Ed's small box 50 watter ?

[Tone Slinger]

Guy's, I cant find that pic of the back of Ed's tour rig (was it '78 Japan?). I remember that small box 50 watter was in that pic. Does anyone know what year that amp was. Didnt Strat78 say it had a standup PT ?

[Strat78]

There are two 50w heads, one looks like a plexi and the other looks like a U.S. import metal panel with polarity switch. I think the one we see in the Pasadena Civic pics is the U.S. import which if I'm not mistaken has all 50/50 filtering and the 2.7k at V1B. We need some 50w experts to pipe in. I have the pic but I have reached my quota here.

[wjamflan]

Is this the one?

[Tone Slinger]

Thats it, thanks Bill

Yep, its definately 2 smallboxes, just like Phil has said. One laydown PT ('68 ?) and one with the standup PT (no later than a late '71/early '72), it still has those little woven output tube retainers/'hats'. I wonder if a more specific date on those two tops could be rendered by this photo, I'm certainly no expert.

[Tazin]

My best guess is that the 50w plexi amp is a '68 and the other 50w is really late '70 or a '71.

[Strat78]

My best guess is that the 50w plexi amp is a '68 and the other 50w is really late '70 or a '71.

When did they switch to large boxes, in 72?
I hadn't noticed those tube retainers before! I'm curious about the filtering differences. It looks like the top amp has the original tall cans, pre-amp and screens filtering, but the mains looks like it was changed to something smaller than the 50/50uf. The top amp has the open bracket choke as well. I,m assuming the plexi 50w's had 32/32 pre, 32/32 for screens and PI and 32/32 mains. What other differences were there.

Also, I know some amps had the extra can on the inside, was that used for amps with tube rectifiers or did some 50w's have that cap so the PI and Screens had dedicated filters.

I imagine that the top amp looks allot like this one on eBay, except for the large box and the bulgin socket.
http://www.ebay.com/itm/Vintage-71-Mars ... 3f41a1e6d4

[Tazin]

My best guess is that the 50w plexi amp is a '68 and the other 50w is really late '70 or a '71.

When did they switch to large boxes, in 72?
I hadn't noticed those tube retainers before! I'm curious about the filtering differences. It looks like the top amp has the original tall cans, pre-amp and screens filtering, but the mains looks like it was changed to something smaller than the 50/50uf. The top amp has the open bracket choke as well. I,m assuming the plexi 50w's had 32/32 pre, 32/32 for screens and PI and 32/32 mains. What other differences were there.

Also, I know some amps had the extra can on the inside, was that used for amps with tube rectifiers or did some 50w's have that cap so the PI and Screens had dedicated filters.

I imagine that the top amp looks allot like this one on eBay, except for the large box and the bulgin socket.
http://www.ebay.com/itm/Vintage-71-Mars ... 3f41a1e6d4

Marshall started phasing in the large boxes for the 50w around '72.

As for the 50w plexi amp....The mains & screens/PI filter caps are 32uF+16uF cans and the pre-amp internal filter cap would have been a 32uF+32uF. As for the circuit type; I'd guess a "Bass".

The other 50w has a 50uF for the mains filtering, and a 50uF+50uF for the screens/PI. The pre-amp filter can is a 50uF+50uF. The circuit type is a "LEAD" as denoted by the dymo tag next to the serial number. This circuit would have a 2K7/0.68uF arrangement for V1b, and a 1K/0.68uF setup for V2a. The nfb resistor was still 47K at this time.

Around 1969 Marshall changed there componet layout on the tag/turrent boards and as a result of this the pre-amp filter can was relocated over near the mains filter can (internally). This is the same postion where earlier 50w amps; sporting a tube rectifier; had the filter cap for the screens/PI.

[Tone Slinger]

Cool, thanks for the info !

[Tazin]

Here's some additional info about the stack of Marshall heads that maybe of interest. It appears that Ed picked up five out of the nine amps shown in the picture upon his arrival in Europe during the '78 tour to combat the ac input voltage issues. The four '78 Super Leads have a Norwegian sticker so they were probably procured in the Netherlands. The 50w plexi may have been acquired around the same time or shortly after (perhaps in England) as a substitute for his other 50w amp.

[Strat78]

Thanks Tazin, your knowledge and help is always appreciated greatly! Hmm, 47k nfb, what was being tapped? My 1973 PCB 50w has the 100nfb/4ohm tap from the factory.
Looking at that pic and another pic showing the front of the stack, it tooks like four of the amps have the polarity switch: the wooden amp, the 12301, the 100w (second one from the floor on right of pic) and the 50w on top. These heads were Ed's original amps. I think the 50w plexi goes way back too. I'll bet the head that is bottom right has that Norwegian sticker as well. The 50w amp on top is the same amp that was daisy chained with the 12301 in the Passadena Civic pics from Fall 77 (right after the first album was recorded). You can see the same tares in the tolex, though the marshall logo was removed later. Bill, do you have the pic showing the front of those stacks and also the Pasadena pics? This thread is shaping up to be a keeper!

[Tone Slinger]

Cool, so the small box metal panel was the one he used some in the '77 club gigs and the small box plexi came later (European tour) ?

[jnew]

Two variac's. Probably one for each of two amps being used as pre-amps's for this setup. A main and a backup. Then each of those having its own support of power amps. Damn, that's a lot of gear. Those roadie's sure earned their pay.

[Strat78]

I think there might be a pic from another gig from around late 77 that shows the plexi 50w. Got to get all these pics into the thread. No Norwegian sticker on the 50w plexi, though by then it was a vintage amp

[Strat78]

Two variac's. Probably one for each of two amps being used as pre-amps's for this setup. A main and a backup. Then each of those having its own support of power amps. Damn, that's a lot of gear. Those roadie's sure earned their pay.

Was there slaving going on when that pic was taken?
Also, from the Pasadena pics you can see that only one variac is present. I would conclude that it was for shaping the tone with the 100w head, all squishy and hairy then daisy chained into the 50w to bring backs some solidity to the mix. The above pic has two of these setups hence two variacs?

[Tazin]

Thanks Tazin, your knowledge and help is always appreciated greatly! Hmm, 47k nfb, what was being tapped? My 1973 PCB 50w has the 100nfb/4ohm tap from the factory.
Looking at that pic and another pic showing the front of the stack, it tooks like four of the amps have the polarity switch: the wooden amp, the 12301, the 100w (second one from the floor on right of pic) and the 50w on top. These heads were Ed's original amps. I think the 50w plexi goes way back too. I'll bet the head that is bottom right has that Norwegian sticker as well. The 50w amp on top is the same amp that was daisy chained with the 12301 in the Passadena Civic pics from Fall 77 (right after the first album was recorded). You can see the same tares in the tolex, though the marshall logo was removed later. Bill, do you have the pic showing the front of those stacks and also the Pasadena pics? This thread is shaping up to be a keeper!

If the 50w is from very late '70 or perhaps the first quarter of '71 then 47K nfb resistor should be fed from the speaker jacks. If slighty later in '71 then 47K nfb resistor would have been fed from the 4 ohm tap on the selector.