Psilocybinator

Hi.

I'm hoping someone here can help me. A few years ago, I was given a vintage Marshall amp head, a JMP P.A. 20, plus one speaker cab. Unfortunately, it didn't come with a power cable... I've been searching the internet, plus electrical and music hardware shops, but nobody seems to be able to even tell me the name of the cable I need, or where to get one. Please see the attached photos, there is a close up of the power input.







I really want to be able to power the thing up so I can see if it still works! The guy that gave it to me said it had been in his attic for a couple of decades and had no idea if it still worked or not. So, if anyone could help me out by telling me where I could find the required cable, I would be most appreciative. If I can't find one, I suppose I will have to get it modified to have a modern power fitting, but I'm sure that will devalue the unit considerably. Last resort option...

Cheers.

Marshall Amps

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Rockbert

A) It's a Bulgin cable, they are pretty easily available on ebay - be sure to get the right size because there are some smaller ones too.

B) But don't just plug in and power on after 20 years, you will risk blowing the filter caps. Take it to a tech who can power it up slowly with a variac and reform the caps.

Nice amp!

Psilocybinator

Rockbert:

A) Thank you!!

B) Thank you again. I'll do just that.

American Viking

Form the caps? They're probably dried out by now. Be in better taste to just replace them as they need to be.

The dielectric compound within the capacitor doesn't have an infinite shelf life. Something that old may continue to work but when the compound (or dielectric paste if you will) is dried out the capacitor does not function like it should and can leak AC/DC voltage where it doesn't belong and hurt the vitals of the amplifier. It's and easy fix and it is proper maintenance of an amp that is that old. Forming caps is not going to correct any issues like that.

Peace out!

strat59

+1 Even collectors will accept pro done cap jobs. A safer altenative than having a Trannie go south. With the 20w heads you only have a couple of caps anyway so no big deal to do.

Attached Images

MAR%208970_CB.jpg (76.8 KB, 19 views)

Psilocybinator

Guys, thanks so much for your help and advice. The rehearsal studios that I use are going to take a look at it for me once I get a bulgin connector. I found some on e-bay, at long last. I can't believe that nobody has been able to tell me the name of the connector that I needed until now! Kudos to all of you.

Do you guys have any idea how much new caps would cost, approximately?

SmokeyDopey

You had this amp for a few years and haven't been able to use it!?
Such torture!

Interesting username, too.
Hope you get the cable soon and crank that thing!

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strat59

For a couple , no more than $20 , check the Values on the two caps, let us know and we will recommend some.

Rockbert

This sounds like a recipe for disaster if your rehearsal studio is anything like mine... Even a well meaning person might just plug it in to see if it works, which is fine except capacitors make a huge mess when they pop, and sometimes they take the power transformer with them. Take it to a qualified tech who will know what to do and can also replace the caps.

Psilocybinator

Yep, a few years man... frustrating to say the least!

Thanks, I will.

Well, to be more specific, the resident tech in the rehearsal will be who is looking at it I appreciate your concern though!

george76

theres a reason they stopped making those bulgin style connectors. its because they are dangerous!

be very careful when using it.

always plug the amp in first, then at the wall. not the other way around. and never have it plugged in at the wall with the other live end just dangling about.

qtws

Hi guys,
I have a JMP 20 PA too - mine has captive mains lead, no mains selector or fuse doofer, and inspection date of 1971. Back panel is printed for selector and fuse. Earlier serial no, too. Stored in attic for 20 years, switched on and still works - altho I got a Class 5 today and the JMP is getting a rest until I can get it serviced.
Bought from a mate for a "pound a watt" in 1990/91 although the mate ended up with my JCM800 mkII & no name 4x12 for which he still owes me the princely sum of ~£250 !!

My 2c - replace that bulgin, as they fall out of the back of the amp easily, spark like hell and are a royal PITA to find if you lose/forget it.

Cheers,

Q

clue

Can't wait for you to get that power cable, because that amp kicks butt. I have one, and it's kicked everything else plexi-like out of my amp arsenal. Load it with some NOS tubes if you can, at least a mullard in v1, and turn it up. The phase inverter is important too. It's basically the guts of the larger 50 and 100 watters of the day, but with EL84s, and you realize that EL84s in this circuit sound like EL34s.

I have a couple Class 5 heads. One is very heavily modded, both have had Mercury Magnetics upgrades. They come close but the PA20 is another world, all the nuance, all the overtones, and sounds huge through my 69 4x12 Marshall 100 cab. Couldn't be more of a spot on vintage tone.