[powerrodsmike]

Help save this tach, send donat...oops wrong website

I got this SW custom series tach, mfg date code may of 68, in a box of stuff that was abandoned by happy tony in my shop.

I don't know if it can or should be fixed. I saw one on ebay with an asking price of 175.00 with no bids so I don't even know if it is worth fixing.

Overall it is in pretty good shape except for some melty looking stuff in the back pc board.
The needle swings and the wires aren't frizzled.

The main melted thing looks like it was a cap of some sort, as it has a + still visible on one end. The white streak heading east is some trail of plastic drizzle that must have squirted out of the thing in its death throes.
There is a resistor right next to it that looks a little unhappy also.

Other than that it looks ok. I don't know how to test the movement, can I hook it to the nearest outlet? Just KIDDING.

Here is a picture.

WWDD?
(What would doc do?)

Later, mikey

Here is the one I saw on evilbay
LOOKY!!

 

[docvette]

Doc here, imp:

Take two brownies and call me in the morning..

Wow! That is an OLDIE...TTL logic..back when they built "Em Big and Bold

First, Check the fuse next to the 0,047 MFD cap..be sure it is not open.

Nest , try if you can , get the MFD value of the Electrolytic Cap on the Card next to the resistor, YES in fact it puked the electrolyte..Which means after you remove it you need to clean the area very well on both sides of the board..that stuff is mildly caustic..Find the value and get a replacement axial Cap, about 50 WVDC, and install it..Before you replace it, ...OBSERVE POLARITY..or it will explode..

measure with a DVOM the resistor and see if you can get a reading through it..if so, note it's value..If you can read the color code on some part of it, go by that..I can't see any other color other than the black stripe and the 20% tolerance band..so a clue is it is low resistance..and will operate + / - 20 % of the rated Value..If you can get that value, get another resistor ,looks to be about 1 watt, and replace it , then the cap..

Test it out, it should run..unless the transistor took a dump..but it looks well buffered..

If you can't get it..let me know..you can send it to me, and I'll try to repair it for you..but you'd miss all that electronic fun!

Doc imp:

 

[powerrodsmike]

Thanks Doc, You DA MAN!!
Chicks dig ya, and guys want to be ya

I will look a little closer at the colors on the resistor, I think they are mostly visible in person. I think that I can see some numbers on that cap as well, if I use my readin' specs

Then I can shuffle down to radio smack and PU some new stuff and do it.

So I guess this one might be worth playing with, huh?

What do you think sizzled it?

Oh and what are the color codes for the hookup wires?

Thank you doc, for helping :thumbup:

Mikey

 

[docvette]

Doc here, imp:

Like land.."They ain't makin' the stuff no more!" .. Yeah , I think if you find a retro guy wanting to complete a set, it probably will bring as much as the guy is willing to pay..for 2 bucks worth of parts..it a pretty good investment! :thumbup:

Could have been a reverse polarity snafu that let the factory smoke out..OR the resistor failed, and the cap spiked and blew the innards outward..LOoking at the photo, that cap may be an input buffer..Note the green wire comes in right at one end?

The hook up may be, Red power, Black Ground, (for sure) and green coil -, White , illumination.

Oh, I forgot, while you have the board out, look for any "open traces" on the printed Circuit side, any you find, clean and dress, (I hear you thinking..The board...Not you..) and add a small wire to "bridge " the gap..solder in place. If it is close to a foot pad, replace the component First..then add the wire.

That should get it running..

Doc imp:

 

[powerrodsmike]

Thanks again Doc,

that old thing will run if it gets hooked to a regular GM HEI, won't it?
I wouldn't want to fix it and refry it. :smash:
(that would be the mikey way)

Later, mikey

 

[docvette]

Doc here, imp:

Yeah, Should be good to go..

just hook it to the white wire at the cap..It should Be "All Good"

Doc imp: