current and works on some volatge be it 5v logic or 12v or whatever.

here's a quick calculator to design your own feedback:
click here

[gbmidyear66]

8939 is the mfgr datecode

Part is made by SGS
http://html.alldatasheet.com/html-pd...1/L9907ND.html

Good Luck

[Paul Workman]

Originally Posted by mike100

OP-Amp gain is dependent on the outside circuitry so to retune for the 8k tach face on the LT4/LT5, I think just the resistors are different. The opamp itself is just a universal chip that drives a certain amount of current and works on some volatge be it 5v logic or 12v or whatever.

here's a quick calculator to design your own feedback:
click here

Thanks for the reply, Mike.

My big concern is the ECM. I don't want to install an op amp (or fully differential op amp, i.e., two outputs as ours have - driving the tach both UP and DOWN the scale) until I'm sure of the configuration and there is no danger in shooting voltage on a line that isn't suppose to have any.

In the short term, I'm trying to get back to square one as soon as possible. The next step will be to reverse engineer the stock op amp, breaking it down to the last lead, and publishing it on the Registry, "just in case" someone needs to replace one. Getting my baby running again (well, actually it runs fine, just no tach at the moment ) is my focus.

But, I want to let you know that I DO appreciate your info. Maybe we can wrestle this down together. When it comes right down to it, there's only printed resistor ceramic pack, two chips, very few diode (rectifiers) and a pin diode. My point is, once the chip mystery is removed, there isn't much at all to the boards!

P.

[Paul Workman]

Originally Posted by gbmidyear66

8939 is the mfgr datecode

Part is made by SGS
http://html.alldatasheet.com/html-pd...1/L9907ND.html

Good Luck

Fabulous!

P.

[WVZR-1]

I've a '93 MY LT1 that's ID'd as 9907A, CS9252J

You're welcome to it if you like!

[Paul Workman]

Originally Posted by WVZR-1

I've a '93 MY LT1 that's ID'd as 9907A, CS9252J

You're welcome to it if you like!

Sending you a PM now

P.

[WVZR-1]

Got the PM and replied!

I included an email address! Drop me an email! Intentions are to drop it at Post Office tomorrow "evening" unless your in "need" of some other "priority" shipping!!

-Dave