Valve Query - UK Vintage Radio Repair and Restoration Discussion Forum

oldticktock · 7th Apr 2010, 11:17 am

Hi,

Just organising my valve shelves and try to get actuals and equivs together. I came across some PY800's which according to the TDSL database are the equivalent of a PY81.

My Radio & Valve Data Book however does not list them as equivalents.

Checking the data for the PY800 against the PY81

The PY800 heater is 19v where the PY81 is 17v, the peak inverse volts are 5250 where the PY81 is 4750, the peak anode is 350v where the PY81 is 450v, finally the peak cathode potential is 5750 where the PY81 is 4750.

Can anyone confirm if these are indeed equivs or not

Thanks
Chris

ppppenguin · 7th Apr 2010, 11:27 am

The PY800 is a slightly uprated version of the PY81 and can be used as a replacement. The extra heater voltage is negligible in a series chain.

kalee20 · 7th Apr 2010, 12:52 pm

I've even got one labelled PY81/800. Don't know what the heater voltage settles at, with 300mA flowing, though...

PY800 can be used as a replacement for the PY81. But not the other way round. So they are not true equivalents.

ppppenguin · 7th Apr 2010, 1:25 pm

I think the PY801 is slightly uprated again. The PY88 has even higher ratings and so can also be used provided you can find another 12V or so for the heater.

PS: Can't see anything against using the PY83 either. The PY80 is similar to the PY81 but slightly lower ratings.

oldticktock · 7th Apr 2010, 1:36 pm

So you can use PY801 in place of a PY81 ?

ppppenguin · 7th Apr 2010, 1:41 pm

Quote:

Originally Posted by oldticktock

So you can use PY801 in place of a PY81 ?

Yes. But strictly speaking not the other way round.

7th Apr 2010, 11:17 am	#1
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Valve Query Hi, Just organising my valve shelves and try to get actuals and equivs together. I came across some PY800's which according to the TDSL database are the equivalent of a PY81. My Radio & Valve Data Book however does not list them as equivalents. Checking the data for the PY800 against the PY81 The PY800 heater is 19v where the PY81 is 17v, the peak inverse volts are 5250 where the PY81 is 4750, the peak anode is 350v where the PY81 is 450v, finally the peak cathode potential is 5750 where the PY81 is 4750. Can anyone confirm if these are indeed equivs or not Thanks Chris

7th Apr 2010, 11:27 am	#2
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: Valve Query The PY800 is a slightly uprated version of the PY81 and can be used as a replacement. The extra heater voltage is negligible in a series chain.

7th Apr 2010, 12:52 pm	#3
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,088	Re: Valve Query I've even got one labelled PY81/800. Don't know what the heater voltage settles at, with 300mA flowing, though... PY800 can be used as a replacement for the PY81. But not the other way round. So they are not true equivalents.

7th Apr 2010, 1:25 pm	#4
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: Valve Query I think the PY801 is slightly uprated again. The PY88 has even higher ratings and so can also be used provided you can find another 12V or so for the heater. PS: Can't see anything against using the PY83 either. The PY80 is similar to the PY81 but slightly lower ratings.

7th Apr 2010, 1:36 pm	#5
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Valve Query So you can use PY801 in place of a PY81 ?