1969 Marshall Red 50 watt Plexi

[khingpynn]

Hi guys and gals.
I recently purchased a 1969 Marshall JMP 50 watt Plexi with Red tolex. It is a low serial number for 69 and has actual plexiglass face plates.
Overal condition is good and it's about 98% original.

I purchased the amp at Long and McQuade south Calgary. A local guy ( drummer ) inherited many things from his Uncle ( guitarist ) and he found the amp in his bedroom closet. On the advice of a friend he brought it to
L&M to sell it. I showed up 2 hours later and as they say "timing is everything".

I know this forum is a great resource for all things Marshall and would like to open up a discussion about this and other amps like it.

What I would like to discuss most is, authenticity, current market value, how rare is it, where to buy parts for maintenance/repair, the pros and cons of screen grid resisters, significant players who used 50 watt plexis, significant recordings using 50 watt plexis, and other interesting stuff about plexis.

Cheers to all.
Craig

Photos








http://i164.photobucket.com/albums/u8/khingpynn/Plexifront.jpg

http://i164.photobucket.com/albums/u8/khingpynn/plexiserialnumber.jpg

http://i164.photobucket.com/albums/u8/khingpynn/plexiserialnumber.jpg

 

[george76]

Looks like a re-cover to me, but happy to be proved wrong...

 

[danman]

Great find! I'm not sure that I have ever seen one of that year with the red tolex...very interesting! Has it been played regularly over the years? If not then you may want to look into freshening up the filter caps just to be safe. Playing the amp regularly helps keep them healthy but if the amp has sat unused for years they tend to dry out. Definitely a good idea to add some screen resistors especially if you will be running current production power tubes. It would be a shame to have a failed tube ruin the trannys in such a nice amp!

 

[Joshabr1]

Looks like a re-cover to me, but happy to be proved wrong...

Same thing I thought. Funny the way the pre amp filter is in there. Board does look original. The stuff that matters anyway. I see some snubbers replaced. Wiring looks a little ratty to me. Are the transformers original? For sure would add some resistors 1k 5 watt?? Over those power tubes. See some funny business around the mains transformer replaced diodes? Re wiring? Just looks sloppy on the inside for that time period to me. Not saying at all its not mostly all there it seems to be. Pics of transformers?

 

[soundboy57]

Looks great, but recovered. The gold piping and string aren't "gold" enough like the original stuff, and the red tolex is too bright, and the texture looks more modern, as well.
Only saying this in case you paid a premium due to the red tolex.

I hope I am wrong, too
Still, a beautiful rare amp in great condition, great score!

 

[Joshabr1]

Edit. Good eye sound boy. For sure recover.

 

[yladrd61]

Same thing I thought. Funny the way the pre amp filter is in there. Board does look original. The stuff that matters anyway. I see some snubbers replaced. Wiring looks a little ratty to me. Are the transformers original? For sure would add some resistors 470ohm 5 watt?? Over those power tubes. See some funny business around the mains transformer replaced diodes? Re wiring? Just looks sloppy on the inside for that time period to me. Not saying at all its not mostly all there it seems to be. Pics of transformers?

Wouldn't you want 1K 5 Watt resistors with EL34s ?

 

[Joshabr1]

Wouldn't you want 1K 5 Watt resistors with EL34s ?

Edited.

 

[m1989jmp]

I see there's an unused hole with a grommet in it next to that can cap to the right? Some of the pot wiring looks unusually sloppy for Marshall, but pots look stock. Also, someone messed with the speaker output ground reference, but that's a minor issue if done properly.
I see the output sockets are bolted to the chassis, can someone elaborate why some have riveted sockets?
Post some more chassis pics if you have em (transformers, filter caps, etc.)
By the way, is that a custom shop Jackson you've got? Looks like a killer guitar...

 

[TAZIN]

The amp is not in that bad of shape considering its age....It looks to be from around April of '69, and of coarse is a Canadian export model. The main tag board looks untouched with the exception of the replaced bias filter caps. The other additional little tag board has had the H.T. fuse re-located to the rear panel and the snubber caps have been replaced.
Other replaced parts include:
The mains fuse holder.
Power cord.
Both switches.
Indicator lamp.
Filter caps.

The good news is that the transformers appear to be original....Bad news is that it looks like someone drilled at least one additional hole on the top of the chassis.

 

[Joshabr1]

I only see 3 pics

 

[khingpynn]

Hi Guys/Gals

Thanx for all the replies. I'll take some more photos of the top of the chassis. It does not look like a re-tolex to me but that said I will take more photos of the inside of the box and see what you guys think.
I see some changes to the wiring and the added fuse holder. Tranformers look original but there again more eyes the better.
I'll post some photos this weekend sometime. I'm hitting the road for out of town gigs this weekend.

Happy Playin
Craig

 

[ampmadscientist]

You need to add the screen grid resistors.
The amp will draw too much current without them.

 

[sct13]

The amp is not in that bad of shape considering its age....It looks to be from around April of '69, and of coarse is a Canadian export model. The main tag board looks untouched with the exception of the replaced bias filter caps. The other additional little tag board has had the H.T. fuse re-located to the rear panel and the snubber caps have been replaced.
Other replaced parts include:
The mains fuse holder.
Power cord.
Both switches.
Indicator lamp.
Filter caps.

The good news is that the transformers appear to be original....Bad news is that it looks like someone drilled at least one additional hole on the top of the chassis.

Agreed, I have one that is very similar

 

[ampmadscientist]

Wouldn't you want 1K 5 Watt resistors with EL34s ?

Yes 1K 5W for EL34.
470 ohm is for KT66.

 

[shredless]

So the big question is....

how much did you pay for it?

 

[khingpynn]

The bigger question is what should I have paid?

I know as little as possible but what is fair market value?

I sent pictures to two reputable Gents who own several and have worked on several Plexi's and both said I was lucky to have a red one as it was the rarest of custom colors.

It does not look re-tolexed as I can see no indication of it... no glue lines or unusual cut lines. The color in the photos here is brighter than it looks and effected by ambient light. I'm also lucky enough to have one of the best teks in western Canada to have gone through it and give it a good going over. He replaced the two bias caps. The power and standby switches are original. On the standby switch the nut was missing so a hexagonal nut has been installed there. The High Tension fuse was moved and yes a hole was drilled in the chassis and a different fuse holder that the original was used. I'm thinking this modification will not drop the value significantly.

Had a busy weekend with out of town gigs... lots of fun had which is always good. More photos to come.

Cheers
Craig

 

[stratburst]

Looks like a re-cover to me, but happy to be proved wrong...

Hard to tell without more pics in and out. It could also be a '71 or '72 box that was swapped out. Regardless, it looks great!

 

[Appetite4distortion]

Hard to tell without more pics in and out. It could also be a '71 or '72 box that was swapped out. Regardless, it looks great!

The box should be original plexi era seeing flat lip under controls. A Post 69 should have round lip.
I believe too it's a recover (possibly old one) due to minor flaws here and there.

 

[stratburst]

The box should be original plexi era seeing flat lip under controls. A Post 69 should have round lip.
I believe too it's a recover (possibly old one) due to minor flaws here and there.

Your'e right, I spaced on the lip. Good call.