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I'm working on repairing my dash / indicator lights on my 1989 312-8. My seat light stays on when the ignition is in the run position. However, it does go off while the key is turned to the start position. I have checked the wires and switches from PTO all the way through to the Molex connector and all is working as it should.  This leads me to believe there is a short or bad component on the board. Check all the diodes and thought I found one that was bad and replaced it to no avail. It shows flow in both directions with a .223 reading which is the same as the diode I replaced.?? 

Does anybody have a close up picture of this board clear enough to see the bands and colors on the resistors they can share??? Mine are worn off on many so I'm not sure of their values.
 

Any other thoughts are appreciated.

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There are a few threads here on (I think...CRS) that board about how guys were contemplating making/reproing  them. I think @bmsgaffer ? was one of the instigators perhaps he can help out. Also might have been @Save Old Iron

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WX11 I've read through those post but there's no pic of the board I need.

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From a 418A...I think it is the same

IMG_0102.JPG

IMG_0103.JPG

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An easy to fix board.

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Posted (edited)

 

Not for me it isn't. I know just enough about electronics to be dangerous LOL.

Edited by Shankstr

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19 hours ago, Shankstr said:

I'm working on repairing my dash / indicator lights on my 1989 312-8. My seat light stays on when the ignition is in the run position. However, it does go off while the key is turned to the start position. I have checked the wires and switches from PTO all the way through to the Molex connector and all is working as it should.  This leads me to believe there is a short or bad component on the board. Check all the diodes and thought I found one that was bad and replaced it to no avail. It shows flow in both directions with a .223 reading which is the same as the diode I replaced.?? 

Does anybody have a close up picture of this board clear enough to see the bands and colors on the resistors they can share??? Mine are worn off on many so I'm not sure of their values.
 

Any other thoughts are appreciated.

 

The proper way to attack this board repair would be to purchase a VOM /Volt, ohm, meter with diode check. Harbor freight has them usually less than $10.  Trying to identify the resistors based on the color of the bands/value can get you into trouble simply because the colors can decay. The best approach is to simply measure the resistors and if they are within the tolerance leave them and if not replace them. There is a tolerance band probably gold or silver band 5% or 10% tolerance.

 

There is something like 22 diodes ,2 zener diodes, one transistor and one opamp. I can't read the numbers on the zener diodes or  the transistor or I would provide a parts list. I would replace all the bad 1N400? diodes with 1N4007's a better diode about the same price and doesn't need to be a fast low noise diode. I simply use the 1N4007's because I buy them by the thousands.

 

With respect to the diode you replaced.... pull one side and test it again and if good solder it back. 

7 hours ago, Shankstr said:

 

Not for me it isn't. I know just enough about electronics to be dangerous LOL.

 

Its very elementary and you are capable of doing it saving money and getting it back 100% again. 

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Whole lotta soldering on that board!

 

And it has to work in a high-vibration environment with big temperature swings. There's a good chance that the solder connections can develop hairline cracks over time -- which makes them highly resistive and eventually intermittent or completely open.

 

I've serviced my own analog gear over the years; one thing I learned is that mobile electronics with traditional through-hole soldered components tend have failures due to solder connections literally wearing out from vibration and expansion/contraction. The worst part is that on things like radio transceivers (CBs, ham mobiles etc) with complex circuitry, if it's operated too long with sections thrown out of tolerance by bad connections in resistor banks or diodes controlling power, other components can wind up getting damaged. Fortunately, that's not nearly as likely on a simple indicator control board that mostly just passes current or doesn't.

 

Step one to fixing something like this is often just re-soldering everything. Don't re-flow the old solder. Use a vacuum desoldering tool or bulb and solder wick to clean up the connections and then re-solder them fresh. It's tedious (which is why shops use a dedicated desoldering tool that works fast) but it restores the fundamental physical connections of the circuit to a good state. For a simple board like that, that might be all that it takes.

 

Also, clean the board. Brush it off, paying close attention to the spaces between the components and the solder pads. Some "dirt" that accumulates from mowing, plus dust from surface rust nearby in the engine compartment is conductive. If there's a thin conformal coating on the board to protect it, it may deteriorate and flake away over time and also trap dirt under where it's flaking up. After a board is re-worked, the conformal coating can be repaired with a new coat. Use a stiff brush and isopropyl alcohol to get the damaged areas clean, and then re-coat. (Search for "conformal coating spray" and you'll find Amazon and other listings for spray and brush-on coatings.)

 

Once the board and solder connections are cleaned up, it's easier to positively identify any bad or iffy components and replace them. Trying to track down bad components on a board with suspect or bad solder connections is like chasing ghosts.

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Careful Eric...the way you sound you may end up getting a board in the mail to go through! ...from more than one of us! :)

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If I were retired I might be able to take up on that... but that's still a few years off. Too much time taken up still workin' for the Man... :lol:

 

If I recall, weren't some later boards "potted" in epoxy to protect them better? Longer lasting, but also not repairable because of the thick epoxy layer.

 

The entrepreneur in me has thoughts of things like that -- but I also know that analog troubleshooting and repair has a high cost in time. That board design looks like it's ripe for developing random faults anywhere -- simple ones, but time-consuming to find and verify.

