Roland TD-20 cracked board - does this look a huge job to repair? - Page 1
Forum section: electronics / repair

author: supernova92
author_rank: Newbie
timestamp: February 09, 2024, 05:29:35 pm
content: I purchased a used item from an ebay seller, the item was not packed well and was damaged when I received it. After disassembling I am seeing a large crack across one of the internal boards (see attached photos).The unit is operational but the group faders on it are not working, those faders are on the other side of the area where the crack travels through. I attached some photos of the other side with the faders as well.I see a bend to the top substrate on the side with the faders, but it does not look like the crack travels through to my eyes on that side.Curious from the photos attached, does this look like a big job to repair? I do some repairs myself on equipment but haven't done much in the way of circuit board trace repair. From what I've read it seemed that I'd need to desolder the faders and rough up the areas between each side on the cracked area and solder them together in some fashion. There seemed to be a lot of methods out there and thought I might create a thread to ask based on what I currently have in front of me.Appreciate any input on this and thanks.

author: supernova92
author_rank: Newbie
timestamp: February 09, 2024, 05:30:21 pm
content: Adding additional photos of the other side with the faders.

author: pcprogrammer
author_rank: Super Contributor
timestamp: February 09, 2024, 07:21:24 pm
content: By the looks of it the traces that might be impacted are only on the bottom side, so you can probably fix it without removing the faders.For the thick traces you can scrape of the solder mask and solder some copper wire on top of it. You could take some thicker solid copper and flatten it with a hammer to make a wider bridge. This also strengthens the PCB.The fader slider pins seem to connect to the vias a bit further up the PCB, so you can use bodge wires to connect from the via to the fader slider. Is easier then scratching up these small traces.

author: fourtytwo42
author_rank: Super Contributor
timestamp: February 09, 2024, 07:27:17 pm
content: Just hope it's only a 2 layer board

author: pcprogrammer
author_rank: Super Contributor
timestamp: February 09, 2024, 07:41:43 pm
content: Quote from: fourtytwo42 on February 09, 2024, 07:27:17 pmIt is not that complex a board, so I doubt it being anything but 2 layer.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: February 09, 2024, 09:59:30 pm
content: I used to try and jumper across the crack, but now I would run thin wires from the fader pads direct to the connector pads.

author: coromonadalix
author_rank: Super Contributor
timestamp: February 10, 2024, 02:51:39 am
content: just gently scrape the pcb varnish, and solder small wire taken from stranded bigger cables, wire wrap ... etc ...lucky you, you dont have many traces to patch, more is finding a way to prevent pcb bending at this position, some re-inforcement are due ...

author: inse
author_rank: Super Contributor
timestamp: February 10, 2024, 07:28:25 am
content: It is most probably phenylic board as fiberglass based does not crack this way.I have never seen phenylic PCBs with more than two layers except this carbon print traces.The crack should either be additionally supported from the case or be strengthened with something glued to the PCB to avoid future damage.

author: IanJ
author_rank: Unknown
timestamp: February 10, 2024, 02:53:27 pm
content: I'd be looking for a robust repair.1. Start with the wide GND at the far left side, scrape the soldermask off and bridge the crack with about 4 short lengths of 1.0mm copper wire. Say, 1cm either side of the crack.2. On the GND cracks between the faders same technique with 0.8mm wire.3. On the signal traces use 30awg Kynar wire and bridge from the soldered joint on the fader across to the nearest VIA or pin on the connector. Scrape the soldermask off the track if you need to and solder to the copper trace.Notes:No reason the repair can't look very nice indeed!On the far left GND crack only you might feel it's worth adding hot glue over the soldered wire just to give it extra stability.......nothing worse than stressing a board after only to see something rip off.On the topside of the board if the board you might be able to soak superglue down into the crack to make it more stable.......but the main aspect of robustness comes from the 0.8mm & 1.0mm copper wire.Avoid liquid soldermask for any type of visual repair.......personally, I think it always looks terrible!Ian.

author: supernova92
author_rank: Newbie
timestamp: February 11, 2024, 10:02:04 pm
content: Thank you for all the responses! For some reason I am not getting email notifications, I was glad seeing all the responses once I remembered posting here and came back.With all the information I feel pretty good about giving this a try, it may be a week or longer but will post back here with any results if I end up doing it here soon.Thanks again.

author: MathWizard
author_rank: Super Contributor
timestamp: February 14, 2024, 04:24:51 pm
content: It's been a few days, but yeah I find it fun to scratch the green coating off traces, and bridge them. Depending on the PCB and environment, it might be better to use a jumper wire back a ways from the crack. Or maybe some glue can be added to the PCB aswell. But sometimes solder right over the crack line is enough, especially if you place a wire lead over the crack/trace too.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: February 14, 2024, 07:55:45 pm
content: Good luck. Certainly mechanically reinforce the board to relieve the crack from undue stresses.

author: inse
author_rank: Super Contributor
timestamp: February 14, 2024, 10:20:22 pm
content: The solder will be the first thing to give way if the board was bent again, I would definitely suggest to solder down copper wire.

author: Paceguy
author_rank: Regular Contributor
timestamp: February 15, 2024, 11:54:58 am
content: As stated by max.wwwang, use some non conductive glue on the crack to reinforce the circuit board. I have repaired cracked boards in the past and fixing the crack first is important if you want the board to be stable and minimize the possibilities of intermittents. Others have given you advise on the method of fixing the pads and traces. I have used the lead cutoffs from resistors and capacitors to make the bridges on fine traces.

author: Gyro
author_rank: Super Contributor
timestamp: February 15, 2024, 02:52:40 pm
content: Another ways to add rigidity to a damaged board is to add strips of PCB material oriented vertically across the board (ie. on their edges) and tack soldered. Obviously this will only work where there are large areas of copper, such as the cracked end of the OP's PCB and maybe in a couple of other places too.The other thing is to prevent the crack from propagating further across the board. This can be achieved by drilling a clean round hole (around 3mm) just past the end of the crack, obviously avoiding any tracks. In the OP's images, the crack appears to stop at a solder pad, which might achieve the same thing, but it's hard to see clearly (the microscopic end of a crack may not be immediately visible).