Full stack, anyone?

playloud

Well-Known Member
Joined
Dec 28, 2020
Messages
636
Reaction score
725
Utterly impractical for those of us who don't have dates at Wembley Stadium in the calendar, but I'd be lying if I said I wasn't tempted... And hey, only 50W!
https://reverb.com/item/54183963-marshall-jmp-1987-50w-lead-full-stack-1969

Couple of interesting things about the head. I haven't seen those silver 22nF coupling caps before, and the mustards that are there appear to be different varieties (horizontal/vertical text). Also blue/brown heater wire and strange pots. Are these possibly original, or is there something awry?
 
Last edited:

neikeel

Well-Known Member
Joined
Feb 12, 2014
Messages
7,102
Reaction score
6,535
Yes interesting. Originally sold in in Watford (England).
The blue/brown heater wire is original
The plastic pots are also original but the Plessey (RS) treble pot is not
The big silver coupling caps are not original (hope they are not 220nF as that PI will be horrible!)
Yes it is odd to see the different 0.022uF (22nF) couplers to the (presumably 0.0022uF (2n2uF) they all look very shiny and new.
This is alos intersting in the context of corrosion on the board mounting screws and the transformer nylocs and screw threads
Presence cap is not original (that era it would be grey like the PI feed 0.1uF cap)
Treble cap in the tone stack is a replacement
Points to note for any buyer are that the bias feed as it is is set up so that bias and HT hit the output valves simultaneously and is associated with premature mains failure. That white wire to the bias feed needs to come off one of the hot ac (red wire feeds direct from the PT lug on the standby switch.
The 16uF bias caps were also an unusual feature around this period.
It has probably sat around hardly used, no signs of hard use or it getting really hot.
If AMS were here he would be on his high horse about the lack of screen resistors which were absent on the first 50w Marshalls from 67 to about 71 when the 1k 3w Welwyns were introduced and wired in series between pin 6 to pin 4. If you have plenty of old Mullards you can stay as you are but if CP EL34 are to be used the subtle mod is a good idea.
Before filter caps get automaticlly junked - inspect and test first (IMO) but in this case if it has stood around unused they will probably fail the leakage and ESR tests anyway.

Cabs definitely been played around with (see mixture of hex and T nuts on the handles, odd wiring and cut about levantt

I have no idea if the value in the US is good/bad or indiffernent but if in UK quite expensive even if all those T1281s are original cones and in perfect working order.
 

Seanxk

Well-Known Member
Joined
May 14, 2018
Messages
957
Reaction score
880
A really interesting and confusing period this for me.
Stand up P/T and all filter caps up top, is that more 71?
The brown Hunts cap did this disappear with this new P/T and rectifier set up?.
I'm thinking is it more 1970 than 69.
 

neikeel

Well-Known Member
Joined
Feb 12, 2014
Messages
7,102
Reaction score
6,535
ry2wi00hhbk0lhnqoipw.jpg

Could be late 69 to 1970 as the A was used from the first metal panels in Summer 69on
Maybe @TAZIN can date it more accurately but the later choke is more 70 I agree.
Old one of mine from similar era:
https://www.marshallforum.com/threads/69-plexi-gut-shots.108521/
 

TAZIN

Well-Known Member
Joined
Mar 18, 2013
Messages
718
Reaction score
427
The amp looks to be from the end of September through the beginning of October 1970. Those big silver colored caps I haven't seen before so they may not be original...Usually around this time frame Marshall used WIMA caps as substitutes (normally the 0.1uF value) for the Mullards. The Mullard 22000pF are original and I see that style in amps within the 7000 range.

EDIT: accidently had 0.01uF when it should have been 0.1uF.
 
Last edited:

Ned B

Well-Known Member
Joined
Nov 19, 2012
Messages
344
Reaction score
420
I can help a little here. '69 ended at around 4100A. This one should be from around March 1970.

It doesn't seem like this would have originally been a "born together" stack though the bottoms may have been a pair from the beginning. I didn't see enough to date the speakers to confirm.
 

Seanxk

Well-Known Member
Joined
May 14, 2018
Messages
957
Reaction score
880
The other confusing thing around the 69 era was the S/ xxxxA and this one too being S/A xxxxA but as we agree now not a 69.
 

Matthews Guitars

Well-Known Member
Joined
Aug 17, 2019
Messages
6,147
Reaction score
9,745
1651413113175.png


Those Daly capacitors are not going to last much longer. Note that the two next to the transformer have had their labels shrunk back to the point that the black insulator discs have been released and appear to be glued in place. The third one also shows a lot of shrinkage. And is the insulator disc missing, or just a different color than the usual black?

If those tubes are original to the amp, that implies the amp has not been run much. Which is the kind of usage pattern that does NOT extend capacitor life.

Overall it's a nice package but is it worth 10K? I have my doubts. I'd like to see the top cabinet at least properly recovered. I think the "stripped and varnished" look is honestly pretty mediocre. Recover it. Make it at least look right from a distance.
 

