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RE: Changing electrolytics in Audio Research D115

Posted by Caucasian Blackplate on June 24, 2009 at 21:57:43:
D115 Questions:

1. Is there any special treatment to the connectors- use or avoid contact enhancer?, cleaning of the terminals?

If they are dirty, contact cleaner isn't a bad idea. A tight connection is all that is needed on clean terminals.

2. I'm assuming this long-stored amp with new capacitors should be brought up on a variac. Suggested procedure?

New electrolytics don't need to be brought up on a variac.

3. Should there be a forming/ burning-in/ stabilizing period before use?

Nah, this should be a time to see if you observe any actual breakin.

SP10 Questions:

I'm really, really looking forward to getting the SP10 and D115 back in use. It needs a new gain pot and I'm debating trying that one,..

1. The gain pot on the Audio Research SP10 is as far as I know a "double" ALPS- the left front component in the photo top- which does look like a double box. This pot the last time I tried it- 2005- makes a terrific scratchy- boomy noise when moved. Is it possible to clean this pot to improve it or is replacement called for?

Yes, do clean it. You can get decent cleaner at Parts Express or Radio shack.

2. How fussy or danger of damage is involved to replace this? I don;t know how it is attached, but think it may have leads through traces on the board.

The "best" way to replace it will likely involve either completely freeing the board from the case, or at least getting the front panel off and some access to the bottom of the board. The nice part about this procedure is that you can't really ruin a broken part. Get yourself a bunch of solder braid and take your time getting the old solder out. I wouldn't expect this to take more than 2-3 hours. That exact pot shouldn't be hard to find.

You might also drag up a schematic and see if you can use motor run caps instead of those Mallory caps. The values will be wildly different, but I know a great many people who have done this with Cary and AR amps with great success. Also, I would estimate a motor run cap is good for at least twice as long as an electrolytic. I have used motor run caps that are at least 50 years old already and they work quite well still.