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" You OT is an 784-128 an Early version of 139 which have no 4ohm winding but 100v output for PA aplication. It was designed for el34 use. You amp is a jtm 50 with no doubt 67 era"
Actually, the markings on the OT are very difficult to read, but the last three numbers look more likely to be 139, not 128. This is why I think it may be a 4 ohm tap, not a 100v. And it is marked JMP on the front, so I would hesitate to call it a JTM 50. I have an email in to the folks at Marshall, we'll see if they can help. And for the record, there is nothing wrong with the customer's amp, he just wanted it looked at, and we decided since one of the original electrolytics was showing signs of residue leaking, it would not be a bad thing to replace the 5 on the board. The cans look to have already been replaced at some point, so we left those.
There are no screen resistors, and I know some would recommend installing them, but I am not in a hurry to change anything in this one.
Actually, the markings on the OT are very difficult to read, but the last three numbers look more likely to be 139, not 128. This is why I think it may be a 4 ohm tap, not a 100v. And it is marked JMP on the front, so I would hesitate to call it a JTM 50. I have an email in to the folks at Marshall, we'll see if they can help. And for the record, there is nothing wrong with the customer's amp, he just wanted it looked at, and we decided since one of the original electrolytics was showing signs of residue leaking, it would not be a bad thing to replace the 5 on the board. The cans look to have already been replaced at some point, so we left those.
There are no screen resistors, and I know some would recommend installing them, but I am not in a hurry to change anything in this one.
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