Recent content by Thinker

  1. Thinker

    Sorry I haven't been on much since I went back to school, were you able to figure out what was...

    Sorry I haven't been on much since I went back to school, were you able to figure out what was causing your issue?
  2. Thinker

    Hey Panasonic Guys- '69 RE-7070 or 70's RA-6600?

    A friend of mine has the RE-7070 and I told him I’d help him service it, would anyone happen to know where I could get a service manual? I checked Hifi engine but they didn’t have it on file and when I search online I can only find a few higher pay manual sites.
  3. Thinker

    Circuit of new to me 6B4G PP amp, Thoughts?

    Thank you for the 47k resistor tip for the fixed bias, I'd remembered reading something about how fixed bias could damage tubes but, I couldn't remember the workaround. Do you think I should leave it fixed bias if I move it to another chassis or would there be a benefit to changing to a...
  4. Thinker

    Circuit of new to me 6B4G PP amp, Thoughts?

    Got it on eBay. It's a homebrew. I'll attach some pics. Left channel grid voltages -47.2v, -49.3v Right channel grid voltages -45.5v, -48.8v The 6SN7's are PSVANE 6SN7-SE's I believe they are called "tennis balls' since they have a globe shaped glass envelope (it's my first time seeing them)...
  5. Thinker

    Circuit of new to me 6B4G PP amp, Thoughts?

    Hi Everyone, I recently picked up this 6B4G push pull amplifier. I normally just stick to single ended amps but, I thought this would be fun to play with. My thoughts were that the extra power would give me the ability to use less efficient speakers and I love the sound of 2A3/6B4G's. The...
  6. Thinker

    Looking for Input on Speaker Design for College Project

    Hi Everyone, I'm fortunate enough to go to a college with a learning lab that encourages independent study. I decided I would like to study speaker design for my project and I'm currently doing research. Having been in the hobby for a while now, I've heard some amazing speakers and I'm...
  7. Thinker

    Lepai 2020TI behaving strange with audio analyzer

    I was wondering about that, so I switched the input and output to float for the ground but still got -5.68 volts on the chassis, I even thought perhaps the float switch wasn't working properly so I cobbled together a patch cable to only connect the center conductor and still got -5.68 volts on...
  8. Thinker

    Lepai 2020TI behaving strange with audio analyzer

    I tried it with only one channel and there was still the -5.68 volts, I'm pretty confused as to what's causing it, doesn't matter if it's the left or right channel. Is it a digital amp thing? I'm thinking about replacing the 4 capacitors with decent ones, not sure if that will make any...
  9. Thinker

    Lepai 2020TI behaving strange with audio analyzer

    Hi Everyone, I recently picked up a cheap Lepai 2020TI to mess around with. I connected to my bench equipment since I was curious to see if it would meet spec. I connected it to my Variac set to 120 volts, my HP8903B audio analyzer, and my 8 ohm 1% non inductive dummy load. I've tested a...
  10. Thinker

    Clamp / Detector Board of Quad 63

    It turned out to be something stupid, the positive speaker terminal was grounding, I replaced the binding posts with new ones and it works great! Phew that was driving me crazy. I think I'm going to stick to magneplanar, cone, and horn speakers after these are finished :-P , though the...
  11. Thinker

    Clamp / Detector Board of Quad 63

    Hi Everyone, I was working on a pair of Quad ESL 63's that were beginning to show signs of aging. One speaker had reduced HV, which was causing slightly reduced volume but, other than that they were operating alright. I thought I might as well replaced the parts on both EHT boards if I was...
  12. Thinker

    Marantz 510 THD above spec

    it's been a while since I worked on it but it ended up being the wires that came from the driver board to the peak indicator board were reversed (I hadn't realized someone had been in it before me and thought they were correct, I take pictures whenever I take things apart.) Once I switched it...
  13. Thinker

    Hafler 220 Help!

    So you got me thinking and I started testing resistors further up, R4 was the culprit. I went and cancelled my order for the 2N3440 but, I've hit another road block. When I went to adjust the bias and DC offset on both side the other side wont go below 120 mV for its DC offset (this amp seems to...
  14. Thinker

    Hafler 220 Help!

    I tested R20, 21 29 30 they all came back within tolerance, I've ordered a new 2N3440 (Q11) just in case. I'm at a loss, what I don't understand is what would cause the higher negative voltages at Q1 and Q2's collectors.
  15. Thinker

    Hafler 220 Help!

    Hi Everyone, I'm having trouble with a Hafler 220, one channel is dead. If you go to adjust the bias which according to the service manual is suppose to be set to 275 mA, all I get is 3.86 mA and it doesn't change if you adjust the pot. I pulled all the transistors on the driver board but...
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