My new Marshall JMP

[EZS]

okay sweet. Thanks man, was getting a little hesitent there for a second. Dont be surprised if I hit you up one of these nights while im in the middle of it with some dumb ass question!

Any time. Ive been inside these JMP's since 1983 when I got my first 76 2204. Hooked ever since.

 

[HamishR]

If it helps here is a detail of a turret board layout for a similar Marshall. It shows how the bias section is laid out in an older Marshall but the concept is the same. Often the 47K which you see connected to the bias trimpot is swapped for a different value to get the bias in the right voltage range. One of the things I always liked about the old PCB Marshalls is that the layout is very similar to the turret board layout so it's easy to go from one to the other. It can be a bit easier to read the turret board layout and how it relates to the schematic though

 

[EZS]

This will clarify some miss information regarding JMP 50w bias resistors. Your 56k on trimmer and 220k range is correct for EL34. Note: the bias range resistor (R8 below) is not the one next to the 22k trim pot. Its before the half wave recto diode.(D1 below)

 

[masonlewisdiesel]

This will clarify some miss information regarding JMP 50w bias resistors. Your 56k on trimmer and 220k range is correct for EL34. Note: the bias range resistor (R8 below) is not the one next to the 22k trim pot. Its before the half wave recto diode.(D1 below)
View attachment 89178

Your the man, I'm ordering some things from mouser/small-bear, and antique electronic supply tonight. So it will take a few days. whats the caps of choice for this thing? Like nichicon I think makes some. as well as f&t sprauge. any advice there? while I'm waiting on parts there's.. no harm done using the amp like I have been right?

Is there anywhere between you and I locally you recommend to get components? I'm in Tacoma. I wish radio shack was still open...
In all those years working on Marshalls(impressive by the way) What kind of experience do you have with the THD Yellow jackets? and/or the Blue(16ohm) hot plate?

 

[masonlewisdiesel]

If it helps here is a detail of a turret board layout for a similar Marshall. It shows how the bias section is laid out in an older Marshall but the concept is the same. Often the 47K which you see connected to the bias trimpot is swapped for a different value to get the bias in the right voltage range. One of the things I always liked about the old PCB Marshalls is that the layout is very similar to the turret board layout so it's easy to go from one to the other. It can be a bit easier to read the turret board layout and how it relates to the schematic though

View attachment 89176

you guys are awesome! thank you so much! I was wondering about that, the layout did kind of look the same! Thank you!

 

[EZS]

Your the man, I'm ordering some things from mouser/small-bear, and antique electronic supply tonight. So it will take a few days. whats the caps of choice for this thing? Like nichicon I think makes some. as well as f&t sprauge. any advice there? while I'm waiting on parts there's.. no harm done using the amp like I have been right?

Is there anywhere between you and I locally you recommend to get components? I'm in Tacoma. I wish radio shack was still open...
In all those years working on Marshalls(impressive by the way) What kind of experience do you have with the THD Yellow jackets? and/or the Blue(16ohm) hot plate?

Tacoma! cool. So the 16ohm HotPlate. Worlds best imho. I have a few. I remember when Andy Marshall was above the Ballard Firehouse in the 80's. Ive taken my amps there a few times and was so inspired. Great guy too. Locally anymore? Fryes? Alphatronics? still in business? Mouser is great, Nichicon are great for bias caps. Anything from Mouser really, just look at data sheets and get low ESR. F&T, for filters. Even the generic Taiwan caps are quality, but for resale wise, stick to cork sniffer stuff. Try a 32/32 in the pre, and the PI. Feels great, but get 50/50 if you dont like it. Put a long ground wire on the Pre cap so you dont have to lift the board swapping that cap. 16/16 is raunchy fyi. JMP's are so easy and fun to work on. But your amp is old and the trace pads are fragile. If they do lift of break, just jump leads together under the board.

 

[HamishR]

As far as caps go these days I'm using F+T for the big electrolytics, (https://www.tubesandmore.com/products/capacitor-ft-multi-section-electrolytic), Vishay BC for the smaller electrolytic (https://www.tubesandmore.com/produc...uminum-electrolytic-021-asm-series-axial-lead), and Vishay Roederstein 630V for the coupling caps (https://www.tubesandmore.com/products/capacitor-vishay-roederstein-630v-mkt1813-axial-lead).

I have also used Sozo and Mallory 150 for coupling caps with excellent results. The smaller black Spragues are ok for the 25/50 size cathode bypass caps but I have recently been experimenting with the Vishay BC for those. I used to use the Sozos for coupling caps, mainly because of internet buzz I guess. But they are a bit of a pain to fit onto a board sometimes, they're expensive and the Vishay Roedersteins work really well and cost a lot less. Plus they come in a wider range of values.

 

[masonlewisdiesel]

Tacoma! cool. So the 16ohm HotPlate. Worlds best imho. I have a few. I remember when Andy Marshall was above the Ballard Firehouse in the 80's. Ive taken my amps there a few times and was so inspired. Great guy too. Locally anymore? Fryes? Alphatronics? still in business? Mouser is great, Nichicon are great for bias caps. Anything from Mouser really, just look at data sheets and get low ESR. F&T, for filters. Even the generic Taiwan caps are quality, but for resale wise, stick to cork sniffer stuff. Try a 32/32 in the pre, and the PI. Feels great, but get 50/50 if you dont like it. Put a long ground wire on the Pre cap so you dont have to lift the board swapping that cap. 16/16 is raunchy fyi. JMP's are so easy and fun to work on. But your amp is old and the trace pads are fragile. If they do lift of break, just jump leads together under the board.

"stick to cork sniffer stuff" Thats comedy man! Love it. I get what your sayin though! components came in saturday, proabably going to do it over next weekend. Also, lookin around for a used blue hotplate (locally first). Seen some for around 250. Was gonna stop by guitar maniacs and see if Rick King has one and is able to hook it up. If you come across one, let me know forsure! My neighbor (the one who helped me get this JMP) was in a band (camerosmith i think?) back in the 90s that came from here, he knows andy and is always tellin me the same thing about Andy being the best at that kind of stuff.

 

[masonlewisdiesel]

Tacoma! cool. So the 16ohm HotPlate. Worlds best imho. I have a few. I remember when Andy Marshall was above the Ballard Firehouse in the 80's. Ive taken my amps there a few times and was so inspired. Great guy too. Locally anymore? Fryes? Alphatronics? still in business? Mouser is great, Nichicon are great for bias caps. Anything from Mouser really, just look at data sheets and get low ESR. F&T, for filters. Even the generic Taiwan caps are quality, but for resale wise, stick to cork sniffer stuff. Try a 32/32 in the pre, and the PI. Feels great, but get 50/50 if you dont like it. Put a long ground wire on the Pre cap so you dont have to lift the board swapping that cap. 16/16 is raunchy fyi. JMP's are so easy and fun to work on. But your amp is old and the trace pads are fragile. If they do lift of break, just jump leads together under the board.

If it helps here is a detail of a turret board layout for a similar Marshall. It shows how the bias section is laid out in an older Marshall but the concept is the same. Often the 47K which you see connected to the bias trimpot is swapped for a different value to get the bias in the right voltage range. One of the things I always liked about the old PCB Marshalls is that the layout is very similar to the turret board layout so it's easy to go from one to the other. It can be a bit easier to read the turret board layout and how it relates to the schematic though

View attachment 89176

thank you sir, got the parts in saturday!

 

[EZS]

FYI, I unboxed my fave Plexi spec to document it. I was surprised to see I used 50/50 across the board for the 50w. So you can disregard my above filtering suggestions. Even though anything above 20u will sound great. Good luck on your resto!