Marshall 1930 Popular - what should I do with it?

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sonicmojo
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Marshall 1930 Popular - what should I do with it?

Post by sonicmojo »

I have an opportunity to get this amp but I'm in a dilemma as to what I would do with it. There are some very strange things going on in it that I'd need to sort out and I may be going down a rabbit hole on this one. It has been modded into some sort of a lead 18W EL84 circuit with tremolo disconnected. The amp works. I wouldn't say it sounds great as is - has balls but sounds kind of fizzy to me. I haven't done anything but play it and look at it to this point.

I see three options here,

1. Take it back to the 10W ECL86 version with one preamp tube and SS rectification (I've read this circuit doesn't sound so good) or
2. Make the mods right and make it into more of a traditional 1958 (2x10) 18W circuit and make the tremolo work again (it seems halfway there already and might sound pretty good if made right)
3. Walk away and let someone else sort this out.....

It appears to have a different PT which makes sense but the OT looks original. It also has Vox rebranded Celestion 7724 speakers (8 Ohm each) instead of what I think should be Celestion 7442 speakers (15 Ohm each). I kind of wonder if that OT, if original like I think, is really suited for the 18W circuitry and 4 Ohm impedance but I cannot find much information out there on these early Marshall combos or their transformers. What kind of impedance were these early Marshall combo OTs looking for, if anyone knows?

Does anyone have any experience with these amps or any suggestions what you'd do with this amp?

Thanks!

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Bryan
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M Fowler
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Re: Marshall 1930 Popular - what should I do with it?

Post by M Fowler »

I would most definitely have it as an Marshall 18w tremolo circuit.
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sonicmojo
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Re: Marshall 1930 Popular - what should I do with it?

Post by sonicmojo »

I'm definitely leaning 18w since it is almost there already although I'd likely strip the board, and redo everything, save what is worth saving, and make it the traditional circuit instead of whatever lead variant it is now. The PI tube in this has been moved to V3.
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Bryan
menger66
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Re: Marshall 1930 Popular - what should I do with it?

Post by menger66 »

Or you could covert to 2061x 20watt, maybe you could use that board adding the needed turret. Or twerk popular circuit to sound good, either way you have a sweet cab to build into seems a can't lose too me.
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Mr. dB
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Re: Marshall 1930 Popular - what should I do with it?

Post by Mr. dB »

When the Harrisons converted these amps to counterfeit 18Ws, didn't they usually use WEM Dominator transformers?
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sonicmojo
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Re: Marshall 1930 Popular - what should I do with it?

Post by sonicmojo »

This thread went dormant because I never acquired this amp over a year ago. Well, fate brought it back around to me again and this time I will be making it mine and properly fixing it up to a proper 1958 18W circuit with working tremolo. Should be fun and I will post progress as I go! The biggest starting question I have is what power transformer is in this thing and whether I should consider changing it out. Looks like all the heaters, including the rectifier are tied to the same secondary. Should I consider a different PT?
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sonicmojo
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Re: Marshall 1930 Popular - what should I do with it?

Post by sonicmojo »

Wow, look at the original grill cloth color! I never would have guessed. I’m thinking of putting in a 1x12 but I’ll have to make an entire new front baffle and just save the old one.
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joeboo88
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Re: Marshall 1930 Popular - what should I do with it?

Post by joeboo88 »

wow that is a real difference. is there any way to clean the cloth?

anyways the reason I'm replying sonicmojo, there was a guy Timbo at Hoffman site that was also doing something with the same amp.
It might help you in some way.

http://el34world.com/Forum/index.php?topic=23293.0

peace, Joe
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Reeltarded
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Re: Marshall 1930 Popular - what should I do with it?

Post by Reeltarded »

Oxyclean, vac with soft soft soft brush.. oxyclean.. vac, oxy, vac, oxy, vac.. viola.

Apply no pressure with the vac brush.. it's only to keep from accidently digging in with the plastic nozzle.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
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pompeiisneaks
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Re: Marshall 1930 Popular - what should I do with it?

Post by pompeiisneaks »

You clean things and you get a musical instrument out of it? :D

Sorry as a french speaker, I love it when people mix Voila and Viola :D

Slap me, I'll recover.

~Phil
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sonicmojo
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Re: Marshall 1930 Popular - what should I do with it?

Post by sonicmojo »

Thanks for the tips on cleaning and the link to the Hoffman thread. I'm definitely keeping the extra tubes in it and not handicapping back to the 1930 circuit. Slowly easing into this project as time permits.....

While I ponder how to approach a rebuild of the board to clean things up and get tremolo working again, I figured I'd check it out as is. EL84 plate voltages were off a lot, around 225V. I found that someone had put the OT center tap on the wrong side of the big 1.5K resistor on the first Erie filter cap. It is now back up around 345V. I guess there is a lot of leeway before it sounds REALLY bad.....and the last guy who owned it used it to record something!

As is, V1 is dedicated to the first channel, V2 for the trem channel, both of these being shared plates/cathodes. V3 is the PI and there is no tremolo circuit anywhere left except for the pots which seem right. Easy way out is I figure maybe I could leave the PI on V3, move a few components at V2 over to the right and use the gap to insert the tremolo back in. I'd use half of V2 for the trem circuit. OR maybe I'll just cut my losses and put in an entire new board and make it look better.......this is my debate.

Does anyone have a resource for a dark red phenolic type board, perf or not? If I do go the new board route, I'd prefer to make it look period correct.
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sonicmojo
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Re: Marshall 1930 Popular - what should I do with it?

Post by sonicmojo »

I'm going to use the existing board for now to see if I can get all the functions working properly with the correct original 18W Marshall values for the most part. The tone stack and plates for the first two tubes were reversed so I had to strip most everything in the first half of the board so I can get it in order again.

I've plotted it out and I can use a couple of terminal strips attached to the standoff screws so that way I don't have to hack it up any worse or remove it to add more turrets that won't match anyway. Nobody will see this but me and you anyway, right? :lol:
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Bryan
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Re: Marshall 1930 Popular - what should I do with it?

Post by Reeltarded »

pompeiisneaks wrote: Wed Jun 06, 2018 4:47 pm You clean things and you get a musical instrument out of it? :D

Sorry as a french speaker, I love it when people mix Voila and Viola :D

Slap me, I'll recover.

~Phil

Jerk! If I dont have my glasses on and Im tapping things out I am lucky it didnt say wax, repeat, whale. hehe
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
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Reeltarded
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Re: Marshall 1930 Popular - what should I do with it?

Post by Reeltarded »

Bryan, finding the tap on the wrong end of the resistor is eye opening, huh? I don't know if you might have caught me saying it before, but I variac 50s and 100s down to where the pilot lights go out. It's a little softer version of itself, but still very good.

I like that.

Board material. GOOD LUCK. My 72 100 project has been on hold for almost a DECADE looking for a right piece.. seems like it's not going to ever be.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
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pompeiisneaks
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Re: Marshall 1930 Popular - what should I do with it?

Post by pompeiisneaks »

Reeltarded wrote: Fri Jun 08, 2018 3:05 pm
pompeiisneaks wrote: Wed Jun 06, 2018 4:47 pm You clean things and you get a musical instrument out of it? :D

Sorry as a french speaker, I love it when people mix Voila and Viola :D

Slap me, I'll recover.

~Phil

Jerk! If I dont have my glasses on and Im tapping things out I am lucky it didnt say wax, repeat, whale. hehe
I know I'm a jerk, but at least I'm stupid :D

~Phil
tUber Nerd!
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