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Changing electrolytics in Audio Research D115

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Posted on June 24, 2009 at 17:08:43
Bambi B
Audiophile

Posts: 3264
Location: Los Angeles
Joined: March 24, 2005






PHOTOS: Top> Audio Research SP10, Below> Back view of Audio Research D115

Mates,

As one of the more technically challenged inmates, I approach any technical task with tube gear with caution.

My trusty Audio Research D115 power amplifier is now 24 years old and has been stored since 2001. I moved a couple of weeks ago and am reviving my main tube system: Oracle Delphi III/SME V /McIntosh MR67 > Audio Research SP10 > ARC D115 > Vandersteen 2C- I thought to change the original 5 large electrolytic capacitors- 4 tall and one short.

These are the big blue ones in the photo above and a known Mallory item: [Mouser Pt/ CGS801T450V4]. If I do this, the parts are about $40 each from Mouser instead of $75 from ARC- plus labour plus saving the wear and tear of sending an amplifier that in the box is 70 lbs twice 1600 miles.

The connection is by screw terminals- no soldering.

D115 Questions:

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

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

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

4. Is trying this myself a false economy and there is likely coupling caps and other parts that should be tested and possibly replaced?

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?

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.

Many thanks. Sorry to bother you with elementary stuff.

Cheers,

Bambi B

 

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RE: Changing electrolytics in Audio Research D115, posted on August 4, 2009 at 11:35:35
jslim
Audiophile

Posts: 73
Location: Illinois
Joined: March 5, 2004
Hi Bambi

I have the same set up as you- Sp10-> D115. I replaced the electrolytic cans about 6 years ago. One of the caps was leaking but I replaced all of them. I didn't give much thought to the details you have mentioned. I did use a variac over a 10-15 minute period to turn it on for the first time. As far as I can tell no problems. I love my D115. I bought it used about 15 years ago. No problems other than the caps.

On the sp10 gain pot, the back plate can be taken off by straightening the metal tabs. Be gentle with the tabs. You can clean the contacts with a q-tip or the like and your favorite cleaner. My scratches pots are silent again. I haven't opened the Alps pot.

good luck and I hope this is helpful. you have helped me many times before.

Jun

 

RE: Changing electrolytics in Audio Research D115, posted on June 26, 2009 at 12:59:46
Karma16
Audiophile

Posts: 1081
Location: White Rock, New Mexico
Joined: October 26, 2006
HI Bambi,
Since your level of expertise is, self-proclaimed, to be weak, I'm going to suggest a very conservative approach.

As suggested by others, test the electrolytics before replacing them. My D250 Mk II Servo is about 20 years old and the electrolytics are perfectly fine. True, I have been using the amp and you have not. Plug it in, speakers and preamp attached, and see what happens. If a fuse blows or you get hum then you should replace them. I think the odds are good that they are OK. If you have problems then check back in.

As for the pots, they can be cleaned. Use Caig Deoxit D5 only. It is great and the others don't work. Take it from somone who has cleaned thousands of contacts in my repair shops. Order on-line from MCM Electronics. Accept no substitutes. Everyone should have a can of this wonderful stuff.

If the pots have an access hole on the lead side closest to the circuit board, you must spray the cleaner in the hole then work the shaft from one stop to the other. Do this numerous times then spay more cleaner in and repeat.

If you can't gain access to the hole, or if there are no holes (the pots are sealed), you have some decisions to make. If they have holes, the pots can be removed for cleaning then reinstalled. The problem is your inexperience is working against you. You could ruin the pots or the circuit board.

Or, you could decide to shake some hard earned money loose and take the preamp to a tech. Or, you could send it to ARC for repair and a complete checkout. This is probably the best solution for the best preamp in the world (except for the SP-11, of course (smile)).

I really don't understand the logic of trying to save money on this repair. It won't be terribly expensive. You have a classic. Why screw it up? Think about it carefully. Be sure to call Leonard first.

Sparky

 

RE: Changing electrolytics in Audio Research D115, posted on June 26, 2009 at 03:27:56
mondial
Audiophile

Posts: 295
Location: S.E. ASIA
Joined: January 14, 2007
DEAR BAMBI,

MY TWO CENTS WORD OF ADVICE BEFORE USING THE VARIAC FOR YOUR D115 W/C YOU HAVE NOT USE FOR A LONG TIME. IF YOUR AMP IS EQUIPPED W/ A RELAY I WOULD ASK SOMEBODY TO BYPASS THIS BEFORE USING THE VARIAC. BECAUSE IF THERE IS A RELAY THERE IS NO WAY YOUR AMP WILL TURN ON UNLESS IT SEES 100V IN ITS RELAY IN ORDER TO TURN ON THE D115'S POWER SUPPLY.


HOPE THIS HELPS,

MONDIAL



(SP 11 MK2, SP 10 MK2, D250 MK2 SERVO, CLASSIC 150 MONOBLOCKS, EC 21 )

 

RE: Changing electrolytics in Audio Research D115, posted on June 25, 2009 at 07:40:42
You really do not need to change the big blue caps unless they are leaking and/or causing hum/blowing fuses. If you bring the unit up slowly on a varic they should be good to go. If they function correctly(and do not draw excess current and explode ;-)) they will give you the same sound as replacements. By the way, the only big caps I every had a problem with was a brand new LCR, spewed crap everywhere.

