KT88 application notes

[Reeltarded]

All of the reputation bestowed upon the Major is that of the 200. They just blow the eff up.

[Turret]

There is no active EQ on DrTube website, as there is no 'The Pig' schematic out there

Here's early preview, no component values, no PS nor bias supply yet, I'm working on it

thanks for posting. a previous schem and pics were posted on the metroboard. and there's new info in the new doyle book as well, claiming that the design wasn't worth much really

I have to buy this book finally...

BTW, I love your 100W Marshall progression article, let me know if you want illustrations for it

[gingertube]

Ian, any gutshots of that VDV-3070 amp? I'd love to see the grounding scheme...

Surf,
No pics,
The PCB layout did have special attention paid to the earthing scheme. everything tied back to a single star earth point.
Should have a couple of boards to get rid of shortly, the Power and Output Trannies are going into a new pair of monoblocks with a quad of 300B in parallel push pull per channel.

Cheers,
Ian

[Roe]

There is no active EQ on DrTube website, as there is no 'The Pig' schematic out there

Here's early preview, no component values, no PS nor bias supply yet, I'm working on it

thanks for posting. a previous schem and pics were posted on the metroboard. and there's new info in the new doyle book as well, claiming that the design wasn't worth much really

I have to buy this book finally...

BTW, I love your 100W Marshall progression article, let me know if you want illustrations for it

thanks for the kind words. Illustrations would be great actually. I'll see if I can find the previous pig schematic

[Turret]

I'll be honored Roe to donate my layouts and schematics. I have quite a few of them half done. It wont take long to finish them up, PM me your email

I haven't done much with 'The Pig' schematic today, but here it is where I am right now. As you see it shouldn't take much time to complete it

Credits goes to superchouf from Dawk's forum who owns proto Major PA - it's really similar to 'The Pig' preampwise (minus 4x2 input/mixing stages, and typical PA topology)

[Danny_J_Glover]

From what I've read, the Marshall Major (aka Marshall 200) power amplifier and output transformer were designed for application by Genalex.

They designed it as they did other push-pull power amplifiers, for linearity and fidelity, like an RF amplifier, and they are expecting sinusoidal, clean signals.

The problem here arises in the feedback topology. The ultralinear connections feed from the transformer to the screens (acting as the limiters) and as long you operate far from the edges of the tube's loadlines, this works.

Guitarists like to overdrive their preamps and power amps, which causes the sinusoids to clip and the voltage to essentially 'clamps' high and low between signal swings. A clamped voltage (for practical purposes) doesn't "change" or alternate, which is required to utilize Maxwell's equations (specifically Amperes law) to make the transformer magnetically conduct the power signal to the load on the output side. Constant current through the primary windings and hence constant magnetic flux through the transformer doesn't generate any current in the secondary windings.


When the voltage clamps, the current stops changing, if the current has no swing (constant amplitude) the curl of the current doesn't induce a changing magnetic flux through the transformer core, which is required to 'Ampere' the signal to the speaker.

The apparent load on the secondary disappears when the signal clamps, making the B+ short to what is normally 40% B+, the negative feedback disappears and screens no longer limit the signal they were previously limiting to 200W. The light overdrive now looks like square waves.

When you replace the power amplifier with what resembles a switching device at this point, going from full-on to full-off and feed that output into a transformer, you've essentially just designed a variable frequency, variable duty cycle flyback converter.

This is worsened by any inductive ripple filter in the power supply which continues to push current onto the capacitors which are not discharging, causing the voltage to climb.

Flyback converters are actually common in tube circuits, but for generating B+ voltages of THOUSANDS of volts from low voltage batteries. Most magnet wire is rated for about 2-5kV, and the Majors were exceeding this resulting in some blown caps, some charred tube sockets, but mostly output transformers that had literally been arc-welded to themselves due to the insulating enamel breaking down.

It's a shame because a 200W ultralinear transformer probably weighs about 20 pounds and was probably the most expensive and tediously constructed part of the amplifier.

A couple rare versions are still in existence AND STILL IN USE IN HIGH GAIN MUSIC TODAY!!! They are most probably the result of a perfect set of production anomalies. The enamel just happened to be thicker than spec, or the parasitic properties of the entire power supply and preamp loads happened to damp the wild oscillations.

Regardless, that amp sounds like an incredible screaming raw beast capable of melting steel and copper and explode out of the speaker because it is, and I love it.

[Roe]

the major differs from the pig, circuit and transformers are different

[jazbo8]

BTW, I love your 100W Marshall progression article, let me know if you want illustrations for it

Sorry for being ignorant, but where can I find the 100W Marshall progression article?

[Roe]

BTW, I love your 100W Marshall progression article, let me know if you want illustrations for it

Sorry for being ignorant, but where can I find the 100W Marshall progression article?

Its in the new doyle marshall book and here:http://folk.ntnu.no/roef/JTM100.html. the different versions differ ever so slightly due to proofreading (or lack thereof) etc

[Danny_J_Glover]

I've always been confused by "The Pig."

Marshall did differ the preamp section from '67 to '68, and though there was no official "The Pig" model, it seems to be regarded as the first revision of the 200 series after their 200 PA amplifier.

It supposedly used some active tone filters and the Partridge transformers, but only a handful of these were made (as many as Marshall received as free samples), after which they returned to using their generic transformers but still with active tone controls.

Did "The Pig" die with the transformer change or the drop of the active tone control?

I know not a single "Pig" was made after 1967. And "The Major" started in '68, but many amp-lovers seem to mix them up, which leaves me mixed up as well.

Regardless, Partridge transformers are Hi-Fi and ultralinear, the power amplifier topolgy and it's inherent dangers remain, though the rating for the Partridge windings may have been superior, leading to surviving amps.

OP: Ampeg did some unconventional things in the power amp section of their huge amps worth googling.[/code]

[Reeltarded]

The GEC amp is the Major.

[Danny_J_Glover]

But I've seen the 1967 Model of the Marshall 200.
(which people claim to be "The Pig" strictly because Mick Ronson called it that) Only the Marshall 200 model from 1967 is known as "The Pig" and it's clear because Marshall made the model number "1967."

It had "Marshall 200" on the front panel, "Marshall Major" on the back panel, and used the Partridge transformers and active EQ, leading me to believe that there is an overlap here.

Marshall wrote, "Marshall Major," on amplifiers that people call, "The Pig."

[Reeltarded]

Both of those amps in that picture are model 1967 Majors. 1970 and 1972. I have lots too many.

[Turret]

The Pig is simply 3knob Major

BTW, Roe sent me few more pictures of other Pigs, he confused me big time

Different chassis, typical power amp topology (no trimmers, no 4 PI output caps), and power supply similar to the ones in JTM45/100's

I think I will end up with two sets of schematic/layouts

[statorvane]

I thought the "Pig" was Mick Ronson's Marshall Major - the one with three knobs. IIRC he used it as a PA amplifier - feeding it with a WEM Dominator (18 watt). There is some concert footage out there where you can catch a glimpse of the Dominator. Hard to see the Marshall though. I perused some YouTube clips of Bowie Live thsi morning. I had thought the clip was Moonage Daydream, but it must have been something else, as and all I could see (clearly) were two Marshall Superlead 1/2 stacks.

Anyway, I do not think it sounded very good as a guitar amplifier. There is a thread on the Metro board (several actually) for the Major/200/Pig, which uncovers the innards of the Pig.