JTM45 REISSUES

[Husky77]

JTM Reissue Question! I just bought an '89 JTM45 reissue head, no.388. Strictly out of curiosity, does anyone know about the lineage of these reissues, general changes/modifications Marshall may have made to these heads over the years, between 1989 and 2021. I see slight differences, some are SS rectifier, some are tube rec...some w FX loop, some without. Some are listed as 2245s, others aren't. Thanks in advance for any help/info and pushing me farther down the rabbit hole

 

[neikeel]

The 89 is first year of reissue - designated 2245.
Always tube rectified, first iteration came with 5881 output tubes.
No effects loop on these

If you are looking at ss and effects loop you are looking at a 1987x (Reissue JMP50 lead amp) not a JTM45.
All the first reissues had MkII next to the on/off switch only the JTM45 has that near the inputs.

You can tell the 89 by the rounder front corners on the cab cut out for the control panel. These had a 100R Arcol resistor instead of a choke. All the filter caps (well both of them were LCR 50uF mains, 50uF screens and 50uF PI and 50uF preamp (only 4 nodes)
Circuit is not quite like original JTM45 as it has different mixer resistors and caps and slightly different bright cap (they used the same board for 2245/1987 and 1959 models with minor changes).

Not bad amps, they will be a bit brighter and stiffer than a vintage 45 (more in keeping with modern tastes - of the time) The transformers are Drakes. OT is good (despite people exorting you to upgrade - don't its all bu*&^it).
The PT on these is smaller than the vintage ones and is 90 off the original orientation which can prompt some coupled hum at low volumes. B+ is around 400v so about 40-50v lower than an original but is easier on the output tubes.

Best upgrades for this would be some NOS preamp tubes (or good testing pulls) a NOS or new testing Mullard (or other BVA) GZ34 and a pair of KT66s (GEC are gold standard, but expensive, and Gold Lions - Russian are very good).
If you want vintage tones first step is replace the preamp can with 16uF/16uF and the mains can with 32/32 and replace the choke with a 3H 100R 250mA rated device.

If you want to amuse yourself along the lines of diminishing returns then next step is a hand wired turret board conversion with fancy caps and resistors (endless discussion possible there).

But best bang for buck stops with a tube change.

 

[Husky77]

The 89 is first year of reissue - designated 2245.
Always tube rectified, first iteration came with 5881 output tubes.
No effects loop on these

If you are looking at ss and effects loop you are looking at a 1987x (Reissue JMP50 lead amp) not a JTM45.
All the first reissues had MkII next to the on/off switch only the JTM45 has that near the inputs.

You can tell the 89 by the rounder front corners on the cab cut out for the control panel. These had a 100R Arcol resistor instead of a choke. All the filter caps (well both of them were LCR 50uF mains, 50uF screens and 50uF PI and 50uF preamp (only 4 nodes)
Circuit is not quite like original JTM45 as it has different mixer resistors and caps and slightly different bright cap (they used the same board for 2245/1987 and 1959 models with minor changes).

Not bad amps, they will be a bit brighter and stiffer than a vintage 45 (more in keeping with modern tastes - of the time) The transformers are Drakes. OT is good (despite people exorting you to upgrade - don't its all bu*&^it).
The PT on these is smaller than the vintage ones and is 90 off the original orientation which can prompt some coupled hum at low volumes. B+ is around 400v so about 40-50v lower than an original but is easier on the output tubes.

Best upgrades for this would be some NOS preamp tubes (or good testing pulls) a NOS or new testing Mullard (or other BVA) GZ34 and a pair of KT66s (GEC are gold standard, but expensive, and Gold Lions - Russian are very good).
If you want vintage tones first step is replace the preamp can with 16uF/16uF and the mains can with 32/32 and replace the choke with a 3H 100R 250mA rated device.

If you want to amuse yourself along the lines of diminishing returns then next step is a hand wired turret board conversion with fancy caps and resistors (endless discussion possible there).

But best bang for buck stops with a tube change.

Ok great, thanks! So, mine is definitely a JTM45 reussue MKII (no effects loop) from 1989..BUT... it does have a ss rectifier. So I assume it was modded? I have a Mojotone British 45 offset head, tube rectified, and this Marshall definitely has a more super lead/1987x kinda thing going on, but honestly it lies somewhere perfectly between the two amps mentioned. Which is great, I just saw a SS rectifier and got confused and super curious

 

[neikeel]

Have they removed the socket?

 

[Husky77]

Have they removed the socket?

I haven't dug into it yet, it's brand new to me so gonna play it a few days and when the new wears off I'll check it out. Thanks again

 

[Matthews Guitars]

My 1999 JTM45 reissue seems to be the same. GZ34 rectifier tube, PC board based, following the general JTM45 design rather closely. No big surprises or alterations aside from not being a point to point wired product of 1966.

