# Help with unknown circuit type

#### Imctkh

##### New Member
Hi there,
I'm trying to repair the remote control for my trolling motor (it's a motorguide Lazer 370RF). The remote is a foot pad with buttons. Inside is a sheet of plastic film with these little white leads running all over it (see picture). The one that supplies power seems to be burnt out. If you try to scrape off the white stuff, there is no metal inside to solder to.

I'm sure if I knew what this setup was called, I could find a video showing me how to repair or bypass the broken lead. However, no combination of words in Google has given me any luck. Anyone know what it's called, or better yet, how to fix it?

Thanks,
Mitch

#### Beau Schwabe

##### Active Member
Do a search for "Silver conductive pen" ... that's how to fix it. You will not be able to solder to it. The next big question is, why would that have burnt out?

#### Nigel Goodwin

##### Super Moderator
Do a search for "Silver conductive pen" ... that's how to fix it. You will not be able to solder to it. The next big question is, why would that have burnt out?
I would suggest it's corroded away, rather than burntout - quite a common occurance on those types of remotes.

#### DrG

##### Active Member
I may not be seeing this clearly, but it looks like it has already been repaired once.

I can't tell if there was a trace in the area between my blue lines that came off, or if there is a trace there, but on the other side.

The area in my red outline looks very much like someone repaired it using some copper tape (something like this https://www.amazon.com/Conductive-Shielding-Repellent-Electrical-Grounding/dp/B076H4NPRR/ref=asc_df_B076H4NPRR/?tag=hyprod-20&linkCode=df0&hvadid=216767879473&hvpos=1o1&hvnetw=g&hvrand=14171606063556337347&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9007812&hvtargid=pla-386214563660&psc=1 but not as wide). Note how you can see that it (the repair piece has been placed on top of the original trace with the repair piece being cut diagonally near the connector).Not sure what to make of the rectangular object within my red area - maybe more of such tape.

Do you have continuity from just before the repair to just after the repair? It may not be working for other reasons. If there is poor continuity, you could replace/redo that trace. Silver pen was already mentioned maybe some kind of conductive adhesive as well. Or, maybe I am just not seeing it correctly.

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#### Imctkh

##### New Member
Do a search for "Silver conductive pen" ... that's how to fix it. You will not be able to solder to it. The next big question is, why would that have burnt out?
Thanks, I will try out the pen.

The reason it's burnt out is because it sunk in the lake (along with my boat)

To DRG's question - I made the mark inside the red circle. I was scraping at the wire hoping to expose some metal that I could solder to. As far as what's between the blue lines, it's not part of the circuit. It's a feature of the plastic pad that the circuit is stuck to.

#### Nigel Goodwin

##### Super Moderator
The reason it's burnt out is because it sunk in the lake (along with my boat)
Like I said, not 'burnt out' simply corroded.

#### unclejed613

##### Well-Known Member
these are known as "membrane keypads". first time i ever saw one was some kind of video game console in the 1980s. i think it was the "Intellivision" controllers were made like this, and there was a part of the keypad that flexed while in use, and eventually the traces would begin breaking. the only "repair" option was ordering a new controller. the breaks always happened on a right angle fold of the membrane, and using silver paint wasn't a very reliable way of fixing it since that corner was always flexing a bit while the controller was in use.

one possible "fix" for this one would be to build a switchbox with real switches. there's not a big complex set of switches, and only 9 wires.

#### alec_t

##### Well-Known Member
The sixth wire from the left going into the connector at the bottom looks pretty corroded too.
+1 for the new switchbox idea.

#### Imctkh

##### New Member
these are known as "membrane keypads". first time i ever saw one was some kind of video game console in the 1980s. i think it was the "Intellivision" controllers were made like this, and there was a part of the keypad that flexed while in use, and eventually the traces would begin breaking. the only "repair" option was ordering a new controller. the breaks always happened on a right angle fold of the membrane, and using silver paint wasn't a very reliable way of fixing it since that corner was always flexing a bit while the controller was in use.

one possible "fix" for this one would be to build a switchbox with real switches. there's not a big complex set of switches, and only 9 wires.

#### Imctkh

##### New Member
Initially I thought I would offer to design a small circuit board with tactile push buttons, but looking at your photos I would consider reworking both boards. The main board doesn't appear to be too complex and looks to measure about 2.5 inches x 2.5 inches. It's hard to see what all is under that silicone which BTW is not the greatest thing for copper traces on a PCB. Normally I charge \$60/hr for contract work, but I would cut that in half for this project. PM me if you want and we can discuss the details further.
Thanks Beau. I am somewhat determined to fix it myself at the moment, but I'll let you know if I fail.

#### unclejed613

##### Well-Known Member
if you can find some ribbon cable (like what used to be used for IDE hard drive cables) you can use that... from the looks of the connector in the picture that shows the 9V battery clip, it looks like 0.1 inch spacing. ribbon cable with 0.1 inch (2.5mm) spacing is inexpensive and easy to find.

the best bet will be to carefully remove the connector, and replace it with one end of the ribbon cable. this requires desoldering the connector. if you need to, find a board you don't care about and practice desoldering/soldering on it first. once you get confident that you can desolder without lifting pads or removing a feed-through, then tackle the controller. if you get a desoldering tool, i think the big blue ones are pretty good since they have a large cylinder volume and strong spring, which makes for a stronger vacuum.

under that silicone which BTW is not the greatest thing for copper traces on a PCB
there's silicone RTV compound available that is non-corrosive, and specifically made for use on circuit boards. it doesn't ooze acetic acid (vinegar) like the household RTV compound.

#### Imctkh

##### New Member
Thanks, you are correct on the spacing. I also have the desoldering tool that you described.

Buying this ribbon cable, we'll see how it goes.

#### Imctkh

##### New Member
I just wanted to give a final update on this, as I find it annoying when I read through a forum and the OP never posts their success/failure.

So I had an issue finding the right size ribbon cable. I bought two different ribbon cables, both of which said they had 2.54 mm center spacing. Both of them had 1.27 mm center spacing. After the second time this happened, I gave up and just used every other wire to get the correct spacing.

I soldered the ribbon cable to the board and connected to the switches you see in the picture to make a switchbox that is kind of like a game controller. It works great, and is actually easier to use than the original foot pedal. It is kind of ugly, but I really care more about funtionality .

Thanks for the help everyone!

#### JimB

##### Super Moderator
So I had an issue finding the right size ribbon cable. I bought two different ribbon cables, both of which said they had 2.54 mm center spacing. Both of them had 1.27 mm center spacing. After the second time this happened, I gave up and just used every other wire to get the correct spacing.
The thing is with ribbon cables of the type which you have, they are intended for use with connectors which have two rows of pins which are 0.1 inch (2.54mm) apart.
The connectors crimp together and pins in the connector body pierce to insulation of the appropriate wire in the ribbon.

Anyway, it looks like you have a working solution to your problem, well done.

It is kind of ugly, but I really care more about funtionality
Sometimes "ugly construction" is the most effective way when you are only building one of them.

JimB

#### Nigel Goodwin

##### Super Moderator
Looks like a large number of expensive switches

We use them at work, nice switches, but rather pricey.

#### unclejed613

##### Well-Known Member
actually, although it is "ugly construction" it's a very nice job. you might want to paint clear paint over the button markings. Sharpie markings tend to come off easily.