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  1. I am, in fact, confused. I thought if four tubes...

    I am, in fact, confused. I thought if four tubes are happy pushing against X impedance, two tubes would be happy with X/2 impedance. Is that not correct?
  2. If you pull two tubes, you need to match with...

    If you pull two tubes, you need to match with half the load. So, on the 8-ohm tap, use a 4-ohm load. Isn't that right?
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    You can test transformers using the neon bulb...

    You can test transformers using the neon bulb trick:

    https://www.premierguitar.com/articles/the-super-secret-transformer-tester-1
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    Same deal as selling used cars to private parties.

    Same deal as selling used cars to private parties.
  5. I'm laughing. When my wife says, "do you have any...

    I'm laughing. When my wife says, "do you have any Chapstick?" I say, "Here, kiss my forehead."
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    If you plug a guitar into the FX return, the...

    If you plug a guitar into the FX return, the volume will be low, but should be clear. You can also plug a line-level signal (like a CD player or smart phone) into the FX return, and you should be...
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    Good job. Except for the griping about...

    Good job. Except for the griping about condensers! There are some good ones for vocals, e.g., Shure SM86, BETA 87A/C.
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    Wow, that's a nice IR camera. Which one is it?

    Wow, that's a nice IR camera. Which one is it?
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    Want to hear a funny story? I noticed that...

    Want to hear a funny story? I noticed that someone had replaced Q1500, the first gain stage, with a modern NPN...all the other transistors are original. So I had a close look, and saw that the NPN...
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    Thank you, Enzo. Here are my measurements for the...

    Thank you, Enzo. Here are my measurements for the first two transistors. Expected values, according to the schematic, are shown in (parens):


    Q1500 Q1501
    C ( 7.7) 7.2 E ( 7.5)...
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    Oops, here's the image: 56425

    Oops, here's the image:

    56425
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    Now I'm tracing signal. I can get about 42 watts...

    Now I'm tracing signal. I can get about 42 watts clean into a 4ohm resistive load, though I see a minor x-over notch.

    On the left channel, I traced the signal degradation right to the input. I put...
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    Kustom K100C-8 repair

    I have a Kustom K100C-8 on the bench. Schematics attached. All functions work, but sound is poor--right channel (simple one) is almost OK, but distorts unpleasantly when hit with a hard guitar chord;...
  14. Thread: Danelectro DM25

    by xtian
    Replies
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    301

    Sounds like you solved your problem! Did you...

    Sounds like you solved your problem!

    Did you replace the 25uF cathode bypass caps?
  15. Thread: Can caps?

    by xtian
    Replies
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    449

    Are you committed to using a can? I prefer to...

    Are you committed to using a can? I prefer to leave the can in place, but bend the tabs out of the way, and install new, radial caps in its place. Easy and inexpensive!
  16. Thread: Danelectro DM25

    by xtian
    Replies
    16
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    301

    Did you try playing thru an external speaker?...

    Did you try playing thru an external speaker? I'll bet the one in the combo is not very efficient.

    OTOH, amp should distort when Volume is maxed. Here's another thread on the DM25:...
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    I don't know! But I'm curious! Why do you need to...

    I don't know! But I'm curious! Why do you need to know?
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    Yes, I can reproduce the DC thing--I just...

    Yes, I can reproduce the DC thing--I just replaced all the tubes and fired up. And instead of inserting an instrument cable, I just used a chopstick to open the input jack's switch (to help eliminate...
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    The switching system sure seems a likely suspect...

    The switching system sure seems a likely suspect for injecting noise into the circuit. And, in fact, I see a browned resistor in the 19vDC supply for the switching system. It measures within spec,...
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    Amp arrived with bad noise, so started...

    Amp arrived with bad noise, so started troubleshooting, and noticed scratchy guitar vol pot, scratchy Volume pots on amp. You know how if it's a dirty pot, the noise is in one place on the carbon...
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    OK, getting into quantum entanglement, here. I...

    OK, getting into quantum entanglement, here. I pulled V1 AND V2, and I'm still seeing DC at the input. BUT! I turned the amp OFF, let the caps drain, and I'm still seeing DC, that sweeps slowly (60...
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    I have tried a variety of tubes in V1...and the...

    I have tried a variety of tubes in V1...and the evidence is getting WEIRD.

    I inserted a 12" instrument cable in the input jack and attached my multimeter to tip and sleeve. I turned the Output...
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    431

    DC is positive WRT ground, and yes, vanishes when...

    DC is positive WRT ground, and yes, vanishes when no plug inserted (input jack is properly grounding the tip).
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    Well, still can't explain the stray DC on the...

    Well, still can't explain the stray DC on the input, but my main issue, nasty hum, was coming from a bad solder joint on the Lead channel's Master Vol pot's connection to the PCB.
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    Mesa Dual Rectifier Maverick -- DC on input

    Well, I read through many Maverick threads here and elsewhere, but did not see any similar info to my issue.

    I am seeing 0.2vDC on the input jack when in Lead mode, 0.1vDC when in Rhythm mode. I...
  26. My thought exactly. I'm mailing Steve my old...

    My thought exactly. I'm mailing Steve my old iPhone 5.
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    Yes, tried applying DC voltage also--no needle...

    Yes, tried applying DC voltage also--no needle movement. What resistance would you expect? Just a few ohms? Strange that the VU meters in both M8 amps burned out, but nothing else was wrong with the...
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    Amp sounds good, is good. Now make it sound how...

    Amp sounds good, is good. Now make it sound how the owner wants, and document your changes. Small cathode bypass caps, treble peaker, bright caps, etc. You can tack these components in quickly, and...
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