1967 or 1968

[67plexi]

Version 6 Super Tremolo 100 Serial # ST/10412

One strange thing is the 370k mixer resistors not 470k.

This a restoration project all the transformers were fried.
I'm not sure if this is a late 1967 or early 1968. The filter board has 4 dual 32uf capacitors stock.
I may make this a Series 5, I have 8 32uf @ 450 volt Capacitors on the way period correct.
I have a set of MARSTRAN transformers on the way 1203-80 PT, 1202-119 OPT, C1999
Choke. The filter capacitors date code 1967. Will see what OPT I prefer.
This is the only information I could find.
Version 6: New power supply, last Superleads with the old (Bassman) preamp circuit (very late 1967)

In late 1967, Marshall made changes to the power supply: Instead of using dual (voltage doubler) rectifiers, Marshall used only one (voltage doubler or bridge) rectifier. So instead of feeding two rectifiers with ca. 95VAC each, Marshall simply feed one rectifier with around 190VAC. This was initially done by bridging the two secondaries of the 1203-80 power transformer (95+95VAC=190VAC). Later, the power transformer was changed to only include one secondary (roughly 190VAC).

The very first of these amps used four 32uf 450v mains filter caps like the earlier amps (cf. 1967 schematic in Doyle, History of Marshall, p. 204). The later amps used only two 100uf caps in series for a total of 50uf (although a few may have used two 32+32uf caps in series for a total of 32uf). These changes in the power supply reduced the number of parts, and probably also reduced costs and ghosting. The screens filtering was typically 16uf (two 32uf caps in series), but some of the later amps had 100uf caps in series for a total of 50uf on the screens. The 50uf gives a tighter and faster amp, whereas the 16uf gives a softer and smoother amp. The 50uf is great for riffing, the 16uf for bluesy solos. Phase inverter filtering was 32uf on some amps and 48uf (16+32uf) on others. The phase inverter filter caps is not longer place inside the chassis on the power board, but on the top of the chassis, near the power transformer like on the later plexis (the hole in the chassis was there already on amps type 5b and 5c, but remained unused).

The preamp voltages were reduced by increasing the voltage drop resistor between the screens and the phase inverter from a single 8.2K to an 8.2K and a 10K in series. Also, the overall voltages were lowered, presumably to increase tube life. The late 1967 schematic shows only 460V on the plates, giving more compression and distortion and less power (http://forum.metroamp.com/viewtopic.php?f=25&t=9722). These amplifiers typically used the Drake 1202-132 OT, although a few appears to have used the Drake 1202-119 or even the new Dagnall C1998. The 1202-132 has a little less bass than the 1202-119, whereas the Dagnall has a crisper and tighter sound with a broader bandwidth than any of the early Drakes. Since the all these early amps are bass heavy (due to its Bassman circuit), I personally prefer the 1202-132 for these amps (and the Dagnall for the later superlead amps). Chokes were typically the Drake 352-114, although a few may have used the 20H Radiospares show in all the early schematics.

On these late 1967 amps, negative feedback was 27k connected to the speakers output rather than the 16ohms secondary, giving more distortion on lower ohms settings. These amps were the last to use serial numbers in the 10.000 range.

[Roe]

dude, you can at least mention that you're qouting someone else

[67plexi]

Roe, Quote:This is the only information I could find.

If you have any information to add it would be great, I think this is a late 1967.

Best regards, Steve.

[Roe]

you're plagiarizing the text I used weeks to write

[myfoot]

This is Roe's

http://folk.ntnu.no/roef/JTM100.html

[martin manning]

Wow, that's quite a piece of work Roe! (and thanks for the link, myfoot!)

[johnnyreece]

you're plagiarizing the text I used weeks to write

I think he's trying to see if he can find any more information than this; not passing it off as his. It sounds like this is a restoration, and your information is all he could come up with. He's looking for more info. His sentence says, "This is the only information I could find..." and then your (very informative) description follows. Well done on that, by the way!

[Roe]

... # ST/10412

One strange thing is the 370k mixer resistors not 470k.

This a restoration project all the transformers were fried....
I have a set of MARSTRAN transformers on the way 1203-80 PT, 1202-119 OPT, C1999
Choke. The filter capacitors date code 1967. ...

the two pictures show a type #7B 68 supertremolo amp. It would probably have dagnall transformers originally (t2562, c1998 and c1999). the mixer resistors look like the standard 470k iskra, by judging from the photograph

[jelle]

Roe, excellent piece of information. Thanks for that!

[martin manning]

I think he's trying to see if he can find any more information than this; not passing it off as his. It sounds like this is a restoration, and your information is all he could come up with. He's looking for more info. His sentence says, "This is the only information I could find..." and then your (very informative) description follows. Well done on that, by the way!

Ya but it's best to include attribution and a link to the source...

[67plexi]

Thank you Roe, For your hard work, I take no credit.
The issue is I ordered this amp no sound sent it to my amp guy and never got my transformers back.
Roger was to send the Transformers out for rewind. Roger moved to Mexico 12 years ago.
And I feel it's time to rebuild this amp now. Looks like I ordered the wrong transformers.
No big deal I will just build a ODS or my SSS build with the transformers I have on the way.
Or I will use the transformers I have on order in this build. I don't care if it is 100% stock at this point.
I own five 100 watt Marshall's in working order some custom colors. One of the best sounding is a
Red 1959 SL-A-8993-A. I got from David Grissom years ago.
I don't play Marshall's any more since I have been building Dumble style amps.

Steve.

[johnnyreece]

Ya but it's best to include attribution and a link to the source...

Oh, absolutely! Just wanted to try to smooth things over. Just my nature.

[67plexi]

A link to Roe's hard work. http://www.thegearpage.net/board/showth ... p?t=927951

Steve.

[ampmike]

Read this kinda fast but I have a 100 super trem from 1969.If pics would help Ill get them to ya.Mine too was thought to have a bad power tranny and I bought a Murcery which I still have but the trannys were fine.It is a great amp.If I can be of any help I would love too.Let me know or PM me.Mikey

[HeeBGB]

I don't play Marshall's any more since I have been building Dumble style amps.

Steve.

This is a travesty against all that is good. You should send them all to me to be played regularly.