Sourcing pots for a Marshall DRP-1

[jondoe]

Hi all,

I have a Marshall DRP-1 with a bad pot and they have very stubby short shafts compared to their bigger Marshall brothers. Has anyone here replaced them and can share where/what they sourced? I'm struggling to find something suitable.

Thanks.

[g1]

Does it match any of these (more on pg.2)?
https://www.tubeampdoctor.com/en/sho...tyle_and_Pots/

[J M Fahey]

Hi all,

I have a Marshall DRP-1 with a bad pot and they have very stubby short shafts compared to their bigger Marshall brothers. Has anyone here replaced them and can share where/what they sourced? I'm struggling to find something suitable.
Thanks.

Where are the pictures?

[jondoe]

Where are the pictures?

Good point

[J M Fahey]

Short and stubby indeed

In principle, Marshall "should" have original replacements.

If not, I am more worried about the long threaded "neck" than by shaft itself, which "in principle" should match Marshall knobs.

So if you get a suitable pot but with a too long serrated shaft, a Dremel[tm] will take care of that in no time.

You will be lacking the side strengthening "wings" but that can be easily solved, I do it all the time.

[jondoe]

It's less of a shaft, more of a nipple!

I emailed Marshall and they have told me they don't stock the part and can't tell me where to get one, so I'm shit out of luck in that respect. I think this pot is the most likely alternative;

https://www.tubeampdoctor.com/en/sho..._vertical_2242

I'm going to trawl through ebay as i'd like to get the cheapest one possible if i'm going to experiment. I don't own a Dremel [tm] either, which I know as a grown man is a terrible thing to admit.

[J M Fahey]

Oh, a file or hacksaw can do, just take longer

Is the original pot 16mm case also?

I repeat, shorter threaded neck might be a problem, please post a picture on how is the pot bolted to front panel, I have a faint memoryb they were mounted to a sub chassis first ... havenīt repaired one for ages.

If you get a cheap $1 generic pot with no wings, I always scratch pot case sides and solder 2 pieces of brass wire instead; not winning any beauty contests but do the supporting job fine.

[jondoe]

Straight through, no washer on either side. I've removed the offending pot and it's marked A10K with a logo [JP].

[J M Fahey]

Now take a sideways picture, so we see the whole body/neck/shaft plus nuts and panel thickness.
Thanks.

And somebody upload the schematic; in my book A10k means 10k Audio/Log, I seem to remember somebody considered it a linear pot.

Schematic will dispel that doubt.

[jondoe]

I couldn't find schematics, although I found a few Japanese websites that had reverse engineered it, this link has the most information i found, mostly in the picture links.

http://www.matsumin.net/diy/jisaku1/DRP-1/index.html



There's a side on shot, the metal body is approx 3mm thick

[J M Fahey]

Thanks, thatīs what I needed.

"front panel" here is not typical #18 to #22 gauge cold rolled steel (or even aluminum) like on 99% of amplifiers but a way thicker aluminum extrusion, thatīs the reason of the matching extra long pot threaded neck.

I think you will be able to source a pot fitting there , same diameter and pin spacing, but I doubt you will be able to thread the nut on it.

Pot will be usable, but maybe somewhat shaky, although if you get one with mounting wings it might be steadier.

That said, some Techs/DIYers have succeeded by opening the dead pot , pulling a resistive wafer from another (a regular one) , and transfering it.

Now we only need to known "which" pot are you talking about. (what does the front panel say? )

[jondoe]

I found a random ALPS pot in my spares box from another repair I did last year, although not suitable, it looks like the thread is long enough. The white line seen in the picture is a credit card so I can get a sense of how much meat would be left on the spindle, not much!

EDIT: I'm also going to carefully pull apart the faulty pot and give it a good inspection and clean.

[J M Fahey]

Yes, the main problem is the threaded neck; you canīt add metal, and even less if it needs a thread, while you can cut/grind the shaft and also extend legs with wire bits to reach PCB if too short.

Still want to know which pot are we talking about.

[jondoe]

Still want to know which pot are we talking about.

Damn it I thought I mentioned that, it's the line input

Currently have the faulty pot in bits, nothing loots broken or worn, but it's all VERY tarnished, so it's going to need a gentle clean.

[J M Fahey]

Now we are talking

VR6 Line Level is A10k or 10k Log or 10k Audio , 3 ways to say the same thing

As of grime, stuff left in a smoky environment for a long time, develops a tar layer, same as ... um .... your lungs (if you are the smoker):

Consider the pedal a "passive smoker" and you wonīt be far from truth.

Iīve had to clean surfaces, inside and out, to get rid of it.

I donīt smoke at all, and sometimes need to leave amps or instruments, case open, a couple days under the Sun to get rid of at least the most offensive part, before actual servicing.

Always mumble about building an "ozone box" to treat smelly stuff but as usual never actually get down to it.
Oh well.