There is a power, but no sound at all. - Roland Kc150 Kc 150 Keyboard Amp Demo Unit Save $

Hi!
At this point, I would just take it to a tech rather than poke around in it. It sounds like the power section is the problem as you have guessed, but without the technical knowledge you'd be shooting in the dark. That particular amp is right on the line of being expensive enough that would be worth repairing, but you might do just as wel to check Ebay for another used one.
Good Luck!

Whether you are experienced in electronics repair?
if not, try this simply way:
1: Test whether the power amplifier is still working. See figure 1.
Power OFF,adjust the EQ settings as shown in the picture.
Minimize LEVEL.Switch ON Power. Touch pin 3 at the INPUT socket by using a small screwdriver or piece of wire / cable.
Slowly raise the LEVEL,a little bit only (as the clock showed 7-8) until
sound is heard in speaker. If not heard, slowly raise again LEVEL.
If audio input signal is heard,it can simply be taken to mean
that the amplifier is working.
If LEVEL at 9 o'clock position,and the audio is not heard,
the possibility of the amplifier is damaged.
Switch OFF the power. Take it to a repair place.


2: When the Power LED is lit, but no sound,
There are many possible causes, one of which is:
I have been getting 3 times similar cases, and all are caused by
two Rectifier-Diode (either or both.) damage on the power-supply-unit.
Remove/desolder,measure, if damaged replace it with a new one.
See figure 2-3.




Hope it helps. Regards.

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Look for a 'monitor' switch, change it's position.

Bad output transistors or bad Soldier joint in output section

Sounds like a resister is bad..

In a word, NO. The line out is line level audio... it has NO power amp and cannot drive a non-powered speaker. I have both of these cabinets myself. You need to use an amp with the non-powered speaker. When using an external amp you will need to make sure you phase the two speakers correctely... you could just reverse the speaker leads of the non-powered one if needed.

Holding the page up and down buttons while powering on supposedly resets it. I have no sound except demos, but no lights showing like yours, and williams tech support said to reset that way but it didn't seem to do anything. Good luck hope this helps!

It sounds like you have NOT connected the power adapter to the box to power it. The guitar sound won't be too loud as you run the hose to your mouth and pick up the sound with a microphone such as a Shure SM57 which then goes to your amplifier. Without the power adapter the internal amplifier will not produce any output.

CHECK VOLUME CONTROL BUTTON.

See if you can hear any sounds via the headphones as a test.