Another pv shit the bed…

  • Thread starter Thread starter JackBootedThug
  • Start date Start date
Is anyone familiar with the pre amp tube assignments in the ultra plus series? I think v1 and v2 are for the gain…v3 is for the loop and verb and v4 is the pi? Maybe 🤔?
 
Suggestions on diagnosing the hum? Think I’ll start by isolating the amp power wise from everything else and see if that helps….
 
Isolated the amp from everything else and it's still there. pulled the input and loop cables...still there. Looks like ole dad is pulling the chassis....
 
Sweet…..
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Any idea what these are? No writing or anything….each one has a different mark on the bottom. Looking through the tube at the bottom v1-7,v2-10, v3-12, v4-19…wtf does that mean?
 

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V-1 is usually the tube farthest from the power tubes so for you it would be all the way to the right.
Put a NOS there & a groove tube next to it going left.
 
Rearranged everything after replacing the shield and its back. Maybe it’s the shield
 
It was fine. Set it on top of the other one, put the shield back on…fired it up and buzzzzzzzzzzz…. Will go back later…right now is not a good time….lol
 
well....V1 seem to be the culprit. Lots of flex on the board while pulling and pushing on the tubes. Lots of play in a couple of the tube sockets. Pulled all the tubes individually starting wit v4. Still had hum albeit reduced after pulling each tube. V1 pulled....silence...no hum. Plus v1 was a lot hotter to the touch than the other three. Tried a different tube and same result. I did notice initially there was no hum but as the tube brightened up it got louder and louder. Any ideas? I would say this is 60 cycle hum... not high pitched like 120.
 
Are the power tubes matched up good?
I’ve seen a hum more than once that turned out to be a power tube mismatch
 
JTyson said:
Are the power tubes matched up good?
I’ve seen a hum more than once that turned out to be a power tube mismatch
Click to expand...
I don’t know brother. I will pull them and try another pair….
 
So over 40 years, twice I’ve had a tube that started drifting at some point and got so far out from the others it induced a hum that sounded like a 60 cycle hum. Once I hook up the Biasmaster it was more obvious.
 
Think I found it. My two chassis screws on the right side are not showing continuity with my meter.
 
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