Mojotone JCM800 build

Rotorcraft230

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I was a teenager in the 80s and the most iconic amp to me was the JCM800 2203/2204. Well here it is 3 decades later I’m building one for my son. Follow along and check out the build. I’m will post lots of pics. I’ve already upgraded to CTS from Alpha, Cliff jacks, and laying out my own circuit board. 982B83C2-4B19-40A3-85B9-FA6B3629A93B.jpeg 018012C3-E8FC-4B53-8B67-CA3F5A2425EA.jpeg 1B304A12-59B3-4A15-B196-7F7391AF24D4.jpeg 2E47D784-CB36-4432-8CA4-2D4EA2A208E7.jpeg A30FF9E9-1E12-461D-86A6-52AE0B4F0F37.jpeg
 

paul-e-mann

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I was just looking at the Mojo 50 watt JMP and considering it. :yesway:
 

Rotorcraft230

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They are good kits,Heyboer transformers and components. We have a Studio Obe with over 1000 hours on it and still going strong
 

playloud

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Looking extremely promising so far!

Why isn't this in "building the classics"?
 

Pete Farrington

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I’ve already upgraded to CTS from Alpha
I think that’s a downgrade. Alpha Taiwan have a better taper (CTS don’t leave the CCW track end pad until the wiper reaches nearly 3 on a 0-10 scale) and a smoother action.
CTS track wafer
4143-DB18-2-B46-4930-81-FB-0805-CFA999-A1.jpg


Regarding the heater wiring, I acknowledge that the normal Marshall arrangement uses sweeping loops to reach the far (4&5) terminal, but it seems ripe for improvement to me. Wiring across the socket eliminates the loop, and if the socket is rotated 180°, the gap between pins 1&9 can be used.
Noval-Socket-Heater-Wiring.jpg
 

playloud

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I think that’s a downgrade. Alpha Taiwan have a better taper (CTS don’t leave the CCW track end pad until the wiper reaches nearly 3 on a 0-10 scale) and a smoother action.
CTS track wafer
4143-DB18-2-B46-4930-81-FB-0805-CFA999-A1.jpg


Regarding the heater wiring, I acknowledge that the normal Marshall arrangement uses sweeping loops to reach the far (4&5) terminal, but it seems ripe for improvement to me. Wiring across the socket eliminates the loop, and if the socket is rotated 180°, the gap between pins 1&9 can be used.
Noval-Socket-Heater-Wiring.jpg

It may be smoother, but I feel like the Alpha taper feels less "substantial", and therefore somehow more "cheap". Perhaps that's silly...

I like your heater wiring. Plan to use it in my next build in fact.
 

Wmacky1

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"I was just looking at the Mojo 50 watt JMP and considering it" Where do you see a JMP 50W from them. I've been looking?
 

jchrisf

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"I was just looking at the Mojo 50 watt JMP and considering it" Where do you see a JMP 50W from them. I've been looking?
 

Wmacky1

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Yeah saw that one. Was looking more for a 1987 style but with EFF loop and PPIMV. I already have a 2203X
 

Rotorcraft230

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So I haven’t made a turret board yet till now, this is what I came up with. I have a rivet squeezer (used to hand squeeze rivets for aircraft repair) and made a mandrel. You can control the speed and the amount of squeez very well. It’s well controlled. None of the turrets are cracked and have been flared for a tight fit. 6850DA75-37F1-440C-8378-DCDE01B7FCE0.jpeg EC8B61A0-8FB3-4FF8-B57F-4E06B320A67D.jpeg DB9246CC-4544-46A3-AC11-D037CBD32F71.jpeg B8ACC902-8EC3-4459-942B-F3FC19B0393C.jpeg A3429796-2BB8-4198-84A1-64338AA3A021.jpeg
"I was just looking at the Mojo 50 watt JMP and considering it" Where do you see a JMP 50W from them. I've been looking?
that’s it the British 50w. The early 2203/2204 were JMP.
 

Rotorcraft230

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It’s not different other than the chassis. If you look at the two kits layout they are just about identical, there are a few component changes and the chassis is much shorter
 

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