Here it is, the original Tach repair service bulletin! - Team Camaro Tech
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post #1 of 38 (permalink) Old Aug 21st, 10, 08:00 AM Thread Starter
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Kelly
 
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Exclamation Here it is, the original Tach repair service bulletin!

Look what I found, is the original 1967 United Delco Electronic Tachometer Service Bulletin in pdf. This bulletin details the testing, diagnosis, and repair of first gen tachs. At the end of the document is a catalog of resistors, capacitors, etc that are used on the tach circuit board (not the flexible printed one behind the instrument cluster, but the small board that drives the tach needle).

Feel free to sticky or archive this so that others can enjoy this document!

http://mysite.verizon.net/racerxtx/A...air_Manual.pdf

Last edited by HwyStarJoe; Feb 15th, 12 at 10:13 AM. Reason: Thank you, Kelly for this info, Everett!
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post #2 of 38 (permalink) Old Aug 23rd, 10, 10:55 PM
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Re: Here it is, the original tach repair service bulletin!!

Kelly,
Want to thank you for posting this bulletin as it will be very helpful in my project.
I am trying to figure out how the factory made the 69 ZL1 transistor ignition work with the factory electric tachometer.
Thanks again.
Bob
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post #3 of 38 (permalink) Old Oct 4th, 10, 07:41 AM
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Re: Here it is, the original tach repair service bulletin!!

Very interesting. Thanks for sharing.

Dave
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post #4 of 38 (permalink) Old Nov 23rd, 11, 07:20 AM
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Re: Here it is, the original Tach repair service bulletin!

This is like finding gold. I worked for Cadillac for twenty two years, and nver saw this. My partner was a 15-a tech, and worked on many of these cars-under warranty!!!!
He always stated that the shop manual was good, but it was these types of bulletins that really got into "heavy diag. and repair". Thanks again
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post #5 of 38 (permalink) Old Mar 22nd, 12, 01:44 PM
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Re: Here it is, the original Tach repair service bulletin!

Very cool, I wonder what we would use in lieu of the ďTach. CalibratorĒ device they have pictured. Similar devices on ebay look pretty pricey.
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post #6 of 38 (permalink) Old Mar 27th, 14, 11:46 AM
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Re: Here it is, the original Tach repair service bulletin!

Old thread, I know. That link no longer works. Anyone have a new link?

Lynn
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post #7 of 38 (permalink) Old Mar 27th, 14, 03:27 PM
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Re: Here it is, the original Tach repair service bulletin!

Link worked for me. If you need it, email me at my home address.
Too big to post here.

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post #8 of 38 (permalink) Old Mar 27th, 14, 03:49 PM
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Re: Here it is, the original Tach repair service bulletin!

Amazing. Now it is working. Couldn't get it go open earlier today.

Thanks for the offer Everett.

Lynn
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post #9 of 38 (permalink) Old Apr 13th, 14, 11:58 AM
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Re: Here it is, the original Tach repair service bulletin!

The article addresses 67 and 68. Does anyone know if the 69 Tachometer is adjustable?

I know I can pull it out and look, but don't wish to pull it out if it isn't adjustable.

Lynn
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post #10 of 38 (permalink) Old Apr 13th, 14, 05:25 PM
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Re: Here it is, the original Tach repair service bulletin!

Verizon servers are not so reliable up-time wise. I bet you just picked the hour a day it is down for backups.

Describe adjustable? They can be calibrated by a speedometer / gauge shop that has the equipment. Home if you have the sign wave stuff on your bench but most folk don't.

Page 4 has 69 Camaro Tach specs.


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post #11 of 38 (permalink) Old Apr 13th, 14, 05:54 PM
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Re: Here it is, the original Tach repair service bulletin!

It should be considered "non-adjustable" to the end-user.
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post #12 of 38 (permalink) Old Apr 14th, 14, 10:45 AM
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Re: Here it is, the original Tach repair service bulletin!

The bulletin indicates a fixed resistor. My tach reads about 8 to 10% high (about 4200 when it should read 3572).

Unless my thinking is backwards (could be) wouldn't a resistor in line from the coil to the tach bring it down?

I can buy adjustable variable resistors really cheap.

Surely somone has tried this.

Lynn
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post #13 of 38 (permalink) Old Apr 14th, 14, 05:51 PM
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Re: Here it is, the original Tach repair service bulletin!

Quote:
Originally Posted by bilodeaulynn View Post
The bulletin indicates a fixed resistor. My tach reads about 8 to 10% high (about 4200 when it should read 3572).

Unless my thinking is backwards (could be) wouldn't a resistor in line from the coil to the tach bring it down?

I can buy adjustable variable resistors really cheap.

Surely somone has tried this.
Lynn,

I'm suprised your factory tach is that accurate to be honest

Here's the scoop. The original "circuit board" that operates the movement (the needle on the tach) is a beryllium oxide ceramic based board in which the factory resistors are actually "etched" in and cut to specification to get the proper value and calibration. They are not the traditional resistors mounted on a through-hole design as we know. These are very prone to drift and going intermittent affecting the original design from the get-go. The solder pads are also prone to lifting and connections go intermittent.

It would be foolish to spend time trying to "tweak" a circuit that has changed from its intended original design. It would be like trying to dial-in a new ignition system on an engine that has burnt valves

That's why people who restore the factory tachs retrofit modern components rather then messing around with the original set-up.

Unfortunately, you really only have (2) choices, live with it as-is until a complete failure, or send it to have it rebuilt and calibrated to proper standards.
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post #14 of 38 (permalink) Old Jul 27th, 14, 08:33 PM
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Re: Here it is, the original Tach repair service bulletin!

My Tach worked, but after an engine rebuild, had a MSD 6AL box added. Now, my tach does not work nor does the ammeter in the console gauge cluster. Any idea what I can do to fix these issue's?
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post #15 of 38 (permalink) Old Oct 26th, 14, 02:42 PM
Mike
 
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Exclamation Re: Here it is, the original Tach repair service bulletin!

I'm rewiring all the original wire under the hood of a 67 RS SS and adding a MSD!
The service bulletin could be useful please could you get me a copy?

Thanks Mike

The link dose not work?
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