NAD - Marshall Lead 12

DirtySteve said:
Alright that does it. My next project is figuring out why my lead 12 died and fix it.
Click to expand...
Mine is going to be more involved though. I think mine is older than yours, it's got the pointer knobs. Even after cleaning the pots and jacks it was still noisy and the pots are scratchy. It was always very bright and didn't sound good, but before I could get into figuring out why it died on me.
 
DirtySteve said:
Mine is going to be more involved though. I think mine is older than yours, it's got the pointer knobs. Even after cleaning the pots and jacks it was still noisy and the pots are scratchy. It was always very bright and didn't sound good, but before I could get into figuring out why it died on me.
Click to expand...
IIRC, you have a mk-II with the combined LO/HP jack, and the bias trim pot?
I think I remember comparing gut shots of yours with my 5002 Lead20.
The boards looked almost identical.
 
fitz said:
IIRC, you have a mk-II with the combined LO/HP jack, and the bias trim pot?
I think I remember comparing gut shots of yours with my 5002 Lead20.
The boards looked almost identical.
Click to expand...

Hmm, I don't know about all that. Mine is an '84.

Ta4fIq9.jpg


I have the potential to do a stack like you, lol. I have this MG15 that I converted to a 110 cab many moons ago. It's been collecting dust for a few years now. I think I could fit a 12" speaker in it, and I could convert the combo to 12" like you did. :hmmm:
Of course I can't get ahead of myself. I have to get it working first....and like it, lol.

EJe5r55.jpg
 
DirtySteve said:
I have the potential to do a stack like you, lol. I have this MG15 that I converted to a 110 cab many moons ago. It's been collecting dust for a few years now. I think I could fit a 12" speaker in it, and I could convert the combo to 12" like you did. :hmmm:
Of course I can't get ahead of myself. I have to get it working first....and like it, lol.

EJe5r55.jpg
Click to expand...
Two 10's are better than one (imo), and a bit easier if you don't have a woodshop in your garage.
Lots of choices for 10" speaker upgrades too.
I briefly thought of going with a pair of 10" creambacks - easy to convert the Park cab back to 10" with a baffle adapter.

But yes, step one is functionality.
 
fitz said:
Two 10's are better than one (imo), and a bit easier if you don't have a woodshop in your garage.
Lots of choices for 10" speaker upgrades too.
I briefly thought of going with a pair of 10" creambacks - easy to convert the Park cab back to 10" with a baffle adapter.

But yes, step one is functionality.
Click to expand...

I have a 10" Scumbach M-something (I forget), a 10" Cannibis Rex and a 10" Greenback. I have more 12" options in my stash.
 
DirtySteve said:
I have a 10" Scumbach M-something (I forget), a 10" Cannibis Rex and a 10" Greenback. I have more 12" options in my stash.
Click to expand...
Another thing to keep in mind is the Lead12 is 8Ω minimum.
Gotta mind your speaker impedance with an extension cab.

I'm using a pair of 16Ω speakers.
With just one, the heavier load reduces the output to about 8-9w.
The extension is a parallel 2nd 16Ω, so back to the rated 8Ω load and full 12w power output.

Don't parallel a pair of 8Ω, or the 4Ω load will toast the output transistors.
You could series an 8Ω internal and 8Ω extension to a 16Ω load.
I can show you how to wire those options if you get to that point.
 
fitz said:
Another thing to keep in mind is the Lead12 is 8Ω minimum.
Gotta mind your speaker impedance with an extension cab.

I'm using a pair of 16Ω speakers.
With just one, the heavier load reduces the output to about 8-9w.
The extension is a parallel 2nd 16Ω, so back to the rated 8Ω load and full 12w power output.

Don't parallel a pair of 8Ω, or the 4Ω load will toast the output transistors.
You could series an 8Ω internal and 8Ω extension to a 16Ω load.
I can show you how to wire those options if you get to that point.
Click to expand...



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All my 10" are 16 ohm and so are most of my 12" speakers. I didn't think it mattered. Maybe that's why it quit on me. :rolf:
 
DirtySteve said:
All my 10" are 16 ohm and so are most of my 12" speakers. I didn't think it mattered. Maybe that's why it quit on me. :rolf:
Click to expand...
Nope, you'd be fine with one 16, or two in parallel.
That's exactly what I just did.
Just don't parallel another 8 with the stock (or other) 8 ohm.

Let's get your little fella rockin' again. :yesway:
Open it up and have a look around for anything suspicious.
 
fitz said:
Nope, you'd be fine with one 16, or two in parallel.
That's exactly what I just did.
Just don't parallel another 8 with the stock (or other) 8 ohm.

Let's get your little fella rockin' again. :yesway:
Open it up and have a look around for anything suspicious.
Click to expand...
I'm remembering how it went down now that I'm thinking about it. I was trying different speakers and it actually died when I swapped the speaker the last time. I think I just have a bad speaker connection from the push on connectors I had just recently put on so I could swap speakers easier. But because I was frustrated with the scratchy pots and super bright highs I just said f'k it and put it on the back burner. I already pulled the chassis and had a look around and even probed around and there's nothing obvious..
 
DirtySteve said:
I'm remembering how it went down now that I'm thinking about it. I was trying different speakers and it actually died when I swapped the speaker the last time. I think I just have a bad speaker connection from the push on connectors I had just recently put on so I could swap speakers easier. But because I was frustrated with the scratchy pots and super bright highs I just said f'k it and put it on the back burner. I already pulled the chassis and had a look around and even probed around and there's nothing obvious..
Click to expand...
So, bringing it back to life may be as easy as a speaker spade connector?
That would be a nice quick fix.

If you've got scratchy pots - even after a shot of Deoxit (or similar) - it may be the solder joints where the pots connect to the board.
You'd need to pull the board to flip it over, but reflowing the pot connections would take less time than getting to them.
 
fitz said:
So, bringing it back to life may be as easy as a speaker spade connector?
That would be a nice quick fix.

If you've got scratchy pots - even after a shot of Deoxit (or similar) - it may be the solder joints where the pots connect to the board.
You'd need to pull the board to flip it over, but reflowing the pot connections would take less time than getting to them.
Click to expand...
But what about the thin bright sound? Could that be a bad solder joint or pot? I should just go ahead and start by reflowing everything, redo the speaker connectors and see what I've got.
 
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