Testing RCA7360 valve on AVO MKIV - UK Vintage Radio Repair and Restoration Discussion Forum

flemming.kirsby · 30th Oct 2015, 11:06 pm

Any suggestions? Have made the following test:

They test OK on my HICKOK 800 tester.
The set up I made are as follow!

7360 / no data / 00 / 154 326 611 / 6.3 / 0 / 250 / 250 / 2.6 / 2.2 / B9A

Getting around 2.4 to 2.6 mA/V on the 5 tubes I have in stock more or less same result as on the HICKOK tester, but there its transconductance measured and it varies in same manner as seen on the AVO.

Pl.s. comment
Best regards

Flemming Kirsby

Radio Wrangler · 30th Oct 2015, 11:34 pm

That's a seriously weird valve.

The AVO VCM certainly doesn't have the facility to control the voltages on the deflectors, so I suspect it treats them as suppressor grids and puts them at cathode potential (they should be at about 25v if I remember)

With equal deflectors, the beam should deliver 50% of the cathode current to each anode and the overall Gm should be about twice what you quote IF both anode currents are combined.

If your tester is measuring one anode at a time (a good idea for checking balance) then you'll get what you've seen, half the quoted Gm.

David

30th Oct 2015, 11:06 pm	#1
flemming.kirsby Diode Join Date: Mar 2015 Location: Birkeroed, Denmark Posts: 3	Testing RCA7360 valve on AVO MKIV Any suggestions? Have made the following test: They test OK on my HICKOK 800 tester. The set up I made are as follow! 7360 / no data / 00 / 154 326 611 / 6.3 / 0 / 250 / 250 / 2.6 / 2.2 / B9A Getting around 2.4 to 2.6 mA/V on the 5 tubes I have in stock more or less same result as on the HICKOK tester, but there its transconductance measured and it varies in same manner as seen on the AVO. Pl.s. comment Best regards Flemming Kirsby

30th Oct 2015, 11:34 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,902	Re: testing RCA7360 valve on AVO MKIV That's a seriously weird valve. The AVO VCM certainly doesn't have the facility to control the voltages on the deflectors, so I suspect it treats them as suppressor grids and puts them at cathode potential (they should be at about 25v if I remember) With equal deflectors, the beam should deliver 50% of the cathode current to each anode and the overall Gm should be about twice what you quote IF both anode currents are combined. If your tester is measuring one anode at a time (a good idea for checking balance) then you'll get what you've seen, half the quoted Gm. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done