NAD - Marshall Lead 12

[fitz]

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.

I was wondering the same thing, but as you said, gotta get it working to track that issue down.

You know...what I'd rather do is turn this thing into a head. I wonder if I could pull that off with caveman tools.

That can be quite an involved project, even with the correct tools...

A speaker out jack, that can be used for the internal speaker or straight to a cab, is fairly easy with the hole where the speaker leads already come through the chassis.
Might be a good first step to seeing if you like the amp with a bigger cab and want to go the head conversion route.

 

[DirtySteve]

Sorry to hijack your thread so bad, I got carried away.. I'll start my own thread when I get into it.

 

[fitz]

Sorry to hijack your thread so bad, I got carried away.. I'll start my own thread when I get into it.

Not a hijacking to me.

I post my shenanigans because I like to show that stuff like this is not impossible, and in hopes that others might want to do something similar.
I do these wacky things because I think it's fun.
Other than buying the amp on the cheap and a few jacks I didn't have on the shelf, the rest of what I used for this was just stuff laying around - albeit leftovers from other projects.

I'm thrilled it got you thinking about your Lead12 and wanting to get it movin' air again.

 

[DirtySteve]

Not a hijacking to me.

I post my shenanigans because I like to show that stuff like this is not impossible, and in hopes that others might want to do something similar.
I do these wacky things because I think it's fun.
Other than buying the amp on the cheap and a few jacks I didn't have on the shelf, the rest of what I used for this was just stuff laying around - albeit leftovers from other projects.

I'm thrilled it got you thinking about your Lead12 and wanting to get it movin' air again.

Ok, cool. Maybe I won't start another thread then.

 

[Thatbastarddon]

Edit: Yes, this is the beer talking.

….and this is the beer listening…

 

[DirtySteve]

Well I think my beer's done talking for tonight.

 

[ibmorjamn]

My bargain Lead 12 was delivered today.
Popped up on Reverb a few days back and I threw a lowball offer at it expecting a counter, but the seller just accepted.

Here's a pic next to the Park bass cab I converted to a 1x12 I'm planning to use as an extension cab.
Same width and depth, but a bit taller than the Park.
A 12" speaker upgrade to the combo is the first thing on my to-do list.

View attachment 107292

And a pic stacked by the 3210 for a size comparison.

View attachment 107293

Described as having scratchy pots and a stiff middle tone pot.
Before I put any power to it, I pulled the chassis and gave it a visual once over, along with a dose of Deoxit in all the pots and jacks.
Everything looked ok, and the stiff pot loosened up nicely.

View attachment 107294

April 19, 1989 date.

View attachment 107295

I disconnected a shoddy switching jack mod in the back panel and repaired the speaker leads.
As expected, the stock G10D-25 is..., um..., underwhelming.

On a good note, nothing looks amiss, and the amp works fine.
Pots are not one bit scratchy as described, and the thing is almost dead quiet with the volume and gain cranked.
Noise floor is fantastic compared to my old Lead20, and the bacon frying noises the Lead 30 used to make.
I guess the Deoxit did the trick and I have no plans to pull the board and mess with solder joints unless a problem emerges.

Rigged up an extension speaker cable and ran the little fella through the VM cab of G12C's.
Also popped a Haze G12T-66 in the Park 112.
Both were a major improvement.

View attachment 107296

Got some old grill for the Park cab, and a few other cosmetic ideas bouncing around the noggin.

Man Fitz, you have all the luck. Good find.
I wish I could find pots for my park amp, several of them are broken .

 

[fitz]

Man Fitz, you have all the luck. Good find.
I wish I could find pots for my park amp, several of them are broken .

Thanks.

Do you have the schematic for the Park (or Marshall equivalent)?
A venture into the chassis could also reveal what the pot specs are.

I get pots from my go-to Tubes and More.

Potentiometers - Brand: Marshall | Amplified Parts

Browse products from the Potentiometers category - listing products sorted by popular, filtered by Marshall, page 1

www.tubesandmore.com

Amp Repair Parts is another that I've used.

Guitar Amp and Pro Audio Potentiometers

Potentiomers (Pots) for Guitar Amplifiers and Pro Audio Gear

amprepairparts.com

 

[GrooVey]

nice job, Fitz!!

 

[ibmorjamn]

Thanks.

