JTM 45/100 - Build story

[BoogieEngineer]

Thanks man, yes i thought it was enough sanded. i wish i could continue the build right now but ... work ... holidays to come ... so it won't be finished soon enough. But anyway, this project learned me patience lol, 20 months looking for parts and i don't even realise yet that it's getting built, still have in my mind the need to find the parts

Good for you. I had lots of fun building mine. I just wish I had the funds to build another. I love mine to death

[Xplorer]

Was it your first amp build ? Yeah, this is exciting, i hope i'm not doing any mistakes. Any advices, judging from the pictures ?
i've set the black and red wires from the OT this way ( isn't it gonna bring noise into the heaters wires ? or is it just the PT that produces such thing ? ), hope it's ok.

And the heaters wires going to the PT ..... well, i've seen both version: they either went to the two outer taps from the group of three .. or they went to some of the group of 6 taps.
i'm not sure yet how to wire the PT. ( and later, about the 490v or 560v tap, i guess i'll have to use the 490v tap first, to reform the caps more safely ? )

i also swaped the previous preamp tube sockets, for some amphenol ones. i realised that it was difficult to insert the preamp tubes, having to force it a lot, and i don't like it. these are fine.

[VintageCharlie]

shouldn't the swamp resistors be 1.5k instead of 5.6k? I thought all of the plexi Marshalls had 1.5k? Or was the 7026 modded?
Nice job on the heaters btw.!

[Xplorer]

Thanks ! i remember the line in the 100w kit , about the heaters :

"This step can not be rushed - careful attention here will pay off
in reduced hum and noise in your amplifier."

and that's what i did on my superlead. And It's not really noisy.

yeah, i've used some 5k6 because on the layout of billy batz, it says 1k5/5k6 , and i remember that some told me that it was better to increase this 1k5 value.
now i may use some welwyn 1k 3w or 5w. some advised me to use some 3w. also it's cool because it's smaller.

i'll have to see at which point i may use some lacing cord. I don't have enough pictures of this step of a jtm45/100 build, before the boards. and i'm concerned by the OT and PT wires connections.

hen ... the orientation of the mustards, with the outer foil ... ^^
and the drift of the CC resistors for some. i scored some old RS 56k CC recently, i may use these if they're good.

Any help for anything i mentioned would be very appreciated guys, as guides and double check.

then, the reforming of the old caps. i may use only one old electrolytic 16uf RS. and later i'd test an Erie 32uf. and probably a rifa 33uf.

But i'll have to let this build away for some weeks, because in a few hours .... THIS !!!!! Greece, wind, landscapes, diving, kite surf...

[Xplorer]

[VintageCharlie]

Argh, isn't amp building more exciting than these postcard adventures?

[Xplorer]

Ha ha. No !
My own pictures ^^
I tell you this is a jtm 45/100 build story... Including the sources of peace for the mind, in order to make a great amp, ha ha

[VintageCharlie]

What are you reading in the postcard with the dirty feet in it? Doesn't look like radiotron's handbook

[neikeel]

Thanks ! i remember the line in the 100w kit , about the heaters :
"This step can not be rushed - careful attention here will pay off
in reduced hum and noise in your amplifier."
and that's what i did on my superlead. And It's not really noisy.
yeah, i've used some 5k6 because on the layout of billy batz, it says 1k5/5k6 , and i remember that some told me that it was better to increase this 1k5 value.
now i may use some welwyn 1k 3w or 5w. some advised me to use some 3w. also it's cool because it's smaller.
i'll have to see at which point i may use some lacing cord. I don't have enough pictures of this step of a jtm45/100 build, before the boards. and i'm concerned by the OT and PT wires connections.
hen ... the orientation of the mustards, with the outer foil ... ^^
and the drift of the CC resistors for some. i scored some old RS 56k CC recently, i may use these if they're good.
Any help for anything i mentioned would be very appreciated guys, as guides and double check.
then, the reforming of the old caps. i may use only one old electrolytic 16uf RS. and later i'd test an Erie 32uf. and probably a rifa 33uf.
But i'll have to let this build away for some weeks, because in a few hours .... THIS !!!!! Greece, wind, landscapes, diving, kite surf...

That's funny as I have just come back from Cote d'Azur and got those sort of views each and every day swimming, snorkelling, came back to England to remember what wind and rain are!

I am doing the same I have some NOS 32/32 for my preamp and Steve Marshall's excellent RS labelled 33uF for the rest, hope to make very precise 7026 copy although a bit cleaner!

[BoogieEngineer]

I use separate 5.6K grid resistors for tube sockets. I read somewhere that that reduces oscillation and makes the output stage more stable. The original uses 1.5K swamp resistors though. Nice job twisting the heaters .

FYI I had to drill a couple more holes to implement Larry grounding. Be prepared for that if you want to do the same.

[neikeel]

Anyone know anything about these?

http://www.ebay.com/sch/plextone2009/m. ... 4340.l2562

[VintageCharlie]

Besides S.Marshall, who took it over from Xplorer, there is another forum member who has mentioned in a pm that he is onto making some repros, but afaik he hasn't gone public with that announcement, so i won't mention his name - maybe he'll check in, in case it is his work.
Looks, nice, except for the chipped hole surroundings of the impedance selector. Though it is very important that the contacts have been done properly so that they don't get loose over time - in case of the impedance selector, the loss of contact might mean a dead OT. Oh, and then there's the price - i have seen original parts for less, but they are extremely rare to be honest, so it might be justifiable for restorations, etc.

[Xplorer]

Wow, someone made it !
More expensive and not as exact as those i had planned to make but very nice anyway. Cool !
They're about 3x the price i paid for my originals though ...

[Xplorer]

More parts.

[Xplorer]

I'm now at the transformers step.
i'd like to make sure i'm connecting things right.

For the output transformer it seems clear, although i'll have to look where the orange and brown wires go.

For the power transformer, the black and red heaters wires should connect on G and I , right ? no matter which side ?
Then, when i'll reform the caps, i guess i should run the 490v tap ( and probably later, when formed, and with a re biasing and good tubes + less current coming in the primary 240v tap, .. the 560v tap, right ? )

the black, brown, red, and green wires coming out of the transformer ( if i use the 240v primary, but with a current closer to 220v hopefully, to reduce the 560v secondary, which is very high for modern tubes ) .... what should i do with them ?

i hope my pictures have no mistakes.
i don't understand yet why there are two 560v tap, and two 490v taps. ( is it for the fuses circuit ? ) . and 0 is for the ground ?
H is also for the ground ?