JTM45 clone - slow blow fuse wiring

benvall · May 2022

Hello,
I’ve had some bits for a JTM45 for around 10 years, I’ve finally decided to give it a go. It’s mostly based on the metroamp instructions but will be getting the modulus transformers shortly.

I have a query about the 500mA fuse wiring.

The metroamp show this as coming from the PT and to the ground, whereas the modulus layout shows it being wired to the standby switch and rectifier socket.

Can anyone explain to me why these are different??

https://imgur.com/a/szKEBu8

I'll use this thread as a bit of a build log, but, as it’s been 10 years already don’t expect regular updates lol.

Thanks all

RiftAmps · May 2022

You can choose to fuse either the B+ rail (Modulus) or the HV CT (Metro). Each way is equally valid and most designers will simply choose either their preferred option, or whichever suits their layout.

A fused B+ rail doesn't protect the transformer against a shorted silicone rectifier diode, but on a JTM45 you have a valve rectifier, so this isn't really an issue (usual caveats apply).

If you want to go overkill, install flyback diodes (1N4007) on the GZ34 socket, then fuse both the B+ rail AND the HV CT.

hollywoodrox · May 2022

Slow blow fuse wiring - that’s a John Mayer song isn’t it

benvall · May 2022

@RiftAmps thanks for the info

benvall · May 2022

Chassis
https://i.imgur.com/sZu8oMC.jpg

Heater wiring started
https://i.imgur.com/ne1g5rf.jpg

Board and wires
https://imgur.com/a/bGIAOn2

Howdy, Stranger!

Categories

In this Discussion

Become a Subscriber!

JTM45 clone - slow blow fuse wiring

Comments