76 FJ40: Instrument cluster circuit board damage (1 Viewer)

[Kire5]

It took out my instrument cluster to troubleshoot the fuel and temp gauges not working and found this damage to the circuit board. Is this repairable?

I also found damage to the fuel gauge - not sure which came first!

 

[sogncab]

My first instinct is to say try scraping back the insulating layer and try applying a glob of solder. Then do something to add insulation back.

Classic Cruisers should have one for you as well.

 

[45Dougal]

Absolutely. Carefully scrape the blue solder resist with a scalpel blade perpendicular to the board to expose a good amount of copper - be careful because the copper is pretty weak and not bonded to the substrate after overheating.

You can also try a very small piece of wire wool with tweezers.

Then cut a 1cm length of thin solid copper wire.
Melt a little solder onto one of the copper tracks with a soldering iron.
Hold the wire across the gap with tweezers and heat one end until the solder flows.
Allow it to cool and then solder the other end. Never move it while it's molten.
Borrow nail varnish from your beauty box and apply over the joint. Boom.

Looks like that is the 7v output pin from the fuel gauge? I'd guess that happened because someone shorted it to the dash surround as the removed it.
I'm not a fan of these old regulators so personally I'd not fix the meter and instead add a linear voltage regulator (see photo).

 

[Kire5]

Absolutely. Carefully scrape the blue solder resist with a scalpel blade perpendicular to the board to expose a good amount of copper - be careful because the copper is pretty weak and not bonded to the substrate after overheating.

You can also try a very small piece of wire wool with tweezers.

Then cut a 1cm length of thin solid copper wire.
Melt a little solder onto one of the copper tracks with a soldering iron.
Hold the wire across the gap with tweezers and heat one end until the solder flows.
Allow it to cool and then solder the other end. Never move it while it's molten.
Borrow nail varnish from your beauty box and apply over the joint. Boom.

Looks like that is the 7v output pin from the fuel gauge? I'd guess that happened because someone shorted it to the dash surround as the removed it.
I'm not a fan of these old regulators so personally I'd not fix the meter and instead add a linear voltage regulator (see photo).

View attachment 3419637

Thank you!! Where can I find one of these linear voltage regulators? I have googled a bunch and am striking out! I found one that are 5V out but not 7V

 

[Kire5]

Thank you!! Where can I find one of these linear voltage regulators? I have googled a bunch and am striking out! I found one that are 5V out but not 7V

I might have found one - does this look right? https://www.mouser.com/ProductDetail/ROHM-Semiconductor/BA7807CP-E2?qs=Bakm8ERcljp0D%2BecpRGTrg==

 

[45Dougal]

I actually used an L7808 (8V) and a 1N4001 diode on the output which reduces 0.6V. I used the same diode on the input to reduce the dissipation slightly.
Note that dropping 5V or so at 1A will generate 5W of heat so screw it to the metal somewhere.
Found both parts on ebay. Check the pin layout for your specific part!