[Hallicrafters] Re: Amperite 4H4C for Halli SX-88 - and another ballast tube option

[Phil Barnes-Roberts WA6DZS]

Pacific T.V. wrote:
> Hello,
> 
> I think if you check the service manual the SX-88 uses a 4H4 not a 4H4C 
> and there is a note about a 4H4C not being suitable as a replacement for 
> the 4H4 in the SX-88. We stock both and our web site is; pacifictv.ca
> 
> thanks,
> 
> John
> 
Thanks, John--

I see you folks seem to carry all the Amperites.

My BAMA Ops&Svc Inst. (for Run1, which I believe this one - S/N 150 - 
is) has no notes about it.  However -

At < http://antiqueradio.org/halli09.htm >, there is a note after the 
SX-88 Tube list; I quote -

"V19  	4H4C*  	Current regulator
V20 	6BA6 	Crystal calibrator

*Although some literature specifies a 4H4 tube, Hallicrafters Addendum 
Sheet 94X1351 states that a 4H4C tube must be used. 4H4C ballast tubes 
are virtually unobtainable at this time. Fortunately, you can substitute 
the readily-available 6V6 tube. The 6V6 provides no current regulation, 
but it has the right filament characteristics and requires no 
modification to the receiver. The purpose of the 4H4C current regulator 
was to help maintain stability when the AC power supply varied, a 
problem that has largely disappeared in modern times. You should 
experience no significant performance difference using a 6V6 in place of 
the 4H4C and the 6V6 will also last longer."

(They also have a typo; V15 is a 6C4, not 6C5.)

I also found a fascinating modern, inexpensive solid-state substitute at 
< http://www.r-390a.net >, under [References], [Tutorials], [Wei Li's 
Pearls of Wisdom], [Ballast Tubes] (a 172-page PDF.)  On pages 10..12, 
K0CQ has invented a simple current regulator across a diode bridge, that 
can be plugged in for a 3TF7, to supply the 300mA for the tubes it 
regulates.  It clips the current sine wave on both half-cycles, but 
needs True-RMS metering to set up right, and _could_ be a noise source.

With a careful resistor sub (ballpark 2.32ohm, 1W), it could supply the 
450mA for V3, the 6U8 in the SX-88.  If you ever come up short of 
product, you may wish to recommend this non-original fix.  Probably 
regulates much better than the iron filament, and can be plug-n-play if 
a customer wishes to go original and can find the tube.

In a tube-based module box (still available somewhere) this could be a 
lucrative sideline.  Some folks are asking $100-150 for such a module.

> 
> At 12:17 AM 8/6/2005, you wrote:
> 
>> Hi, Guys&Gals--
>>
>> I'm looking to get a 4H4C ballast tube (probably by Amperite) for the 
>> Hallicrafters SX-88 I'm going to be restoring.  It doesn't need much, 
>> but it will get re-capped (there are already a few Orange Drops under 
>> there, among the Black Beauties and Tiny Chiefs; need to finish the 
>> task.)
>>
>> If the tube isn't available, do you know where I can get a pre-built 
>> current regulator module as a replacement?  There have been some 
>> designs on the reflectors, but nothing for sale.  I can build it if 
>> need be.
>>
>> Absent a commercial regulator module, might you know where I could 
>> find an octal module (plug/case) to build it into?
>> -- 
-- 
vy 73, WA6DZS Phil Barnes-Roberts < mailto:WA6DZS at arrl dot net >
(Kitbuilder, Designer, Cybersmith) Voice: 626-791-0851h
There are No Passengers on SpaceShip Earth;
We are All Crew, and need to start acting like it.

-- 
73, Phil Barnes-Roberts WA6DZS mailto:WA6DZS at arrl dot net
All else aside, RF to the other fellow's antenna is what counts.