A local gent donated some gear to the high school campus station I'm building in return for my help in rehabilitating an old audio processor, a 231 "MAP II" multi-band AM processor made by Inovonics. He too has a project which his processor will be going toward.
Here's the quandary: With the age of the processor we replaced all the tantalum capacitors and the majority of the op-amps as there were some that ran warm or were incorrect substitutes. The AGC and Peak limiter sections come into alignment fine using the procedure outlined in the manual but all 8 of the bandpass compressors don't come close.
Their output levels operating in proof mode can't be adjusted low enough to make the required alignment level. Almost the opposite is true when taken out of proof, as the output level will become much lower than the required operating level. This is most notable on the very low end and the very high end. The only other active components that haven't been replaced are the transistors and FETs but pulling them and checking them with my Sencore Cricket show they test good. Troubleshooting is much more difficult to do since there's no expander card for the unit - powered-up troubleshooting becomes quite a challenge.
I'd like to help the guy out since he was nice enough to donate gear for my school station project. The thing is so simple I can't imagine what could make all 8 band compressors act out of the ordinary. Perhaps somebody who remembers this unit might have a helpful tip to offer. It would be great to locate an expander card or else I will have to break out the old etching kit and create one from scratch.
Here's the quandary: With the age of the processor we replaced all the tantalum capacitors and the majority of the op-amps as there were some that ran warm or were incorrect substitutes. The AGC and Peak limiter sections come into alignment fine using the procedure outlined in the manual but all 8 of the bandpass compressors don't come close.
Their output levels operating in proof mode can't be adjusted low enough to make the required alignment level. Almost the opposite is true when taken out of proof, as the output level will become much lower than the required operating level. This is most notable on the very low end and the very high end. The only other active components that haven't been replaced are the transistors and FETs but pulling them and checking them with my Sencore Cricket show they test good. Troubleshooting is much more difficult to do since there's no expander card for the unit - powered-up troubleshooting becomes quite a challenge.
I'd like to help the guy out since he was nice enough to donate gear for my school station project. The thing is so simple I can't imagine what could make all 8 band compressors act out of the ordinary. Perhaps somebody who remembers this unit might have a helpful tip to offer. It would be great to locate an expander card or else I will have to break out the old etching kit and create one from scratch.