So I have a slant plexi faced K100c-7 that just decides to not work on occasion. Last night at practice it just stops working. The light is on. I hear the wump when I turn
it on but no signal at all. I checked the cord from the guitar. Usually you can tap the plug and hear a little static. Nothing. Switched speaker cabs nothing. This has happened before and I switched cords and it worked. This time nothing. Bring it home works fine. Voltages are within in range. Am I dealing with a overheating issue? Its not hot in my room. I guess Ill have to wait til it happens again and just open it up right then and there to search for the issue. I just thought someone might have some insight. I am at a loss.
Thanks in advance for any help.
stevem Messages: 4733 Registered: June 2004 Location: NY
Senior Member
The fact that the pilot lamp stays on rules out the thermal circuit breaker and the thump at turn on means that atleast the final section of the output stage is working , so this would leave a bad solder joint or a transistor failing .
When the amp does cut out does turning up or down the volume or treble control change the level of hiss heard from the speaker ?
Thanks for the prompt responses. I will take your advice and go through my cords and troubleshoot again just to be sure I did not miss anything obvious.
I can hear the thump but the amp is pretty quiet compared to my other Kustom amps. I did fiddle with the volume and plugged into both high and low inputs as well as plugging into the other channels and could hear any noise. I even gave a couple whacks that would usually cause a reverb tank sound and nothing happened.
Thanks again for the help.
More clues, that helps. To me it sounds like it might be a preamp power supply problem. The power amp still thumps, neither channel passes signal and no reverb crash.
The low voltage power supplies are located on the power amp pc board. Check to see that you have + and - 8 volts dc coming out of the regulators. Try probing the board with the well known chopstick and see if you can make the problem return.
Shaun_Musings Messages: 323 Registered: April 2009 Location: Reading, MA
Senior Member
I love using those old 1970s coil cords. One worked intermittently... I knew it was the cord because I have two of the same and a few others. One day I got sick of it going in and out, unscrewed it and pulled back the shielding to see like... three strands connected. Snip, solder, done, sounds like new!
stevem Messages: 4733 Registered: June 2004 Location: NY
Senior Member
Coil cords are a failure waiting to happen from day one!
The strain placed on the connections is on average far greater then a regular type cord and some are molded without any strain releave to them!
stevem Messages: 4733 Registered: June 2004 Location: NY
Senior Member
You would not want to travel in a air plane with the same percentage of failures that have befell coil cords I would think! Lol!
Many of them to this day have infearor sheilding also!