All PCB build suddenly stop working

[ChriTracker]

I made a couple of diy effects pedal using both toner transfer and a perfboard. Ive already built a RAT, muff, crunchbox using a copper clad and they all work fine before. Some of my perfboard build like a booster and a delay also worked fine and sounds great. Unfortunately I stopped building diy effects for quite some time now due to my work. Not even one has made it through an enclosure, just bare pcbs with components on top and wires laid waiting to be soldered in place.
Past week I made a chance to visit my drawer full of pcb and tried to test them again. All toner transfer based circuit are not working but the perfboard built are still functioning great. What seems to cause my toner transfer build to fail???

Thanks in advance,
Chris

[antonis]

Without photos you'll only get answers like:
"Toner decided to transfer itself back also taking with it any bored copper track formed by it..) 

[thermionix]

Wild guess here.  Some traces of etchant remained on the boards, corroded solder joints over time.

[ChriTracker]

[url=https://ibb.co/b00Njz]

@thermionix
Do you think I have corroded solder joints in there?
How to avoid those?
Thanks

[EBK]

Do any of the solder joints move when you wiggle the pots or wires?  And have you checked for continuity between the pot terminals and their corresponding traces on the board?  I'm wondering if the issue is mechanical fatigue leading to cracked traces.

[thermionix]

It the second pic, the white stuff around the joints might indicate some corrosion, but I'm not sure of that at all.  I get white stuff from flux vapor while I'm soldering sometimes, but it looks a little different.  As Eric says, take some measurements with a meter.

[intripped]

Have you tried and cleaned the PCBs with some kind of contact cleaner?

[ChriTracker]

@EBK
No, it didnt wiggle. The pots are firmly attached/soldered to the pcb. I will trace the pot connectivity later. Will give you update on this
@thermionix
I haven't use flux on my soldering?
If I remember I run the tip of my iron between solder joint to check for solder bridge thats why 2nd photo has some white stuff around the joint.
@intripped
I will try to use contact cleaner but I dont have any idea on how to and what cleaner?
Thanks

[thermionix]

I haven't use flux on my soldering?

There's probably flux IN your solder, "rosin core" is the term you see often.  If you really used no flux at all you would have trouble getting good solder joints.

[intripped]

@intripped
I will try to use contact cleaner but I dont have any idea on how to and what cleaner?
Thanks

I use a toothbrush and a isopropyl alcohol-based contact cleaner in a spray can. Some soft paper, also.

I think that any contact cleaner for electronical use will do, anyway.

There are dry and with lubricant cleaners; I use a slightly lubricating cleaner, so that I can use it for potentiometers also.

[ChriTracker]

I haven't use flux on my soldering?

There's probably flux IN your solder, "rosin core" is the term you see often.  If you really used no flux at all you would have trouble getting good solder joints.

Sorry I didnt know about that. I'll keep that in mind thanks for pointing it out. Just a newbie after all.. 

[ChriTracker]

Before I checked the continuity of my build. I twitch the pot a little and it worked. Do you think I have a faulty pot? The pots are firmly soldered to the board. Or do you think the corossion caused it?

[EBK]

I would suggest reflowing the solder where the pots are connected to the board.  You are potentially asking a lot, mechanically speaking, of those solder joints and board traces, which are only on one side of the board with non-plated holes.  Reflowing the solder may bridge any small cracks that could have formed.