Koch Studiotone problems

[Jabs]

Hi Everybody, I am a newbie here and I am desperately relying on your help. My new purchase (though second hand unit), a KOCH STUDIOTONE recently started to create problems. Being on the edge of Europe (Bulgaria) I have no official service around or at affordable distance. While waiting for the Guys from KOCH to respond, if anyone has a STUDIOTONE service manual or schematics, I would really appreciate if he would share it with me I am in touch with good and qualified engineers here, but without "blueprints" we risk too much. Thanks ! Thanks and Thanks again )
Cheers to all,
Yavor

[Structo]

What are the symptoms you are experiencing.

Have you tried new good tubes?

[Milkmansound]

if the tubes test ok - you may want to have a look at the circuit card and make sure there are no cracked solder joints. These amps are made on a PCB and that is a common failure point

you probably do not need an exact schematic - if you know tube circuits, you can find similar amps and get the basic idea from known schematics

good luck! and remember there are high voltages inside!

[Kagliostro]

Here the link to the user manual where you can see the block diagram of the amp (sorry, no schematic)

http://www.koch-amps.com/images/stories ... %202.0.pdf

K

[Jabs]

Hi to All. And thank you for taking time to answer. Meanwhile, I have contacted Koch and am waiting also for their response. The current problem is minor, but really irritating: even when the Clean channel Volume knob is turned to "zero", sound is still audible, at a level which should normally be 1-1,5. That happened during a gig. I had the amp inspected by one of the best local Tube Amp engineers ( I am a simple and straight forward guitar player , who is servicing my gear for years. It is not the tubes, and not the pot itself. The amp is constructed in a rather weird way, disassembly of prints and diagnostics seems virtually impossible without de-soldering cables. We do not want to risk without service manual, "reverse engineering" might be done, but for such tiny issue seems not appropriate... I attach a couple of pics to your attention. Any ideas? Thanks a million.

[Jabs]

Hmmm... failed to attach pictures, anyway, if anyone is interested, might send by mail.