Do you have the schematic for the Park (or Marshall equivalent)?
A venture into the chassis could also reveal what the pot specs are.

I get pots from my go-to Tubes and More.

Potentiometers - Brand: Marshall | Amplified Parts

Browse products from the Potentiometers category - listing products sorted by popular, filtered by Marshall, page 1

www.tubesandmore.com

Amp Repair Parts is another that I've used.

Guitar Amp and Pro Audio Potentiometers

Potentiomers (Pots) for Guitar Amplifiers and Pro Audio Gear

amprepairparts.com

I thought studio sound quit selling that stuff a couple of years ago?
Thanks

 

[ibmorjamn]

Thanks.

Do you have the schematic for the Park (or Marshall equivalent)?
A venture into the chassis could also reveal what the pot specs are.

I get pots from my go-to Tubes and More.

Potentiometers - Brand: Marshall | Amplified Parts

Browse products from the Potentiometers category - listing products sorted by popular, filtered by Marshall, page 1

www.tubesandmore.com

Amp Repair Parts is another that I've used.

Guitar Amp and Pro Audio Potentiometers

Potentiomers (Pots) for Guitar Amplifiers and Pro Audio Gear

amprepairparts.com

I do not have a schematic but I can get it pretty easy.

 

[DirtySteve]

So I was just about to pull my Lead 12 chassis when I had an aha moment. It took me a while, but I finally located my headphones and verified that my amp does work after all. In fact it sounds better with the headphones than I ever remember it sounding. Of course I played it too long so now my ears are ringing like crazy reminding me why I can't use headphones anymore. So I screwed up something when I added those push on connectors to the speaker wires. I'll have to redo them and I'm still going to pull the amp and re-clean the pots and check around. I might go ahead and reflow the solder joints just to be sure.

Plus I want to pull it all apart so I can give it a good cleaning and see if there's anything I can do to repair that hole in the grill cloth.

 

[fitz]

So I was just about to pull my Lead 12 chassis when I had an aha moment. It took me a while, but I finally located my headphones and verified that my amp does work after all. In fact it sounds better with the headphones than I ever remember it sounding. Of course I played it too long so now my ears are ringing like crazy reminding me why I can't use headphones anymore. So I screwed up something when I added those push on connectors to the speaker wires. I'll have to redo them and I'm still going to pull the amp and re-clean the pots and check around. I might go ahead and reflow the solder joints just to be sure.

Plus I want to pull it all apart so I can give it a good cleaning and see if there's anything I can do to repair that hole in the grill cloth.

 

[fitz]

I finally located my headphones and verified that my amp does work after all. In fact it sounds better with the headphones than I ever remember it sounding.

Scratchy pots with the headphones?

 

[DirtySteve]

View attachment 107330

Yep. lol

 

[DirtySteve]

Scratchy pots with the headphones?

Not that I could tell, maybe after I did the deoxit before and then it sat they cleared up? I've never heard of that, but I can't think of any other explanation.

 

[fitz]

Not that I could tell, maybe after I did the deoxit before and then it sat they cleared up? I've never heard of that, but I can't think of any other explanation.

Prolly didn't hurt.
Just working the pots back and forth can also clear of the scratchies sometimes.
I get that with pots on my amps from time to time if I don't adjust anything for a while.
I do a lot of tone shaping with pedals, so usually only the volume gets a regular workout.

Get the speaker spades fixed and take her for a test flight.
I'd skip pulling the board if it's not necessary.

 

[DirtySteve]

Believe me I was twisting the poo out of them after I cleaned them. Yeah, I don't think I'll pull the board just yet, it looks brand new inside, a lot cleaner in here than I remember.

I can't see anything wrong with my connectors. They're tight, no broken strands and I can't pull the wires out. I didn't solder them, maybe I should solder them.

 

[DirtySteve]

I want to change the power cord for sure, it's got what looks like an old vacuum cleaner cord on it. I have plenty of spare amp power cords. I found 3 of them today looking for my headphones.

 

[fitz]

Yep, looks a lot like the 5002 Lead20 I used to have.

I can't see anything wrong with my connectors. They're tight, no broken strands and I can't pull the wires out. I didn't solder them, maybe I should solder them.

Those look good to me.
I little solder in the spade crimp wouldn't hurt.