Vehicle PCB repair using the Circuit Writer Pen

ian field

Joined Oct 27, 2012
6,536
Happy Sunday everyone,

I followed your advice and was able to get solder to stick to the iron. Within minutes I was solder things down. I bypassed the 3 traces using wire from a Cat6 cable. I known this was ill advised but it worked. I was able to solder that wire to sever all links point locations. Some of the joints are shiny, some are not. I thought I did pretty well for a novice. Unfortunately the vehicle still isn't starting. I'm getting no ignition at all so I may have a seperated problem or more board issues. Here are some pics of my progress.
View attachment 114118
View attachment 114119
View attachment 114120
View attachment 114121

Thanks, -Z
The standard "kludge wire" that manufacturers use to fix production PCBs that have missing tracks, is usually called Kynar or wire wrap wire - shop around and find a bargain price somewhere.

You can strip multi-strand wire for a single strand to fix very fine tracks - but using multi-strand as-is carries the risk of a stray strand shorting.

For most routine cracked PCB repairs, I use anything from 22swg to 16swg tinned copper wire - it contributes a lot to bracing up a cracked board, especially if you lay a number of 16swg side by side on a broad track.

TC wire is a lot easier to use if you feed a length off the reel and stretch it straight.
 

Thread Starter

ZionXIX

Joined Oct 17, 2016
16
When I check for continuity, I get perfect number when checking from beginning to end of traces but Im also getting some when checking for shorts between the repair traces. Somehwere around 300ohms. I dont know where the cross talk is happening. I thought about severing some of the trace near each repair side just to make sure nothing can interfere. What do you guys think?

Also if I could, I would change the thread title to "Vehicle PCB Repair" since I have moved away from the silver stuff.
 

AlbertHall

Joined Jun 4, 2014
12,345
300Ω isn't a short between tracks, it is just the current going some other components on the board and is nothing to worry about.
 

ian field

Joined Oct 27, 2012
6,536
When I check for continuity, I get perfect number when checking from beginning to end of traces but Im also getting some when checking for shorts between the repair traces.
.
Some capacitor ESR meters will give DC resistance readings as well as AC ones - most are designed for in circuit testing, so any semiconductor junctions in circuit do not affect the reading.
 

Thread Starter

ZionXIX

Joined Oct 17, 2016
16
So in trying to backtrack my steps. When the vehicle was showing symptoms, I pulled the ECU and it had 2 blown capacitors but the truck still cranked fine and would die 30 seconds later. After I removed capacitors, cleaned the board (causing further damage to some of the traces), and putting new capacitors in, the truck would not crank. After bypassing traces still no crank. I soldered the Capacitors on before I took some of this forums suggestions and I did have trouble getting the solder to flow. It basically just made a nice glob on the underside of the board. I dont think it flowed all the way through the holes on the board. They are nice and shiny though! Would adding some more solder from the top side be an issue?
 

AlbertHall

Joined Jun 4, 2014
12,345
If the capacitors are fitted in plated through holes then you might have pulled out the through plating when removing the original capacitors (not too difficult to do).
If there are tracks on the top of the board to the capacitor pins check that there is zero ohms between the top and the pad on the underside of the board. If not then the pretty way is to remove the caps and put apiece of thin wire through the hole and solder to the top of the board, then fit the capacitor and solder the wire and the cap pin underneath the board.
 

Thread Starter

ZionXIX

Joined Oct 17, 2016
16
If the capacitors are fitted in plated through holes then you might have pulled out the through plating when removing the original capacitors (not too difficult to do).
If there are tracks on the top of the board to the capacitor pins check that there is zero ohms between the top and the pad on the underside of the board. If not then the pretty way is to remove the caps and put apiece of thin wire through the hole and solder to the top of the board, then fit the capacitor and solder the wire and the cap pin underneath the board.
I checked all my soldered wires and capacitors. They all have 0ohms from one side of the board to the other. I found 2 additional bad capacitors and replaced them. I'might starting to run out of ideas for this board.
 
I'm not sure if this was stressed. The green layer is "solder resist". Solder does not stick to it. It's not conductive.

You have to scrape it to get to bare copper. You would be better off tinning both the trace and the wire.

65W is probably a little too hot. Try an incandescent light bulb in series with the line.
e.g. 40 to 100 W.
 

Thread Starter

ZionXIX

Joined Oct 17, 2016
16
I'm not sure if this was stressed. The green layer is "solder resist". Solder does not stick to it. It's not conductive.

You have to scrape it to get to bare copper. You would be better off tinning both the trace and the wire.

65W is probably a little too hot. Try an incandescent light bulb in series with the line.
e.g. 40 to 100 W.

All of the solder resist in has been removed from the problem areas. I was able to get solder to stick quite easily. The 65 watt is working really well now after I reconditioned the tip. In all seriousness the traces and capcitors should all be working now. I'm kinda stumped.
 

Thread Starter

ZionXIX

Joined Oct 17, 2016
16
Well I have put repairing the board on hold for now. I finally got a replacement and that has fixed the problem and the 4runner is now running. I do plan to keep working on it as a personal project so I might pop in with questions from time to time. Thanks guys.
 
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