 

Thanks! I appreciate your "take it easy, wait and see" approach. Plus, some variac questions, posted on June 25, 2009 at 12:49:18
Bambi B
Audiophile

Posts: 3264
Location: Los Angeles
Joined: March 24, 2005



PAINTING: "Death of a General Electric 6550A"

Chris O,

The above painting was done in commemoration of having let an output tube in the D115 run probably a year past it's normal use such that it arced and took a sacrificial resistor with it. Pilot error- audio ignorance. Penalty: five weeks without the amplifier and a $XXX fine.

The problems with my technical ignorance in audio is that I end up being:

1. overly cautious and consequently fussy and obsessive about things I've heard about that don't warrant it and, simultaneously,

2. neglecting things that I never heard about that end up making expensive sparks and smoke.

So, armed with the idea that I'm not likely to do harm, my plan with the D115 is to initially clean the tube pins and plugs and bring it up on the variac. Just to confirm:

1. There will be no preamp connected. I should have the D115 connected to the speakers for the variacalating?

2. I've always been very casual about the variac- how long at each voltage. Thinking back, I have been impatient and sometimes have done this too quickly. So I can gauge whether I'm within a reasonable range- how would you incrementally increase the V's on a power amplifier that's been asleep for 8 years?

I appreciate your "take it easy, wait and see" approach to electrolytic capacitor replacement in the D115. Truth be told, I just moved and don't have the the time for additional projects- it's a miracle I can find a spoon when I need one. And, a further miracle I can afford to put something in the spoon,..

Thanks again!

Cheers,

Bambi B

 

Agreed, posted on June 25, 2009 at 09:08:56
BlackPlasticSound
Audiophile

Posts: 275
Location: sunny Texas
Joined: March 19, 2002
Agreed. I would not automatically assume they need replacing.

(Whether you want to try for performance improvements with motor-run caps is another matter.)

best, John

 

RE: Changing electrolytics in Audio Research D115, posted on June 24, 2009 at 21:57:43
Caucasian Blackplate
Industry Professional

Posts: 5698
Location: Seattle
Joined: June 18, 2004
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.

 

RE: Changing electrolytics in Audio Research D115, posted on June 24, 2009 at 20:55:05
Eli Duttman
Audiophile

Posts: 8177
Location: Monroe Township, NJ
Joined: March 31, 2000
Hi Guy!

Caig Labs makes stuff especially for dealing with controls. It used to be called moving contact lubricant (MCL). Perhaps that's still its name.

If the ganged stereo volume control is "shot", a bit of scrambling may be needed. Your photo suggests the unit has the no longer manufactured "Black Beauty" conductive plastic control as OEM. Find out the value needed. Michael Percy shows some stock of Noble controls that may be an easy fit. Frankly, if a PEC KK series hot molded Carbon part can be "shoehorned" in, you will get better sound.

Eli D.

 

RE: Changing electrolytics in Audio Research D115, posted on June 25, 2009 at 13:10:07
Bambi B
Audiophile

Posts: 3264
Location: Los Angeles
Joined: March 24, 2005



Eli Duttman,

Good to see a familiar name here- I feel like a foreigner among the people that know how to use DMM's.

The photo is not of my SP10, but is captioned on arcdb as a MKII. I've always heard these gain pots referred to as "double ALPS". ARC does supply a replacement- about $80 I think, and this is known not to be identical to the original, confirming your comment that they are no longer made.

The idea of a "PEC KK series hot molded Carbon part" is intriguing. It's interesting how components have evolved so far- all those boutique pieces. I saw a series of photos of capacitors and showing the same value cap, in 30 years the size seems to be 1/2. And, even the wires have improved dramatically since 1985. Now, if they could only make a 6922 exactly like a 1959 Amperex,..

Cheers,

Bambi B

 

RE: Changing electrolytics in Audio Research D115, posted on June 25, 2009 at 18:06:52
Eli Duttman
Audiophile

Posts: 8177
Location: Monroe Township, NJ
Joined: March 31, 2000
>>The idea of a "PEC KK series hot molded Carbon part" is intriguing.<<

PEC stuff is not "boutique". PEC makes MILSPEC industrial parts. The hot molded Carbon technology has been around for a VERY long time. Done right, it kicks serious butt, both sonicly and mechanically, at (sic) reasonable cost.

DigiKey carries the items of interest. For instance, their catalog # KKA1041S28-ND, a likely candidate at 100 KOhms, costs 33.05 USD.

Eli D.

 

RE: Changing electrolytics in Audio Research D115, posted on June 24, 2009 at 18:04:45
GTCharlie
Audiophile

Posts: 970
Location: Philippines
Joined: December 9, 2004
Hallo Bambi. If you're replacing your old lytics, with exactly the same value, brand & model, then all you ensure is good contact - whether it's a screw in or soldered. Lytics need break-in, but don't worry about that. Just let it run and enjoy. Re your vol.pot. Where is it in the pix? the green pair on the right? or the pair in the middle? Try an electrical contact cleaner, if that doesn't work, then you have to replace.

 

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