69 Superlead Build Diary

[harkkam08]

Hey guys just before George Shut the store down I bought one of the last kits so here is my build diary hoping to get some reviews, tips and comments on whats good and what could use some improvement.

I am putting in
Piher/Iskra Resistors
NOS Mustards/ Hunts Erie and Lemco

Mullard Reissues in all preamp tubes

Some vintage cloth covered solid wire
Metal Panels

Its a hybrid monster here are some pics

[harkkam08]

more pics

[harkkam08]

Hey guys is it okay to use 1/2 watt resistors for the filters?

[FourT6and2]

What's with the 10 watters on the power tubes? Those are huge. Everything looks ok so far, I'd twist the OT secondaries and the way you have the OT primaries routed (to the front of the chassis and then back to the sockets) may cause some noise issues with the pots and presence circuit. But, I'm not sure.

The resistors you've used on the filtering cans are a waste, in my opinion. Just some metal-film will work fine. I used something like 200-300k here to reduce ghosting. But it's up to you. And I'd use something higher than 1/2 watt.

As a reference, you can check out all my build photos here: http://haftelm.deviantart.com/gallery/?catpath=scraps" onclick="window.open(this.href);return false;

[harkkam08]

Hm.. thanks.

The 1/2 watt filter resistors isnt that the rating marshall used?

I was looking at their schematic and all resistors unless labeled are 1/2 watt

[avguy49]

Screen/Grids are rated at 1K 5W and everything else is 1/2 watt I believe.

My $0.02

[neikeel]

Hm.. thanks.

The 1/2 watt filter resistors isnt that the rating marshall used?

I was looking at their schematic and all resistors unless labeled are 1/2 watt

No, the resistors on the filter cans are at least 1w and possibly 2w. It is arguable that 56k is too low a value and 220k is probably better.

[VintageCharlie]

I'm pretty sure they put 2w on the filter cans - it's the only place i see original 2 watters on the old Marshalls (i have been looking for 2w 56k's for this purpose for quite some time, but never found any). I don't know if 1w would be enough, but 1/2w certainly sounds very risky. Also, Marshall didn't spend a cent where it's not needed, so i guess the 2w resistors on the filter cans is a minimum - they'd have used 1w, if it worked ok, as these would be cheaper. Please correct me if i'm wrong, as i'm interested in this too, but i have seen only 2w in these spots.
1w for the power supply resistors and on the preamp filter can is correct.

Good luck on the build! Looking forward to further pics

Regards,

VintageCharlie

[rockstah]

2watt resistors are here - http://www.surplussales.com/Resistors/C ... Comp_5.htm" onclick="window.open(this.href);return false;
Mark

[neikeel]

I have been keeping my eyes open for these too.
Philosophically you have to wonder why Marshall put these on the screen caps other than to help discharge the caps to earth. If they were on the mains caps you could understand a sthey help balance the voltage between the series aspect of the cans either side of the centre tap. You don't really need them there at all and I would tend not to use them if I have 500v rated cans.

[VintageCharlie]

Would it be safe to go with 2w cc's as opposed to cf's? I might go with AB cc's for this purpose if yes. Thanks!

[VintageCharlie]

Btw. what value 2w resistor should i use on dual 32uF caps. It's 56k for the dual 50uF's - would it be the same for 32uF dual caps or should it be lower/higher?

[neikeel]

Btw. what value 2w resistor should i use on dual 32uF caps. It's 56k for the dual 50uF's - would it be the same for 32uF dual caps or should it be lower/higher?

Depends upon what you are trying to achieve

[VintageCharlie]

I want to achieve that the whole thing doesn't blow up in the first place
I'm asking because i have never seen what Marshall used on the 32/32uF filter caps that can be seen on some 68 100w's - SL's and SB's - i guess the resistors are always beneath the board as i haven't seen anything on the top, but afaik, there has to be something between them?
I'd be interested in the value originally used by Marshall - not going after any specific "effects"

[neikeel]

I want to achieve that the whole thing doesn't blow up in the first place
I'm asking because i have never seen what Marshall used on the 32/32uF filter caps that can be seen on some 68 100w's - SL's and SB's - i guess the resistors are always beneath the board as i haven't seen anything on the top, but afaik, there has to be something between them?
I'd be interested in the value originally used by Marshall - not going after any specific "effects"

Nope the early amps with cap boards did not use them.

They appeared with the 69 all caps up top amps.

I do not think you need them, and if you do decide to put some on you will find 220k better as they will discharge slower and be less likely to cause ghosting.