[net.micro.cbm] c64 cassette problems

stottlem@ittral.UUCP (Bill Stottlemyer) (03/06/84)

Thanks to everyone who responded to my request for cassette loading 
problems. Most of the solutions suggested moving the cassette deck
away from the monitor/tv. I had, of course, already tried this. It
didn't help. I was primarily interested in learning the technique of
adjusting the head azimuth. I know how to do this on analog decks but
digital decks present a real problem. Where do you look to determine
if the high freq response is optimum? You can't look at the output-
it's aready squared up by the logic circuitry. You can't look at the
head terminals- not enough signal there. Does the cassette deck use
a high gain pre-amp (i.e op amp) input stage? The output of this stage
would be the ideal place. Can anyone supply me with a copy of the 
cassette deck schematic?  I can't seem to locate a copy in any of my
Commodore papers.

While investigating this problem, I opened the cassette case to take
a look see. I found several bad solder connections on the PC board.
Under one glob of solder I found a small star washer shorting two
adjacent pc tracks. (So much for Commodore's quality assurance). This
deck looks like it had been returned for repairs and the technician
used a blowtorch. I resoldered the PCB and checked it out with a 
magnifying lens. Finally, I adjusted the head azimuth ( without
using a scope). The unit seems to perform much better now. I still
encounter an occasional load error but I guess I can live with it.

Again, Thanks to all who took the time to respond.

                                  Bill Stottlemyer