khstudio
Well-known member
[quote author="dale116dot7"]If you have access to a 'scope and you can look at a few waveforms, you can tell pretty quickly. Keep in mind that all of the proprietary chips are in the digital section, and they are usually relatively well protected from outside stuff.
My PCM60 needed to have its DRAM replaced. It worked fine after that. Another common problem with PCM60's (and so many other machines like it) are broken ceramic filters. You can troubleshoot this with a 'scope. Look for signal at TP6. That is the filtered signal before going into the D-A section. Look for signal at TP12 and TP13. Those are the signals coming out of the D-A. Look for signal at TP15 and TP16. If the signal disappears between there, you've got a toasted ceramic filter. TP16 should be 1/2 the amplitude of TP15.
Before doing any of those checks, when in normal (non-bypassed) mode do you get dry signal? If not, you gotta get that working first. The dry signal does not go through any of the digital reverb section, unlike on many newer 'verbs. The PCM70 I thought was the last to run dry through a separate analogue path.
Also, check for +/- voltage across any of the op-amps (5532's). Note that the bypass switch is actually a relay-based bypass.
-Dale[/quote]
Dale,
Thank you.
:thumb:
I'm turning on my scope now... I'll get back with the results.
My PCM60 needed to have its DRAM replaced. It worked fine after that. Another common problem with PCM60's (and so many other machines like it) are broken ceramic filters. You can troubleshoot this with a 'scope. Look for signal at TP6. That is the filtered signal before going into the D-A section. Look for signal at TP12 and TP13. Those are the signals coming out of the D-A. Look for signal at TP15 and TP16. If the signal disappears between there, you've got a toasted ceramic filter. TP16 should be 1/2 the amplitude of TP15.
Before doing any of those checks, when in normal (non-bypassed) mode do you get dry signal? If not, you gotta get that working first. The dry signal does not go through any of the digital reverb section, unlike on many newer 'verbs. The PCM70 I thought was the last to run dry through a separate analogue path.
Also, check for +/- voltage across any of the op-amps (5532's). Note that the bypass switch is actually a relay-based bypass.
-Dale[/quote]
Dale,
Thank you.
:thumb:
I'm turning on my scope now... I'll get back with the results.