'74 Marshall Super Lead Circuit

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silverwulf
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'74 Marshall Super Lead Circuit

Post by silverwulf » Mon Sep 30, 2019 12:42 pm

Hi all,

Long time observer here (going on 10 years now?), don't think I've ever posted. Folks here are a wealth of knowledge, so I wanted to see if anyone could give some insight here. I picked up a '74 Super Lead that currently has US made Tung Sol 6550s. I'm sure it will need the typical maintenance when it gets here later this week, but I wanted to get any input as whether the circuit looks stock, anything unique to note, concerns I should be aware of, etc?

https://imgur.com/a/ascPfs1

Thanks all :toast:

danman
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Re: '74 Marshall Super Lead Circuit

Post by danman » Mon Sep 30, 2019 6:33 pm

Everything on the inside looks original. There is one resistor on the right end of the board next to the diodes that looks discolored. May be age or may be a replacement. I can not see the cap cans on top to tell if they are originals or not. If they are, it would be a wise choice to replace them with fresh caps to prevent any future transformer damage and to be sure that the amp sounds it best. Very nice amp overall!

silverwulf
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Re: '74 Marshall Super Lead Circuit

Post by silverwulf » Mon Sep 30, 2019 7:06 pm

Thanks! Yeah, the filter caps are original Daly's. I believe the Tung Sol 6550 date codes are from '74, so I suppose it's a possibility they could be original as well. "Rosemary" signed (if it matters) and from around March '74.

Curious to fire it up and see how it goes when it arrives!

awangotango
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Re: '74 Marshall Super Lead Circuit

Post by awangotango » Sat Nov 23, 2019 9:17 pm

looks all original with stock tubes. dpdending on usage they may still be good. look for white dust buildup on top of plates and/or darkening of the silver top gettering.....a few things you may want to swap or mod.....the 10uf bias caps often need swapping at this point since leaky caps here can lead o runaway bias and may ruin your tubes.....and since they dont affect tone, its something to do.....i'd clip the legs high up leaving the original legs soldered to board and just solder on new caps to those rather than taking up board and desoldering the full caps......over at V1 i'd get rid of the 220/330uf blue cap and swap with a 2nd .68 (unless you play strats and like that gigantic cap)......You can also swap out a resistor and change to el34's if the 6550's are too loud or harsh.....6550's rock but only at high volumes and if they are NOS..modern 6550's are pretty cold ime.....the classic- riot 'fire down under' is a prime example of cranking 6550's. as well as early Kiss possibly.....i'd swap to electro harmonix el34's though...if the original large filter cans are looking good -the y look fine on bottomm check top for bulging- , i'd leave them. but maybe disconnect the jumper on the screen caps to half their used value/use half of each can rather than both sides as it is stock with the jumper on the two +can terminals....this will soften the feel of the amp and make it less stiff.......the presence is the resistor/.68 instead of more common .1uf with no resistor....the '74 .68 setp gives more mid growl which helps fill out the cleaner 6550 but it can sound a bit woofy or odd depending on the pickup and speakers you use.....if so,id swap it out for standard .1uf cap there so that it doesnt dip down into the mids and just alters the top end .......i'd leave the volume bright cap and everything else......the '74 is a sweet amp. they tend to have good trannys and reasonable plate voltages (450 to 500)......the feedback is likely 100k to 4 ohm tap which is not much. can be mushy. again this was done likely to help give soem distortion to the 6550......you may wan to tighten that up with a 56k on 8 ohm tap or something similar.....and then you have the option of a piggy backed .68uf on v2a to give some more upper end gain rather than the full power amp gain given by the low feedback on the stock setup......otherwise you shouldnt have to do much to tune that amp and get it sounding sweet.....nice amp ! y&t dave menniketti recorded their first 6-8 classics with that amp....

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