Advise Needed - Gain Pot and Deoxit

[Lazarus Short]

The Arcam's gain pot is an Alps unit and the outside reads `'919m`' and then separately `'10KAX2."

 

[George S.]

Hmm, someone with more experience than me please comment. Does the brass tube pull straight off the shaft leaving what is simply a Alps pot as found in this link? https://www.audiolights.gr/eshop/proionta.php?products_id=2884&language=EN

 

[George S.]

Here is another. https://www.aliexpress.com/item/4000600412897.html

 

[George S.]

Can't tell from the photo if the mark on the brass tube flat is from a set screw for a knob or a staking point to secure the outer most shaft to the brass tube. Bet that brass tube pulls straight off the pots single shaft and will go right onto a replacement pot. Wonder if it's glued on or just a simple press fit. Has anyone any experience with this set up?

 

[Lazarus Short]

Can't tell from the photo if the mark on the brass tube flat is from a set screw for a knob or a staking point to secure the outer most shaft to the brass tube. Bet that brass tube pulls straight off the pots single shaft and will go right onto a replacement pot. Wonder if it's glued on or just a simple press fit. Has anyone any experience with this set up?

The pot is for left and right channels, and coaxial - one shaft inside another. Each channel has its own knob, one behind the other - no need for a separate balance control. The mark on the outer brass shaft is made by a setscrew.

 

[George S.]

The pot is for left and right channels, and coaxial - one shaft inside another. Each channel has its own knob, one behind the other - no need for a separate balance control. The mark on the outer brass shaft is made by a setscrew.

Bummer, dual shafts. I see there are "specialists" in England that work on Arcam. Maybe contact them. I'll continue to look.

 

[George S.]

If you can't find a original, think about getting one of those single shaft versions, using it for parts to fix your dual shaft. Think it's doable if one has the tools, patience, and skill.

 

[Lazarus Short]

https://www.parts-express.com/ALPS-RK27-10KA-Audio-Taper-Potentiometer-Solid-Shaft-023-204

This unit from Parts Express, has the same code as the one in the Arcam. Would it do?

 

[George S.]

The parts express looks like a sealed unit and is of totally different construction. Notice the similarities between your original unit and the ones I linked to. Notice the tabs that can carefully be bent out to disassemble the unit, then carefully bent back in after reassembly.
Maybe it would be best to contact a Arcam specialist in the U.K. for the part, or look for a parts unit, or get the other amp fixed.
Also, you mentioned you had that pot off the board once. You do have good connections to the board? Doesn't hurt to add a little rosin flux to the solder joint and carefully reflow it.
If it was mine, and I knew the pot was bad, but couldn't find a new one, I'd search out one of those pots I linked to, I'd find one from a trusted source in the country I live in, carefully disassemble both pots, find out exactly what the issue is with a ohm meter, and reassemble using what I need from the two.
But, you've got to have the tools, skill, and patience to do it.
I think that was one of Perry's "WOPLSniffer" points he was trying to get across the other evening.

 

[VSAT88]

Temporarily jump the thing out till or if another is found ??

 

[Lazarus Short]

An update for you all: I ordered the pot from Parts Express, stripped the Arcam down to the bare board - care must be taken because of the sheer weight of the transformer - and desoldered the old pot. I had done it before, but the solder sucker made it fairly easy. Then, I soldered six solid-core wires into the holes - the new pot was close, but no banana - assembled everything (took a while) and soldered the wires onto the new pot. Connected to source, speakers...and power. On power-up, nothing blew up. Started the music, and twisted the volume...MUSIC!

IT WORKS!!!

While I was at it, I put on new heat sink compound - the outputs bolt onto an aluminum block, then heat sink, the rear panel, more heat sink, and finally the cooling fins. Thanks to all for help and adivce!

By the way, I checked the original receipt - I bought this amp in August of 2001, so I've had it almost twenty years, and used it very little. Now, it's going to be a daily driver.

 

[VSAT88]

Awesome ! That's what I'm taking about !!

 

[laatsch55]

Good job Laz!!!!

 

[George S.]

Cool! Good job!

 

[Lazarus Short]

An update: All was good for a while, and then the amp was up to its old tricks, that is to say, no sound or intermittent sound. Crank it up, and suddenly...sound. Not good on speakers, however. It sat unused for many weeks. Over the past few days, I've been thinking the relay next to the power supply transformer might be at fault. I opened the Arcam up again, popped the cover off the little relay, powered up the amp, and watched the contacts jump together, then off, and contacts went to their rest position. Off, on, off on, they seemed to work OK. But just to be sure, I made a tool out of strips of abrasive paper soaked in DeOxit. I snuggled the paper between the contacts and ran it up and down a few times on each pair of contacts. It seems to do the trick!

 

[J!m]

These plasma control consoles I work on here have open frame relays in them.

Every 30 years or so, it becomes necessary to fold a strip of crocus cloth and drag it across the contacts, and then wash them out with contact cleaner.

 

[VSAT88]

Totally agree. I clean the selector switch contacts on the Kenwood C2 basically the same way. de solder the switch, pull it out, take it apart, let the contacts sit in De-oxit, use sheets of paper in between the contacts to clean them and put it all back together. The slightly abrasive quality of the paper is perfect.

 

[Lazarus Short]

I'm glad to see that my off-the-cuff idea was sound...and I just realized that I'm now an amp up from yesterday! Yay!!

 

[VSAT88]

I need to count my amps. Do integrated amps count ?

 

[laatsch55]

Hell yes!!