Hi there,
The 5E3 is cathode-biased, no need to worry about that. Check out Fuzzy's post and replies. This amp runs HOT.
I had a PT prob right out the gate with mine and I thought I changed the recto with the PT, but it's a dead ringer for a brown base Sylvania 5Y3GWT. I'm not sure what Nik uses but this is not a Sovtek. Point being, check that rectifier tube. If it's that brown base, no labeling just 5Y3GWT stamped on top, it's a goodun and built like a tank. If not, go NOS on your 5Y3 ($30-40 maybe less), it'll run cooler and probally last a lifetime.
On power tubes, I highly recommend the Tungsol new issues. They're heavy duty, run cooler and sound great. They are a little more expensive but, IMO, worth it.
I hope this helps a little. You could go Ga-Ga on the NOS thing and well worth investigating but I think this will give you a great start.
SammyC   

I also run Weber blue and silvers in an open back RME heirloom cab. KILLER.
I use that cab with a JTM45, an 18 watt lead channel clone and on occasion the 5E3 (in a Weber tweed cab). Can't say enough about Weber. Once I convert the 5E3 to 6L6's (KT66'S) ,via Mercury Magnetics, that 4 Ohm combination is gonna be SICK, as will be the 15A150 (great speaker btw),
Sammy

Hi Kids,
This should be fun and will be continued down the road.
I was planning to purchase the 5X3 kit 1. I believe Nik used his 5F4 (Super) PT and OT. There are some basic component changes (power resistors and the wirewound bias resistor) and the GZ34.
Early on I think it was a stacked (more iron and unloaded B+) PT in the original 5E3 chassis cutout (stay with me now).
Since I'm in the middle of a JTM45 build, I needed a combo for on the go situations. I got my Ceriatone 5E3 back from my buddy and let him use one of my 18 watt heads. (here we go...whew!!) I'm back to the original 5E3 Chassis.
Paul, at Mercury (like Nik, very helpfull and generous with the time and info), recommended the tweed deluxe FatStack PT (FTDP-E-FS/350V B+ unloaded) and the BF Vibrolux OT (FBFVL-O/ 8 Ohms)(or the FTS-OS/ 8 Ohm tweed super would work as well). Also recommended was the (FC-TSUP) tweed super choke.
With the choke, can I go with the 5F4 layout (10k 1watt power resistor and the wiring)?
Thanks for bearing with me, it should be a hoot,
SammyC
PS...I do have a Variac (HIGHLY recommended for the crazy things we do)

I Ordered a completed 5e3 (no cab) and didn't have to. Actually the shipping was a little less than expected as well.
SammyC

  :)Thanks a lot. I first saw this cradle on U tube (A Metro Amp build) and couldn't find plans. Very nice indeed,
SammyC