[Hallicrafters] The hot SX28 6V6s

[Richard Knoppow]

----- Original Message ----- 
From: "Warren Elly" <w1gud4 at gmail.com>
To: "Asif Khan'Nick'" <hallicraftersx28 at aol.com>
Cc: <Hallicrafters at mailman.qth.net>
Sent: Monday, October 31, 2011 7:38 PM
Subject: Re: [Hallicrafters] The hot SX28 6V6s


> AC line voltage is especially critical with transmitters 
> like ef johnson rangers - most were wound for 110 volts
> The variac is the AMers friend
>
> 73
> Warren W1GUD
>
> On Oct 31, 2011, at 10:31 PM, "Asif Khan'Nick'" 
> <hallicraftersx28 at aol.com> wrote:
>
>> The fact that the tubes run real hot could be also be due 
>> to leaky caps ! Also a solid state rectifier in the power 
>> supply could also boost the voltages in the power supply. 
>> Are you also using the correct impedance speaker?
>> Nick
>> -----Original Message-----
>> From: Guido <laffitte at prtc.net>
>> To: hallicrafters <hallicrafters at mailman.qth.net>
>> Sent: Mon, Oct 31, 2011 6:55 pm
>> Subject: [Hallicrafters] The hot SX28 6V6s
>>
>>
>> The heat problem in the 6V6s of my SX28 was basically 
>> solved by lowering the AC
>> oltage to 110. Household voltage here sometimes soars to 
>> 125VAC. Lowering the
>> oltage with a Variac reduced the heat to what one could 
>> consider warm and
>> ormal. It was hot to the point where one could not touch 
>> the lid just above the
>> ubes.  The tubes still have some bluish glow left though. 
>> This tells a lot
>> bout the importance of operating these older rigs at the 
>> voltage for which they
>> ere designed. Anyone remembers when the voltages came up?
>> 73s
>> Guido KP4FAR

    At the time the Johnson Ranger was built standard line 
voltage in the US was 115V or 117V. It has gotten higher, a 
way for power companies to economise on copper. A good 
solution for equipment which is on all the time is to run it 
from a Sola constant voltage transformer. Similar resonant 
transformers were also made by other companies. They have 
the advantage over a simple Variac of regulating the voltage 
which can make a noticable improvement in stability 
especially in equipment which is sensitive to filament 
voltage variation. They are also excellent transient 
filters. Sola transformers turn up used fairly frequently. 
The only caviet is that some have bad capacitors in them 
causing the output voltage to be quite different than 
intended. I think some may also have another problem beside 
the capacitor that also causes off-voltage operation, but, 
when they work right they are excellent.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com