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    You increase R67 because it works. Decreasing...

    You increase R67 because it works. Decreasing R58 won't. R67 is only 470 ohms. The bias voltage is the result of the voltage divider the two resistors form. R58 is 47k. If I knock R58 all the...
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    As was said, -57 on the grids will be even...

    As was said, -57 on the grids will be even cooler. And so what is wrong with being a bit cool anyway?
  3. That's not how JFETs work. SOurce to drain will...

    That's not how JFETs work. SOurce to drain will be a lowish resistance, UNLESS you turn it off with a gate voltage. What resistance? I don't know, I usually expect something like 50-200 ohms. ...
  4. 50 or 60, equivalent in terms of what we are...

    50 or 60, equivalent in terms of what we are doing.

    OK lifting those caps clears my JFETs. So much for that. Thanks for checking them.
  5. I worry more about JFETs in the gate area. The...

    I worry more about JFETs in the gate area. The Source/drain path is a low resistance until turned off by the gate. But the gate can get leaky to the S-D path. And that can inject noise into the...
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    Difference in DC resistance of winding. Read...

    Difference in DC resistance of winding.

    Read the thing I posted about the Vactrols. They are equivalent. I don't know which numbers are which, but the document describes the diffrences in types....
  7. Thread: Peavey Bandit 112

    by Enzo
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    I am old, I have no schedule. I might sleep all...

    I am old, I have no schedule. I might sleep all afternoon. Tomorrow might be opposite.

    1.5 hours? So you are in that Labrador zone?
  8. Thread: Peavey Bandit 112

    by Enzo
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    133

    So monitor its control pins and see if they...

    So monitor its control pins and see if they toggle when you channel switch.
  9. Don't use continuity tests, use resistance. ...

    Don't use continuity tests, use resistance. Using continuity, yo8u can't tell if continuity means 1/10 of an ohm or 110 ohms.

    R50 opens the current path through the tube, so it is essentially the...
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    Doesn't need to be linear. It is used as a...

    Doesn't need to be linear. It is used as a switch. LED is ON or OFF, not slowly dimmed down.

    I doubt the reverb tone is from the transformer, rather the circuit around it.

    70240102 is the...
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    And look at most any Peavey amp, they use a very...

    And look at most any Peavey amp, they use a very similar circuit.

    What with the companies merging and such, I haven't been on Accutronics site in a long time, but they used to have a generic drive...
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    Please just start a new thread. Diodes and...

    Please just start a new thread.

    Diodes and caps? The 12AX7s are in parallel, so I'd be looking for an open R82. I'd verify there is something like +6v leaving D24, D18. And verify AC between...
  13. When he reported no hum on B and A it was because...

    When he reported no hum on B and A it was because he had the masters for those at zero. When he advances the masters, THEN those other channels gains advance the hum.
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    And for a very fun experiment, disconnect the...

    And for a very fun experiment, disconnect the tiny speaker, and connect the amp to a 4x12 cab of your choice. Amazing.
  15. Well, the lord does work in mysterious ways...

    Well, the lord does work in mysterious ways...
  16. It is either coming in through the mains, or it...

    It is either coming in through the mains, or it is being radiated and picked up by sensitive circuits. SPikes can ride the mains. Switches on things like fans or furnaces or sump pumps or even the...
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    Do this: stop looking for some exact thing. It...

    Do this: stop looking for some exact thing. It is like asking how many shakes of salt should I put on my steak? The only ears you have to please are your own. There is no right and wrong, there...
  18. We are trying to narrow down where it comes from....

    We are trying to narrow down where it comes from. Leave the master volume controls at some mid point. We are only interested in the first stage controls - the ones called GAIN. So all three gain...
  19. OK, so really there is hum coming from the first...

    OK, so really there is hum coming from the first stage, and is available to hear on all three channels once they are turned up. Pick a channel like B or C, we have hum. Now run the tone controls up...
  20. OK then, so it is more like either channel makes...

    OK then, so it is more like either channel makes hum when gain turned up. Pulling V1 stops hum, so we know the hum is happening in that first stage somewhere.

    Certainly try a different tube in...
  21. Actually not the way to look at it. You have a...

    Actually not the way to look at it. You have a channel, and it is either noisy or it is not.

    Optocouplers are simple. A light inside shines on a photocell inside. A photocell is a resistor that...
  22. Thread: Theremin Repair

    by Enzo
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    Keep it simple. Touching L7 makes it work loud? ...

    Keep it simple. Touching L7 makes it work loud? OK, then is there continuity from the volume antenna down to L7? In other words is there an open L8, L9, L10 or the connections between or up to the...
  23. You didn't measure impedance, you measured...

    You didn't measure impedance, you measured resistance. Two 8 ohm speakers in series is 16 ohms, regardless of the DC resistance. DC resistance usually measures lower than nominal impedance.
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    Specs/schmecs, it is a 12AT7 tube driving a...

    Specs/schmecs, it is a 12AT7 tube driving a reverb transformer. I'd drop a Fender in there in a heartbeat.

    meanwhile, pull the transformer, it needs to come out anyway, right? Open it up and see...
  25. I have no idea how much of the company is left,...

    I have no idea how much of the company is left, if any, but used to be long ago you could call Tandy and they would send it out. usually the owner manual included schematic on last page. If that...
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    Optos are optos. A light source - in this case...

    Optos are optos. A light source - in this case an LED, compared to the neon bulb in a Fender - and one or two photocells. Photocell is a light sensitive resistor. Dark the resistor has high...
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    Of course I was just poking fun, but how is it...

    Of course I was just poking fun, but how is it you have 604 ohm resistors in stock? Is that a standard 1% value and I am just not aware?
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    OK, now exactly WHY would you (or anyone else for...

    OK, now exactly WHY would you (or anyone else for that matter) have 604 ohm resistors in stock? I can see maybe 1760 ohm resistors or even 221.4k, but 604?
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