FPS 2000 random volume change

[i_like_sparks]

Hello,

I have one of these oldies but goodies:
https://assets.hardwarezone.com/2009/reviews/others/fps2000/fps-2000.htm

Unfortunately it has started to randomly change volume every few minutes. It usually starts after a 1-2 hourse of use. Any idea what might be the cause? It's rather hard to debug due to the randomness.

[benj38]

Bad connections or a bad speakers' relay (if the unit has one) are the first things that come to mind.

[wraper]

Changes volume setting or just loudness with volume setting remaining the same?

[i_like_sparks]

Just the volume setting. It does have an external volume/on-off knob, so I suspect it might be the potentiometer, but didn't have much success in cleaning it yet. Also I'm still puzzled where the randomness comes from. It's not crackling or so, it just changes randomly every few minutes.

[wraper]

Just the volume setting. It does have an external volume/on-off knob, so I suspect it might be the potentiometer, but didn't have much success in cleaning it yet. Also I'm still puzzled where the randomness comes from. It's not crackling or so, it just changes randomly every few minutes.

Isn't it an encoder (can rotate indefinitely, no end stops)? Can it be disconnected?

[thehesiod]

I have this exact same problem.  I just tried soaking the volume potentiometer in pure alcohol while messing with it, not sure it's going to solve the issue.  I have another issue as well.  If I have both analog inputs plugged into the back of the bass, but only one plugged into my laptop, swiping the L/R fader from middle to enabled side drastically changes the volume.  Anyone else have this issue?

[thehesiod]

verified it did not fix the random volume issue.  I'm guessing now it's a capacitor problem, I'll have to go through them all

[thehesiod]

ok I fixed the random volume issue (I think).  Wrote a blog entry about it here: http://hesiod.blogspot.com/2020/06/fixing-random-volume-on-cambridge.html

[i_like_sparks]

It's been some time but I wanted to be sure that the issue is fixed. I swapped the volume potentiometer with an identical newly bought one. This requires opening the little black controller, but isn't too hard. The issue has been fixed now for several months.