Having played it cranked, I must say that while it does have some attractive tones available to it, I prefer the Superlead circuit for cranked up rock and roll. The 45 is a bit mushy for me.

 

[Kinkless Tetrode]

Does it have plug in SS rectifier? That's all you need to do to change a JTM45 to SS rectification. Can you post a photo?

 

[neikeel]

My 1999 JTM45 reissue seems to be the same. GZ34 rectifier tube, PC board based, following the general JTM45 design rather closely. No big surprises or alterations aside from not being a point to point wired product of 1966.
Having played it cranked, I must say that while it does have some attractive tones available to it, I prefer the Superlead circuit for cranked up rock and roll. The 45 is a bit mushy for me.

Humour me Plug your guitar into Hi channel 1, set volume on that channel to 8, bass on 2, mids on 9-10, treble 8 and presence on 7-8 and see if it is mushy then?

 

[Matthews Guitars]

Those are about my usual settings. And then when I plug into any of my three Superleads, yes, in comparison the JTM45 is still a bit mushy.

Bass below 2 on the JTM45 is pretty much essential for any clarity when pushing the amp. But even with that issue taken care of, it is just a more mellow toned amp than a Superlead.

 

[Kelia]

Those are about my usual settings. And then when I plug into any of my three Superleads, yes, in comparison the JTM45 is still a bit mushy.

Bass below 2 on the JTM45 is pretty much essential for any clarity when pushing the amp. But even with that issue taken care of, it is just a more mellow toned amp than a Superlead.

Agree with lowering the Bass knob !

 

[Husky77]

Does it have plug in SS rectifier? That's all you need to do to change a JTM45 to SS rectification. Can you post a photo?

 

[neikeel]

I can't make out the lettering on the OT but someone has spent a lot of cash on those transformers (see my post above about OTs!). It looks like the amp has been converted to a 50w JMP and possibly a different board judging by the redrilled holes and washers in the chassis top. Probably sounds a million miles off a real JTM45 (which is definitely a taste thing).
My first JTM45 was an 89 (to replace my Fender Deville). I put in a MM OT and hated it (they make high quality gear, no mistake but IMO better for high gain, multi-stage shredding machines, not old school vintage blues/rock amps which you ride the guitar controls with feel, which is what a good JTM45 is for).
Please humour me and take a couple of gut shots so that we can see the rest of the spec.
Depends what you want it for.

 

[Husky77]

I can't make out the lettering on the OT but someone has spent a lot of cash on those transformers (see my post above about OTs!). It looks like the amp has been converted to a 50w JMP and possibly a different board judging by the redrilled holes and washers in the chassis top. Probably sounds a million miles off a real JTM45 (which is definitely a taste thing).
My first JTM45 was an 89 (to replace my Fender Deville). I put in a MM OT and hated it (they make high quality gear, no mistake but IMO better for high gain, multi-stage shredding machines, not old school vintage blues/rock amps which you ride the guitar controls with feel, which is what a good JTM45 is for).
Please humour me and take a couple of gut shots so that we can see the rest of the spec.
Depends what you want it for.

So the JMP50 makes sense cause it sits perfectly (IMO, for my ears) between the two amps. Still has feel of JTM but just a little more balls. The seller is unsure whether its tuned to bass or lead specs but feels like lead spec to me considering the high end

 

[neikeel]

If the tone stack slope resistor is anything to go by then it is lead spec (would need to see all the values to be precise).
As suspected it is a Hoffman board with modern mf resistors and polyester caps and well executed. I would expect it to sound very much like a 1987X. Million miles from a vintage JTM45, but sounds like your other amp covers those bases nicely. Wonder why they chose to do that to a JTM45 rather than build a clone from scratch?

 

[Husky77]

If the tone stack slope resistor is anything to go by then it is lead spec (would need to see all the values to be precise).
As suspected it is a Hoffman board with modern mf resistors and polyester caps and well executed. I would expect it to sound very much like a 1987X. Million miles from a vintage JTM45, but sounds like your other amp covers those bases nicely. Wonder why they chose to do that to a JTM45 rather than build a clone from scratch?

No clue, but I love what it does. Gonna get the Mojotone Brit45 going (its had issues blowing fuses since I've had it...which isn't long) and then I'll have my vintage style JTM45 back and running

 

[Jimmi James]

I just purchased a 1989 JTM45 reissue. The serial number is a sticker on the back panel (0053X) Is it unusual for the serial number to be a sticker? I know they changed to a bar code and serial number sticker at some point in the 90's but this does not have a bar code.

 

[dro]

If they have a factory fx loop it a 1987x, the also have SS rectifier.

JTM45 2245 RI the one in my avitar, is what I've been playing for the last 25 years.

This is my second one. From around 2005 I think.

If it's too loud, you're too fucking old.