Zener Diode, Stud Cathode or Anode?

[M Fowler]

Interesting, I tried that 60tc variable bias pot (limiter) and got interesting shred tone with a Ceriatone Express.

Mark

[JamesHealey]

I've used a 75v 75w Stud mounted Zener.. the polarity is cathode stud, but it's all they had! no reverse anode!!

It appears to be working fine though, i've also put a 12nF 400v cap in parallel with the Zener to shunt the hash that it puts onto the power supply.

The pre-amp tubes are biased fine as the pre-amp was designed to run on these voltages in the first place not the higher ones, and the bias winding is producing the correct voltages, i've got it as follows:

415v plates biased at 39mA. which is just shy of 70% diss, which these old Mullard XF2 can take all day long.


Seems to be working and sounding pretty fantastic, the noise the Zener was putting onto the power supply was horrid, the 12n cap really helped.

[M Fowler]

Are you using that limiter control and is yours wired to the prescense pot as shown. I find the limiter sounds pretty cool without changing the tone but just didn't work well on the Express.

[JamesHealey]

my amp is a cross breed between the Komet and the Express pre-amp.

with wreck output section.

[jaysg]

...i've also put a 12nF 400v cap in parallel with the Zener to shunt the hash that it puts onto the power supply.

Did you hear and/or look at the hash on a scope, or were you taking someone's word for it? (just wondering)

[JamesHealey]

I could hear it clear as day, I never bothered looking it up on the scope.

I just found some strange things happening with a '65 Deluxe Reverb I just serviced.. i might post my findings in the tech forum makes for an interesting read.