Variable 6922 heater to cathode voltage limit...?

[ashok]

I found the following ( +ve) voltage limits for the heater to cathode voltage for the 6922 tube.

1. Telefunken 150 V
2. Raytheon 70 V
3. RCA 120 V
4. ( E88CC ) 50 V

Do they really vary so much between different makes?

Does anyone know the published limits for the Sovtek 6922 and Electro-Harmonix 6922 ?
Thanks.

 

[EC8010]

Do they really vary so much between different makes

Probably not, but the testing method and limits applied probably do.

 

[Tubes4e4]

Re: Re: Variable 6922 heater to cathode voltage limit...?

Probably not, but the testing method and limits applied probably do.

Indeed.

And moreover, isolation between heater and cathode gets worse over time. Certain datasheets (*) even define one of the "end of life" conditions for that tube via h-k leakage current at stated positive and negative h-k voltages.

So, h-k ratings given by manufaturers really depend on a lot of additional conditions - what they think is acceptable under the circumstances they considered.

Maybe the sometimes very lowish h-k ratings especially found for ECC88 and the like are not oriented so much at actual h-k isolation capabilities, but much more by noise issues and demands - considering the original/native and intentional usage ECC88 was designed for.

Regards,

Tom

(*) F.e, see Philips E188CC datasheet.