vultures
Well-known member
I've got a JCM900 on my bench that I picked up from my buddy for insanely cheap. It had it's output transformer replaced with what looks like a JMP100 Plexi transformer from Electro Harmonix. The only problem is this transformer is heavier than a pigs ballsack, during shipping it ripped out of the chassis, broke some tubes, banged up some tube sockets and bent the chassis up real nice. My buddy was too afraid to even turn it on, didn't want the hassle of bringing it to a tech and paying (what he thought would be) an arm and a leg for repairs on a 900.
After getting inside the amp, not a single thing is wrong with it on the inside. Nothing I can find wrong inside the circuit. No blown resistors, not even a leaky cap. So the only next option is a play test. Plug it in and the amp absolutely rips. Sounds surprisingly great for a JCM900 with a weird output transformer. I shaped the chassis back to square, and I thought about remounting this transformer with some stainless steel L Brackets, but I don't think that's the right move. The mounting hole isn't big enough and the transformer pinches some of the wires. It wouldn't be great to have it break through and these leads shunt to ground one day. Alongside the risk this hunk of iron will tear out again if it's ever on the road. I think I need to replace this with an original JCM900 transformer. I plan on offering this back to my bud for the price I paid him + the cost of the stock transformer.
Anyone have experience with some of these?
$118 - Hammond 1750P - Looks to be reversed pin out from stock Marshall schematics, but would work fine.
https://www.hammfg.com/part/1750P
$315 - Axiom M-4100-100-O from Mercury Magnetics - At the bottom of the page. Premium price, but no spec sheet available? Kinda lame, the allure of spending more with the potential joy of not knowing that the fuck it is
https://www.mercurymagnetics.com/pr...0-watt&filter_product-type=output-transformer
$107 - Mojotone British 900 Style 100W - Now we're getting somewhere, idiot proof schematic, matches up with the JCM900 4100
https://www.mojotone.com/British-900-Style-100-Watt-Output-Transformer
$139.95 - "Genuine" Marshall 100 Watt Output Transformer - This is the bad boy I'm leaning towards if it's actually genuine.
https://www.amplifiedparts.com/products/transformer-marshall-output-100-w-jcm900
After getting inside the amp, not a single thing is wrong with it on the inside. Nothing I can find wrong inside the circuit. No blown resistors, not even a leaky cap. So the only next option is a play test. Plug it in and the amp absolutely rips. Sounds surprisingly great for a JCM900 with a weird output transformer. I shaped the chassis back to square, and I thought about remounting this transformer with some stainless steel L Brackets, but I don't think that's the right move. The mounting hole isn't big enough and the transformer pinches some of the wires. It wouldn't be great to have it break through and these leads shunt to ground one day. Alongside the risk this hunk of iron will tear out again if it's ever on the road. I think I need to replace this with an original JCM900 transformer. I plan on offering this back to my bud for the price I paid him + the cost of the stock transformer.
Anyone have experience with some of these?
$118 - Hammond 1750P - Looks to be reversed pin out from stock Marshall schematics, but would work fine.
https://www.hammfg.com/part/1750P
$315 - Axiom M-4100-100-O from Mercury Magnetics - At the bottom of the page. Premium price, but no spec sheet available? Kinda lame, the allure of spending more with the potential joy of not knowing that the fuck it is
https://www.mercurymagnetics.com/pr...0-watt&filter_product-type=output-transformer
$107 - Mojotone British 900 Style 100W - Now we're getting somewhere, idiot proof schematic, matches up with the JCM900 4100
https://www.mojotone.com/British-900-Style-100-Watt-Output-Transformer
$139.95 - "Genuine" Marshall 100 Watt Output Transformer - This is the bad boy I'm leaning towards if it's actually genuine.
https://www.amplifiedparts.com/products/transformer-marshall-output-100-w-jcm900
