[Question] Marshall Major 200 Watts

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Bombacaototal
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[Question] Marshall Major 200 Watts

Post by Bombacaototal »

Recently I've been looking into the Marshall Major 200 watts for clean sounds

I am just wondering what is everyone's opinion about this amp. It is a pinnacle part of SRV sound and probably none of the factory amps left in the original state given the unreliable built famous for melting and blowing up

I know some people do 100watts replicas which don't sound the same due to different transformers

Is there anyway to make it more reliable? How is the sound compared to a 100watts Super Bass
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sonicmojo
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Re: [Question] Marshall Major 200 Watts

Post by sonicmojo »

I have access to a few early 70s Marshall Majors and I also have a '69 Super Bass. I had one of the Marshall Majors in my house at the same time for a while. They are different beasts but I love them both. I was considering getting the Major but the wattage makes it difficult to reasonably use. I just got a Fryette Power Station 2 which can handle 200W but I'm kind of afraid to hook it up to a Major.

If you are looking for pure, loud clean, the Major is a good bet. I can't speak to the failure rate but the three my friend owns all have original trannies. I've read that you shouldn't push the front end with pedals but I've not really gone to school on the circuit to understand why that would matter.
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Bryan
Bombacaototal
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Re: [Question] Marshall Major 200 Watts

Post by Bombacaototal »

sonicmojo wrote:I have access to a few early 70s Marshall Majors and I also have a '69 Super Bass. I had one of the Marshall Majors in my house at the same time for a while. They are different beasts but I love them both. I was considering getting the Major but the wattage makes it difficult to reasonably use. I just got a Fryette Power Station 2 which can handle 200W but I'm kind of afraid to hook it up to a Major.

If you are looking for pure, loud clean, the Major is a good bet. I can't speak to the failure rate but the three my friend owns all have original trannies. I've read that you shouldn't push the front end with pedals but I've not really gone to school on the circuit to understand why that would matter.
Thanks a lot for the reply. How does the sound of the Major compre to the Super Bass. One of my friends just got a 1973 Super Bass and I will try it this weekend. I am into late 80's SRV type of clean sound which is why I am considering the Major
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sonicmojo
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Re: [Question] Marshall Major 200 Watts

Post by sonicmojo »

I actually don't own the '69 Super Bass but it is at my house for a while. I'll probably grab the Major again and run through them in the next few days. I'm kind of considering the same thing, Major vs Super Bass. This Super Bass must be modded to Super Lead based on what I see inside but It is pretty much the same. I think you can do more things with a Super Bass/Lead but if you want the headroom, go for the Major if you find a decent one. I think the Majors are starting to get harder to find.
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Bryan
Bombacaototal
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Re: [Question] Marshall Major 200 Watts

Post by Bombacaototal »

sonicmojo wrote:I actually don't own the '69 Super Bass but it is at my house for a while. I'll probably grab the Major again and run through them in the next few days. I'm kind of considering the same thing, Major vs Super Bass. This Super Bass must be modded to Super Lead based on what I see inside but It is pretty much the same. I think you can do more things with a Super Bass/Lead but if you want the headroom, go for the Major if you find a decent one. I think the Majors are starting to get harder to find.
Yes, I think they are becoming a rare beast. Might be worth getting someone to build a clone if that is the direction I am going after!? I'm just a bit concerned with the reliability
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Post by Stevem »

I have rebuilt no less then 3 of them for a fellow, and they sound great especially with beefed up filtering , but they do weigh a ton and cost near as much!
You might be in the look out for a Ampeg Vt-22 head as these baby's Crank also , but cost way less !
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

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Bombacaototal
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Re: J

Post by Bombacaototal »

Stevem wrote:I have rebuilt no less then 3 of them for a fellow, and they sound great especially with beefed up filtering , but they do weigh a ton and cost near as much!
You might be in the look out for a Ampeg Vt-22 head as these baby's Crank also , but cost way less !
Thanks a lot for the suggestion. Just out of curiosity, what is the approx cost of rebuilding them

I am also curious as to how the sound of the Ampeg Vt-22 head compares to it? Thanks a lot
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Post by Stevem »

Well the biggest thing is the 100% price difference of the four KT88s over the 100 watt heads EL34s, the two extra 100/100 uf filter cans only add 50 bucks to the rebuild.
Many of them have bad / shorted OTs, and thats like 400 bucks for a replacement, or 600 to rewind one!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Bombacaototal
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Re: J

