This is a commercial Yaquin that you are modifying?
Of a DIY copy of the Yaquin?
You replaced the input pot (wiring not shown on schematic) with a 'better' pot?
Or did you add a pot to the amplifier where there was none before?
Good pics of the pot area and the cap replacements might help to spot problems.
I'd look carefully at the pot wiring, again, if it were my project.
It's commercial Yaquin that I upgraded the caps and pot. It's an integrate amp os the pot is built-in
Put the old caps back would be a lot of work again so I haven't tried it yet.
I have been checking around with all the ground issues to make sure the input, switch and pot have a perfect ground. Otherwise, the rest of wires and solders are good.
Anyway, it's my bad, that's embarrassed. I have Mark Levinson amp that I can throw any wires at it and never get any hum except my first experience with tube amp which it's very sensitive to the wires. I usually use XLR for SS and don't have RCA wires around, so I use the video wires for audio connection between the DAC/Preamp and tube amp, turn out the audio wires caused the hum even it's only 1 foot long. I did test the audio wires with SS amp with no hum so I thought it should work with tube amp but I am wrong. So far I can get up to 75% volume now and the hum from 75%-100% sounds smaller than between which it's not big deal. 50% level is too loud, don't need more than that. It also solved the thump problem too.
I believe the original pot is 20k and the replacement is Japan ALPS Volume control 27 type pot 50k. Not sure that causes the hum or not but I will put back the original one later when I have time.
Not sure where the location at "adding a grid stopper resistor to the first triode", If you can tell me me pins # then I can figure out.
Thanks for everyone trying to help out. If the hum starts from 75-100% is it normal or not support to? I am not sure if I want continue to get rid of the hum or not.
Put the old caps back would be a lot of work again so I haven't tried it yet.
I have been checking around with all the ground issues to make sure the input, switch and pot have a perfect ground. Otherwise, the rest of wires and solders are good.
Anyway, it's my bad, that's embarrassed. I have Mark Levinson amp that I can throw any wires at it and never get any hum except my first experience with tube amp which it's very sensitive to the wires. I usually use XLR for SS and don't have RCA wires around, so I use the video wires for audio connection between the DAC/Preamp and tube amp, turn out the audio wires caused the hum even it's only 1 foot long. I did test the audio wires with SS amp with no hum so I thought it should work with tube amp but I am wrong. So far I can get up to 75% volume now and the hum from 75%-100% sounds smaller than between which it's not big deal. 50% level is too loud, don't need more than that. It also solved the thump problem too.
I believe the original pot is 20k and the replacement is Japan ALPS Volume control 27 type pot 50k. Not sure that causes the hum or not but I will put back the original one later when I have time.
Not sure where the location at "adding a grid stopper resistor to the first triode", If you can tell me me pins # then I can figure out.
Thanks for everyone trying to help out. If the hum starts from 75-100% is it normal or not support to? I am not sure if I want continue to get rid of the hum or not.
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