TAZIN

Well-Known Member
Joined
Mar 18, 2013
Messages
718
Reaction score
427
The other confusing thing around the 69 era was the S/ xxxxA and this one too being S/A xxxxA but as we agree now not a 69.
The 'S/ xxxxA' serial number setup was available for the first 2,900 amps. But, the 'S/A xxxxA' serial number setup was also being used at the same time starting around S/A2000A. So it is possible to see two amps with the same serial number but differing a prefix (e.g. S/ 2212A & S/A 2212A).
 

TAZIN

Well-Known Member
Joined
Mar 18, 2013
Messages
718
Reaction score
427
The metal panel Tremolo 50s had a T / A prefix right from the start.
Yes, this anomaly appears isolated to just the 50w Lead (1987), Bass (1986), and perhaps the Organ (1989) models.
 

proxy

Well-Known Member
Joined
Sep 2, 2010
Messages
825
Reaction score
471
Utterly impractical for those of us who don't have dates at Wembley Stadium in the calendar, but I'd be lying if I said I wasn't tempted... And hey, only 50W!
https://reverb.com/item/54183963-marshall-jmp-1987-50w-lead-full-stack-1969

Couple of interesting things about the head. I haven't seen those silver 220nF coupling caps before, and the mustards that are there appear to be different varieties (horizontal/vertical text). Also blue/brown heater wire and strange pots. Are these possibly original, or is there something awry?

Utterly impractical for those of us who don't have dates at Wembley Stadium in the calendar, but I'd be lying if I said I wasn't tempted... And hey, only 50W!
https://reverb.com/item/54183963-marshall-jmp-1987-50w-lead-full-stack-1969

Couple of interesting things about the head. I haven't seen those silver 220nF coupling caps before, and the mustards that are there appear to be different varieties (horizontal/vertical text). Also blue/brown heater wire and strange pots. Are these possibly original, or is there something awry?
IMG_20210306_110416.jpg
 

playloud

Well-Known Member
Joined
Dec 28, 2020
Messages
636
Reaction score
725
Yes interesting. Originally sold in in Watford (England).
The blue/brown heater wire is original
The plastic pots are also original but the Plessey (RS) treble pot is not
The big silver coupling caps are not original (hope they are not 220nF as that PI will be horrible!)
Yes it is odd to see the different 0.022uF (22nF) couplers to the (presumably 0.0022uF (2n2uF) they all look very shiny and new.
This is alos intersting in the context of corrosion on the board mounting screws and the transformer nylocs and screw threads
Presence cap is not original (that era it would be grey like the PI feed 0.1uF cap)
Treble cap in the tone stack is a replacement
Points to note for any buyer are that the bias feed as it is is set up so that bias and HT hit the output valves simultaneously and is associated with premature mains failure. That white wire to the bias feed needs to come off one of the hot ac (red wire feeds direct from the PT lug on the standby switch.
The 16uF bias caps were also an unusual feature around this period.
It has probably sat around hardly used, no signs of hard use or it getting really hot.
If AMS were here he would be on his high horse about the lack of screen resistors which were absent on the first 50w Marshalls from 67 to about 71 when the 1k 3w Welwyns were introduced and wired in series between pin 6 to pin 4. If you have plenty of old Mullards you can stay as you are but if CP EL34 are to be used the subtle mod is a good idea.
Before filter caps get automaticlly junked - inspect and test first (IMO) but in this case if it has stood around unused they will probably fail the leakage and ESR tests anyway.

Cabs definitely been played around with (see mixture of hex and T nuts on the handles, odd wiring and cut about levantt

I have no idea if the value in the US is good/bad or indiffernent but if in UK quite expensive even if all those T1281s are original cones and in perfect working order.

Great info, as always. How do you know it was originally sold in Watford?
 

Ned B

Well-Known Member
Joined
Nov 19, 2012
Messages
344
Reaction score
420
The amp looks to be from the end of September through the beginning of October 1970. Those big silver colored caps I haven't seen before so they may not be original...Usually around this time frame Marshall used WIMA caps as substitutes (normally the 0.1uF value) for the Mullards. The Mullard 22000pF are original and I see that style in amps within the 7000 range.

EDIT: accidently had 0.01uF when it should have been 0.1uF.
I just realized I misread the serial number as 5229A instead of 8229A which puts it in TAZIN's date range during the short period amps were inspected by the seemingly very "pretentious" ;) Claude Venet.
 

playloud

Well-Known Member
Joined
Dec 28, 2020
Messages
636
Reaction score
725
Claude Venet is the dealer stamp. It was a music shop in Watford in early 70s.

Another mystery solved! I remember the idle speculation about Mr. Venet a few months ago. You wouldn't happen to know if he was the arrogant Frenchy this very forum had him pinned as, would you?
 

Ned B

Well-Known Member
Joined
Nov 19, 2012
Messages
344
Reaction score
420
His stamp includes the title of electrical engineer. I have had US export amps with his stamp.
 

Latest posts



Top