Gathering Parts for 2 Jtm 45/100 endblock builds

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mightymike
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Gathering Parts for 2 Jtm 45/100 endblock builds

Post by mightymike » Mon Oct 21, 2013 6:39 am

I I haven't been building the last 2 years while on the road. I have a JTM 45/100 I built in 2005/2006.. But it has the modern Voltage switch, and the Panel isn't the most most accurate. It plays amazing. . That's the most important thing, but I'm itching to build an over the top top masterpiece.
On these builds I will have the Rifa caps on the Power board, some Eries, NOS resisters, and NOS mil spec mica output tube sockets good up to 1000v.. Nos mustards, NOS or accurate repro Voltage and IMP Switch. Bulgin... The whole 9 yards.

The one I built has George Iron @500v. Part of me wants to try the 520v Martrans.. Still deciding while parts are arriving. The 500v does sound really Good.

I'm llooking to source accurate boards..

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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by Strat78 » Mon Oct 21, 2013 9:50 am

What about Chris's 45/100 tranny's. His PT can be wired for B+ of 560, 500 or 460v. To go easier on the tubes I was leaning towards a B+ of 460v. He can do the OT as well. Mike, are you going to go for the high polish chassis look? :drool: Also, what choke will you be using? I have an original Radiospares 20H going in mine. If you can find a source for boards let me know. I sent allot of cash to Ray Domzalski for two sets of boards only to be strung along for the last five months, I'll never see those boards. :x I did manage to get two sets of NOS orange board material from Brian, but I'll need a good drill press and staking tools to put those to use. Maybe we can get some guys together for some group purchases to save a little cash, perhaps on the head cabs.

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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by mightymike » Mon Oct 21, 2013 2:20 pm

The choke I have in my JTM45/100 build, I got from George back in the day. It was a Heyboer, and just looked at the amp, and the frigin sticker is gone. I just looked at it. I'll see if my guy Ken is still around, and I can take measurements of my board in my JTM 45/100 Dickenson spec. The one I have is a little different. I used all F&T 47uf on the board, and used a v2 bypass cap.

This time I will go with the Rifa, and gulp.. no bypass cap. I'm I'm addicted to them.


And yes I'm going with polished aluminum. As far as Chris goes, I have a 470/430 laydown Drake coming, and I already have one of his JTM 45/100 ot that has been in a box for 7 years waiting for me to use it. To compare to the Heyboer build, but I would rather just build a whole new amp.

If I could get an actual JTM45/100 PT off him with the multiple voltages you said, that would be great. I would get that and another Black Flag OT, but the 460v Drake PT was all he had right now

Maybe I will build it with the 470/430 PT. His PTs have Terminals, and are easy to swap.

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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by neikeel » Mon Oct 21, 2013 2:52 pm

I modded my 45/100 build (from 2006) to Dickinson spec, all Pihers but a dual 16 RS preamp can
- early Metro PT with 540 on the plates, sounds very, very nice as it is even with Gold Lions (keeping the GECs).
That choke is 7H IIRC.

I have another in kit form with Marstran trannies, but I will use same spec resistors and preamp can for sure (I have x3 of those 16/16uF RS caps NOS left).

Like you I have all the other parts NOS (inc selectors) but have the international octals not ceramic valve bases.

Post your progress, mine may take a while with all my other commitments!

These amps really clean up well and have good playing dynamics - don't spoil it with a big v2a cap :thumbsup:
Neil

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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by mightymike » Mon Oct 21, 2013 6:00 pm

It wasn't that big. Just a little tiny 330uf BC lol.
The thing I love most about the JTM 45/100 other than the thick tone, is the way it goes into feedback so beautifully. Practically like a Fernandez Sustainer. Mine has Gec Smoke Bottles and Valve Art.

Do you have the part# for their 7h Choke?

I do want to go true to spec this time.

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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by neikeel » Tue Oct 22, 2013 5:29 am

True spec for mid '66 on is a Drake 354-114 which is 3H.

The 20H were random on 45/100 AFAIK and they do sag a lot as although the H rating is high the current rating is low.
Neil

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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by mightymike » Tue Oct 22, 2013 11:18 am

I think mine is a 3

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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by Strat78 » Tue Oct 22, 2013 3:28 pm

Breakup and sag, I'm so there! Below is a quote from Roe's The Evolution of The 100W. I have found this info very intrieguing, so much so that I put my RS 20H choke into my 12xxx last night just to hear it for my self. As soon as I get the bugs out with the new c1998 installed, I'll report back. There is an odd 20H, 70ma, 690 ohm choke on eBay right now.

"The choke (inductor) on these early amps appears to have been the Radiospares 20 henry choke often seen on the early Marshall schematics. The Radiospares choke is different from the Drake and Dagnall chokes used later. The Radiospares choke is rated for 20 henry and 70mA, whereas the Drake and Dagnall are rated for 3 henry and 100mA. It also has a have a high resistance (690 ohms) compared to the later chokes (110 ohms). This high resistance gives more voltage drop across the choke than with the later chokes. When running the amp hard, screen voltages (and preamp voltages) will sag more, giving a softer response with more breakup."

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Henry Chokes me up.

Post by JimiJames » Tue Oct 22, 2013 7:22 pm

Strat78 wrote:"...Breakup and sag... I have found this info very intrieguing, so much so that I put my RS 20H choke into my 12xxx last night just to hear it for my self..."
Rob's findings on choke affecting Tone which I thought was cool to know about. :thumbsup: http://forum.metroamp.com/viewtopic.php ... 60#p111758
[IIRC Stan (bmf5150) & Mark (rockstah) also have done multiple swaps to hear; with 3H up to 20H]
RIP Mark Abrahamian-rockstah -classmate/roommate
RIP Ben Wise -StuntDouble- comrade-in-arms

__________________________________________
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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by mightymike » Tue Oct 22, 2013 10:31 pm

I remember trying a 10h Merc in one of my first standup 69 kits, and thinking it was stiff. I have used 3h in everything since

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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by neikeel » Wed Oct 23, 2013 5:07 am

Strat78 wrote: There is an odd 20H, 70ma, 690 ohm choke on eBay right now.
Can't find it :(
Neil

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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by Strat78 » Wed Oct 23, 2013 5:37 am

neikeel wrote:
Strat78 wrote: There is an odd 20H, 70ma, 690 ohm choke on eBay right now.
Can't find it :(
Actually it is 60ma, 650ohm:
http://www.ebay.com/itm/Stancor-Choke-f ... 2c7348f073" onclick="window.open(this.href);return false;

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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by mightymike » Tue Nov 05, 2013 7:00 am

Polished Chassis, end block and panels on their way. That was kind 9f the lynch pin for this project. I have some mil spec octal tube sockets that are good up to 1000v. I have rifa 33uf axials, and period correct diodes (forgot what they are called) so my tone board is set. I need a good NOS Treble and Mixer cap, a PT, and boards.

It's going to fun to A/B the 2 JTM 45/100s

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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by Twistingcrow » Mon Jul 07, 2014 5:09 pm

Hi!
What's up on this pair? Are they done and singing? :P

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Re: Gathering Parts for 2 Jtm 45/100 endblock builds

Post by neikeel » Tue Jul 08, 2014 4:15 am

Twistingcrow wrote:Hi!
What's up on this pair? Are they done and singing? :P
I was thinking the same (not that I can talk :roll: )!
Neil

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