My next thought would be to pull V1 and see if the hum is still there, however you need to check if C10/11 voltage rating will stand the HT check C12/13 Voltage rating and compare to C10/11
You have to accept that the caps are old?
You have to accept that the caps are old?
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If you are following this on the schematic you can see all measured OK on V1 compared to both sides. and now we have eliminated everything up to C3
you freaked me out about leaving it on to long.
so as soon as i heard the hum i switched it off so have just tried again
hum on both channels but more so on the left.
would not want to be in bomb disposal...
so as soon as i heard the hum i switched it off so have just tried again
hum on both channels but more so on the left.
would not want to be in bomb disposal...
If the hum is only on the Left, replace V1 and remove V2 left channel. The output tubes are isolated with C4/C6.
Sorry phone rang.
right THEN
Pulled V2 Left hum now reduced in volume about the same as the right channel.
right THEN
Pulled V2 Left hum now reduced in volume about the same as the right channel.
OK
We need to find out if its a tube problem so swap V2 Left and right see if the fault changes channel
We need to find out if its a tube problem so swap V2 Left and right see if the fault changes channel
If it does its the tube!
If it stays the same on the left then we need to take some measurements!
If it stays the same on the left then we need to take some measurements!
Ok swapped valve to the right channel all ok
put right channel valve in left channel no hum. eh!
all is quiet, a small amount of hum on both channels but ear is next to the speakers.
looking closer at V2 socket contacts seem a little grubby so have just cleaned these out.
you think this may have been the cause? spent mst of last night swapping valves but the hum was still there??
put right channel valve in left channel no hum. eh!
all is quiet, a small amount of hum on both channels but ear is next to the speakers.
looking closer at V2 socket contacts seem a little grubby so have just cleaned these out.
you think this may have been the cause? spent mst of last night swapping valves but the hum was still there??
C5 may have leakage! As a last resort!
If all is now OK I would put the suspect tube in the right socket then if it is the tube the fault will show on the right channel!
If all is now OK I would put the suspect tube in the right socket then if it is the tube the fault will show on the right channel!
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Swapped them back hum returned.
on closer inspection with a maginfiying glass a what looks like a very small crack in V2
valve base.
on closer inspection with a maginfiying glass a what looks like a very small crack in V2
valve base.
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