Velleman K8010 monoblock tube amplifiers

[bonnel]

I have pair of Velleman K8010 monoblock tube amplifiers and they are continually burning value on left of amp. My friend also have pair and experiencing same problem. Any suggestion on what is going on and how can I find a solution.

 

[Burnedfingers]

Can you post a schematic??

 

[bonnel]

the complete manual is at :
http://www.vellemanusa.com/downloads/0/manual_k8010.pdf

 

[michaelcpu]

Hello

We've not had this problem. And I know this is old, but it sounds like something isn't upto spec 100%. Or a mistake was made in their assembly. I would double check everything (be safe about electricity).

Heres a review we did on this Amp. We did it for fun, not many people look at this stuff. And there was no reviews on line. Let me know how this turned out and if you got it fixed.

Velleman Class A K8010 Tube Monoblock Amplifiers - Review! - YouTube

 

[baudouin0]

Is the plate on the valve on the left glowing red. If so the bias is set too hot. I can see from the schematic that if the bias pot wiper goes O/C then 0V is put of the grid and the valve will pop. I think if I had this amp I would convert it to servo bias.

 

[rayma]

Or a leaking coupling capacitor.

 

[baudouin0]

Could be although modern caps are used. The grid leak resistors of 220k + pot + 100k exceed the value on the KT88 datasheet so there could also be thermal runaway. I would be using 100k but this requires changes to the driver stage. This I found on the WEB so cannot vouch to stability etc. The screen resistors have been changed too. It does seem to indicate a problem in this area. Check also that the bias pots are properly soldered.

 

[rayma]

Lift one end of each coupling capacitor to the output tubes, and see if the problem is gone.

 

[baudouin0]

Err this thread is 2008 woops.