New Marshall JMP 1978 NMV

[OdgeUK]

Hi Folks,

Have just taken delivery of a 1978 JMP 50W 4-holer and pulled the chassis to see what lies beneath. I already have a '73 version of this model but I had to have this one as the price was good and I needed a donor for a possible RockStah Mod5 attempt.

First picture here. More to follow. Are these "Lego" caps?

The tubes are interesting. The output tubes logo has burnt off leaving only a flaking remnant, unable to see the manufacturer but "EL34" can be seen in a very 80's style text.

v2 and v3 appear to have a Blackburn Mullard code on them, but the ECC83 logo /font is not one I've seen before.

[OdgeUK]

[stef]

Hey, I got the same ecc83 tubes in v1, v2 and v3 inside my 1978 SL.. Those flashed really bright but also made a lot of cranking noises so I swapped them all but still have them and thinking about trying one of them again for the v1 or v3..

[demonufo]

Are these "Lego" caps?

Yep.

[Bunnest]

beautiful example...you have a couple of those chicklet style also, the green and white ones..i bet she has that Judas Priest tone for daze...

[demonufo]

beautiful example...you have a couple of those chicklet style also, the green and white ones..i bet she has that Judas Priest tone for daze...

They're not chicklets. The chicklets are the yellow Philips MKT-P caps that look like bubblegum chiclets (hence the name) and featured exclusively in '72 Marshalls.

All the bright yellow ones in this picture are chicklets, although the one in the top right in the only period correct one for '72 Marshalls. Mine were etched/moulded with the writing, the earlier ones in the Marshalls were printed on.

The green and white caps never did attain a nickname that I'm aware of. FWIW, these caps are still available from Vishay (were Philips caps originally, I think?) but are now red, as opposed to green in '76 and white in '78.

[OdgeUK]

I find it interesting that for all this talk of Mustards and Chicklets and Lego caps, that I never see any reference to the small clay coloured caps in my 73.



They have TCC printed on them but you rarely hear/see any mention of them here or at Plexi Palace.

[demonufo]

Or the brown ITT caps used around '76-'77 for that matter.

[stusixtysix]

odge

i have a '73 with identical brown caps in the same positions as your pic. the mustard at V1 cathode and the Lemco's on the mixer bypass, tonestack and original brightcap too; in fact looked identical to your pic before i did some value swapping. still have all the orig bits put aside .

[Bunnest]

Your technically correct Dem, but I call all the Mullard gum like caps chicklets...green, white and yellow...actually, don't u think the green and white ones truly resemble chiclet gum???

[demonufo]

Your technically correct Dem, but I call all the Mullard gum like caps chicklets...green, white and yellow...actually, don't u think the green and white ones truly resemble chiclet gum???

Very true. In fact, I think they "more" resemble gum. Hence why I also previously thought these green and white caps were the ones everyone called chiclets myself.

[OdgeUK]

Well, had a chance to crank this baby in rehearsals. Really great tone but didn't have the chance to directly compare it to my 1973.

Plenty of Gain on tap, a real crushing overdrive. The only thing I could say is that the amp was a little 'dark' but this might have something to do with the fact that the other guitarist was trying out his Fender Pro Junior which obviously had a lot more cut.

I also noticed it was maybe not as loud as my 1973 as I was using an attenuator and found that I could actually run the amp on -4db and zero attenuation (reducing the amp volume a little) without killing people. Later on though, I realised that I had made a bit of an impedence mistake, I ran the amp into a 16ohm hotplate but the amp was set to 8ohms as I was using an 8ohm cab at the studio. Do you think this could have caused damage?

[OnTheFritz]

Those mid-late 70's 50 watters had a pretty low plate voltage. That most likely accounts for your volume reduction compared to your '73.
I had a '78 that was almost 100 VDC lower than my '79 100 watter. Never understood why Marshall Dropped the voltage of the 50's so much when a two valve amp has less headroom to begin with.
I doubt the 1 click miss-match on the output did any harm in the slightest.
Looks like a clean amp, enjoy!

[RockinRocket]

beautiful example...you have a couple of those chicklet style also, the green and white ones..i bet she has that Judas Priest tone for daze...

They're not chicklets. The chicklets are the yellow Philips MKT-P caps that look like bubblegum chiclets (hence the name) and featured exclusively in '72 Marshalls.

All the bright yellow ones in this picture are chicklets, although the one in the top right in the only period correct one for '72 Marshalls. Mine were etched/moulded with the writing, the earlier ones in the Marshalls were printed on.

The green and white caps never did attain a nickname that I'm aware of. FWIW, these caps are still available from Vishay (were Philips caps originally, I think?) but are now red, as opposed to green in '76 and white in '78.

zombie thread!!
You probably know by now but not all chickets are the same. Those newer ones shown mkt are polyester, Marshall used polycarbonate. The upper right chicklet isn't period either. The old ones looked like pressed fiberglass composite not the smooth plastic of that (.068?)

[demonufo]

Awesome stuff. Actually I had no idea.
I can't even remember what that top-right one looked like now. I sent it to Neil almost as soon as I had received it, iirc.