Pot replacement, identify correct pot?

[ofens]

Hi guys, I have identified a pot that needs replacing on my amp. I'm looking for advice on getting the correct replacement and fitting it.
See attached pic of the pot in question.
It looks different to all the others, and I was told by the seller it was an attenuator mod done some years prior.
The amp has worked fully without any issues for a year, for home practice at low volumes and loads of gigs at high volumes, and this has only just started happening in the last couple of weeks.

What I'm asking:
What is the correct part (pot) that I need to order / get hold of?
Based on what I've explained (including below info), is there anything else I should be considering, that might not have been obvious to me?

Further info:
Amp is a JCM 800 2205.
The issue: amp cuts out intermittently (zero sound, instant cut out) and sound returns completely and fully when I rotate one particular pot back and forth a few times.
The amp does not power off or create any other noise, hiss or hum, it remains on but just completely drops all sound. When it returns, it is instantly straight back to what it should be.
Also, there is no loss of tone or moments of lower volume, just completely quiet then completely back in.

What I have tried already:
—Replace all valves (needed doing anyway): no change, problem exactly the same before and after.
—Contact cleaner in all pots (actually inside having opened the amp up), and rotate loads of times (also needed doing TBF!): seemed to fix initially but problem returned after a couple of days, exactly the same.
—Contact cleaner in valve seatings, in case there was an issue there: no change.

Hope to get some ideas, happy to answer questions for any more info needed!
Cheers

 

[ofens]

Using Google lens search, I have found something that looks very similar:
Is this the correct part?

DLG220K​

Dual Log 20mm Control Pot with 6mm dia x 15mm long. Metal Body with Round ¼ inch 6.3mm D shaft for grub screw or push-on knobs.

PCB pins 5mm spacing 220K Log
(Sorry can't post the link to it yet as I'm new and not done five posts yet...)

 

[Jon Snell]

That potentiometer was made by Lorlin, many years ago.
Give it some TLC, a squirt of switch cleaner/lubricant will get it going again.

 

[fitz]

Using Google lens search, I have found something that looks very similar:
Is this the correct part?

DLG220K​

Dual Log 20mm Control Pot with 6mm dia x 15mm long. Metal Body with Round ¼ inch 6.3mm D shaft for grub screw or push-on knobs.

PCB pins 5mm spacing 220K Log
(Sorry can't post the link to it yet as I'm new and not done five posts yet...)

Take the shaft nut off and pull it back from the chassis to look for some kind of identification.
An image search could come up with any dual pot.
See if there is a rating - the one you have may not be 220K
Taking the knob off will let you know what shaft type you have.
There is also a difference between logarithmic / audio (A) and linear (B).
And, the pot in your pic is solder lug, not PCB pins.

 

[Tatzmann]

That potentiometer was made by Lorlin, many years ago.
Give it some TLC, a squirt of switch cleaner/lubricant will get it going again.

He did this already, pls read the whole thing not just bits and bops and blurt out an answer.

Ok friend, what do we have here?

We have a 2205 that has a 2nd master, surely a ppimv installed, which can make sense in that particular model because the standard master configuration is quite unsatisfying when trying to make that amp sound good at very low volume levels.

So you have sprayed this dualpot already and you are very sure that the dropouts are caused by that pot?

Before changing anything make sure that the effectsloopjacks are cleaned properly. They are the usual suspect for that type of fault.

 

[fitz]

Look for this:

 

[Gutch220]

I wouldn't be sold 100% that this pot is the issue. It would be very easy to just replace this dual concentric pot & caps wired to the board. You'll likely need to take it out anyhow to see both values. The problem could also be a loose or corroded connection somewhere. If you feel safe about it, I'd remove the amp from the chassis so that you can get a clear view access to the guts, and power it on like normal and play a looped guitar through it. Then take a little wooden/plastic stick and start touching vulnerable location where a bad connection or solder joint might come into play, (this post, FX jacks, socket connections, etc. This would just be start. It's possible you can replace this pot and the problem still happens.

 

[ofens]

Thank you for the replies so far, all good insights and encouraging!
I got the amp tray open (again) to get some pics, and I also put more contact cleaner in on this pot just in case.
I noticed it is still a little stiff, and the shaft has a really sticky residue on it. I sprayed contact cleaner inside the dual pot and also at the shaft where it enters the pot itself.
(I also put more contact cleaner in the effects loop send/return jacks, as also suggested above.)

No change to the cutting out.
I did notice that this pot sounds scratchy when being turned.
When the cutting out happens, it always abruptly resumes with some twiddling of this pot (sometimes very quickly, sometimes takes a while).
Elsewhere I have seen mention of the "tap test" to see if a loose connection within is present, but on trying this a number of times, I am not finding it to have any effect.

