Well, I hope it's the rectifier wiring! I checked and it looks like the standby switch is OK. Talking about the rectifier's diodes... I used the schematic that uses no diodes. I guessed that would be fine, as it's not used neither in this schematic nor in metroamp's manual.

But now you mentioned it, should I use those diodes? I thought the valve rectifier already worked as a diode rectifier. Oh, I also wanted to ask if it's normal to measure about 0.4 ohms between pins 2 and 8 of the GZ34 valve rectifier.

Anyway the amp is at my parent's house so I won't be able to check this until this weekend. And this time I'll be using a lightbulb current limiter.

I mean, with only the GZ3 tube installed, the power switch ON and the standby switch OFF (standby mode), the 500mA fuse blows after about 10 seconds. I don't know if it helps, but I measure 42 ohms DC between the 350V (high voltage)  ends and their common (0V) end.  Is that OK? Or it's that what's blowing all the fuses I have?    I mean, while the fuse is not blown, I actually measure 350V between he terminals and the common, and 42 ohms DC is gonna be  much more in AC.

Perhaps it's something I've connected incorrectly, but I've been unable to locate any errors... Other option would be a bad GZ34.

Hi, I'm trying to build a JTM45 using the Ceriatone transformers. I'm used to building circuits, although I had never built circuits using valves. Instead of a 6.3V indicator, I use an Amber lamp. I connect one end to the 120V OT wire and the other end to the 0V wire next to the 120V one, this is the only difference with the schematics of ceriatone. I wired the amp using the schematics of ceriatone.com and I'm using the pdf file to power up the amp, testing point to point before installing each tube . The problem comes when I put the first tube, GZ34. The 500mA fuse is then blown and I measure 0 volts DC on the stand-by switch, when (according to this, page 20, point D) I should measure 325V DC. I've been re-cheking the whole circuit and I can't find any mistake. I'm checking everything again but perhaps I'm lucky and someone here can help me.