Fuse on HV CT to Ground, Yea or Nay?

[pdf64]

Ah yes, I think I see it now; it's the lower impedance to ground after the rectifier that acts to push the bias tap below ground potential?
Thanks for bearing with me

[martin manning]

If the bias tap is separated from ground by a resistance, and current is flowing into the secondary at that point, then voltage must drop across that resistance. That means the bias tap is below ground.

[pdf64]

So, given there's a space going spare for a (single) fuseholder on the OPs DR back panel, what's the best use for it?
My vote is for a F300mA after the rectifier / reservoir, before the feed to OT CT and choke, to mitigate stress on the B+ due to tube shorts, which seems the most likely failure mode.

For a single B+ fuse, any reason not to use a a fuse in the PT B+ CT ground return for amps without a bias tap, eg cathode bias, bias derived from full winding AC30 AC50 JTM45?

[NickC]

She's done and she sounds great!

Modifications:

"extra" hole (polarity switch) used for fuse holder (spare fuse)

bias test points on back panel

tremolo circuit caps changed to slow the trem rate

switchable bright caps on both channels (on pull pots)

3-spring reverb pan, and 0.0022 verb cap instead of stock 0.0033

back panel switch to disable NFB

"Larry" grounding scheme (nice and quiet)

Heyboer PT and Mercury Magnetics OT

JJ 5U4GB rectifier tube (rather than GZ34) to knock down the B+ from 493V to 454V