Post by Bombacaototal »

Stevem wrote:Well the biggest thing is the 100% price difference of the four KT88s over the 100 watt heads EL34s, the two extra 100/100 uf filter cans only add 50 bucks to the rebuild.
Many of them have bad / shorted OTs, and thats like 400 bucks for a replacement, or 600 to rewind one!
Wow, that's steep. Thanks for sharing the info :)
strelok
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Re: [Question] Marshall Major 200 Watts

Post by strelok »

My understanding with regards to the Major's failure rates has to do with the fact that ran it in Ultra-Linear mode with some 700 volts on the plates. The other was the flyback voltages would tend to cause arcing between the screen and plate pins on the power tube sockets.

If you're brave enough to build one you might consider not running UL and/or lower plate voltages though that will impact the sound. From what I understand though, as long as the output section is running clean, neither of these things is a problem. I know of someone who uses one essentially as a pedal mule. The thing pretty much never makes it above 1 on the volume knob and its insanely loud.

One thing I would definitely recommend though for any major is heat shrink over the screen and plate pins of the power tubes to help minimize the chances of arcing. From what I understand that's one of the main factors in fried OT's.
Bombacaototal
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Re: [Question] Marshall Major 200 Watts

Post by Bombacaototal »

strelok wrote:My understanding with regards to the Major's failure rates has to do with the fact that ran it in Ultra-Linear mode with some 700 volts on the plates. The other was the flyback voltages would tend to cause arcing between the screen and plate pins on the power tube sockets.

If you're brave enough to build one you might consider not running UL and/or lower plate voltages though that will impact the sound. From what I understand though, as long as the output section is running clean, neither of these things is a problem. I know of someone who uses one essentially as a pedal mule. The thing pretty much never makes it above 1 on the volume knob and its insanely loud.

One thing I would definitely recommend though for any major is heat shrink over the screen and plate pins of the power tubes to help minimize the chances of arcing. From what I understand that's one of the main factors in fried OT's.
Interesting comments. Thanks for the tip on the UL as well
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martin manning
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Re: [Question] Marshall Major 200 Watts

Post by martin manning »

strelok wrote:My understanding with regards to the Major's failure rates has to do with the fact that ran it in Ultra-Linear mode with some 700 volts on the plates. The other was the flyback voltages would tend to cause arcing between the screen and plate pins on the power tube sockets.
About 600V per annotated schematics. Why would UL operation contribute to OT failures? UL means screen and plate pins are at a fixed voltage ratio, Which is not the case for the ~constant screen voltage of a normal power stage.
strelok wrote:One thing I would definitely recommend though for any major is heat shrink over the screen and plate pins of the power tubes to help minimize the chances of arcing. From what I understand that's one of the main factors in fried OT's.
I would think that an arc could sneak under the heat shrink to an adjacent pin without any trouble.

I recall reading somewhere that increasing the screen resistors to 1k helped prevent meltdowns.
strelok
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Re: [Question] Marshall Major 200 Watts

Post by strelok »

I totally forgot the Majors only used 250R on the screens. I suspect 1k's would help as well.

Its not so much that its running in UL mode just that, from everything I've ever heard the Majors run much higher than 600v, which could just be due to higher modern line voltages. kt88 screen voltage has a max of 600v and in UL of course if the plate voltage is much higher than 600v the screen will be too. So the idea would be to make another node to run the screens off of in the power supply and run them as regular pentodes with the screens in the 500v range. Of course now you're into the whole thing of modifying a rare vintage amp...building a new one I'd certainly want to make sure the plates stayed at or below 600v in UL mode.

Of course all the failures due to arcing etc can be avoided by not pushing the amp into hard clipping, and god help anyone around you if you are doing that. :lol:

You're probably right about the heat shrink too. I suppose it might help a little but it might also just find someplace else to arc. I suspect the flyback voltage could potentially reach 2kv. Supposedly Marshall started using ceramic sockets because they'd get arcs through the plastic of the tube socket. No idea if that's true or not.
Bombacaototal
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Re: [Question] Marshall Major 200 Watts

Post by Bombacaototal »

Does anyone have a good schematic of this amp?
strelok
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Re: [Question] Marshall Major 200 Watts

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