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NAD: '73 Marshall 50 watt

buddy7168

Gold Supporting Member
Messages
1,136
I got my '73 Marshall today. It has a few replacement parts and some cosmetic flaws but I got a good deal and more importantly it sounds great!

The pcb looks good except some funkiness with the NFB resistor. The only issue that is bothering me is that the power cable is frayed and the amp has a death cap. I'm definitely going to replace the cable. Should I also rewire to remove the cap or does it not matter as long as I have a three prong cable?

Anyway, here are some pics!





 

JeffHaddad

Silver Supporting Member
Messages
662
Congrats! I have an earlier '73 (still hand wired board) and it sounds spectacular! Got a good deal 'cause of a couple holes in the back ( plugged) and a mod I un-did.
 

Fulldrive-1

Senior Member
Messages
5,926
'73 was the year Marshall changed these from solder-board to PCB. I don't know what month that was.
 

Hacksaw

Time Warped
Platinum Supporting Member
Messages
10,208
Nice score! I see it's fitting in with the rest of the family just fine.


Ya, loosen the screws on the power tranny and bend it back. Ya ok it bugs me just a tad. :D
 

DrainBamage

Member
Messages
2,407
I would disconnect the polarity switch since the amp is grounded. You can leave the death cap there once its disconnected if you wish.
 

buddy7168

Gold Supporting Member
Messages
1,136
Nice score! I see it's fitting in with the rest of the family just fine.


Ya, loosen the screws on the power tranny and bend it back. Ya ok it bugs me just a tad. :D
Thanks, yep the new kid is fitting right in. It sounds great doing leads over the 2204 with a ditto looper.

Straightening the transformer is on my todo list. I've seen it on a couple other amps while I was on the hunt and I always wondered how that happens.
 

buddy7168

Gold Supporting Member
Messages
1,136
I would disconnect the polarity switch since the amp is grounded. You can leave the death cap there once its disconnected if you wish.
Yea I'd like to get it disconnected but I think it's cool to leave it in place since it's a bit of history. Anyway once it's disconnected it looks like two wires will need to find a new home. There's a light blue from the PT and a yellow that's connected to the top of the mains fuse. Any idea where they go? If not NBD I'll post a specific thread in the tech forum. Thanks!
 

tone?

Member
Messages
4,535
Holy **** look at the size of the PT.
What's the B+ on that amp? Curious.

Also I would put a 500pf bright cap on there.
 

buddy7168

Gold Supporting Member
Messages
1,136
Holy **** look at the size of the PT.
What's the B+ on that amp? Curious.

Also I would put a 500pf bright cap on there.
I haven't measured yet. I'm going to put in some different tubes and rebias in the next day or two. I was going to order a stock value bright cap. What do you like better about 500pf? Just a bit less extreme?
 

AndreasG

Member
Messages
2,056
Great head. I had mine '73 head since I was 16. A year ago I disconnected the bright cap on the first channel and it's much more managable at lower volumes that way
 

Jason_77

Senior Member
Messages
7,198
Congrats! I bet that sounds killer! If you're going to install a bright cap, I'd get a pair of alligator clips and try a variety of different values at the volume you prefer to run it. Right now, I have a push/pull volume on my super lead clone I built that toggles between 500pf and 5000pf. 500pf around 6 on the volume gives a good Led Zep TSRTS through AC/DC sound but as you back down the volume, it can be a little too bright. 5k does the typical 70s marshall sound really well. It's more of a bass filter than anything so you can get a really overdriven sound without it being too flubby. I go back and forth between using 120pf and 500pf because the 120pf sounds better for cleaner, lower volume settings. I could install a 6 position rotary switch and use a number of different values but I prefer to keep this looking un-modded. I'll most likely tweak the normal channel to be better suited for cleans.
 

tone?

Member
Messages
4,535
I haven't measured yet. I'm going to put in some different tubes and rebias in the next day or two. I was going to order a stock value bright cap. What do you like better about 500pf? Just a bit less extreme?
I like 500pf cause it's enough to back off on the volume and play some cool lower gain stuff like was mentioned. If you don't have the bright cap on there it gets too dark for my tastes and takes away from that Marshall kerrang.
And it's great for lower volume stuff for blues abs semi cleans
 

tone?

Member
Messages
4,535
Congrats! I bet that sounds killer! If you're going to install a bright cap, I'd get a pair of alligator clips and try a variety of different values at the volume you prefer to run it. Right now, I have a push/pull volume on my super lead clone I built that toggles between 500pf and 5000pf. 500pf around 6 on the volume gives a good Led Zep TSRTS through AC/DC sound but as you back down the volume, it can be a little too bright. 5k does the typical 70s marshall sound really well. It's more of a bass filter than anything so you can get a really overdriven sound without it being too flubby. I go back and forth between using 120pf and 500pf because the 120pf sounds better for cleaner, lower volume settings. I could install a 6 position rotary switch and use a number of different values but I prefer to keep this looking un-modded. I'll most likely tweak the normal channel to be better suited for cleans.
Very good points. I feel the same way. I used to clip out the bright cap but that was stupid.
 

buddy7168

Gold Supporting Member
Messages
1,136
Thanks guys, I guess I'll order a few different caps to see what I like. I agree it's a bit dark with no cap at all.
 

buddy7168

Gold Supporting Member
Messages
1,136
I finished my changes to the amp tonight. I think it's pretty close to stock. Here's what I did...

Added bright cap (5000pf)
NFB wire to 8ohm tap
Removed Death Capacitor
Replaced
- Power Cable
- Indicator Lamp
- 2n2 Cap (nos mustard)
- nfb Resistor (nos piher)
- Electrolytic Caps on pcb

Photo after the changes...


With the family...
 






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