Hello everyone,
I have a Problem with the K8020 Valve Preamp. The amp works fine about 10-15 minutes, then the output level drops continuous to Zero on both channels (left and right), comparable to a fade out at the end of a song.
because the amp works fine at the beginning, i think it’s a temperature Problem.
Can you give me an advice which components in the circuit i should check.
Thank you very much
Is it possible that the IC VK8020 causes my problem? How can I check the IC?
Is there any chance to get a new one, because it’s a programmed IC…
So, i have checked the circuit für several times.
at the first time i found a problem with the voltage reegulator V1. it becomes very hot after a few seconds and so the heating voltages of the tubes decreases to a value of about 2V.
Then i cooled down V1 with a cooler spray, the amp works about 1 minute and then the proplem came back.
I changed V1 but the problem is still there.
Could it be that the 18V ouptput of the transformer is broken or wihich parts could cause my problem?
I hope that the Support can help me or can give me a hint to solve my Problem!
Thank you very much