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

[jeremy-ca]

Thanks Greg.

I would assume that the HRO will run fine on 180V and stay cooler plus drift 
less.

I'll find some schematics but at first guess I'd think that the 3 stage cap 
version uses a second choke. This could be bypassed, the 8 mF's could be 
upgraded to 20-30 mF and the result would be a bit more voltage as well as 
better hum filtering.

Ive run my NC-101X and NC-200 on as little as 90 VAC and speaker volume is 
still more than enough for a big room. Granted they have PP audio but a 
single 2A5 is no slouch.

I'll take this project one step at a time.

BTW, are you interested in those E178 HRO photos I took and offered to you 
and Barry a few days ago? Already sent to Barry. The hand written and IRC 
resistors may interest you as they are identical in size and construction 
making me wonder if they didnt make both. I confirmed with a digital 
micrometer. Is there any documentation that states that National actually 
"built" their own?

Carl
KM1H


----- Original Message ----- 
From: <WA1KBQ at aol.com>
To: <national at mailman.qth.net>; <boatanchors at mailman.qth.net>
Sent: Monday, November 05, 2007 7:44 AM
Subject: [National] Re: Correct PS for a very early HRO?


>
> 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
>
>
>
>
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