R/E/P > Bruno Putzeys (Designer) - Dave Hecht (Master Tech)

Studer A810 Popping

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My Studer A810 Is popping when switching between Input (Inp.) and Rep. on the right channel.
When I swap the line amplifier cards (1.820.714) the pop follows the card.
I swapped the LM393, 5532 and the MM74C374N op amps between the two cards and the pop stuck with the original card.
             It looks like the switching takes place between the 374 , LM393 and the SD211 are these  SD211 the likely culprit. I hope not as they seem hard to find.

Any caps in the signal path? Thats a likely culprit.

When I first got the machine I recapped all the electrolytic caps( and all the RIFAs) the only other ones on the board are solid aluminum or ceramic. I haven't ever seen any of them go. Have you experienced any problems with them?

Solid alis are usually pretty good. But the click will be a d.c.offset somewhere. Could be a switch chip. The best way is put it on an extender card and follow the audio path with a scope. The 810s etc used Analog Devices Multiplying Dacs quite a bit, could be one of those?

Downloaded the manual. Looks like those fet switches could be suspect, but first check the dip switch settings. Some of the switch combinations have conflicts.


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