 

Business-wise, better solution is to replace the board unless you're handy with soldering yourself. The components are cheap commodities. A new simple two-sided board isn't hard to design and have custom-manufactured, but costs for small production runs aren't all that attractive. That tends to be the show-stopper, unless you can locate a good enough deal on board production. That's before dealing with soldering assembly. There's enough solder points in close proximity on that board to make hand assembly in quantity both expensive and hazardous in terms of concentration of fumes produced -- which means it has to be done under a ventilation system. I'd actually be concerned if I were re-working that board myself, and deliberately do a row at a time and then take a fresh air break. And custom manufacturing of discrete, through-hole soldered board assemblies has gone way up now that pick-and-place surface-mount technology has taken over. But re-designing and contracting out a modernized board has a high cost of entry, too. Not impossible, but the lead time isn't fast or cheap. That's why hobbyists who do custom electronics for other hobbyists tend to go the kickstarter route, and still run into funding and deadline problems.

 

Something to think about, but I suspect I gotta retire first... about five more years or so off.

 

Thinking out loud now... I could probably re-work one or two boards occasionally, but it wouldn't be fast at all. Because my time gets spoken for far more often than I'd like, and with that kind of board, you just never know what you'll run into. Maybe it's the classic solder re-work, maybe resistors have gone out of tolerance and have to be replaced. Electronic components are cheap commodities, but unless you have wholesale buying power, you're subjected to stocking shortages and production gaps that hobble the retail sector. In other words, Chinese manufacturers crank out production runs and ship them on their schedule -- not anyone else's -- and outfits like Mouser and Digi-Key that sell them have stock fluctuations because of it. I had a heck of a time finding the correct switches in stock to repair a wheelchair lift on my wife's van once because of it. (That's a time-sensitive repair if there ever was one!) So electronics repair can have a high frustration factor for the little guy. Not sure if I'm prepared to jump back in right now or not. :scratchead:

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Posted (edited)
8 hours ago, EricF said:

Whole lotta soldering on that board!

 

And it has to work in a high-vibration environment with big temperature swings. There's a good chance that the solder connections can develop hairline cracks over time -- which makes them highly resistive and eventually intermittent or completely open.

 

I've serviced my own analog gear over the years; one thing I learned is that mobile electronics with traditional through-hole soldered components tend have failures due to solder connections literally wearing out from vibration and expansion/contraction. The worst part is that on things like radio transceivers (CBs, ham mobiles etc) with complex circuitry, if it's operated too long with sections thrown out of tolerance by bad connections in resistor banks or diodes controlling power, other components can wind up getting damaged. Fortunately, that's not nearly as likely on a simple indicator control board that mostly just passes current or doesn't.

 

Step one to fixing something like this is often just re-soldering everything. Don't re-flow the old solder. Use a vacuum desoldering tool or bulb and solder wick to clean up the connections and then re-solder them fresh. It's tedious (which is why shops use a dedicated desoldering tool that works fast) but it restores the fundamental physical connections of the circuit to a good state. For a simple board like that, that might be all that it takes.

 

Also, clean the board. Brush it off, paying close attention to the spaces between the components and the solder pads. Some "dirt" that accumulates from mowing, plus dust from surface rust nearby in the engine compartment is conductive. If there's a thin conformal coating on the board to protect it, it may deteriorate and flake away over time and also trap dirt under where it's flaking up. After a board is re-worked, the conformal coating can be repaired with a new coat. Use a stiff brush and isopropyl alcohol to get the damaged areas clean, and then re-coat. (Search for "conformal coating spray" and you'll find Amazon and other listings for spray and brush-on coatings.)

 

Once the board and solder connections are cleaned up, it's easier to positively identify any bad or iffy components and replace them. Trying to track down bad components on a board with suspect or bad solder connections is like chasing ghosts.

 

 

I guess since I have several degrees in electronics one of which is a Masters I will have to disagree with the negativity of the post. ANY competent technician could repair that board in less than 15 minutes provided it isn't potted. The board in the picture would be VERY simple to repair.

 

Simple common sense would allow one with very basic technical skills to master that very primitive board. Its very possible to get by the coating if there is one and obtain basic resistance readings. Once the board is functional one can tear it down clean it up and resolder the components using a rosin core solder with a small amount of silver in it.

 

Basically if you can read a meter  run a soldering iron and can use either a desoldering station or primitive solder wick you can fix the board.

Edited by 6bg6ga

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Well, that's basically why I'm not eager to jump into board repairs without a quick turnaround solution beyond just re-work. Because if I don't keep a large stock of (upfront investment) replacement components on hand, the minute I get hit with a supply shortage on a dirt-simple board repair needing an op-amp, I'll get an email like that. Don't want the stress.

 

Easy to do re-work yourself. I did it when the equally simple -- and stupidly expensive power window circuit control board went out in an older Land Rover. Heck, no test equipment required -- the burned spot from overcurrent was obvious, and checking the circuit was easy with a meter and a power supply for functional checks. Reconditioned replacements and repairs were expensive because the little shop that would bother take on the work got fed up with getting kicked around by customers who griped whenever something beyond the shop's control happened and slowed down the turnaround time.

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Posted (edited)

Like I said ....the board is very repairable as long as it isn't potted. The silicone can be cleaned off and the parts readily checked and or replaced. This repair is something anyone can do if they are capable of reading a meter doing a few checks and has some soldering skills.

 

If someone would like to work on a replacement board I would be more than happy to help.

 

 

 

Edited by 6bg6ga

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