Marshall Black Panel JTM45 vintage reproduction Monkeymatic project

[xtian]

I have a repeat client who has sent me all the parts for, "the very rare Black Panel JTM45 from the Kronemeyer collection." Let's go!

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Target images:

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[dcribbs1412]

Very nice!

[xtian]

First issue: PT is undocumented, so I'm trying to figure out the windings and connection terminals. At bottom left are heaviest wires, clearly the 6.3v heater winding with CT. At top right is likely the HT winding with CT. The terminals marked "NC" on my yellow sticky note are not connected to each other or anything else! But the two remaining terminals are connected. After experimenting with low AC voltage, I went ahead and applied 120vAC to the terminals I marked "Primary?", and I got the voltages marked in red, only half of what I expect. No sign of the 5v heater winding.

What's wrong here? Do I need to remove the top end bell cover to find if there's a fault?

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[pdf64]

Consider asking on the Marshall forum, neikeel there is an expert with vintage Marshall stuff.

[xtian]

I noticed the voltage selector jumper is...not jumpered! I added a wire.

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However, this just deepened the mystery. Now three of the terminals are connected together, and one is still not connected to anything. I also removed the end bell--all the wiring inside appears to be OK.

[xtian]

Here is a list of DC resistance measurements between the PT's terminals. Makes no sense for a healthy PT.

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[GAStan]

Any luck with this?

[xtian]

I found that the primaries are the two terminals at the right side of my drawing. Secondary voltages were good. However, I determined there is no 5v winding, and my client aborted the project until he can find a suitable replacement. He's not interested in new iron, only vintage.

[GAStan]

Hopefully he locates one, looks like a cool project. Glad you got it sorted out.

[eddiep]

sweet project

[Matthews Guitars]

In thge event that you are looking for repro front and rear panels, I have an offering for you and anyone else who is doing Marshall restorations and reproductions.

I make the highest quality, most authentic reproduction front and back panels for JTM45s and JMP era Marshalls that you can get.
I make them in plexi and also for the JMP metal panel era. I've been making the metal panels for some time and the plexi panels are a new venture for me.

Not even Marshall has replicated the original bronze powder based gold painted panels that they stopped making at the end of the plexi era in mid 1969.
But I do. It is labor intensive. But it's a labor of love as I am a Marshall enthusiast myself. I started this project to get what nobody was offering. I figured,
I found a need, I will fill that need and make the project pay for itself.

I now make JMP and JTM45 panels in bronze powder based gold paint. The color match is as close as I can get it, not being sure exactly what those original gold
panels looked like 54 years and more ago.

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5 types in "standard" gold, not bronze powder based paint.

5 plexi types_sm.jpg

[rooster]

Weird thing here? The chassis you show has the PT and the OT oriented the way I would build an amp - however - when Marshall made these amps the orientation was diff. In the Marshall product the coils were turning the same direction (in a line) and not with the OT 90 degrees to the PT.

This post caught my eye because I have a Ceriatone JTM100 clone here that I'm replacing the OT in.

Before I make the leap, does anybody have a thought on the subject? Thanks.

[xtian]

does anybody have a thought on the subject? Thanks.

Use headphone trick to listen for best iron orientation!

[Reeltarded]

Weird thing here? The chassis you show has the PT and the OT oriented the way I would build an amp - however - when Marshall made these amps the orientation was diff. In the Marshall product the coils were turning the same direction (in a line) and not with the OT 90 degrees to the PT.

This post caught my eye because I have a Ceriatone JTM100 clone here that I'm replacing the OT in.

Before I make the leap, does anybody have a thought on the subject? Thanks.

Turn the OT 90°! Yes.

[rooster]

Thanks for the comments. I'm turning it 90 degrees, there's room and I know this has always worked for me. As to the headphone deal, yes, I appreciate there are a few ppl who abide in this method but I'm not that anal about the task. Besides, it always looks wonky and, too, I've never seen any white paper science regarding this, only hear of ppl who swear it's The Way. However, I appreciate both suggestions and appreciate that both of you took the time to respond.

Oh, I also see that the Plexi faceplates are discussed on the Marshall forum. I would love to get me a JTM Black Flag for some reason (?), but I also learned on the Marshall forum that all of the Plexi plates are being sold for $95. Hm.