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  1. Replies
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    I've found the twisting technique works very well...

    I've found the twisting technique works very well as long as the board is in good shape. Trouble is we want to remove those caps because they have leaked in which case the board is corroded and the...
  2. It looks like from your photos this is the type...

    It looks like from your photos this is the type of rivet you have. The rivet at arrow A has been soldered already. The important thing is that solder must not flow to point B.
    It's a delicate and...
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    Here is the Service Bulletin. ...

    Here is the Service Bulletin.

    https://music-electronics-forum.com/attachment.php?attachmentid=56146&stc=1&d=1575168856
  4. Take a close look at the rotary switch wafers....

    Take a close look at the rotary switch wafers. Where there are terminal lugs and switch contacts connected by rivets, solder the rivets on both sides to make sure the connection is solid.
    Be very...
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    185

    I made one last attempt and soldered the diodes...

    I made one last attempt and soldered the diodes and bridge rectifiers from the top - still no luck. I didn't see any noise on the power rails.

    btw I don't know how this thread ended up in...
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    Thanks for that information. I tried re-soldering...

    Thanks for that information. I tried re-soldering the power diodes, bridge rectifiers, header plug, and all power transistors from the bottom of the board but no luck, crackling is about the same.
    I...
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    185

    Scope is DC coupled, and the noise is only in the...

    Scope is DC coupled, and the noise is only in the low amp. The problem in locating the noise is that almost every component is within the feedback loop.
    Sometimes with a tube amp I will disconnect...
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    Gallien Krueger 1001RB Crackling

    I have a Gallien Krueger 1001RB that I present here just as a puzzle since I have just about given up on it.
    It has intermittent crackling not affected by heat gun or freeze spray so I can't track...
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    Soldering to the rivets is risky, They could...

    Soldering to the rivets is risky, They could loosen and cause intermittent problems. If I don't have a pot with pins I mount one with the lugs up and run 3 wires to the board.
    I would never solder...
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    I had an interesting repair on a homemade PA amp...

    I had an interesting repair on a homemade PA amp made with a toroidal transformer. The complaint was that it hummed, had always hummed.
    The builder had connected the AC ground wire to a lug at the...
  11. For a quick and cheap HV probe I made a probe tip...

    For a quick and cheap HV probe I made a probe tip extension with a 10 Meg / 1 Watt (500V rated) resistor. My probe is a Tektronix P6106 rated at 500V so I should be good to 1000V.
    The HF response...
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    I have seen problems with the 82K and 100K PI...

    I have seen problems with the 82K and 100K PI plate resistors so often in the Hot Rod/Blues Deluxe/DeVille series I automatically change them in every amp I see.
    With the PI pulled out the noise...
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    Here is my re-draw of the control circuit and...

    Here is my re-draw of the control circuit and trimmer locations. Not sure if I'm 100% correct. If you can, post some closeups of the board from various angles including under the cardboard shield in...
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    Here is a cleaned up but still not very readable...

    Here is a cleaned up but still not very readable schematic and instructions and what appears to be a re-draw of same. I notice there is a capacitor missing at the input transistor collector in the...
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    Some spray cans have adjustable spray, though my...

    Some spray cans have adjustable spray, though my favorite pot lube Nu-Trol seems to have discontinued that recently.
    ...
  16. Thread: LM3886 Curiosity

    by dmeek
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    1
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    183

    LM3886 Curiosity

    I have a Marshall AS50D in with a distorted output complaint. It turned out the LM3886 had a fair amount of crossover distortion with or without a speaker load.
    Never seen this before. So I replaced...
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    Here's the schematic, ...

    Here's the schematic,

    https://music-electronics-forum.com/attachment.php?attachmentid=55694&stc=1&d=1571787056
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    That's the newer series. I don't have a schematic...

    That's the newer series. I don't have a schematic for that one. The MN3204 chip is the bbd delay, pin 3 is input. other than that these SMD boards are very hard to trace without a schematic.
    Check...
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    Here is the M-117 schematic. Which version...

    Here is the M-117 schematic. Which version schematic do you have?

    https://music-electronics-forum.com/attachment.php?attachmentid=55569&stc=1&d=1571150504
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    1,533

    My meter, the Heathkit IM-104 is slow too, it's...

    My meter, the Heathkit IM-104 is slow too, it's still a mystery to me as to why. I think the main advantage with taut band meters is that there are no pivot bearings, so no friction. The reading is...
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    1,533

    Here are a couple of nice folding meters. They...

    Here are a couple of nice folding meters. They sell for about $1000 each, a little over my budget.

    https://music-electronics-forum.com/attachment.php?attachmentid=55442&stc=1&d=1570458863
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    This is my Go-To meter. Bought it in the mid-70s,...

    This is my Go-To meter. Bought it in the mid-70s, use it daily. FET input, 50KHz bandwidth, taut-band meter. Best analog meter I've ever found.
    If I need a little more accuracy I have a Wavetek...
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    I used a Weller DS-100 for a long time. The base...

    I used a Weller DS-100 for a long time. The base unit has a solenoid air valve, it needs an external vacuum pump running continuously. Didn't work all that well so it sits on my junk shelf.
    I found...
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    As mentioned in post #4, sometimes JB Weld...

    As mentioned in post #4, sometimes JB Weld doesn't bond with the plastic. I've been using JB Plastic Bonder for a while now. It seems to be better but the jury is still out.
    Maybe giving the plastic...
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    I wouldn't worry about that. It plugs into the...

    I wouldn't worry about that. It plugs into the mico USB port. I suppose eventually the latest software will require newer hardware but you could keep using it as is with the old phone (or tablet)...
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    I have a Flir One which plugs into my Android...

    I have a Flir One which plugs into my Android phone. There is also an Apple version. It's been useful in repairs for finding hotspots though after a few years I don't think it's paid for itself yet....
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    There is an ABS glue found in the plumbing...

    There is an ABS glue found in the plumbing section of any hardware store. I've never used it for anything other than gluing ABS drain pipes together. Maybe worth a try.
    There is also a PVC glue for...
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    I use 2-part epoxy like JB Weld or a new one I'm...

    I use 2-part epoxy like JB Weld or a new one I'm trying JB Plastic Bonder https://www.jbweld.com/products/j-b-plastic-bonder-syringe I would not use any 5 minute epoxy.
    Sometimes I will use Krazy...
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