Advise Needed - Gain Pot and Deoxit

[Lazarus Short]

Given the untimely demise of my Cyrus 2 (one of the best-sounding amps I ever owned) I need a replacement. Sometimes it's best to look to your own resources, and I have this Arcam Delta 60. It sounds amazing, but the gain pot is off and on...mostly off. Every time I think I've got it working, it is only for a time, and then no sound again. I have Deoxited it a few times, and the last time I did it I dripped it into the top of the pot, and it seemed like more of the stuff got into the innards than when using the direct spray. I'm thinking about desoldering the pot from the board (done that before) and zapping it in the ultrasonic cleaner with some Deoxit. If I do, should I follow up the Deoxit with something, and if so, what? Please feed me some ideas that work.

 

[George S.]

Pictured is a original Phase Linear attenuator potentiometer from a 400 amp. It kinda of works, but is scratchy, and Deoxit would probably fix it, but I replace them IF there is a good sub. If no good sub, I would spray Deoxit into a small plastic bottle cap, and suck it into a syringe that has a very fine needle. The needle then carefully goes into accessable areas of the pot, putting the Deoxit where needed.
If this doesn't work, then it's time to carefully open it up and clean with qtips and Deoxit, ohm out the lugs and tracks, then lube with Fader Grease and reinstall. Hopefully you don't have a sealed unit unable to be opened.
Don't think I'd put a pot into a ultrasonic cleaner and expect it to live. Some pots have tracks made out of conductive plastic. That's one reason for measuring resistance when they're apart.

 

[mlucitt]

Agree with George, sometimes you just have to open them up and surgically clean them. But if you have a replacement, that is the best way to deal with a noisy or intermittent pot. I have good luck with Bourns, the inexpensive ones from China are not worth the time.

 

[FredR]

2nd for Bourns.

 

[Phase Linear Phanatic]

This has question has probably already been addressed somewhere else in another thread I'd imagine, but for the sake of this particular thread allow me to ask; Do we have a preferred Bourns part# for the 700B Attenuator pots? Out of nine amps I have maybe 7 scratchy ones. I'm thinking about just replacing them all as a matter of course if the price is right...............

 

[WOPL Sniffer]

There is more to life than Deoxit spray. You need to "FLUSH" with Deoxit, but you have to lube them too like they came from the factory. There is such a thing as Deoxit Fader GREASE which you need to use or you will be spraying that thing every month until it dies. Go to the deoxit site and look up Deoxit grease. The spray will help loosen up the dried up 40 year old grease so you can flush it away, then you lube it.

 

[George S.]

Good point. Small jar of it in the photo. Do you always take them apart, clean and grease, or just inject it and work it in after the spray.

 

[George S.]

This has question has probably already been addressed somewhere else in another thread I'd imagine, but for the sake of this particular thread allow me to ask; Do we have a preferred Bourns part# for the 700B Attenuator pots? Out of nine amps I have maybe 7 scratchy ones. I'm thinking about just replacing them all as a matter of course if the price is right...............

I use these, my understanding is PL used the same pots on 400s and 700s. As to if they are the same "taper" such as linear or audio taper, I don't know. WOPLSniffer recommended these on a old thread. Mouser 652-PDB241GTR02104B0 Linear taper 100K Bourns 20% Round Shaft great fit, OK feel when turning. Might want to take your old ones apart, clean and grease so they all match.

 

[WOPL Sniffer]

This has question has probably already been addressed somewhere else in another thread I'd imagine, but for the sake of this particular thread allow me to ask; Do we have a preferred Bourns part# for the 700B Attenuator pots? Out of nine amps I have maybe 7 scratchy ones. I'm thinking about just replacing them all as a matter of course if the price is right...............

aren't you the one replacing you LED boards because the filter tape is old????

 

[Phase Linear Phanatic]

I use these, my understanding is PL used the same pots on 400s and 700s. As to if they are the same "taper" such as linear or audio taper, I don't know. WOPLSniffer recommended these on a old thread. Mouser 652-PDB241GTR02104B0 Linear taper 100K Bourns 20% Round Shaft great fit, OK feel when turning. Might want to take your old ones apart, clean and grease so they all match.

