[Amps] transformer from dielectric heater tspa

[Larry Carman]

Thanks for the info, John. 
450 mA of plate current sounds right for the 5868. 
When I connect the primary of the transformer to 230 VAC I'm getting about
4700 volts AC from ct to outer leg of the secondary which seems a bit too
much for the 5868. The unloaded primary draw is .45 amps which seems quite
high. For all I know, this may be normal for these types of transformers.
I'm afraid that part of the primary winding may be shorted together. LaRose
could have added very little filtering which would cause a huge voltage drop
when powered up therefore justifying the seemingly high secondary AC
voltage. 
The unit used a tube rectifier. Gotta be pretty old stuff.
Many thanks,
Larry N5BIP

-----Original Message-----
From: John T. M. Lyles [mailto:jtml at lanl.gov] 
Sent: Tuesday, May 09, 2006 11:09 AM
To: amps at contesting.com; lncarman at swbell.net
Subject: transformer from dielectric heater tspa

I checked at home, and my WT LaRose dielectric preheater uses the 
5868 triode. It is a THERMALL model 9, about 2.5 feet tall. It has a 
plate current maximum (trip out relay) at 450 mA. Perhaps this is 
similar to the one Larry has a transformer from. In any respect, that 
tube is rated for 450 watts of dissipation, and the various 
datasheets for the TB4-1250 version and the 5868 Amperex version show 
~0.5 Amps of plate current at 4 kVDC. I would then make a guess that 
the THP-4 transformer is in this range of current rating. It may have 
run slightly higher voltage, but the current shouldn't go up much.

73
John
K5PRO

>  >Date: Sun, 7 May 2006 16:50:54 -0500
>  >From: "Larry Carman" <lncarman at swbell.net>
>>Subject: [Amps] thp-4 HV transformer
>>To: <amps at contesting.com>
>>I picked up a very old HV transformer, in good condition, which came from
a
>>RF heater which ran a 5868/TB4-1250 tube. The model number on the
>>transformer is THP-4. I have no idea who manufactured it or when it was
>>made. Maybe someone can tell me more about it?  When I connect 240 to the
>>primary I get a .45 amp primary current draw with no load on secondary.
Is
>>this typical for very old transformers?  The secondary is center-tapped
with
>>? the secondary winding above the other ? on the core. I get about 4700
VAC
>>from center tap to either of the other secondary legs. It weights 46 lbs.
>>Maybe this would be a good HV trans for a 4-1000 tube. Any help
identifying
>>this dinosaur would be appreciated.
>>
>>Regards,
>>
>  >Larry N5BIP