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Tach amp pics

Started by 1980sdga, 31 March 2011, 12:47 PM

1980sdga



I'm hoping that I just have a cold joint somewhere on the PCB. A couple of the joints around the "3" look a little dodgy.  There was a US nickel where the cigarette butt is supposed to be...

Anyone have any luck getting one of these working? Any advise?  I haven't tackled the component side yet.

calvin streeting

I agree point near 3 is bad and maybe a few others.. clean flux and gve them all a reflow. (use lead solder, not new lead free crap, if you can)..

Good Luck

1980sdga

Thanks, that's the plan.  I've wiggled the dash wiring with no result and everything else is working. Even the clock!  Not sure how accurate it is  :P

The crank sensor looks OK and the little magnet is in place so I'm thinking it's the amp.

koan

Many of the joints look crusty to me, I'd be doing them all, getting rid of the older solder with a sucker before putting more on.

koan
Boogity, Boogity, Boogity, Amen!

1980sdga

No dice...

I soldered some of the bad looking joints and still no tach.  I may do all of them but it's not looking that promising. 

I remember reading something about a guy who actually figured out all the components and the Radio Shack replacement parts.  I'm no electronics guru though...

TJ 450

It's quite likey to be failed capacitor, although I can't remember that particular circuit.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

Big_Richard

Quote from: TJ 450 on 31 March 2011, 07:23 PM
It's quite likey to be failed capacitor, although I can't remember that particular circuit.

Tim

You wont, because its only fitted on diesel engine cars - they dont have ignition coil pulses to count so the tacho relies on that device to monitor the front diagnostic engine rotation sensor.

Big_Richard

Ive also heard that the issue can be the socket that the amp plugs into in its little housing. Im guessing the pins that grip onto the contacts fatigue over the years.

1980sdga

I'll check into the pins next. Wiggling it around didn't seem to have any affect and I sprayed it with some contact cleaner.

sshanky

I thought it was my tach amp. I got a parts car, swapped them out, still no tach. Then, I replaced the actual tach and it worked. So, you might find that it is actually the tach that's failed.