Recent content by haskellbob

  1. H

    volume control doesn't reduce one channel to zero. In a few seconds it almost does...

    That makes good sense and would seem to be the answer. But I tried connecting the ground pins to nearby ground points, and to the chassis itself, with no change. I disconnected the two wires going to the center tap, and that made no difference. I also measured resistances. At the low volume...
  2. H

    Can't quite figure out the function of the fourth terminal on a potentiometer.

    Wow am I late. I'm sorry. Would you believe that I have another problem? I don't have the one channel taking time to "warm up" anymore; now I'm wrestling with a volume control that won't go down to zero volume. I've been discouraged; electronic stuff is just a hobby and leads to more...
  3. H

    volume control doesn't reduce one channel to zero. In a few seconds it almost does...

    Hello! I have a Heathkit AR-15 receiver. I recently began having this problem: The volume control does not reduce the volume to zero, on one side only. The right side If I turn the unit on right after turning it off, there is sound there at a pretty high volume, which drops after the...
  4. H

    Can't quite figure out the function of the fourth terminal on a potentiometer.

    The attached fragment of a circuit is for the preamplifier board of a Heathkit AR-15 receiver. The volume control potentiometer has a fourth terminal. I can see that it has something to do with the Loudness (bass-enhancement) control, which is either on or off. Something is bypassed when the...
  5. H

    Heathkit AR-15 sound problems

    Will do. Thanks.
  6. H

    Heathkit AR-15 sound problems

    I do think something is thermally sensitive. When the temperature goes up in the afternoon all I get is distortion. But right now it's cool outside (and inside) and it's working fine. What tend to be the most thermally sensitive components?
  7. H

    Heathkit AR-15 sound problems

    I will do that. Where should I measure; what are the most important voltage points? And: supposing it's not a capacitor and there's a DC shift - what would cause that?
  8. H

    Heathkit AR-15 sound problems

    Hi all. I have this Heathkit AR-15 here, and it has had this symptom: One channel takes a good fifteen seconds to come fully alive. It moves from zero sound through distorted sound to full-on sound. But then at intervals it gets distorted again. I think it has finally decided to die, though...
  9. H

    Heathkit AR-15 sound problems

    Sure enough. Left the rig on and went to breakfast. When I got back, pure distortion on the right channel. The old boy just can't keep it up. (is there Viagra for old receivers?). But the missing channel, fed through another amp out of the preamp, sounds fine there. That pretty much proves the...
  10. H

    Heathkit AR-15 sound problems

    Hi Bob, this is Bob (???) with an update: Connected preamp output to alternate amp and sound is great. Of course, now the original amp, connected to smaller speakers, is working fine too. It knows it is under scrutiny, the little bugger, but it will have to give up the ghost eventually. I know...
  11. H

    Heathkit AR-15 sound problems

    Hi all. I have this Heathkit AR-15 here, and it has had this symptom: One channel takes a good fifteen seconds to come fully alive. It moves from zero sound through distorted sound to full-on sound. But then at intervals it gets distorted again. I think it has finally decided to die, though...
  12. H

    Heathkit AR-15 receiver - problem with multiplex circuit

    Hi. I have an update. The culprit turned out to be a .001 mfd disc cap. Interesting coincidence with your experience. The manual, in the "Troubleshooting" section, mentioned this as a possible cause. I have heard it's rare for those capacitors to fail, so I wonder what caused it? Maybe its being...
  13. H

    Heathkit AR-15 receiver - problem with multiplex circuit

    It's still producing clear sound. Sorry I didn't notice that you'd asked for the voltage between them, but it got measured anyway! Point of order: The base of Q410 is 4.99 volts. So 5 volts. The schematic says 4.5. I still have my fingers crossed. I'm hoping the replacement of capacitor C413...
  14. H

    Heathkit AR-15 receiver - problem with multiplex circuit

    Hi. The receiver is still ungarbled... I never answered your question: yes, everything went as expected in the alignment. Also, I re-measured the voltages at Points 3 (11.97) and 4 (12.72). I don't know what changed or what mistake I may have made in measuring before. What are their ideal...
  15. H

    Heathkit AR-15 receiver - problem with multiplex circuit

    I'll do that as soon as: a) the sound gets garbled again, or b) a couple of days have gone by with no garble. I'll let you know the values I get when I do it. Thanks.
See more
Top