I've attached more pics of the pot itself here, and these show the only markings it has:
LOG B
OMEG (the small italic text; I understand this to be the brand name)
IMEG (around the outside, similar to the LOG B bit)
MADE IN UK

I have never had the issue at gigs playing loud (Master at 10 and this pot at 5 or more). I don't know if this is relevant. But I also don't know if that is still the case as I can't test to that volume at home.
On that note, I can say that when it kicks back in, there's no delay or quietness, it goes straight back to full volume immediately.
Grateful for any additional comments / ideas...

 

[Gutch220]

the IMEG is really 1 MEG, ...or 1 million ohms, and the LOG B part is the taper. I don't know if it's the same for both pots, but you could always measure it.

 

[fitz]

Thank you for the replies so far, all good insights and encouraging!
I got the amp tray open (again) to get some pics, and I also put more contact cleaner in on this pot just in case.
I noticed it is still a little stiff, and the shaft has a really sticky residue on it. I sprayed contact cleaner inside the dual pot and also at the shaft where it enters the pot itself.
(I also put more contact cleaner in the effects loop send/return jacks, as also suggested above.)

No change to the cutting out.
I did notice that this pot sounds scratchy when being turned.
When the cutting out happens, it always abruptly resumes with some twiddling of this pot (sometimes very quickly, sometimes takes a while).
Elsewhere I have seen mention of the "tap test" to see if a loose connection within is present, but on trying this a number of times, I am not finding it to have any effect.

I've attached more pics of the pot itself here, and these show the only markings it has:
LOG B
OMEG (the small italic text; I understand this to be the brand name)
IMEG (around the outside, similar to the LOG B bit)
MADE IN UK

I have never had the issue at gigs playing loud (Master at 10 and this pot at 5 or more). I don't know if this is relevant. But I also don't know if that is still the case as I can't test to that volume at home.
On that note, I can say that when it kicks back in, there's no delay or quietness, it goes straight back to full volume immediately.
Grateful for any additional comments / ideas...

Omeg is a brand.
1 MEG is the resistance.
I'm confused with LOG B.
B usually means Linear.

Edit: just found something that says B is logarithmic in Europe / linear in US.
So, 1 meg, Logarithmic, solder lug, double pot.

 

[dtier]

Both sides of this pot would have to fail simultaneously to give the symptom that you have which is not likely. The cleaner used on pots should be a tuner cleaner with lubricant, like Deoxit, to keep them rotating smoothly.

Have you tried a patch cable in the effects loop?

 

[Gutch220]

...yea, like Dexoxit 100

I wonder if they're both 1M or if it could be different on each pot

 

[ofens]

Both sides of this pot would have to fail simultaneously to give the symptom that you have which is not likely. The cleaner used on pots should be a tuner cleaner with lubricant, like Deoxit, to keep them rotating smoothly.

Have you tried a patch cable in the effects loop?

I've been using WD40 brand Contact Cleaner (pic of can to show what it is attached)
(not normal WD40!)
Is there a likelihood that DEoxit will suicceed where this has not?
And could you conifrm which is teh correct Deoxit, as I see from Google there are different versions... thanks!

Re: effects loop, yes, i have tried a patch cable here; no effect. I also applied a good dose of my contact cleaner in the jacks, both sides to ensure all through it.

 

[ofens]

Omeg is a brand.
1 MEG is the resistance.
I'm confused with LOG B.
B usually means Linear.

Edit: just found something that says B is logarithmic in Europe / linear in US.
So, 1 meg, Logarithmic, solder lug, double pot.

Aha! Thank you for clarifying that. I see now.
Omeg brand, 1M resistor.
(And yes I'm familiar with the "Log B" as a type.)

 

[Chris-in-LA]

Regular Deoxit

https://www.amazon.com/dp/B08N39YQMP?ref=ppx_yo2ov_dt_b_product_details&th=1

 

[Pete Farrington]

I've been using WD40 brand Contact Cleaner (pic of can to show what it is attached)

The can states that the cleaner leaves no residue, ie it’s probably just IPA.
Whereas pots and switches have moving parts so lubrication is necessary.
IPA will dissolve and flush out the original lubrication.
A lubricating cleaner, ie that leaves a lubricating residue, is what’s needed here.

 

[dtier]

Regular Deoxit

https://www.amazon.com/dp/B08N39YQMP?ref=ppx_yo2ov_dt_b_product_details&th=1

This^^^ I would also consider checking your impedance selector. Rotate it several times to clean the contacts.

 

[Resident 217]

What is the pot for, the FX loop?
Why not just get rid of the mod.
Replace the pot to original spec if there was one there in the first place.
Probably a B10K stereo or something.

 

[dtier]

It appears to be a type1 ppimv described as a attenuator.

 

[TassieViking]

Just get a dual gang B1M pot and replace it, it will cost less then a cup of coffee and if it is scratchy its best to replace it for peace of mind.