Can We Discuss Major Pigs?

[Reeltarded]

And that is why we don't see Pigs for repair.

The failures on the late models are ALWAYS flyback doodah or a tube melts and turns the amp into a parts bin with a Marshall logo.

Zeus.. put down that bolt.

[Littlewyan]

Yeah I vaguely remember reading about how these amps were basically on the edge when running clean. Stick a fuzz pedal in front, get some square wave distortion going and they'll blow up.

[The Ballzz]

The Pig had tremendous voltage. Over 700 and the poor screens melted.

Majors don't have a lot less. UL supply is end of the line. Melted screens ahead. Modern tubes need not apply. (that is why about one of ten still operates with original transformers) The 6550 exports are still extant in much larger numbers.

Screens at 650?

Dawk said the flyback potential is about what it takes to create life from stitched together convicts. Have you ever seen one of his rebuilt transformers? Not cheap. He was a nut.

Yes, Dawk certainly qualified as a nut! In the mid '70s he did some amp work for me. One of the times I visited his single wide trailer shop near Cortland, NY, I had the opportunity to play one of Ritchie's scalloped fretboard Strats through one of his (claimed to be 400 watt) modded Major stacks, at volume! Absolutely BRUTAL! At the time, he had two of Ritchie's full stacks and one of Jon Lord's in lined up along one wall of that tiny trailer! The work he ws doing for me was resurrecting a blackface Super Reverb into a fire breathing and self destructing pile of useless POO sporting 6550s! I had to pressure him to redo it as mostly stock to be able to use it!
Those Were The Days!
Gene

[Reeltarded]

There has never been a more pedal friendly amp for bedroom levels lol

[The Ballzz]

I built a shrunken version of one years ago as I was more interested in the preamp sounds than the power. 2xKT66 instead of 4xKT88 and called it the Piglet.

Very Cool! Please share more info. How many watts-ish? How did it sound? Willingness to share a schematic? I'm especially curious as to the voltages at the PI and preamp nodes?

This was exactly the kind of reply I was hoping to elicit from this fabulous brain trust!

Enquiring Minds & All That,
Gene

Watts-ish: 45-50
Sound: great...a bit limited but a novel and interesting concept where you basically have one really bright preamp and one really dark one and you blend em.
Schematic: below. its quite similar to the 'vintagekiki' one posted in the OP. I did a lot of research and comparison with photos and the rare Pig PA schematic floating around.
Voltages: dont have them but I wasnt trying to match anything specific. I used pretty standard 50W Marshall iron so the plates were ~450VDC

My sincerest thanks for sharing all that. Any chance of a link or such to the mentioned "rare Pig PA schematic floating around?" Do you have any estimate of the "crossover frequency" and slope/overlap between the Bass and Treble channels? While the circuitry of the Treble looks like a classic high pass and the Bass like a low pass, I'm not savvy enough to ascertain the frequencies and/or db per octave by simply looking at component values.

I think you may have inspired me to attempt a 6V6 version of this amp, just for poops & giggles!

Thanks Again,
Gene

[oj]

The Sound City 50Plus MkIV took that tone control idea a step further, adding a mid control.
I don’t regard them as being active tone controls, but I’ve been overruled on the matter by the super brains on MEF
http://soundcitysite.com/Sound_City_LB_ ... ematic.pdf

To bad the schematic so bad and hard to read .
But thanks to Pont that out!

[The Ballzz]

Hey folks. It dawned on me that I've never thanked all you great folks for your spirited and informative contributions to this quest for knowledge of these amps. Unless and/or until I tackle building one of these, most of my my questions have been well answered. This thread was truly inspirational for me.
Thanks Again To All!
Gene

[Colossal]

Reeltarded has one he can sell you

[The Ballzz]

Ya know,
Looking at the schematics for these Pigs and Piglet, it strikes me that the two channels of the preamp look an awful lot like a crossover! Is there anyone here who knows how to determine the crossover frequency and the dbs per octave slope, as well as whether or not there is any overlap between the Bass and Treble channels? This would seem to be quite an interesting topic. It might be fun to build a similar amp with either a variable crossover point or even to control the frequency cut in of each channel separately. This could create a mid range boost or cut feature for some pretty precise tone shaping. While I understand the ins/outs/pitfalls of the full on Pig power section, the preamp is quite interesting and might lend itself to some pretty cool innovations?
Thanks,
Gene

[Matthews Guitars]

Consider KT120 tubes as an option. They'll handle the voltages.