I have purchased a Magnetic Components OT (Magnetic Components calls it a "50W Marshall Power, Laydown Mounting"). Before I rip and replace I can't quite line up all the connections. I live in Minnesota (North America). Here's a chart listing my connections:

Ceriatone            Magnetic Components
Labels                 Labels

E                         ?
O                         ?
120V                   120V
0                         5V
5V                       5V

350V                    345V
0                         ?
350V                    345V
3.15V                   315V
0                          ?
3.15V                   315V

1. Any idea what connection I use for the Ceriatone "E" connection? This connects to ground, but the Magnetic Component (MC) OT has no connection labeled either E or ground.
2. The Ceriatone connection labeled O (adjacent to the 120V) connects back to the AC input. Would I use the MC connection labeled COM?
3. The Ceriatone connection between the two 350V labeled O; would I use the MC 345V center tap connection (labeled 690V CT @ 150mA)?
4. The Ceriatone connection between the two 3.15V labeled O; would I use the MC 3.15V center tap labeled 6.3V CT @ 5A?

Did I purchase the wrong output transformer--or am I just challenged by conflicting labels?

Any advice would be greatly appreciated.
Regards, Paul.

OK, it's been a while since I started this topic. I have finally got back to troubleshooting my JTM45.

I have removed all tubes, upon applying power the fuse blows. So I have unsoldered all the output connctions from my power transformer and it still blows a fuse.

I suspect I have a faulty power transformer and I must acquire a replacement. Any advice on where to purchase a replacement?

Thanks,
Rocko

When I look at my Power transformer I see three sets of wires per your description:
1. a yellow pair labeled 0 and 5V, going to the rectifier tube;
2. a purple pair with both labeled 350V, going to the rectifier tube, and
3. a brown pair with both labeled 3.15V, going to all tubes except the rectifier tube

I will disconnect the three sets of wires, test, and then add each one back in, one at a time, to see which blows the fuse.

More later.

I pulled the two power tubes and the rectifier tube, inserted a new fuse, attached the power cord, turned it on and it immediately blew the fuse. I then removed the three small tubes and got the same result--blown fuse. So according to your troubleshoting tips, there is likely a short somewhere. I have gone in with my volt-ohm meter looking for shorts but cannot find any.

Any other troubleshooting ideas?

I purchased my JTM45 about four years ago and last summer it started blowing its fuse. We were playing an outdoor gig in Minnesota on one of those hot and humid nights. After the fourth song it blew its fuse (the fuse that can be replaced from the back of the head). I have replaced the 2A fuse but the head will blow a new fuse as soon as you turn it on. I have tested all the tubes in a tube tester and they all look good. There was no smoke or burning smell. The inside of the head looks OK--there are no exploded caps, no burnt components, no weird smells. Continuity checks all appear good. All resistors measure OK. I cannot check any voltages because the fuse blows the instant I turn the head on.

Anyone have any good next steps in troubleshooting?