SV20H Components

dax_the_ax

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I’m looking for the V2 cathode .68 and also the .0022 in this board. Anyone have the locations or a darn schematic?? Thanks
I need a pro voltmeter I think.

Dax
 

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dax_the_ax

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Well I figured it out and it’s kinda strange. The V1 .0022 Coupling Cap I’m looking for is a .0033!!! I always put a .022 in my builds here (Albeit I’ve only done 3) that’s why I’m here. I’m a Marshall nut, but not a master at Amplifier Circuits. This thing is mounted balls to the wall flush to the board!! Any advice on getting it out while leaving the board in?

Thanks
 

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mad5066

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I think you'll definitely have to take the board out to remove that cap correctly. No way around it.
 

Pete Farrington

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If the pcb is through hole plated, and you’ve got a good iron and skills, you could carefully destroy the current cap with a pair of snips.
Obviously, don’t cut off the top side of the legs; need to tweezer them out whilst being desoldered.
 
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Moony

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Yes the components are through hole and you could apply solder from the backside of the pcb.
I wouldn't recommend to snip bigger polyester caps as they could be really sturdy inside and if you put too much pressure on it you might damage a trace of the pcb (though those green pcbs Marshall uses these days are well built and you can work on them without any problems).
When I modded JVMs I always put the pcbs out of the amps. And I don't see, what's the problem with it. Take some photos before you do that and/or mark the several wires you have to disconnect so you know their location.
 

dax_the_ax

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Boy, if I just had a Schematic, I’d connect my .022 to each leg destination. Leave the .0033 in there. .025 is no big deal. I shined a light underneath, just can’t see where each leg of the .0033 goes. Somebody out there maybe know?? I’d be fired up to figure that out.
 

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johan.b

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The sv20 is based on the 1959SLP which was based on a particular example of the 1959 from the sixties. Google the 1959slp schematic and you should find the components. The numbers on the board don't match but the circuit does. The loop and other amp is different though. It's not a hard circuit to trace
J
 

Gene Ballzz

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@dax_the_ax
I've worked on cars, machinery, wood, guitars and electronics for the majority of my 67 years! It has been my experience that most attempts to avoid "should do it this right way" procedures, in the interest of saving time and/or labor, invariably lead to added labor, time and operations to cure problems caused by trying to cut those corners! In other words: "Pull the circuit board and do the job right, or don't do it at all!"

Trust Me On This One!
Gene
 
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mad5066

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Like I said before you probably won't be able to get that cap out without removing the board. The caps body sits flush to the board so the leads can't be snipped in this case. There's not a lot of room to get an iron under there without probably hitting other things.
 

dax_the_ax

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May try this once I ring out the Component starts and destinations. Non destructive, not too invasive and removable
 

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j_flanders

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I’m looking for the V2 cathode .68

 
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dax_the_ax

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Well I listened. I raised the board properly and replaced the .0033 with a .022 Sozo. And…. I don’t dig it. It got a little more thick, but also became a little more loose, flubby. I guess Marshall kinda knows what they are doing. I think I’m going back to .0033. I like tight!! I mean other resistors are different from a Superlead also, like the 470k’s. They are not there!! I guess it all works together.
 

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dax_the_ax

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Mine sounds killer with no jumpers! Straight in to Treble channel. It does have the Hot Mod V2. Really really great. I don’t even know why I’m messing with it. It’s in a 100 watt big box.
 

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junk notes

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The sv20 is based on the 1959SLP which was based on a particular example of the 1959 from the sixties.
Marshall's description does reference the iconic 1959SLP, but a JMP® 1959SLP MK II others wondering and trying to figure out if that mean mid 70s.
Google the 1959slp schematic and you should find the components.
Was the cap an .0033 or .0022?
 

junk notes

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Well I listened. I raised the board properly and replaced the .0033 with a .022 Sozo. And…. I don’t dig it. It got a little more thick, but also became a little more loose, flubby. I guess Marshall kinda knows what they are doing. I think I’m going back to .0033. I like tight!! I mean other resistors are different from a Superlead also, like the 470k’s. They are not there!! I guess it all works together.
Going from a .0033 to a .022 will have a greater affect than that of a .0022 in a Superlead :2c:

What year is your head?
 

johan.b

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Marshall's description does reference the iconic 1959SLP, but a JMP® 1959SLP MK II others wondering and trying to figure out if that mean mid 70s.

Was the cap an .0033 or .0022?
 

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junk notes

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cool thanks @johan.b!
okay, another question, the early Superleads schems had the .0022 there. What year does that schem represent? (SV20 is a MKII) IOW when did Marshall change from .0022 to .0033?
 

johan.b

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Again, the 1959SLP was based on a particular example in the marshall collection that Jim thought sounded the best. The .0033 value probably just represent a drifted or out of tolerance component in that particular amp
 

junk notes

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Again, the 1959SLP was based on a particular example in the marshall collection that Jim thought sounded the best.
Yes of course, as mentioned on Marshall website, but we all are trying to find out the year, and if the schematic is representing the MKII?
 

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