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  1. Replies
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    The Dude abides! The Heath IP-17 is like...

    The Dude abides!

    The Heath IP-17 is like Figure 5 except it uses 2 6L6s paralleled for the pass element.

    I can't think of a good article at the moment but a compressor consists of two circuits...
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    I wouldn't call the plate of B "feedback". The...

    I wouldn't call the plate of B "feedback". The signal on the grid is not audio, it's a DC voltage that follows the amplitude of the audio input.
    The 10uF cap kills any audio.

    As JMF said B is...
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    I'll take a stab at it. The audio path is...

    I'll take a stab at it. The audio path is passive. I re-drew it to make more sense. The audio path is C2 to R2 to C3. Triode A is the AC to DC converter, response time set by C4
    Tiiode B is the...
  4. I would modify it like this. The LED resistors...

    I would modify it like this. The LED resistors could be anywhere from 220 ohms to 10 K depending on the LED specs and the brightness needed.
    ...
  5. I wonder if D24 is a misprint in the Parts List....

    I wonder if D24 is a misprint in the Parts List. On the schematic it looks like D2A. There is a D2A called "High Brightness" in this Glow-Lite catalog:
    ...
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    Many Fender models of that vintage ran a ground...

    Many Fender models of that vintage ran a ground through all of the pot brackets in series, for what reason I don't know. One cracked solder connection on a pot bracket and the ground goes open.
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    The zip file contains the images from that site...

    The zip file contains the images from that site that I saved by screen capture. They are a bit fuzzy but I don't see why you can't print them.
    I have another, better copy of the schematic only:
    ...
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    Here is the PC5068 ...

    Here is the PC5068

    https://music-electronics-forum.com/attachment.php?attachmentid=54110&stc=1&d=1561495844
  9. Here's the complete service manual with a circuit...

    Here's the complete service manual with a circuit description

    https://music-electronics-forum.com/attachment.php?attachmentid=54092&stc=1&d=1561470138
  10. Replies
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    Here it is ...

    Here it is

    https://music-electronics-forum.com/attachment.php?attachmentid=54086&stc=1&d=1561387226
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    OK thanks. There's just one other capacitor and I...

    OK thanks. There's just one other capacitor and I wasn't sure if the 3 circled resistors were 470 ohms or 4.7K. Also need the pot values. And the little disc cap in the upper right
    I'll post an...
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    I'm halfway there with the Lead 50 schematic. I...

    I'm halfway there with the Lead 50 schematic. I can finish it in a day or two.

    edit: Here it is. A few capacitor values I couldn't see, The power amp section looks to be identical to the bass 50
    ...
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    Many years ago in the early days of digital...

    Many years ago in the early days of digital clocks I saw a single panel comic in some magazine where a bedside clock read out in words: "THE BIG HAND IS ON THE TWELVE AND THE LITTLE HAND IS ON THE...
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    There is DC voltage on Pin 2 (and pin 1 and 3) of...

    There is DC voltage on Pin 2 (and pin 1 and 3) of the op-amp. I think about 15 Volts. The .01 cap isolates the DC from the input, but lets the audio pass through.
    Without the cap there would be 15...
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    Look at page 3 there is another ZD1 and ZD2

    Look at page 3 there is another ZD1 and ZD2
  16. Back in the early 80s a local guitarist brought...

    Back in the early 80s a local guitarist brought me his Marshall amp for repair. Unrelated to the repair was a modification he had had done called a "Claret Power Control" (patented).
    It was...
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    That was the old bright input. Those components...

    That was the old bright input. Those components aren't needed anymore. For a future experiment you could connect a footswitch to short that terminal to ground. It would be some kind of treble boost....
  18. Thread: Conn Dynalevel

    by dmeek
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    Here's the patent for a slightly different one....

    Here's the patent for a slightly different one. Can't find the patent for the light tower model.

    https://patents.google.com/patent/US3200899

    and another
    ...
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    Here's the mod. First remove all the yellow wires...

    Here's the mod. First remove all the yellow wires and there's one trace to cut under the IC. If you don't have 68Ks you can use the 100Ks-not much difference.
    ...
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    Can you take one more photo of the foil side? Its...

    Can you take one more photo of the foil side? Its too overexposed on the left. Also a shot of the whole component side.

    I see the 4136 quad op-amp there which suggests it's more like the Bass 50
    ...
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    470K would probably be better but it depends on...

    470K would probably be better but it depends on the rest of the input circuit. Can you post some close-up photos of the circuit board , both component side and foil side?
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    I just worked on an old amp with separate reverb...

    I just worked on an old amp with separate reverb speaker recently - can't remember the make/model at the moment, anyway the reverb spring was driven from the main amp output along with the main...
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    One minor problem with the mod is that the volume...

    One minor problem with the mod is that the volume will not go to zero. With the Gain control at minimum the op-amp will be at unity or gain of 1. Not sure how quiet that will be in real life.
    Just...
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    I didn't notice that. Maybe they meant 10PF. ...

    I didn't notice that. Maybe they meant 10PF.

    Here is a simple mod to change input to 1 Meg.
    https://music-electronics-forum.com/attachment.php?attachmentid=53952&stc=1&d=1560435613
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    It seems like the designers at Vox didn't...

    It seems like the designers at Vox didn't understand op-amps in those early days. Look at the Supertwin schematic:...
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    The tap might be for 240V. It won't hurt to try...

    The tap might be for 240V. It won't hurt to try it. If it is 120V double the amperage of the fuse.
  27. I haven't seen a Thomas Vox amp recently but...

    I haven't seen a Thomas Vox amp recently but years ago I saw them regularly. Most problems were caused by leaking electrolytics. Those black axial ones are particularly bad.
    Just replace them all...
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    Did you check the 10K plate resistor on the 6CG7?

    Did you check the 10K plate resistor on the 6CG7?
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