HELP! Circuit board

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matthon

matthon

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I have a rally dash, and I am having an issue with the smaller circuit board on the left- the 2 upper bulbs will not light.
This is the board that has the lights for the high beam indicator and 3 dash lights for the speedo.
I have tried 3 different circuit boards, multiple bulbs, cleaning the copper, sanding the copper, putting on a jumper wire, soldering, blah blah blah.
No matter what I try the high beam light and the lowest bulb are the only ones that will light up.
The 3 prong connector has power.

I am losing my mind, can anyone help me get it back?
 
There are only 2 bulbs for illumination on the samll boards. The 2 others are left turn and indicater ( brake or high beam ) Do yo have the gauge housing grounded ?
 
RedFish said:
There are only 2 bulbs for illumination on the samll boards. The 2 others are left turn and indicater ( brake or high beam ) Do yo have the gauge housing grounded ?
Click to expand...

If it is not grounded through the harness, then no.
Is there supposed to be a ground wire directly from the housing to the car?

I was thinking that, but then I see no place for a ground and all the other lights are working, including the left indicator and the high beam indicator- which are on the same board.
 
matthon said:
If it is not grounded through the harness, then no.
Is there supposed to be a ground wire directly from the housing to the car?

I was thinking that, but then I see no place for a ground and all the other lights are working, including the left indicator and the high beam indicator- which are on the same board.
Click to expand...

Absolutely ! If the gauge housing isn't chassis grounded the voltage limiter will seek a ground , fry a board, some gauges, self destruct.
I have a board here I'm repairing for another menber that experienced just that. He fryed more than this one board while playing with a panel out of the dash and hanging from the wires.
And as far as seeing no place for a ground wire... very little of these cars has a ground wire. Its mostly and eventually ALL chassis grounded through the metal bolts and screws.
 
Please note...
Many here have seen the solid state voltage regulators and some are using them.
NEVER supply 12 volts to one of those before its chassis ground is sufficient.
Similar proceedure applys to ignition modules, system voltage regulators, etc... Make a good ground first !
 
RedFish said:
Absolutely ! If the gauge housing isn't chassis grounded the voltage limiter will seek a ground , fry a board, some gauges, self destruct.
I have a board here I'm repairing for another menber that experienced just that. He fryed more than this one board while playing with a panel out of the dash and hanging from the wires.
And as far as seeing no place for a ground wire... very little of these cars has a ground wire. Its mostly and eventually ALL chassis grounded through the metal bolts and screws.
Click to expand...

Thank you, this proves my instinct was correct as I was thinking the housing needed to be grounded- but it also proves I'm a dummy because I never tried it! From what I remember, there aren't any screws that go through the housing and hold the plastic gauge panel on, but I'll check again; either way I'll make a ground wire.
So, all 3 of my boards must have been fried in the same place!
Sounds like a design flaw.
I searched for a thread that delt with these but no luck, this is invaluable info. Thank you!
 
Actually the mounting screws go clear through the plastic and bolt the housing to the dash.
 
proves I'm a dummy because I never tried it! From what I remember,

THERE ARE NO DUMMIES HERE.
THERE ARE JUST GUYS THAT KNOW ABOUT THESE PROBLEMS WE HAVE. THANKS
 
I had a similar problem on my 1966 Barracuda. The Oil Pressure and Ammeter lights would not work and the Oil Pressure would read intermittently. After cleaning the mounting screws for the board and all the contacts, it turned out that the 3 pins the harness connects to were loose and had a poor contact to the circuit board. The pins are pushed through and tabs bent over to make them tight. Over time the tabs weaken and fall off causing the problem.

I ended up finding some small (and I mean small) screws and screwed them in from the back making the pins tight and restoring the contact of the pins to the board. I double checked the clearance to the back of the gauage assy. and put a piece of electrical tape on it as a precaution. All is functioning now.
 
I was just cleaning up the ralley dash for my '68 Fish when I decided to check the ground side of the bulb pads to "ground." Some of the pads were 0.1 ohm, but one was 179K ohms to ground, just a little different. Corrosin under the ground screws where the steel screw meets the copper pad, cleaned up and put dielectric grease on the screws before reinstalling. That corrosion would have led to some interesting headaches in the near future.
 
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