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  1. 1mike161

    RT-909 Level Problem

    Good idea. I'll give that a try next. Thanks again!
  2. 1mike161

    RT-909 Level Problem

    Thanks! I did think of that and I cleaned all the suspect switches with Deoxit. However, I was concerned that the Deoxit was not working it's way into the switches properly -- I'm not sure if I was spraying into the correct holes.
  3. Drop

    Drop

    Pioneer RT-909 Block Diagram
  4. 1mike161

    RT-909 Level Problem

    My RT-909 has a problem where the output on the L channel during FWD Play drops by two meter segments on an intermittent basis. The problem is cleared by pausing and un-pausing playback. Reversing play direction (FWD to REV then REV to FWD) also clears the problem. I have confirmed this by...
  5. 1mike161

    Amplifer Wave Form Problem

    I am trying to build a kit AM/FM radio and I have run into something strange after completing the amplifier section. The output wave form is not symmetrical. It doesn't look like clipping to me either. It looks like the push/pull transistors don't have enough current to complete the wave...
  6. 1mike161

    Hello!

    Hello, my name is Mike. I joined AK in September of 2015 and since then I have gotten a lot of help and information from the site. I am an audio and electronics buff with lots of Pioneer gear from 1970's & 1980's -- mainly Spec series and blue fluorescent components. I think my system sounds...
  7. IMG_1089

    IMG_1089

  8. IMG_1092

    IMG_1092

  9. AMFM-108CK

    AMFM-108CK

  10. 1mike161

    Recording Problem Pioneer CT-F950

    I am experiencing a recording problem with a Pioneer CT-F950 tape deck. The recorded level on the left channel is significantly less (about half) than the recorded level on the right channel. Obviously I can compensate for this with the input level control, but I would prefer to fix the...
  11. 1mike161

    Pioneer CT-F950 Recording Problem

    Good idea. I also thought that I might have a bad "wire" and not a bad head. I've got the deck put back together, but I will revisit when I get the time.
  12. 1mike161

    Pioneer CT-F950 Recording Problem

    I examined the head with a jewelers loupe and could not see any evidence of wear. How is the inductance measured? Are there other tests that can be performed on a head?
  13. 1mike161

    Pioneer CT-F950 Recording Problem

    The 950 still works great as a player and I don't record that much anyway. I have a CT-F750 I can record with if I need to. I was really just trying to see if I could fix it. I have had pretty good luck repairing amplifiers over the years and thought I could take on a tape deck. And...
  14. 1mike161

    Pioneer CT-F950 Recording Problem

    I decided to swap the head channels, left for right, since I figured out how to get to those wires. And...the problem reversed. Now the right channel has the problem. So, I have a bad record head.:( I guess I'm dead in the water now -- I don't think it will be easy to find a replacement...
  15. 1mike161

    Pioneer CT-F950 Recording Problem

    Last night, I measure the VR's without taking anything out of the circuit. They are supposed to be 33k ohm, and they both measured between 1 ohm and 30k ohms. So, I think they're OK unless you think the caps must be lifted from the circuit to get an accurate measurement. I am comfortable...
  16. 1mike161

    Pioneer CT-F950 Recording Problem

    Yes, the unbalanced signal occurs at the junction of C325 & L301 compared to the junction of C326 & L302. And, yes, I did not use an input signal when checking the bias circuit. I will try the "divide and conquer" method on the suspect components, saving the head for last. Do I need to remove...
  17. 1mike161

    Pioneer CT-F950 Recording Problem

    First, let me thank you for helping me! I think I figured out how to get to the head wires, so I will try to swap the them this weekend. I applied a signal generator to the input terminals on the deck. I observed a balanced signal with a dual trace scope at IC1001 pin 9 Left channel and...
  18. 1mike161

    Pioneer CT-F950 Recording Problem

    I sent you the schematic. Let me know if AK reduces it to the point you can't read it. By swapping the head channels I would be ruling out (or confirming) the possibility of a bad record head, right? I'm probably in trouble if it's the record head -- I don't think replacements exist.
  19. 1mike161

    Pioneer CT-F950 Bias Problem

    My Pioneer CT-F950 is not recording properly on the Left channel. The recorded level of the left channel is significantly less than that of the right. I think I have traced the problem to the bias amp. I determined that the recording signal is good (balanced on all tape types and across many...
  20. 1mike161

    Hello!

    Hello, my name is Mike. I joined AK in September of 2015 and since then I have gotten a lot of help and information from the site. I am an audio and electronics buff with lots of Pioneer gear from 1970's & 1980's -- mainly Spec series and blue fluorescent components. I think my system sounds...
  21. 1mike161

    Pioneer CT-F950 Recording Problem

    The bias signal imbalance occurs after the "matching transformers". I'm not sure what these components actually do, but it doesn't look like they are adjustable. The signal difference is half -- one bias channel is half the other in terms of wave magnitude. Any advise on how to proceed? I...
  22. 1mike161

    Pioneer CT-F950 Recording Problem

    I did not clean/deoxit the bias select switch. I couldn't find easy access to it and I didn't have time to do a lot of dismantling. I did demag the head. After checking the bias output with my scope, I measured an imbalance between the "L" and "R" channels. The "L" channel is half the...
  23. 1mike161

    Pioneer CT-F950 Recording Problem

    I was wrong on the signal measurements prior to bias injection. All frequency tests show the left and right channels are perfectly balanced. I think one of my digital multimeters gave me a bad reading. When I swap meters, the .888mV and .415mV readings also swap. I retested everything with a...
  24. 1mike161

    Pioneer CT-F950 Recording Problem

    Test results from measuring recorded output: Standard Tape & Bias: 333 Hz L = R 1K Hz L = R 10K Hz L = R Metal Tape & Bias: 333 Hz L = R 1K Hz L = R 10K Hz L > R Chrome Tape & Bias: 333 Hz L > R 1K Hz L > R 10K Hz L > R The Following is incorrect...
  25. 1mike161

    Pioneer CT-F950 Recording Problem

    AudioWizard, I don't think I have any normal bias (standard) tapes, but I will test that type if I can find one. I will perform the test with different frequencies and see what happens. I do have a scope so I can check the level before and after the bias injection. Great tip! Thanks!
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