Those didn't short, they didn't even reduce resistance, they were just marked wrong.
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Marshall Artist, extremely low volume output.
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How did you measure?
While I would call it unusual to get numbers like yours, all the tube cares about is the voltage across the heater terminals. So to get the BEST measurement, you'd put one probe terminal on pin 9 & the other on pin 4/5. That should be 6.3V +/-10% or so.
If you're keeping one probe on ground and checking the two sides of the heater individually, that may explain your numbers. Also, the tubes don't really care whether that 6.3V is AC or DC.
Justin"Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
"Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
"All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -
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PS: got a schematic?
Justin"Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
"Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
"All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -
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Schematic : Marshall_artist_30w_3203.pdfExperience is something you get, just after you really needed it.
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Yes, you were right. I still had one probe connected to ground. I have sine placed one probe on p9 and one on p4-5 and have a reading of 6.3 vac. This is the schematic i am using: https://drtube.com/schematics/marshall/3203pwr.gif
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Originally posted by mfreqmaster View PostPI voltages: p1 434v, p2 7v, p3 31.5v, p6 221v, p7 18.5v, p8 31.5v
I'd expect pin 2 to read about the same as pin 7. This makes me suspect that C12 is leaky. Try disconnecting the inner conductor of the input cable that goes to it and remeasure pin 2 and pin 7. BTW the grid voltages are obtained measuring between cathode and grid to avoiding loading the grids with your meter and getting silly results.Experience is something you get, just after you really needed it.
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Measuring the 6.3V at the socket terminal is just the first part. It doesn't necessarily mean the voltage is getting to the tube pins. That is why I asked if you can see both sides lit. You might have to turn off the lights.Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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Ok. I'd suspect the coupling cap like nick suggested, but the plate voltage is high, rather than low which is what I would expect from a leaky cap.
So still suspicious of that side of the PI tube not conducting. Have you checked the resistance of the pin1 plate resistor?Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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Originally posted by g1 View PostOk. I'd suspect the coupling cap like nick suggested, but the plate voltage is high, rather than low which is what I would expect from a leaky cap.
So still suspicious of that side of the PI tube not conducting. Have you checked the resistance of the pin1 plate resistor?Experience is something you get, just after you really needed it.
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Sorry for the delayed response. Hobbyist here with limited time to devote to this. I wiggled the tube socket while on and got a huge change in hum volume/static. So I strongly suspect the 12ax7 socket is bad and not allowing the tube to conduct. I've got a spare. Problem is on the 3203 the socket is riveted in. Any suggestions on how to remove it?
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Originally posted by mfreqmaster View PostSorry for the delayed response. Hobbyist here with limited time to devote to this. I wiggled the tube socket while on and got a huge change in hum volume/static. So I strongly suspect the 12ax7 socket is bad and not allowing the tube to conduct. I've got a spare. Problem is on the 3203 the socket is riveted in. Any suggestions on how to remove it?
nosajsoldering stuff that's broken, breaking stuff that works, Yeah!
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