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  1. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    I finally found it! The trace on the negative leg of C113 was messed up. I went to pull the cap to test it and the trace came right off. I jumpered the cap over to Q105 and the noise is gone. I can now hear my tape! Thanks for your help @kellys_eye. I still have more reading to do, but I've...
  2. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    Still testing everything I can in and around IC501. Introducing signal at the preamp side of Q204, Q205, R223 all produce sound at the headphones. These points on the 100 series, left side, produce zero sound. I've tried swapping the Q104 and Q105 with Q204 and Q205 with no change. I lifted one...
  3. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    I had a Eico 322 Signal Generator given to me a while back. It wasn't working, but I took the time to open it up and found some bad tubes in it last night. Swapped in some good ones and it seems to be working ok. This may not seem relevant, but this morning I went to work testing the Otari...
  4. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    Do you have to disconnect the signal path to trace the noise? I know that the problem went as far back as the preamp chip. If the problem is ahead of that, and you don't disrupt the signal, will it still show up at the preamp or before it? I'm assuming it's a transformer because of the...
  5. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    Good news / bad news time. Turns out this does not actually affect both channels equally. I was checking voltages at switches SW302 and SW402 (SEL-REP Channels 1 & 2 respectively) and found that pin 1 of 302 had zero voltage. Pin 1 of 402 had -18V. Short version is, I pulled both switches...
  6. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    I have not yet tried disconnecting the signal path to isolate the problem, but I had previously pulled, and tested the JFETs Q106 - Q111 using the working Otari. None of them caused the noise in the other unit. However, I did go ahead and test voltages on them today. With current settings (Low...
  7. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    It is on both channels. By breaking the audio path, do you mean jumper it to ground?
  8. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    Visually, they're in pretty good shape. There are a few speckles, but little wear. I've cleaned them two or three times over the course of about a week and a half just to make sure they're good. Also, I can unplug where the heads connect to the amplifier board and the noise is still present. I...
  9. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    All the resistors in the oscillation circuit are well within tolerance and the diodes seem to be working fine. I tested them in circuit with my multimeter in diode mode. All the electrolytic caps in this section were replaced prior to discovering the noise issue, but I'm considering swapping...
  10. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    Ah.. I see it. Not quite sure how that ties in to the preamp just yet. I'll have to study the schematic a bit more later. I swapped IC506 with the one from the working unit and adjusted VR502 after marking where it was. Neither change affected the noise.
  11. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    I've also replaced the electrolytic capacitors with brand new Nichicon ones
  12. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    Hopefully this will work. It only covers the board I'm working on. The preamp, IC501, is in the upper left section. I'm guessing that the bias oscillator part is either under it, or to the left
  13. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    Yeah, unfortunately, the file is too large to upload here and snapping a screenshot will just make everything unreadable when you zoom in. HiFiEngine is a reputable website. They do require you to register, but everything is free and they have thousands of schematics and service manuals. I've...
  14. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    I've been using a schematic that I downloaded from HiFiEngine, but I don't really know what I'm looking for to identify the bias oscillation circuit. However, if it's on the board with the preamp and main amp, I'm pretty sure it's DC powered. There are only two circuits that go into the preamp...
  15. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    Ah, that seems a bit over my head, but I've been doing some reading on it. Would the bias oscillator affect both channels evenly? Would that be before the preamp typically? I'll have to do a lot more research on it apparently
  16. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    I understand what you're saying, but the way it's running now, you can't hear anything but static even when the tape is playing. At max volume the static is louder than the playback signal. I have two of these Otari's and the tape plays fine on the other one. There's almost zero noise on the...
  17. KilgoreCemetery

    Noisy Otari MX5050 BII-2 Tape deck

    As soon as the unit is powered on, there is a constant static noise in both channels. You can hear it through the headphone jack, as well as the output connection. It doesn't register on the VU Meters, but it also makes any playback with known good tape extremely quiet. I've been using an...
  18. KilgoreCemetery

    Pioneer SX-838 Protection Relay Clicking

    Yeah, you have to register. But, it's free and HiFiEngine is THE place to go when you need manuals for vintage audio equipment. No, I'm not a spokesperson, I'm just saying that from experience. I could upload it to mediafire, I guess, but I don't need the file shrunken down so much as I need...
  19. KilgoreCemetery

    Pioneer SX-838 Protection Relay Clicking

    Less than 6.8 MB evidently. Beyond that, I'm not sure.
  20. KilgoreCemetery

    Pioneer SX-838 Protection Relay Clicking

    This particular Pioneer receiver has a protection circuit that actuates a relay to prevent things like DC voltage going to your speakers. The problem is that the relay randomly clicks on and off. I've checked for DC voltage at the output transistors and found, what I would consider, a normal...
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