Avt275 issue

Milc man

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So thanks for having me, I have a bit of electronics background but not audio. I have an avt275 that I use regularly however one of my friends was plugging his iPhone into it to record using the emulated line( I lent him the amp) he recalls a loud pop then nothing. I replaced the two 2.2ohm resistors near the power supply as they was cooked. Now it all lights up again but even with nothing plugged in as soon as I turn on I get a loud hum. This hum is coming through both loudspeaker ports, emulated port and headphones. I have replaced the tube with a brand new one and it’s still the same. I checked for dc at the speaker cable and had none. No obvious signs of discolouration or burning etc on the board. I’m at a loss. Anyone any ideas? I love this amp
 

Milc man

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A bad filter cap will hum like that .
So the hum Doesn’t come out of one of the emulated ports. I checked the contacts on the ports and had 48v ac on the emulated line out where the Jack actually plugs in?
 

Milc man

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Also tested the caps and they seem to be charging to infinity
 

Milc man

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I can’t get any sound out through any output except this hum
 

Milc man

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Another update. Checked what was actually coming out the inputs.
Right loudspeaker 0v
Left loudspeaker 2/3v
Headphones 50v
Emulated output right 50v
Emulated output left 0v
F sends/returns 0v

all seem to be ac. I’m so confused
So far new tube. New resistors 2.2ohm 1watt.
C193 charges to infinity very very slowly. Could this be the issue?
 

Adieu

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Lesson: don't let Apple users near your gear
 


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