Circuit board repair question - Page 1
Forum section: electronics / repair

author: turbosol
author_rank: Newbie
timestamp: September 24, 2025, 11:00:15 pm
content: Hello, I'm completely new to repairing electronics and have a super basic question. In the pictures below I have a circuit board to a vintage stereo that came broken in the mail, it appears none of the main traces were damaged so I glued the board back together, but there are two solder spots that were broken. Are these connected together? And can I just re-solder them? It's really hard for me to see if it had a bridge between the two spots but I think it did, I just don't want to do something wrong and fry this thing.P.S this circuit board is a sub board that the A/C power goes to.

author: turbosol
author_rank: Newbie
timestamp: September 25, 2025, 01:01:35 am
content: Oh also, does anyone know what those broken areas might do specifically? Here are some pics of the full board

author: golden_labels
author_rank: Super Contributor
timestamp: September 25, 2025, 07:17:12 am
content: Welcome to the forum.First the mandatory warning: be careful, while repairing mains-powered devices.Even when they’re not powered.While this is not the case for this particular question, mind that:Input capacitors (not present here) remain charged for some time after you disconnect the device from power. The amount of energy is sufficient to seriously hurt your fingers, throw your arm into something, or cause you to lose balance. Andwhat they are connected to may be hard to predict!Even experienced people misjudge how sneaky these beasts are.(1)In a broken device you can’t even trust the circuit is as it was meant to be: there may be connections, that shouldn’t be there.Power supplies carry large currents and, at the same time, are expected to work unattended. A sloppy repair or a poor choice of repair materials may easily lead to a fire.A properly designed PSU isolates the device from mains voltage, and offers proper noise filtering. A careless repair, some element skipped, some component sticking out too much, chemical agents used affecting creepage distance etc. may break that.Now to the question.I’m confused. It seems they serve no purpose.The manufacturer uses non-standard component references. But fortunately they use them consistently and even mark clearly alternative configurations. Following that convention, all affected parts (9911 through 9914) are links.(2)If they were connected to something, I’d guess they’re test points. But there is no connection to any net on the board. Unless I’m blind.Perhaps we’re seeing a classic example of no communication between teams. The circuit designers drawn some links for whatever reason they had. Maybe housekeeping, explanatory drawings, or satisfying DRC. The PCB designers received the schematic and, after laying out things, they were left with 4 links. With no right to deviate from the schematic they placed them in any free space.Given the above, it seems the repair was not really needed. But, since the attempt has been made, two notes:Resoldering broken solder joints is correct. Preferably remove old solder completely with a wick and use fresh one. Mixing material from both may lead to a poor joint.While glueing, choose the adhesive right. Generally exposies are the best idea. There are many threads on the forum on that topic, refer to them. Cyanoacrylate adhesive (aka “superglue”) may work, but its use may be questioned where flammability from high temperature exposure is an issue. It’s also tricky mechanically. While it has exceptional tensile strength, it breaks easily under shear stresses, is vulnerable to fatigue, and may be very picky about glued surfaces preparation.(1)To give you the idea: I once made a mistake of not discharging them, believing I’ll be working away from these capacitors. What did I miss? The capacitor had a connection to one radiator through a transistor tab. I discovered that while having my finger stuck between the radiator and ground. I was lucky that they were already partially discharged.(2)Well, it’s “obvious” from the photo they’re links on your PCB. What I mean is that they are not intended to be anything else in any other configuration.

author: ftg
author_rank: Frequent Contributor
timestamp: September 25, 2025, 09:05:55 am
content: Quote from: golden_labels on September 25, 2025, 07:17:12 amI would think they are test points for verifying various PSU signals. ThePCB has Philips logos, so it might be old enough to actually have been designed by Philips. So it could be production line or repair diagnosis related testpoints.

author: wraper
author_rank: Unknown
timestamp: September 25, 2025, 09:21:25 am
content: Broken area does nothing for device's operation.

author: Zenith
author_rank: Frequent Contributor
timestamp: September 25, 2025, 10:16:33 am
content: If you can find the schematic (search on line), you should be able to reconcile it with the PCB, and find out exactly what those points are supposed to do.

author: turbosol
author_rank: Newbie
timestamp: September 25, 2025, 01:45:08 pm
content: You guys are amazing, thanks so much for the helpful information! Yeah I was wonding if those went to nowhere because I didn't see any circuit traces going to it, I think i got really lucky on the spot that broke. I'll try and power it up tonight, thanks again!

author: Kean
author_rank: Unknown
timestamp: September 25, 2025, 01:54:56 pm
content: Like the others I am a bit confused by this, as those jumper positions serve no obvious purpose.One explanation might be that the populated position indicates some type of manufacturing info rather than using a label.e.g. intended supply voltage (115V vs 230V).

author: turbosol
author_rank: Newbie
timestamp: September 26, 2025, 12:06:58 am
content: Yeah it's strange for sure. Just fyi, the board is out of a philips magnavox FW775p stereo system, this line of shelf stereos has about 8 variations/ models so I wonder if those spots are utilized on other models with more options? I have no idea. But anyway, I powered it up today and it worked fine so I'm a very happy man! Thanks again guys.