ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I am embarrassed to admit this, but here goes. While replacing belts on my Beocord 5500, I forgot to unplug the unit and it was in standby. I touched the metal frame of the drive mechanism against the top circuit board which was in the service position and 'POP'. I found a blown resistor at the R28 location, replaced it to no avail.
When I play back a tape, it sounds like the voices are on helium, even though the tape speed seems correct. All other tape functions seem to work properly, although I have not tried recording.
I then replaced approximately 20 resistors, transistors and caps in the same electric path. Again, no joy. I have come to the conclusion that the area in the board I have been working on is for record, not playback. Again, still not tested because I really do not need it to record.
I can read a schematic to figure out what to replace, but can not for the life of me figure out where I should be concentrating my efforts on this board. Parts are cheap and I do not mind replacing a bunch, although the whole board might be a problem.
So, can anybody tell me where I should be looking on this board? Or perhaps someone has a circuit board for sale.
Thanks for all the help.
R28 is in the bias oscillator. Is it running at the correct frequency and voltage (depending on tape type) ?The bias osc. is not active in playback so there must be something else wrong, are you sure about the tape speed ?Is the power supply giving out clean and correct voltages ?
Martin
Hey Martin - Thanks for the info. I am not totally sure about the tape speed, but when I listen to something with both voice and music (Peter and the wolf is the only cassette I have available) the instrumentation sounds close to correct, but the voice is way too high pitched. I would appreciate it if you could tell where to measure the tape voltages and where the test points are. I can not find anything in my service manuals (I only have schematics).
Thanks - Brian
Measure the power supply outputs and check with a scope for ripple.The tape speed is checked with a strobe- or pegel tape or, for a rough estimate, by compared listeningto f.e. a CD with the same audio material.