Help Authenticating a Vintage JTM45 Half Stack

[Shane S]

Hello Marshall forum,

This is my first post here and I was pointed to this forum by members at TGP as helping me authenticate a vintage Marshall halfstack that I am in the process of purchasing. The current seller has owned this amp since the early 1990s. I had the opportunity to play through it 21 years ago and it was one of, if not, the most amazing sounding amplifiers that I have ever played through… I recently reconnected with the owner and he is ready to move this setup to its next custodian. This will be my first ever Marshall amp and first vintage amp purchase in 28 years! I am thrilled to have the opportunity to own this amplifier.

He imported the head and cab from England. I never questioned the authenticity until he told me that it was purchased from Music Ground… The hair on the back of my neck stood up as some quick research shows that they were notorious for selling fake Marshalls going back to the 1990s.

I know the amp has been serviced and has some replaced components. It currently has EL34s. I do not know if it was shipped originally or was modified to take the El34s. I believe the logo has been replaced at some point. Could the members here please take a look at these photos and determine if the amp is real? I can get additional photos if needed. Thank you so much in advance!

 

[Shane S]

 

[BygoneTones]

Apart from the block logo that tall B cab looks legit and ridiculously clean to me. They are so rare in that condition.

Although you are right to be very sceptical if it came from music ground.

It's a shame they removed the original logos for whatever shady reason.

Speaker date codes Feb 67.

 

[Mrmadd]

I like it!

 

[arthur.lowery]

Looks pretty much like my JTM Black Flag, apart from it has an aluminium chassis. It would be nice to have a serial number. Mine was 10348, and originally had a valve rectifier, so it's nice to see how mine was orginally.

There's a bit of rework around the tone stack (usually pink wires). Maybe the screen grid resistor(s) were added (and are there grid stoppers?).

If you are going to put in an IEC mains socket, just do it from the rear of the chassis - no filing required, apart from maybe the lip of the new socket in places so it fits snugly to the round Bulgin hole.

Looks as though it has a 33K ohm feedback resistor (purple wire to Presence). This can cause ultrasonic oscillations as some settings (see my earlier posts). I would make it 75 K or more, though it depends on the speaker tap used. An oscilloscope across the speaker is handy! Might be OK though, with its dedicated 'speaker.

I like the cover - maybe you could sell some copies on the forum!

 

[London John]

Get rid of the block logo and you’re off to the races.

 

[michelebis]

It looks like late 66 early 67, both logos are not correct. The cab is very nice!

 

[Garth Rocket]

Hello Marshall forum,

This is my first post here and I was pointed to this forum by members at TGP as helping me authenticate a vintage Marshall halfstack that I am in the process of purchasing. The current seller has owned this amp since the early 1990s. I had the opportunity to play through it 21 years ago and it was one of, if not, the most amazing sounding amplifiers that I have ever played through… I recently reconnected with the owner and he is ready to move this setup to its next custodian. This will be my first ever Marshall amp and first vintage amp purchase in 28 years! I am thrilled to have the opportunity to own this amplifier.

He imported the head and cab from England. I never questioned the authenticity until he told me that it was purchased from Music Ground… The hair on the back of my neck stood up as some quick research shows that they were notorious for selling fake Marshalls going back to the 1990s.

I know the amp has been serviced and has some replaced components. It currently has EL34s. I do not know if it was shipped originally or was modified to take the El34s. I believe the logo has been replaced at some point. Could the members here please take a look at these photos and determine if the amp is real? I can get additional photos if needed. Thank you so much in advance!

Nice first Marshall!!

 

[Ned B]

The bottom is the "gem" here assuming those 20 watt speakers are in good health and the cab is original as it appears to be. You have the bottom "tall" cab of Hendrix's Monterey 100W stack which is very rare especially in that condition.

 

[Brewster]

Holly Grail combo you got there. Congrats on your first Marshall amplifier. Beautiful even with the noted concerns above.
Thanks for sharing and enjoy them.

 

[Lo-Watt]

Wow That's really nice! Congratulations!!!

 

[Brown Recluse]

Shane, Is the amp currently owned by a guy named Doug?

 

[Fernieite]

Why does the indicator light change from the small round amber style to the larger red square? 2 different amps seem to be shown here...

Could be my coffee hasn't kicked in, I suppose.

 

[TAZIN]

A bit of an odd serial # for a late '66 build. I would have figured something in the 8XXX range. The amp has a fair share of replaced components including resistors, caps, wires, filter caps and pots.

Why does the indicator light change from the small round amber style to the larger red square? 2 different amps seem to be shown here...

I think what you're seeing is the square lenses part of the Indicator must be broken and fell off in the one photo.

 

[Shane S]

Thank you so much to everyone who has chimed in and provided feedback.

@Fernieite, @TAZIN is correct. That was a older photo. It has since been replaced. TAZIN and @arthur.lowery are correct that it has been serviced and has replaced components. Most importantly, the iron is orginal, it sounds like the voice of god through the 4x12 cab and it is VERY quite when at idle with the volume cranked.

@michelebis is correct about replaced logos.

Here are photos taken yesterday of the setup:

 

[BlueX]

Looks really cool, and I'm sure it sounds heavenly!

 

[Brewster]

Wow, that cabinet is so fine. That is a wet dream all by itself. Congrats, and hope you have years of enjoyment with them both.
Cheers

 

[BygoneTones]

That cab is amazing. Don't think I've seen one that clean before. What is the date code on the top left speaker with the grey tab?

I'd be double checking whether the block logo is original or not by looking for script logo holes underneath. Unlikely, but you never know.

 

[BygoneTones]

If you zoom in on the top left speaker there's what appears to be some red tape on the cone. Possibly a cone repair?

 

[TAZIN]

That cab is amazing. Don't think I've seen one that clean before. What is the date code on the top left speaker with the grey tab?

I'd be double checking whether the block logo is original or not by looking for script logo holes underneath. Unlikely, but you never know.

So, would this cab have butt joint corners or a finger/box joint?