[Hallicrafters] Re: [Boatanchors] solid state replacements for 5R4 rectifier tube

[Barry Hauser]

Hi Bob:

I don't know of a source offhand.  I have an old 5U4 "Solidtube" which
basically consists of a potted octal tube base with two rectifiers in it.
 You really don't need the tube replacements, you can either harvest the
base of a defunct tube or buy fresh bases from AES and others.  Then just
solder in the appropriate rectfiers - allowing a healthy margin for PIV
and wattage.  You can also solder the rectifers to the appropriate tube
socket terminals.  I've seen some cases where the leads were thick enough
that someone just bent and trimmed them and inserted them into the socket
on top.

However, retrofitting solid state rectifiers usually results in higher B+
 than specified, and in combination with higher line voltages -- 120 to
as high as 126, which I have here, vs. the 110-117 of yesteryear -- you
can be way over, and possibly enough to exceed the working voltage of
some components.  You would have to check the B+ and add a dropping
resistor to get it back down as needed.  Even that 5U4 replacement came
with a little instruction sheet warning of exceeding B+ level and that a
resistor might be needed.  (Imaging the TV set owner who thought -- "Oh
goody, I can replace that 5U4 that's always burning out once and for
all", then reads the caveat.  Didn't say anything about that on the
outside of the package.

In addition to "too high" there's such a thing as "too quick".  With
solid state rectifiers, the B+ turns on immediately -- ahead of the
warmup delay of the filaments of the tubes in the set.  I'm not totally
up on this aspect, but it's supposed to be a bad thing for tube
longevity.  Might be theoretical, as many R-390A's are running with solid
state rectifiers in place of their 26Z5W's and many report no problems.

Unless you absolutely must reduce heat, I'd stay with the tubes.  For the
5R4, you might want to go with the heavy duty replacement -- 5R4WGB or
5R4WGA/B/Y  -- usually made by Chatham but also others, like Raytheon,
Cetron, etc..  These look like ice cream cones - the flat bottom kind --
and have extra thick glass envelopes -- coincidently flat-topped.  They
cost a bit more but still available at reasonable prices.  I don't know
if they'll physically fit in the HT-32 -- nearly twice the diameter of a
regular 5R4 w/o "shoulders" (ST type).  

Running out of B/W here.  If you want some sources for those, let me
know.

Barry




, On Fri, 8 Feb 2002 19:58:30 -0600 "Bob Raley" <raley at emptychair.net>
writes:
> Does anyone on the list know of a source for these?  I checked with 
> AES and
> they don't stock them.  If you know of a source please let me know.  
> I'd
> like to purchase a couple of these to replace the 5R4 and 5V4 in my 
> HT-32.
> 
> Thanks..................................Bob kg5r
> 
> _______________________________________________
> Boatanchors mailing list
> Boatanchors at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/boatanchors
> 

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