UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - AZ31 as rectifier for a stereo Mullard 3-3?

qualityten · 3rd May 2021, 7:22 pm

Thanks for this prompt guidance. I did not know that valves like the AZ31 are rather scarce. I only remembered I had one when I saw that it had been used in the Ferguson circuit and thought it would look rather nice!

Reading the Ferguson service manual, I see that it has a total HT current of 94mA, so just under the 100mA limit of the AZ31. Out of interest, the four tuning scale lamps are powered by the heater supply to all the valves except the EL33s.

Noting Andrew's comment in post #5, if I use an EZ81 can I power all the heaters via the winding intended for the EL33s? If not, it'll have to be silicon. Or the transformer might be better used in another project in the pipeline that is also SS rectified and uses just four ECL82s.

3rd May 2021, 7:22 pm	#12
qualityten Octode Join Date: Feb 2009 Location: Wallasey, UK. Posts: 1,312	Re: AZ31 as rectifier for a stereo Mullard 3-3? Thanks for this prompt guidance. I did not know that valves like the AZ31 are rather scarce. I only remembered I had one when I saw that it had been used in the Ferguson circuit and thought it would look rather nice! Reading the Ferguson service manual, I see that it has a total HT current of 94mA, so just under the 100mA limit of the AZ31. Out of interest, the four tuning scale lamps are powered by the heater supply to all the valves except the EL33s. Noting Andrew's comment in post #5, if I use an EZ81 can I power all the heaters via the winding intended for the EL33s? If not, it'll have to be silicon. Or the transformer might be better used in another project in the pipeline that is also SS rectified and uses just four ECL82s. Last edited by qualityten; 3rd May 2021 at 7:30 pm.