MK II Super Lead 100

[EBE]

My son brought home a MK II Superlead 100 tonight that belongs to a friend of mine. It has problems, I am told. The board is a PCB with the solder joints all underneath the board. The board is labeled Marshall ST1 1ss 202. I am not sure how old this amp is but everything looks original. There a few broken connections, etc. This thing has 6 50x50 cap cans with one sitting under the PCB. Why would they put a cap can under the board? Does anyone know is the schematic for this amp is available somewhere?

Norm

[objectivedays]

http://www.schematicheaven.com/

You might be able to find the schematic on there. If it has a PCB, I belive that it has to be 1973 or newer. I think that Marshall switched to PCB midway through 1973. Good luck with the amp. Later...

Allen

[zaphod_phil]

There's a lot of Marshall amp model history and schematics on http://www.drtube.com/marshall.htm So you may be able to find out some more about that specific amp model.

[EBE]

Thanks Phil, I found it.

Would I be completely insance to pull the PCB and put an eyelet board in its place?

Norm

[guster00]

Hell no, Norm! I'd say go for it, if the owner is not looking to keep the amp completely original in its factory form. The eyelet board would probably be an improvement, at least as far as the construction (cap can under the board???!!!) and for ease of tweakage. My .02

John

[Plexi]

""There a few broken connections, etc. This thing has 6 50x50 cap cans with one sitting under the PCB. Why would they put a cap can under the board? Does anyone know is the schematic for this amp is available somewhere? ""


How old is the amp.. ?? What kind of tolex is on it..? has it got the bigger elephant hyde? what kind of switches..toggle or rockers?

the one cap under the board.. if you need to replace it..usually you don't need to remove the board..you can loosen the clamp, and they usually have enough extra wire to pull the cap out,and rewire the new one.

A Mk ll should have had or came with 6550s in it.. Really even the PCB ones aren't too hard to repair. I like to use shielded cable to the inputs,and to and from signal connections .. this takes alot of noise or oscilation problems out of the amp.
Most of these just need some good maintenence..clean sockets..check for those loose connections, clean pots and jacks.. and tighten them.
New tubes and rebias the amp.

Richie

[EBE]

This one has 6550s. My tube amp books give mods to run EL34s to make it sound like Marshalls are supposed to sound. Is this true/advisable? The cabinet is beat to heck, plastic corners. It looks like 2 of the input jacks were purposely disconnected and taped off. Also there is a pot/jack looking device on the right side of the front panel that has resistors on it that is NOT wired into the circuit. I have no idea what it is. Richie, if you have to work on the board what is the best way to get to it? I would assume it would probably need all the cap cans replaces. Bad assumpution for this model?

Norm

[Plexi]

"""Is this true/advisable""" Well it depends on who you ask..lol
I think Marshall should have EL34s..And i like them..But some like the 6550s..and they can make a very loud amp..
Plastic corners.. sounds like a later amp.

I've seen amps like your describing.. i asked once..what happened to the power cord?.. they replied.."well the dog like to chew on it"..LOL


Well if you want to remove it completly,you can draw a pic of where everything goes..
If you just want to lift one side,and look under it..or you can get to most of it by removing just a few connections,that are on the pot side of the board.. Down by the bias pot,there is a connection terminal,sticks up off the board.. those wires have to be removed.. think it has a couple wires.
Then once you start lifting,you'll see what others you have to take loose.

Richie

[goneracin]

Norm
I have a 50 watt '76 head that was pcb also. The easiest thing if you are working on the pcb is to unbolt all the pots and input jacks, and pull them through the holes, and stand the board straight up. That way, you can get to all the solder joints and do it cleanly. Ive seen alot of marshalls that someone modded just by clipping the parts off the top and leaving little "pegs" stickin up and soldering to them, but that looks like ass, very amatuer....lol. I replaced my pcb with a ptp turret board. Very nice, musch easier to work on too. I have a TON of full sized marshall info, just email me and I can send whatever schematics/layouts etc you want. And I like the sound of el34's better than the 6550's, but thats kind of a personal pref thing. The new "winged c" svets sound pretty damn good for a new, cheap tube. Check out http://www.lastwordsmusic.com/clay/marshall.html also, this has prettymuch any marshall info youmigh ever need, and Clay is a very good dude also.
Let me know if you want any layouts or schems, and I can email them to you.
Take care
Bob