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    Turns out Fliptops has them for $140 +. Not...

    Turns out Fliptops has them for $140 +. Not cheap, but a way out of this.
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    "Regarding OT specs, the 7027A datasheet suggests...

    "Regarding OT specs, the 7027A datasheet suggests a ~70W OT with a primary impedance of 6k to 6.5k. "

    How specific do these specs have to be? I found a 50 -60 watt Magnetics Components Classic...
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    It did not blow on the limiter.

    It did not blow on the limiter.
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    Perhaps I was not clear, but this is the first...

    Perhaps I was not clear, but this is the first thing I did. I can power up the amp with a rectifier in, with no other tubes, and I measure B+, bias and filament voltages, with bulb barely glowing.
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    Help with Ampeg OT

    Dang. I did a bunch of work for a restoration of a '69 0r '70 Ampeg Jupiter B-22x, and upon the initial power up stages on my light bulb limiter, it misbehaved. I first powered it up with no tubes to...
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    I'd say you are measuring some cap voltage.

    I'd say you are measuring some cap voltage.
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    Or stab themself in the gut with a Weller.

    Or stab themself in the gut with a Weller.
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    See anything wrong here?

    Hmm, I wonder why this isn't working? Probably the same guy who replaced the OT in this 65 Bandmaster and didn't cover the wire splices. I need to test this transformer before firing this thing up....
  9. Thread: Stabbed myself

    by Randall
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    Stabbed myself

    While working on an amp today, standing which I almost never do, I got a capacitor shock and involuntary stabbed myself with my hot soldering iron. It went into my shirt and then out. I have a nice...
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    Tubes passed the gas test on my Hickok.

    Tubes passed the gas test on my Hickok.
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    Well, today has been another learning experience....

    Well, today has been another learning experience. While I was in there measuring around, I discovered one of the 220K grid resistors was 454K, and the other was 241K, as well as the 82K/100K PI plate...
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    I'm not sure what we are trying to narrow down, I...

    I'm not sure what we are trying to narrow down, I measure -65v at pin 5 with fresh grid resistors, and 68/62mA with a bias probe with 468v on pin 3 with the originals. And as I said, 11ma with new...
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    Tube chart says AB763. I owned this very same...

    Tube chart says AB763. I owned this very same model and year for decades, it's the drip edge model.
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    Super Reverb bias and tubes

    I've got a real clean '69 Super Reverb in for a cap job and AC cord. It has what I am guessing are almost all the original tubes, including a pair of Sylvania 6L6CGs the owner really wants to keep....
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    To keep things in perspective, for me at least,...

    To keep things in perspective, for me at least, the customer requested a "PPI Master Volume" install on his amp. I did as requested, and he loves it. It cost him $80, and he's happy, so THE END. :)
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    I've used it a few times with no problems, albiet...

    I've used it a few times with no problems, albiet with a 1MA pot instead of the 500KA I originally was asking about here. In each case it was never to drive an amp to bedroom levels, it was to take...
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    Hey, if it worked for Trainwreck.....

    Hey, if it worked for Trainwreck.....
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    Tainwreck master volume question

    I installed this PPI master volume in a 100 watt Marshall type amp. I have done it before using a 1MA pot, but I liked the taper of a 500KA pot this time. After sealing back up, I find myself...
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    "Are the other e-caps in this amp the same blue...

    "Are the other e-caps in this amp the same blue make and model? Or does it look like it was a replacement at some point?"

    Aside from the filter cans, there are only 2 other e-caps in this amp, the...
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    "I'd lift one end, if it measures 300-360uf,...

    "I'd lift one end, if it measures 300-360uf, leave it be. "

    Well, of course so would I if I had reasonable access to it. Not wanting to disconnect umpteen connections to measure a cap, but if the...
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    Someone already did that.

    Someone already did that.
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    Indeed it does. Customer opted to replace the...

    Indeed it does.

    Customer opted to replace the filter cans, which means lifting the board, so that cathode cap is getting replaced while I'm in there. Be interesting to see what it measures out of...
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    "Drawn as not electrolytic? You mean without a...

    "Drawn as not electrolytic? You mean without a polarity +? Look at the rest of the schematic, NONE of the electrolytics have a polarity sign."

    Good point.

    I realize it is in parallel with the...
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    Marshal JMPl cathode cap question

    70's JMP Master Volume Lead 50 watt has a 330uF cathode cap for the Low side of V1. It is drawn as not electrolytic, but it sure looks like one. The writing is facing down, so I can't read anything....
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    nevetslab, I think in your version if the wiper...

    nevetslab, I think in your version if the wiper is turned too far or all the way down, or if the wiper fails, you lose all bias voltage to the tubes. Wouldn't it be better to use the pot as a two leg...
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    adding an adjustable bias pot

    I am refurbishing an old Ampeg Jupiter, and wish to make the bias voltage adjustable. Would replacing the 39K R38 with a 50K pot do the trick?

    Also, why is the 100K R40 spec'd at 2 watts? Doesn't...
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    What part of Maine?

    What part of Maine?
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    So in retrospect, if the shorted feedback...

    So in retrospect, if the shorted feedback resistor caused the screech, but the way too big 6V6 cathode resistor caused it not to conduct, how was it the screech got through? And it was very loud.
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