NAD '93 Marshall 4501 Dual Reverb

[marshalltsl]

Hi.
Huge NAD, lol. I'm amazed. It looks new. Pots and Jacks outputs feels like a new amp. Original EL34 tubes. I closed JCM900 circle. I have all 3 models (MKIII, SL-X, DR). All them 50W EL34 tubes. In fact it's my second DR. I had a 4102 but It was a 5881 tubes amp. Much less gain than '92 or '93 DR. I sold It and I bought a Valvestate 8240 many years ago.

I'm thinking I could made a new rear panel, It fit on my Astoria empty cabinet. I think It will sound better with a big cab without plastic lateral handels.

 

[marshalltsl]

Let's check bias. Looks like a brand new amp.

 

[marshalltsl]

Bad news. I don't have bias voltage in a one tube. Let's see what it's wrong with It. I guess one tube is bad. All fuses are ok.

 

[marshalltsl]

As you can see on right socket valve pin 8 and pin 1 are not join. Because It was so cheap. Always I buy JCM900 with issues, lol. Fixed It. New old tubes. All ok. Let's see how it's sounds.

 

[syscokid]

Wow, the amp looks immaculate! Hope the bias issue is an easy one to solve…

Edit: You fixed it! Congrats…

 

[marshalltsl]

I'm really happy. I'm really lucky. All works fine. When I tryed at home It has a little hum. That is why I did test bias. Now I know because it's unused amp.

 

[marshalltsl]

FX pot control was bloked. I clean It with tuner contact cleaner. Fixed it. I think It lack some bass on It. Maybe it's normal. My MKIII and SLX (heads) has more bass sounding. Even with 2X1960AX It's a treble amp on Channel B. Anyway perfect with 75T speakers. Maybe because it's a combo circuit. It lack some bass even with master at 10. But averall I'm really happy. There is bass mod on somewhere. Let's see.

 

[67plexi]

The Tesla pre war Czechoslovakia made EL34 OO getter are some of the best ever made

 

[marshalltsl]

One Tesla tube from this JCM900 It's unused. I Preamp Marshall tubes looks brand new. I tryed other ECC83 tubes as well. I want check all components values because could be a wrong value. Maybe It has a dry cap. Even when I turned on It smells like a new amp.
I bought It with original tags and owner manuals. Amazing.

 

[SG John]

The Tesla pre war Czechoslovakia made EL34 OO getter are some of the best ever made

View attachment 92521

Pre-'68 Soviet invasion?

 

[marshalltsl]

Pre-'68 Soviet invasion?

I don't know. One valve is bad. Could be is tube bad because a false Contact on negatives socket pins?

 

[marshalltsl]

506
B5.
Tube on the right is bad.

 

[syscokid]

506
B5.
Tube on the right is bad.

Might be a photographic illusion, but the tube on the right looks a little toasted and a lot of its flashing is gone compared to the other tube.

 

[marshalltsl]

Might be a photographic illusion, but the tube on the right looks a little toasted and a lot of its flashing is gone compared to the other tube.

Yeah. You are right. It don't do nothing.
Today It sounds awesome. No brightness sound or treble at all. All EQ at 5.