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PPM3 Page 23
TROUBLESHOOTING GUIDE
If your PPM3 does not work at all, recheck the following:
• correct orientation of VR1 and the ICs (see PC board layout diagram).
• You should be able to measure the voltage on the input and output
terminals of voltage regulator VR1. The input should be whatever the
supply voltage is specified at, while the output should be 5 VDC +/- 5%.
• correct polarity of all electrolytic capacitors.
• correct orientation of diodes
• all solder connections
STILL HAVING TROUBLE?
While we had hoped that it wouldn’t come to this, if you are still having trouble
with your Phone Patch Mixer, here are a few additional suggestions.
Use a methodical, logical troubleshooting technique. Most problems can be
solved using common sense. A volt-ohm meter and a clear head are usually
all that are needed to correct any problem. Most problems are due to
misplaced parts and/or bad solder connections. Working backwards through
the assembly steps will often lead you to the problem. Revisit the extensive
theory of operation included in this manual and try to apply it to your specific
problem.
Have another set of eyes look through your work. Here at the shop we have
often run into a “stone wall” of a problem only to have a fellow technician see
our obvious error. It is sometimes very difficult to see your own mistake; taking
a break can often solve this common problem.
Make sure that you have “checked” all the assembly steps boxes; you may
have forgotten one or two of them.
PROBLEM: I get no audio when doing the initial test of the audio section.
SOLUTION: Check the volume level on your source to be sure it’s up loud
enough for you to hear. Next check your stereo or other device to be sure it’s
on, that it’s set for the input you’ve connected to it (AUX or other . . . whatever
an external source is on your particular stereo) and make sure the volume is
loud enough. Another thing to check is that the volume pot, R2, is turned up
enough for you to hear the output from the PPM3. You should always use