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Argus25 · 18th May 2018, 12:56 am

Keith,

I can't recall exactly but I think the primary of the TV22 lopt has around 2000 turns and the secondary close to 3000. So for arguments sake if it is all working ok and say there was some EHT around 7kV to 9kv (But I don't know off hand what the value is for a TV22) then one could expect the peak anode voltage on the H output valve to be about 2/5 x 7kV or well over 2kV peak, which would normally destroy a x 10 scope probe (usually only good for 700V) and damage a scope's input circuits too. Even a x 100 probe might not be rated for such a high peak voltage, but some are rated to 2.5kV, but it still can be pushing it for the anode of a line output valve:

https://docs-apac.rs-online.com/webd...6b80c645f1.pdf

The best probe is one of these but they are darn expensive:

https://au.rs-online.com/web/p/oscil...robes/7966702/

Probably lucky when you did the test the EHT and other voltages were low.

Hugo.

18th May 2018, 12:56 am	#6
Argus25 No Longer a Member Join Date: Oct 2016 Location: Maroochydore, Queensland, Australia. Posts: 2,679	Re: Bush TV22 flyback pulse Keith, I can't recall exactly but I think the primary of the TV22 lopt has around 2000 turns and the secondary close to 3000. So for arguments sake if it is all working ok and say there was some EHT around 7kV to 9kv (But I don't know off hand what the value is for a TV22) then one could expect the peak anode voltage on the H output valve to be about 2/5 x 7kV or well over 2kV peak, which would normally destroy a x 10 scope probe (usually only good for 700V) and damage a scope's input circuits too. Even a x 100 probe might not be rated for such a high peak voltage, but some are rated to 2.5kV, but it still can be pushing it for the anode of a line output valve: https://docs-apac.rs-online.com/webd...6b80c645f1.pdf The best probe is one of these but they are darn expensive: https://au.rs-online.com/web/p/oscil...robes/7966702/ Probably lucky when you did the test the EHT and other voltages were low. Hugo.