rasping sound from Dared VP-16

[strawberry]

Hi all. I created a user name so I could ask a question.

I had a solid state amp running and wanted to listen to one of the speakers hooked up to this tube amp. 2x6sl7 and 4x6v6. But I disconnected the cabling at the speaker and fed the signal into the output of the turned-off tube amp. Now that channel of the tube amp is damaged, sounds raspy. I looked at the components and none looks burnt. I replaced the yellow thin signal-in capacitors, but no difference. Could it be a burnt diode? I replaced all tubes and the sound is the same raspy on the one channel I had hooked up to the solid state output.

I don't have a volt meter at this point but will go buy one soon. It's the right side of the amp as seen in the picture that is bad. The only component not seen is a square plastic thing on the other side, maybe a AC to DC converter.

Any suggestions are welcome.

 

[Alastair E]

Probably killed an output transformer....

Inputting power to the output transformer can produce dangerous voltages that cause the Tx to go shorted turns...

 

[strawberry]

Sounds right. Oh, well.

 

[strawberry]

Update. I tried a new set of power tubes on both channels and now the amp sounds good again. Not sure how I screwed up the testing the first time around. This amp is a good choice but it needs to have the volume control and the selector control switched out for better parts. They will begin to crackle after a few years.

 

[strawberry]

While it worked for a while a crackling sound came back on the left channel. I replaced all tubes today but the distortion is still there and the output noticeably lower. An angy humming sound is coming from one of the components at the very center of the circuit board, don't know which.

Could one of the big capacitors have become fried? The bottom right 6v6 socket burnt out a new tube to an instant bright glow, but not the next new tube in. Could have been a bad tube.

 

[DF96]

You might find that fault tracing before component swapping is a somewhat more efficient method of fixing faults. Just my experience.

 

[strawberry]

I seem to have found the problem. It was one or both of the small feed back, ceramic, pF, capacitors on the bad channel. Are these feed back only, or do they change the pitch in any way? One channel is running without them and one with. The sound is "the same" from both channels to my ears. Perhaps I do not need to buy replacements?

There is a slight humming from the center of the circuit board where the cluster of big electrolytic capacitors are. Does that mean one or several have gone bad? The three medium sized are all 2x220 uF black, 1x100 uF blue, all 100V. The three big black, 400V, I can not read easily.

I got this break through by asking a professional service place of tube amps, by email, what could have gone wrong. I got the reply back that it sounded like arcing. I googled arcing and it had to do with capacitors, and so I began with the signals caps and the, assumed, feedback caps. I am glad to have my tube amp back and running.

 

[strawberry]

PS. If you own this tube amp you need to replace the volume potentiometer and the selector. They go bad and create a rasping sound as well. Chinese crap components.