Originally posted by mort
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Good eye g1.
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Yes. The published schematic has always had that mistake. Use a 0.01uF.
Good eye g1. -
Yes, like in V1 stage here:
http://www.prowessamplifiers.com/sch...kelly_facs.pdfLeave a comment:
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Can you check those C & D node readings with V1 removed?
And double check V1 pin7Leave a comment:
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I assumed, hopefully correctly, that the bias caps should be oriented wit their positive end on ground... is that correct?Leave a comment:
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Yes, V1 seems to be the problem area. First, there is a typo, pin1 resistor should be 150K, not 150.
Do you have roughly 245V at that supply node feeding V1 plate resistors?
Do you have those diodes to pin7 reversed by any chance? There should not be DC on pin7.Leave a comment:
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Having a hard time debugging this one...
One time only, for a good friend who's building me a Tele in trade, I'm doing a copy of a Jim Kelley Single Channel Reverb head. Started on it a long time ago and just got around to finishing the wiring on it. The problem I'm having is no sound. There's an occasional bump on the speaker while probing the power tube pins but otherwise not a sound.
I'm testing it in 30w mode (2 center power tubes only) and without a reverb tank attached.
I've gone over the layout and wiring several times and did find a couple mistakes an corrected them. But still no sound.
note: during initial start up a meter probe shorted a power tube plate to its heater pin momentarily. It shined a small bright light for a moment and blew the B+ fuse at the same time I was able to reach for and disconnect power. Doesn't seem to have affected the B+ but the heater circuit is running at 5.9vac(virtual CT in place -- 2 100ohm resistors to ground). I didn't get a heater voltage reading before the short occurred so I don't know if that caused any damage to the heater windings. Resistance on the OT primary is 90 ohms and 45 ohms each between the center of the primary and each outside lead, so the OT seems normal the best I can tell.
Voltages all seem normal except for the plate voltage to V1b is rather low.. gonna replace the resitors that feed plate voltage to V1 and see if that helps.
Enzo has been in my brain telling me to "test parts of the circuit" so been checking resistance from cathodes to ground, and in various other parts of the circuit making sure the resistance adds up to what it should across parts of the network. So far all is normal. Everything that should be grounded is grounded... I also hear Enzo saying "look for horses nor zebras", so I'm looking for my simple error somewhere but just can't seem to find it.
Does any of the following data help you to help me get closer to the problem?
Also, I have a signal generator but before I go trying to use it, thought I would ask if there are places in the circuit where I should absolutely not drop a signal in? I've only ever put signal into the input jack of an amp circuit, never droppped one in the middle somewhere. I'm imagining I should be able to drop one on to the power amp first, then work my backwards until I get find where the disconnect is?? Any help is appreciated.
V1
p1 103.6
p2 .00
p3 .57
p6 49.24
p7 1.5
p8 1.33
V2
p1 463.6
p2 .08
p3 7.98
p6 463.6
p7 .08
p8 7.95
V3
p1 141.9
p2 .80
p3 2.17
p6 105.1
p7 -.19
p8 .80
V4
p1 159.8
p2 .12
p3 1.7
p6 272.8
p7 274.6
p8 272.8
POWER TUBES
p3 476.8 & 477.1
p4 476.1 & 475.9
p5 -63.9 & -63.9
p8 0 & 0
schematic: http://www.jimkelleyamplifiers.com/12.jpg
Leave a comment: