02-11-2017, 11:05 AM
It would not hurt to replace the four coupling caps with high quality 630V polypropylene film, and add fusible metal film resistors to the cathodes of the output tubes.
The seller wrote in the listing that the unit was in working condition. Have you powered the receiver up at all? I have a feeling it will work as is if you bring it up slowly with a variac to reform the electrolytics. It would be good to know if you have any existing problems before replacing any parts.
If it was mine, what I would do is first check for any shorts on the B+ supplies. Then remove the output tubes and monitor the output of the B+ supply as you bring up the AC line voltage slowly over the course of an hour or so. Stop when the B+ supply reaches about 250V. Make sure that none of the electrolytics is getting warm and if any are stop and shut it down.
If you get to this point without problems, check the negative bias supply at the negative can terminal of C98 and make sure you have negative voltage at that point. If it is ok then I would reinstall the output tubes, connect speakers and again bring up the AC voltage slowly until your B+ supply reaches 350 V. Make sure there is at least -22 V at the can of C98. At this point it will either work, or you have existing problems.
This is the procedure I use with any tube equipment built after the 1950's before changing parts.
The seller wrote in the listing that the unit was in working condition. Have you powered the receiver up at all? I have a feeling it will work as is if you bring it up slowly with a variac to reform the electrolytics. It would be good to know if you have any existing problems before replacing any parts.
If it was mine, what I would do is first check for any shorts on the B+ supplies. Then remove the output tubes and monitor the output of the B+ supply as you bring up the AC line voltage slowly over the course of an hour or so. Stop when the B+ supply reaches about 250V. Make sure that none of the electrolytics is getting warm and if any are stop and shut it down.
If you get to this point without problems, check the negative bias supply at the negative can terminal of C98 and make sure you have negative voltage at that point. If it is ok then I would reinstall the output tubes, connect speakers and again bring up the AC voltage slowly until your B+ supply reaches 350 V. Make sure there is at least -22 V at the can of C98. At this point it will either work, or you have existing problems.
This is the procedure I use with any tube equipment built after the 1950's before changing parts.
