60 hz hum, right channel, Elekit TU-8200 (non-dx)

Hello everyone:
I have a elekit tu-8200 (non-dx). After years of stellar service, the amp has developed what seems a 60hz hum in the right channel. It is not very loud but is is there (it was not there before).
The hum is independent of the volume knob, and exists with nothing at the inputs.

I swapped the opt and no change. Swapped pre-amp tubes, no change. Swapped output tubes, no change.
It seems a component at this point. Any pointers?
Thank you for all and any info you can provide.
Marco
p.s. I am a kit builder, not a DIY self-er...
 
Hello:
Thanks for the reply and pointer.
I have the tubes that came standard with the kit (output are electro harmonix 6L6 GC). I also have used KT 88 as output . The amp is connected with the jumpers in pentode mode. The hum is present using both types of output tubes. I will check the fet.
Marco

Marco
 
Fixed!

Hello Viktor:
You were right. At first, touching around, I had managed to make the hum appear on both channels. :sigh: Probably damaged the mosfet on the left channel too...
I ended up replacing all four MOSFETS (02n60ZH) and all is fine again.I am happy to have ordered 8, so now I have a spare set.

The original mosfets appear discontinued, so I got the only replacements I could find on the Mouser website. They are not quite the same (they are a bit smaller and have no hole to screw mount them, 02n60ZG) but the ratings (600V 4.8Ohm) appear similar.



Thanks!
Marco
 
Last edited:
super

Hello Viktor:
You were right. At first, touching around, I had managed to make the hum appear on both channels. :sigh: Probably damaged the mosfet on the left channel too...
I ended up replacing all four MOSFETS (02n60ZH) and all is fine again.I am happy to have ordered 8, so now I have a spare set.

The original mosfets appear discontinued, so I got the only replacements I could find on the Mouser website. They are not quite the same (they are a bit smaller and have no hole to screw mount them, 02n60ZG) but the ratings (600V 4.8Ohm) appear similar.



Thanks!
Marco
 
Success...sort of :)

While Getaudio were very helpful they didn't have any spares in stock and instead suggested i buy some replacements on the open market. So i did, but ended up with a slightly different part in my haste. I bought SPU02N60S5 in the TO251 case, these are without the screw hole. Decided to chance it and after checking the pinout and installing them into my 8200 it's back to its former glory, the hum is gone.

I tried to ensure the little critters had good contact with the PCB, but time will tell if they are long lived.