Thanks George. That was going to be my next question. What kind of resistance do they give? aka. "How do they feel" when turning? If I have to replace ONE, I'd replace BOTH, so they matched.

 

[WOPL Sniffer]

I use these, my understanding is PL used the same pots on 400s and 700s. As to if they are the same "taper" such as linear or audio taper, I don't know. WOPLSniffer recommended these on a old thread. Mouser 652-PDB241GTR02104B0 Linear taper 100K Bourns 20% Round Shaft great fit, OK feel when turning. Might want to take your old ones apart, clean and grease so they all match.

some here do not need to take them apart. You can fuck them up if you don't know what you are doing.

 

[Phase Linear Phanatic]

aren't you the one replacing you LED boards because the filter tape is old????

Well, if you read the thread for my 700B, in the end, I found out it was NOT the filter tape. I went back and took each and every one of them apart, and the tape had NOT been changed by me at all. It was indeed the LED's that had gradually dimmed over time as Joe had said. I ended up replacing the boards. So now if they dim over time; they will ALL dim at the same rate.

BUT........What's your point?............

 

[Phase Linear Phanatic]

some here do not need to take them apart. You can fuck them up if you don't know what you are doing.

Completely agree with this. I'd rather buy a new taper and replace it. It's the same point you made on replacing the Rectifier while you're in there. No sense in keeping 40yr old parts if you are replacing everything else. Or your customers would think you're "A cheese-weenie". I wouldn't buy an overhauled engine and keep the old water-pump. I'd replace it ALL.

 

[WOPL Sniffer]

My point was, some are more prone to fucking things up. Replace/repair??? Yes, if you have the capability. I missed your post because I had you on ignore.

 

[George S.]

My point was, some are more prone to fucking things up. Replace/repair??? Yes, if you have the capability. I missed your post because I had you on ignore.

Perry, do you use a needle to flush and another needle to inject the grease? You've most probably had your hands on more old switches and pots than anyone else here. Just been wondering how to get the grease in on items we may not want to disassemble.
Read one of your old posts on using the D100 rather than the D5. Makes sense to use the D100 concentrate if one can add some lube.

 

[Lazarus Short]

I spoke quite some time ago on the phone to a fellow at Arcam, and he told me...

...the pot for that amp had not been made in ten years...

...and to put a few drops of synthetic oil in the pot after cleaning, which I did.

 

[George S.]

I spoke quite some time ago on the phone to a fellow at Arcam, and he told me...

...the pot for that amp had not been made in ten years...

...and to put a few drops of synthetic oil in the pot after cleaning, which I did.

Post a photo and part# of it.

 

[Lazarus Short]

A part number is possible, but Ubuntu 20.4 is not letting me access photos from Shotwell...so a photo is not probable.

 

[George S.]

No smart phone? If your able to post a photo someone on the forum would most likely be able to help you in regards to fixing the pot or replacing it with a suitable substitute. Part # alone probably isn't going to work.

 

[mlucitt]

I use these, my understanding is PL used the same pots on 400 II's and 700's. As to if they are the same "taper" such as linear or audio taper, I don't know. Mouser 652-PDB241GTR02104B0 Linear taper 100K Bourns 20% Round Shaft great fit, OK feel when turning. Might want to take your old ones apart, clean and grease so they all match.

And only $3.23 each at Mouser. Phase Linear lists their pots as P/N 129-0005-0 "100K Linear (R138)". So the Mouser-sourced Bourns potentiometers are an exact replacement for the original CTS (Chicago Telephone Supply) potentiometers. If you see a number on your pots that starts with 137 or R137, that would be a CTS pot. The numbers after the manufacturer code is the date code. Some of mine: 8114 = 14th week of 1981, 7815 = 15th week of 1978, 7421 = 21st week of 1974. You get the picture.