JBL CSMA1120 amplifier

[Bterrier]

I recently picked up a jbl csma1120. Seems to work well, however the bass and trebles knobs are missing. I wouldn't mind if there were still a way to adjust the bass and treble, but there is nothing to turn, just printed circuit board behind the holes.

Is this repairable? How to these knobs work and install. I was expecting to see a shaft of a potentiometer where the knobs are missing.

[petehall347]

Re: JBL CSMA1120 amplifier

pictures please .
is there a remote ?

[Bterrier]

Re: JBL CSMA1120 amplifier

No remote. It is more of a commercial amp. It can run 4 or 8 ohm loads as well as 70v and 100v systems.

I will upload a few pics later tonight.


https://jblcommercialproducts.com/en.../csma-180-1120

[R_J]

Re: JBL CSMA1120 amplifier

Looks like they are/were screwdriver adjustments, no knobs, so they are either pushed in or broken

[Bterrier]

Re: JBL CSMA1120 amplifier

Yes, the plastic piece/knob that you would turn with a screwdriver is missing. Im tryng to find a solution. If I can get those pieces from JBL, how would they be installed. Im confused how they work

[Bterrier]

Re: JBL CSMA1120 amplifier

Photo attached. Printed circuit board within the holes. It actually looks like the head of a screw, and the lighting wasnt so good in my work area, I actually tried to use a screwdriver to turn it.

There are also 2 pads/contacts above the screw print, I'll try to get a better photo when I can

[R_J]

Re: JBL CSMA1120 amplifier

It looks like the controls are still intact and could be adjusted with a small screwdriver if needed, getting those little extentions from jbl???, good luck
if not this pdf might help

[Bterrier]

Re: JBL CSMA1120 amplifier

No, it can't be adjusted with a screwdriver. This is my issue.

I know it looks like a Philip's screwdriver would work, but that is only an image of a Philip's screw head which is printed on the circuit board. There are no moving parts.

[R_J]

Re: JBL CSMA1120 amplifier

Those are APC brand pots (apc spain), just like in the picture I provided (3rd pot), the blue is the pot, the white with the cross is the part that turns, and the black is what is left of the broken knob. You don't use a philips, you use a small flat blade, like a jewelers screwdriver.

Whats left of the black knob might be able to be pushed out, It depends on how the pot is mounted.
The pdf I provided has shafts that should work if you can not get the originals from JBL
If it is a CA6 size pot Page 4 number 6031 looks similar, If its a CA9 page 12 has the shafts

[Bterrier]

Re: JBL CSMA1120 amplifier

Thanks for the info. After further inspection, it appears you are correct. It seems as the plastic extension is broken off flush with the pot. How would I go about attempting to remove the broken piece?

If I am unsuccessful, I will replace the pots but I am trying to avoid that if possible because everything seems to be functional.

[R_J]

Re: JBL CSMA1120 amplifier

Just use a small screwdriver that fits the slot, that black plastic should just push out the back of the pot. It should take very little force so no hammer

[Bterrier]

Re: JBL CSMA1120 amplifier

Thanks I didnt realize the back was open. All set now, just need the extensions.