7JP4 Heater protection in series string sets

[bandersen]

Here's a lengthy discussion of the topic: http://antiqueradios.com/forums/viewtopic.php?t=132513

I find the specs on the P6KE8.2CA kinda confusing. I was expecting one of those values to be 8.2

Breakdown voltage - 7.79
Clamping voltage - 12.2
Working voltage - 7.02

[jr_tech]

Thanks for the link... lots of good info there. I went ahead and ordered some 8.2 devices, will give them a try to see what they do to the RMS voltage at the 7JP4 heater pins during turn on surge and normal operating conditions.

Still scratching my head over the specs that you posted, will try to determine the slope of the voltage vs current curve around the 8.2 voltage point. Possibly it could have considerable slope.

jr

[Findm-Keepm]

Originally Posted by bandersen

Here's a lengthy discussion of the topic: http://antiqueradios.com/forums/viewtopic.php?t=132513

I find the specs on the P6KE8.2CA kinda confusing. I was expecting one of those values to be 8.2

Breakdown voltage - 7.79
Clamping voltage - 12.2
Working voltage - 7.02

8.2V is the "nominal" point at which it draws 10 mA current. Higher Value (>9.1V) TVS diodes are typically specified at 1 mA.
1 mA current is also the specified current for most MOV's "varistor voltage" and the same for some silicon carbide (old school) varistors. There are exceptions, but most modern datasheets adhere to the "voltage at 1 mA" standard.


I have a Fluke 332D voltage standard - handy for checking higher voltage varistors (VDRs) - my NOS and removed stock all checks within about 5% of the varistor voltage. It's kinda cool to "dial-up" to the 1 mA current, and read the voltage directly from the front panel knobs. $2,000 tester for 50 cent parts... Also handy for checking meters and ammeters.