questions about a broken dual pot on a bass.

[eh là bas ma]

Hello,

Something heavy fell on my bass, and the top of the Bright/Volume dual potentiometer is broken. The top is controling the volume.

I'm trying to fix it, but it's soldered on a small pcb and it looks like im not going to be able to desolder and replace it.

Im thinking about leaving it, and do an extra hole for a volume pot, because there is some room for it.

I mean connecting an A25k pot to the pcb volume pads, do an extra hole on the white plastic plate, and that's it.

When i'll turn the Bright pot, i guess it might also change the Volume, but i ll be able to set it how i want with the extra Volume pot ?

Do you think it could work ?




Every suggestions and observations are welcome

 

[Robert]

Is the problem removing it, or finding a suitable replacement?

 

[eh là bas ma]

Is the problem removing it, or finding a suitable replacement?

Removing it. It's tightly soldered with 6 pads. If i try hard, im afraid i will overheat the pcb.

An alternative solution would be breaking the dual pot casing and be able to desolder and pull off each pin, but im not sure it's doable ?

 

[giovanni]

Removing it. It's tightly soldered with 6 pads. If i try hard, im afraid i will overheat the pcb.

An alternative solution would be breaking the dual pot casing and be able to desolder and pull off each pin, but im not sure it's doable ?

Robert taught me how to desolder stuff like that. Put a giant blob of solder touching all pads, and as the heat reaches all pins, the pot will come loose very easily and quickly. You should be able to do this with any decent iron, no special tools required.

 

[eh là bas ma]

Robert taught me how to desolder stuff like that. Put a giant blob of solder touching all pads, and as the heat reaches all pins, the pot will come loose very easily and quickly. You should be able to do this with any decent iron, no special tools required.

a big blob that will cover all 6 pads ?

Isn't there a chance that the heat will damage the pcb traces ?

 

[Robert]

Blob each group of three together, then angle the iron so it heats both blobs at the same time.

Don't force it or you'll damage a trace, the pot should fall out on it's own.

Take good photos of both sides of the board before you start just in case. This wouldn't be too difficult to just wire up without the board if you had no choice.

Are you going to be able to find that pot? A mixed taper concentric pot like that could be tricky to find.

 

[eh là bas ma]

Blob each group of three together, then angle the iron so it heats both blobs at the same time.

Don't force it or you'll damage a trace, the pot should fall out on it's own.

Take good photos of both sides of the board before you start just in case. This wouldn't be too difficult to just wire up without the board if you had no choice.

Are you going to be able to find that pot? A mixed taper concentric pot like that could be tricky to find.

Thanks for your replies.

I'm going to look for a replacement. I think it's a B250K and an A250k, it reads B254 and A254.

So i guess if i find a dual B250k or a dual A250k, it should be fine, i dont really care about it, i usually set both values at noon.

Once i'll get the replacement, i ll try your idea with 2 blobs.

For now, i soldered an A250k to the Bright pads. Sounds like when i turn the original pot it changes the Volume (which is weird, the bottom should control the brightness, but it's probably jammed).

With these 2 controls i should be able to play the instrument.

Instead of doing an extra hole, i ll use the active/passive toggle switch hole for the extra Bright pot, and i'll stick the toggle with tape inside the enclosure.

 

[Bricksnbeatles]

You can also carefully dremel parts away before desoldering the leftover pins.

 

[Feral Feline]

Another option is to cut out that pot-PCB altogether, trace and recreate — doesn't look like there's much going on there; means replacing the non-broken pot as well.

In fact, looks like the PCB is for ease of manufacturing assembly — you can probably offboard wire the entire thing.

 

[jimilee]

Robert’s way or a solder sucker will work just fine.

 

[eh là bas ma]

Another option is to cut out that pot-PCB altogether, trace and recreate — doesn't look like there's much going on there; means replacing the non-broken pot as well.

In fact, looks like the PCB is for ease of manufacturing assembly — you can probably offboard wire the entire thing.

Good point.

I ll do the tracing before trying Robert's suggestion, for safety. And if i really can't unsolder it, i ll try to break open the pot to unsolder each pin one by one. If that still doesn't work, i'll get rid of the pcb and rewire the controls.

The other pot reads MN254, i guess a stereo B250k will work. This pot controls the bridge/neck pickups balance.