KLH R3100 stereo receiver volume won't adjust

I've never worked on one but my guess is either the rotary encoder or its interface chip.
If your careful you may be able to take the encoder apart and clean it.

 

Remote may be set to some obscure setting.

 

It looks similar to a potentiometer and is located behind the volume knob.

I wouldn't rip it apart just yet.
A valid point was raised by Harald Kapp;
If the volume display reads out up/down consistently (incremental numbers) while turning vol knob. The encoder is probably fine. Otoh, If the numbers jump around it could be bad/dirty.

Take some pictures of the circuit board and perhaps we can narrow it down. Digital stuff can be hard to diagnose without a scope.

Any chance you've got a schematic?

 

@bbullsj, I don't know your skill set or your understanding of electronics, but honestly, you might be better off just having it serviced by a pro.
Without a schematic and proper test equipment it may be very difficult/nearly impossible to fix. Not to mention you and the forum may need the patience of Job.

My knowledge is limited, but here's my take on where to look if you still want to tackle this:
The encoder has two outputs seen in the traces seen in the blue circle of the (one) picture you posted.(as well as a third ground pin.)
If you follow them they likely go to a interface chip that decodes the volume encoder position and then likely outputs to a op amp chip that changes the gain (volume) to the final amp. There may be a separate ic for the digital display, or they may all on one chip.

You could start by writing the numbers on the ic's you think may be related to the volume circuit. A google search of them should find out their function.

With no schematic you'll likely need to draw out the component connections by following the traces on the pcb like a roadmap until you can understand how it works.

You may get lucky and find the problem without much ado, but if they are surface mount (smd) you will of course need hot air soldering abilities to replace them.

 

Check on YouTube for videos related to this model. There's at least one that discusses repairs of it.

 

Perhaps a close up picture of the square "black bug" IC that connects to the encoder traces would help.
Better yet, Take one from the top so we can read the numbers, and one from the bottom so we can see which way the traces go.

 

I'd be taking a wild punt and say it has nothing to do with encoder or the big fat 30 pin processor chip and more to do with amp signal input somewhere, perhaps even common power supply problems.
Thing is it is cheap to begin with so how far does one go really.

 

Well, it's a good unit to learn on. Through hole components should be easy to solder with plenty of room, and if you screw something up it wouldn't be much a loss.

I would think if the amp signal input was bad only one channel would be out or low.
I guess it depends how low the volume is.

A likely suspect is those 4558 opamps that could control the gain.

 

Sir bbullsj . . . . .

If you are trying to use the radio as your sole signal source for testing, it may have a problem with it.
There are also options for OTHER signal inputs, try one or all of them to see if they put out a full audio spectrum level of adjustment on THEM .
Or if they respond just as the present test source does.

I find nothing current on this KLH model, as they now seem to be a Chinee product, riding on the OLD renown KLH name sake.
BUT . . . . up in post #13's evaluation, he likes its sound . . . but knocks the built in receiver . . . me . . . I LIKE the units honeycomb heatsink .

73's de Edd
. . . . . . . . . .

Last week I bought a new phone. I took it out of the box, hooked it up to the wall . . . pressed redial. . . . .
and then the phone proceeded to have a nervous breakdown.