'67 Super PA pics - repair in progress, update - more pics

[neikeel]

This has shorted on the third output valve base (heaters to screen resistor). That screen resistor is now open circuit, shortly to find out if more serious damage done. The fuses are ok and sent to me with no output






Everything else on static testing is ok. Will replace the resistor, remove the output valves and fire it up and go through usual drill to see what gives.
Once it is working owner wants the AFD mod and as it has already been modded I do not have a problem with that. I have some period bits for it (see board and socket etc). Will use PD Burnetts version (except for 1000pF on mixer and will use another filter node for added gain stage
I was hoping to use a stock front plexi panel but the spacing is off on the switches . Will still look better with repro panel. Don't want to drill the chassis. A custom panel might work - unless anyone out there has a plexi PA front panel looking for a home?

Oh and edit - you can see my own AFD Trem chassis and box in the background - need a bit of free time

[Roe]

keep us updated! perhaps it would be a good idea to check whether the choke has survived?
a sound report with black flag specs would be great. does it have the 1202-119 or the 1202-132 by the way?

[D-Max]

Cool, another 8 can dual rectifier Super PA.
A single 8.2K for the PI filtering.

Is the original plexi backpanel still there? What's the serial number?

[neikeel]

Cool, another 8 can dual rectifier Super PA.
A single 8.2K for the PI filtering.

Is the original plexi backpanel still there? What's the serial number?

Yes, the original rear panel is still intact, IIRC around the 20000 mark but will report back tonight.

Hope all iron has survived.

It has a -119 OTwith 8, 16 and 100v out.

[yngwie308]

What's your plate voltage?
Great to see the dual rectifier there and those original caps!
This looks to be an awesome amp and seeing the standup filter caps is cool!
yngwie308

[sniperschool]

I feel the need to confess/point out that this amp worked flawlessly for me for 10 years
It was left in a barn outside Tokyo and was iced over for nearly 2 months
Also once left on by mistake for 3 weeks non stop with no speaker connected outside las vegas in 100 degree heat
And has been dropped from lorries and stages so many times
And travelled around the world countless times without a flightcase
These are just some of the horrors that I feel compelled to admit I put it through
It never once blew a fuse or valve in that time
And up until I broke it a few months ago (by just fiddling around inside I might add!) it still had mullards in it that must of been there for 25+ years
It sounded lovely
I feel thoroughly ashamed that I could kill such a strong amp!

[yngwie308]

Don't worry it's impossible to kill a Marshall completely and it will be born again..
yngwie308

[neikeel]

I am sure that it will live again.

I have added swamps to each output valve (1/2watt 4k7 Pihers), had to replace the screen resistor ( I only have Welwyns - anyone got a spare RS to match?) and redo the screen wiring.

The reason it blew was the brown wires you see used as screen wires were tacked onto the lugs and the blob of solder a mm or so from the heater lug , so Sean you are forgiven

I have replaced the wires on V1 with screened stuff and added back the extra preamp valve and made a small perforated paxolin board with a dedicated filter can (only 8uF/500v) 100k plate resistor, 470k divider with 820pF bypass cap, 10k on cathode and RS 0.022uF. (See SIR thread). Luckily I have spare Pihers (although no Iskras) in these values.

Then I ran out of solder

But as I have a half stack to ship out and a lecture/seminar to prepare tonight it is probably just as well. Rest of the house has been struck down by gastric flu which is knocking people down like flies at the moment..............who next?

I confess that the elephant covering was not stuck on very well and underneath it is almost (apart from one edge and corner) pristine fine levant on an intact narrow top vent cab.

What it really needs now is a custom plexi front panel and custom headbox front panel (like the one that you see in the pic above - Mojo made it to trem size - $69), question is has it earned it Sean

[lifer]

wow- pretty!

do the PA's sound much different from a lead?

[sniperschool]

Wow
So the person that wanted it to look like a JCM 800 (no nanes mentioned) at least left me with the original box
How kind of them!
The plexi panel sounds great but I will check the store room tomorrow as there were a few bits that came with it when I purchased the amp including a plexi looking panel that i never paid attention to but could be the original
If it's not then just let me know how to order the US panel you mentioned
It would be wrong for you to have done all of this and then for me to leave it unfinished
Sorry to hear about the house being struck down
Hope the solder fumes protected you

[neikeel]

So far so good. Need to get solder but too much work to get done before band rehearsal tonight

Have leads on panels at the moment. May only need to get the custom cutout headcase front panel but can only do that when the size of the plexi panel is known - it will need to be slightly off set as the switches need to be accessed but the spare PA jacks need to be covered.

What band were you taking this thing around the world with?

[sniperschool]

Very cool
Just keep me posted as to what I need to do (if anything)
The head travelled around with my band and then a few bands on my old label that I would tag along with
It was mainly used for recording and that's where it ended up being stuck in some crazy places
I will look for that panel this afternoon

[sniperschool]

I looked and looked but still haven't found the front panel that I think is around here somewhere
So i guess I should go for the US one you mentioned
Found this though
Does it look like it would be the original back for the amp?

[neikeel]

That looks like the rear panel, wonder what is underneath.

I am afraid all the other elephant levant fell off in my hands Underneath is black-on-green levant in very good condition (the drill holes for the 80's corners hardly show and it has vintage patina.

The front panel is the original allthough the narrow wings of the cutout had been cut off and wider ones of a standard 100watter had been glued on. Will probably be able to make new ones the right size once we have the plexipanel, but newer Marshall levant (all I have) is black on black and looks ok unless you look very closely.

Lots of solder in stock again - just need time to test it as it was before adding the switchable extra stage.......

[neikeel]

Some pics:
First tidied up head cab, under the elephant was this-


Here is the rewired screens, afraid best old yellow wire match I had, also added swamps on each output valve grid-


New board in pre-amp as a switchable extra gain stage. Amp was already modded to 2203 preamp using those little polyester caps etc so no guilt. I used some NOS bits for that vintage vibe



See SIR thread for schematic, like 6burgh's but with extra filter and 190k swamp. I have space to put a pot in (funnily enough an old RS 1meg to match the rest but will give it a whirl first

Sparky (AKA Rich M) is making up a front panel similar to this but with the toggle holes undrilled so that I can fit it without drilling the chassis. We will accept the lettering being off for now


New front panel fitted.

Ideally would like a piece of black on green levant for it but I have not even tried looking for rocking horse manure.
Will tart up the wiring when tested, up and running