DBX1231 question

[bsco]

Got this unit here and both gain control pots are broken...they are supposed to be B50K but I take it that a regular 50K pot won't work as the pot has to sit at the 12 o'clock position and is varied either to the left or right to cut or boost the signal?? I couldn't find a schematic anywhere on line so that is why I am posting here...maybe it is supposed to be a certain taper??
Cheers

[The Dude]

'B' is a linear taper pot. It shouldn't be too difficult to find one. Got a picture? It would help to know physical size, knurled or d shaft, shaft length, PC board mount?, etc.

[g1]

I think a regular pot would still work. The 25K point would be neutral, less resistance would cut, more would boost.
Does it have a center detent?

[The Dude]

I believe the DBX part number is 40-2138. Full Compass has it listed but not in stock. You may be able to find it elsewhere.

https://www.fullcompass.com/prod/065...hold-input-pot

These look like they would also work if you cut the shafts down. And, they're in stock.

https://www.digikey.com/en/products/...-0312/11652777

[bsco]

'B' is a linear taper pot. It shouldn't be too difficult to find one. Got a picture? It would help to know physical size, knurled or d shaft, shaft length, PC board mount?,etc.

The pot has a stepped feel to it as you rotate the shaft ....it is marked B50K....and it is a D shape...pc mount...shaft length, 1/2 in maybe a bit more...I put the one I have there in and when I try it out I'll let you guys know what it sounds like.....
Cheers

[bsco]

I think a regular pot would still work. The 25K point would be neutral, less resistance would cut, more would boost.
Does it have a center detent?

I don't think it has a center detent as it is a stepped control...I will double check tomorrow...
Cheers

[bsco]

I believe the DBX part number is 40-2138. Full Compass has it listed but not in stock. You may be able to find it elsewhere.

https://www.fullcompass.com/prod/065...hold-input-pot

These look like they would also work if you cut the shafts down. And, they're in stock.

https://www.digikey.com/en/products/...-0312/11652777

The first link....I have a few of those and that is what I used......I'm going to check it out tomorrow to see what it sounds like.......
Cheers

[bsco]

Ok. Checked out the unit today and the pot that I installed acts like a regular volume control....problem is I do not know it the original is correct...both pots were busted...the owner tried to replace one of them with a 500k pot out of a guitar...the other pot had it's contact board completely snapped off with only the three pins left soldered in place....I will have to check with the owner to see what he wants to do....
Cheers

[g1]

Can you post a schematic? edit: never mind, I see you could not find one.

[bsco]

Can you post a schematic? edit: never mind, I see you could not find one.

I tried to find one but came up empty...sorry

[J M Fahey]

.the owner tried to replace one of them with a 500k pot out of a guitar

Hey!!! A pot is a pot, isnīt it?
It even has 3 legs!!!!!

I tried it in the guitar first and it DOES regulate volume!!!!!

[bsco]

Hey!!! A pot is a pot, isnīt it?
It even has 3 legs!!!!!

I tried it in the guitar first and it DOES regulate volume!!!!!

If the owner is ok with the way the pot works, then I can replace both of them.....I feel sorry for the owner...he saw this unit at a local thrift store/pawn shop and passed it by the first time as they were asking $150 for the unit...then the price dropped to $99 and they snatched it up...was told that it was working.......of course no warranty as it is used....and the pawn shop probably paid $20 to the previous owner....oh well.....such is life......

[g1]

Ok. Checked out the unit today and the pot that I installed acts like a regular volume control....

That is correct. Just verify that it doesn't completely kill the signal when full counter-clockwise.
The original was 41 step, so it would be more precise for matching left and right channels. Aside from that, regular pots should be ok.

[Leo_Gnardo]

That is correct. Just verify that it doesn't completely kill the signal when full counter-clockwise.
The original was 41 step, so it would be more precise for matching left and right channels. Aside from that, regular pots should be ok.

I agree, don't sweat the so-called "stepped" pot. After all, the steps are simply "detents" - ridges that simulate the action of a real switch. "Precision" isn't their strong point, they're selling us the sizzle but there's no steak. Real volume control switches that do have precision are found in some seriously expensive hi fi equipment and mixing consoles, typically cost upwards of US$ 50-60, double for stereo, and also take up a hell of a lot more room than a dinky 16mm pot.

30ish years ago the manufacturer of Tube Works guitar amps used detented pots. (But... no tubes, hence the name, right? ) I've had to fix a couple, those pots always get noisy & won't respond to cleaners. So ordinary non-detented pots is what they get. Given the lousy tone of those amps, the job's only marginally worth doing.

[bsco]

That is correct. Just verify that it doesn't completely kill the signal when full counter-clockwise.
The original was 41 step, so it would be more precise for matching left and right channels. Aside from that, regular pots should be ok.

It does kill the signal when full CCW.....if he is ok with that then I will go ahead and finish it for him....god only knows how long it will take to find proper replacement pots....