Tach Repair

[BA80]

Anyone here do tach repair? I have 2 tachs that look really good but they don't work.

[DiverRay]

Greg,
There was a thread about the repair. IIRC, it had to do with the standard and the fuel gauge. The tachs are electric, and run off the AC side of the charging system. My guess is the grease is old and hard, or a wire has come loose at a solder joint. The hard part is taking off the metal bezel without doing damage. You need to pull the tach apart to repair it, but the repairs should be easy.

[BA80]

Yeah, when I first got my SG the tach was FUBAR and I took it apart. Never did figure out what it was that I was supposed to fix. I ended up just replacing it.

I'm just a bit too heavy handed for that kind of delicate work. It's something electrical , the one tries to work but jumps and the other just lays there. Both the needles move freely though.

[natemoen]

Must be cold down there in OK today, you have sleeves on!

[BA80]

Must be cold down there in OK today, you have sleeves on!

Yup, it was a little chilly riding yesterday. Pouring rain today.

It'll be sunny and 75º tomorrow while I'm at work.

[BA80]

Anybody got a wiring diagram that shows an SF tach? My Clymers manual shows the wiring for the tach lights but not the tach for the SF.

It shows the tach in the SG diagram though.

[crazy steve]

Greg, the factory manual doesn't show anything more than what Clymer does... ... so I guess the answer is no, no SF tach diagram. They all wire the same though (other than the differences between models like the fuel gauge/lights) according to the FSM, so the SG diagram should work.

[BA80]

That's what I thought but at one time someone on here said the wiring was a little different between the two. I don't see a difference.

I got this tach apart and everything seems to be in place and attached properly. I can take a 1.5v battery and directly jump the tach motor and it works. The signal is getting lost somewhere in the circuitboard. I have no idea how to test the other components.

[BA80]

I know some of you out there are electronic geniuses. Help me out here.

Here's some pics of what the buisiness part of the tach looks like.







One of those components is bad on that circuit board. I suspect the large capacitor on the side the wires hook to because it's the only thing that looks even remotely unusual. It looks like the bottom between it and the circuit board has blown out.

[TopCatGr58]

Hey Greg,

Once I saw those large fluid filled capacitors, I was going to suggest you replace them as a first thought. They dry up, or overheat after a while...30 years qualifies for "a while"! I had 2 pro grade editting VCRs that had died, and aside from some little 3 pronged voltage regulator that was clearly showing signs of overheating, all of the capacitors looked okay. I first replaced the Voltage regulator chip, but then it would only turn on for a few minutes. Advice from a local TV/Electronics repair shop when I brought the internal power supply in to them was to replace ALL of the fluiditics...about 12 capacitors! I did that, and they have worked flawlessly ever since!

You can get the size/power rating from the side of the capacitor, and can get them in 1-2 packs off of ebay very easily and cheaply! Go for it, what have you got to loose!?

T.C.

[crazy steve]

I know some of you out there are electronic geniuses..

Well, that wouldn't be me...

Most of the bits attached to that board are common parts; if you were willing to spend some time and a few bucks on it, you could replace most of the parts with a trip to Radio Shack. Most are resistors, easy to check with your multimeter, with a few capacitors and diodes. But you do have one IC (integrated circuit) on that board (the long black thing) and that will be the piece that will be hardest to replace I suspect; without knowing how it's supposed to work, it will hard or impossible to troubleshoot...

[BA80]

Hey Greg,

Once I saw those large fluid filled capacitors, I was going to suggest you replace them as a first thought. They dry up, or overheat after a while...30 years qualifies for "a while"! I had 2 pro grade editting VCRs that had died, and aside from some little 3 pronged voltage regulator that was clearly showing signs of overheating, all of the capacitors looked okay. I first replaced the Voltage regulator chip, but then it would only turn on for a few minutes. Advice from a local TV/Electronics repair shop when I brought the internal power supply in to them was to replace ALL of the fluiditics...about 12 capacitors! I did that, and they have worked flawlessly ever since!

You can get the size/power rating from the side of the capacitor, and can get them in 1-2 packs off of ebay very easily and cheaply! Go for it, what have you got to loose!?

T.C.

Exactly what I had in mind TC. I looked them up online and Radio Shack has those capacitors for like $.40 each.

It ain't no good the way it is. Maybe we'll all learn something.






Or not

[Rasputin]

Good Luck with your repairs! If that fails I do have an extra or two around here.

[BA80]

Thanks Doug, Might just take you up on one if I can't make any headway on this endevor.

I put the electronics from another inoperable (broken) tach into one of those in my pics and it appears to be working ok. I'll have to mount it up and give it a real world test.

not holding my breath