power section fuses

[deci belle]

Thank you, Pete! 5mm LEDs… I guess the JCM900 schematic I was deciphering said 5mm (not 5ma) and I appreciate the voltage spec for the EL34 too!!

[deci belle]

This is where my 5E3 power section is at with PT 2ndary (Slo-Blo) and center tap (Fast) leads fused.

The OT primaries have the conjunctive filter between them. Chuck told me a big 10k R and a 1500pF 2kV cap would be about right for a 5E3.

Each flyback diode going to GND has a 470k R and .01uF 1kV cap in parallel so no single diode will get hit harder than any others in each string.

The rectifier has the safety diodes from the drawing on the yellow paper from another thread.

Right now I'm just using 500mA fuses so I can play the amp. I'm waiting for 250, 300, 375mA fuses to see how low I can go.

[Steve Conner]

The capacitors you're using to share voltage across your flyback diodes total up to about 1500pF across the OT primaries, the same again as your conjunctive filter, but without the series resistance. I think they might kill the high end somewhat.

[deci belle]

Ok, Steve!

To be honest, I don't even know how the caps and resistors do what they do (or how they hurt higher frequencies, for that matter)— it's just a mod I did to my bf Showman's SS rectifier.

I can just run those diodes off the plates by themselves then.

When I build the safety circuit for my bigger amp, I'll use the Gas Discharge Surge Suppressor instead of the conjunctive filter to try that out too. There are already wires under the board to eyelets hidden under the big 10k R for the surge suppressor for when I want to try that on the 5E3.

Is it advisable to use a conjunctive filter AND surge suppressor?

I'm also questioning the fused CT on the PT. Maybe I should rather fuse the OT's CT.

Anyway, thank you for the tip!!

[deci belle]

I made the fuse-board for my Showman on a pedestal using the choke's chassis mounting holes.

The tandem fuse-blocks are for the PT's 2ndary; the one on the upper right is the OT-CT; the pwr tubes' cathode fuse has that 10k 3w in parallel.

Hey you were right about the high-end getting squashed, Steve. I found out when I removed those caps and resistors from the diode-strings!



Thank you all for the help!