[Boatanchors] Re: Correct PS for a very early HRO?

[WA1KBQ at aol.com]

Actually any of the National Velvet AB  supplies 5880, 5887, and 5897 will 
work with HRO receivers equipped with 2.5  volt tubes but there are some 
differences to be aware of. Early HRO's were  actually supplied with type 5897 power 
supplies originally designed for FB-7  receivers. It is interesting to note 
most 5897 supplies have an ID plate on top  stating the supply was especially 
designed for FB-7 receivers. Type 5897  supplied about 230 volts B+ for 
loudspeaker operation and was dubbed the  short-wave listener supply. For 
communications work using headphones National  recommended type 5887 which supplied 180 
volts B+. Both 5887 and 5897 supplies  had black wrinkle cabinets. Type 5880 was 
available in three different styles  but is essentially the same supply; 
later ones had better filters. National  Velvet AB 5880 predates both 5887 and 
5897 and was originally designed for SW-5  Thrill Box receivers. National Velvet 
AB 5880 had a brown wrinkle cabinet with  black shading, an in-line on/off 
switch and it's filter was a Mershon three  section wet electrolytic. A later 
type 5880 with a black wrinkle cabinet and  small ID plate was sold for SW-3 
receivers and the latest 5880 with a gray  cabinet was sold with model HFS super 
regenerative VHF receivers.Type 5880  furnishes 180 volts B+. It is interesting 
to note early National advertising  recommended if you were interested in a 
new FB-7 receiver and already owned a  type 5880 power supply it was not 
necessary to purchase a different power  supply. National advertising went on to say 
that because 5880 had more filtering  it was a more expensive supply than 
necessary for FB-7 receivers. I would have  to re-examine the schematics but I 
believe the main difference is B+ at 230  volts versus 180 volts and 8uf- 8uf 
dry type electrolytics for the FB-7 power  supplies versus the 5880's 8uf- 8uf- 
8uf wet type. Later 5880's, especially the  gray ones would have been equipped 
with dry electrolytics.

Regards, Greg  




************************************** See what's new at http://www.aol.com