Randall RT2/50 Amplifier - Schematic needed

[shadygreentree]

Hi All
I have one Randall RT2/50 that is blowing HT fuse. I have tried pulling out the tubes suspecting a short but still no luck. I would appreciate if someone can share a schematic or service manual.

Thanks

Sandeep

[Enzo]

Someone may have the schematic, but tube amps tend to all be alike basically, especially when they blow fuses.

Look up light bulb limiter, make one, and use it. Stop blowing fuses.

Some places to look:
Shorted rectifier.
Shorted filter cap.
Shorted flyback diode.
Shorted output transformer.

Does the position of the standby switch matter? Does it even have a standby switch?

Power off, discharge any caps that are holding. Measure resistance from the plate pin of each power tube socket to ground. Any low resistances? measure resistance to ground from the output transformer center tap. Is that a low resistance? If either of those is low, which one is lower, plates or center tap? measure from hot side of each filter cap to ground, any show low resistance?

While I hope we come up with one, there is a lot you can do in a tube amp without a schematic.

[shadygreentree]

Hi Enzo
Thanks for the reply. I do have a light bulb jig and not blowing fuses. Just blew one initially now I know there is a short when the bulb light up at full brightness.
Thanks for the tips, I can start looking around. I was just hoping someone had the schematic that will make things lots easier for me.
Thanks once again for your response, very much appreciated.

Regards

Sandeep

[Leo_Gnardo]

What Enzo suggested ^^^ plus "foreign objects" loose inside the amp. A favorite is busted-off guitar plug tips. Loose nuts, bolts, other hardware too. Murphy's law tells us they will wedge themselves between chassis and energized circuit points. Got kids? They like to stick things into jacks and vent slots too, little blighters. Remove chassis, look carefully, turn chassis upside down, give it a shake & a couple knocks, maybe something metal will fall out.

[shadygreentree]

Thanks Leo_Gnardo
Will look at it and come back to report what I found.

[shadygreentree]

Hello All
Thanks once again for the replies. Finally I was able to fix the amp. The short was on one of the anodes connection of power tubes. It is a double sided PCB, the track where OT wire connects to PCB has burnt and shorted with ground, it was underneath one of screen resistors thus didn't show on visual inspection.
By the way, Randall amps were kind enough to send me a partial schematic.
Cheers
Sandeep