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Old 1st August 2019, 08:20 PM   #1
IvanGT is offline IvanGT
diyAudio Member
Join Date: Aug 2019
Location: Tulum, MX
Default TU8200 Loud noise on Right Channel then pilot lamp goes Red.

Hi everybody,

I'm having issues with the right channel of my TU-8200.

From time to time, it started making some ugly loud noise, first intermittent every 1-2 seconds and then, in a matter of 10 seconds it goes to a continuous noise (like a needle scratching a vinyl very hard) until the amp pilot lamp goes red. Then I have to turn the amp off, wait a little bit and turn on again.

It started like 4 months ago (amp is 1.5 years old). First time it happened, I powered it off, then on again and nothing else for the next month. Then it became a weekly thing. Recently it happens daily and now it's a matter of minutes then boom, so I stopped using it yesterday. I use this amp everyday, for about 8 hours a day. It didn't used to happen right when I turn the amp on, but after a few hours of use. Now it's after 1-2 minutes of turning it on.

In these last months, I changed tubes (both pre-amp and power), installed the DX capacitor upgrade a couple months ago... still the same issue. Visual inspection of the circuit board didn't reveal anything abnormal. It was all like new.

It is worth mentioning that when the noise is being produced, the inside glow of the right tube increases accordingly.

Yesterday I bought resistors and capacitors based on an upgrade list vkung posted in a thread:
TU-8200 upgrade parts

I read in other threads some people have had a similar issue. Somebody mentioned that it is possible thermal expansion may affect some resistors, and that's why I bought all these new resistors and capacitors and will install them as soon as I get them, but I am playing in the dark here so I don't know if that is going to fix it. But I want to understand and learn about the issue.

it is unfortunate I don't have the skills nor knowledge to perform the necessary tests on the board, so my only way to fix it is to replace components.

What do you think may be happening here?

Whoever reads this, I want to thank you for participating in this forum. I love music and I bought the Elekit TU8200 to understand a little bit more of the electronics involved into its reproduction and get into the audio tube world. I thought it would be my "gateway amp" to more "serious" ones, but even if others may sound better, whatever that means, this is "my amp" and it fulfills my needs. I am learning so much with this amazing piece of equipment and with the community around it that right now, I have no desire to change amps, even if they sound better. With the TU8200, because I build it, learned the basics with it and became very familiarized with its sound, I can notice how and understand why any change in the amp or in my audio setup affects the music that comes from it, and it is such an amazing beautiful experience. Thanks for teaching me so many things with your experiences and knowledge!
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Old 2nd August 2019, 03:35 AM   #2
vkung is offline vkung  Canada
diyAudio Member
Join Date: May 2005
Location: Vancouver BC Canada
I think you have a bad tube on the right channel
YOu need to replace the right channel FETs and the power tube
RED LED it means that you have too much current on the right channel
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Old 2nd August 2019, 05:21 AM   #3
IvanGT is offline IvanGT
diyAudio Member
Join Date: Aug 2019
Location: Tulum, MX
Hi vkung,
thanks very much for your answer.

I used different tubes in that socket. First time it happened I was using EH 6L6. Then I used EL34s, then KT66s. Switched them across channels too. Always whatever tube is in the socket for the right channel. My deduction was that tubes were fine and the problem was something else.

A question arises: even if the tubes are were not the issue, may have those been affected by the excess of current during those incidents?

Also, any other possible causes that might come to your head?

I just found that post with your reply from a year ago:
TU 8200 problem

Seems it's a common issue.

Would you sell me the FETs and the rectifiers if you have them in stock?

Thanks vkung
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Old 3rd August 2019, 07:35 AM   #4
vkung is offline vkung  Canada
diyAudio Member
Join Date: May 2005
Location: Vancouver BC Canada
the R version will not have this problem
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