Hallicrafters S-77 ballast resistor.

[Jim Simmons]

Bryan,

I have an S-77, and it's in operational order...Does need new filter 
caps however.  (Hum problem).

The S-77 info on the ballast in Sams Photofact Folder Set 146, Folder 7 
dated 9 Sep. 1951 for the 117V version is:

VOLTAGE readings (In reference to common negative) with POWER ON and 
line voltage at 117 VAC. Volume control at max.  Receive/Standby switch 
in Receive.  No signal input.  Best place for common negative is at the 
- (negative) lead of the electrolytic filter capacitors.  Since this is 
an AC/DC set (no power transformer) common negative and chassis ground 
are not electrically the same for resistance and power voltages.  The 
chassis is connected to the common negative through a parallel RC 
network which makes them both common for RF currents.
Pin 1 ~ 0 V
Pin 2 ~ 95 VAC
Pin 3 ~ 117 VAC
Pin 4 ~ 117 VAC
Pin 5 ~ 0 V
Pin 6 ~ 0 V
Pin 7 ~ 85 VAC
Pin 8 ~ 90 VAC

If the line voltage is different than 117 VAC, then these voltages will 
be different also.  (Ratio should be approximately the same).

RESISTANCE reading between the pins of the socket and common negative 
(POWER OFF)
Pin 1 ~ 0 Ohms
Pin 2 ~ 55 Ohms
Pin 3 ~ 117 Ohms
Pin 4 ~ 117 Ohms
Pin 5 ~ Infinity
Pin 6 ~ 0 Ohms
Pin 7 ~ 49 Ohms
Pin 8 ~ 52 Ohms

The standard tolerance of voltage and resistance measurements are 
plus/minus 10%

Hope this helps you.
Jim Simmons ~ N5MSJ

On 7/20/2010 5:57 PM, Brian Goldsmith wrote:
> Greetings to all.Would anyone have the full details of the ballast resistor
> R38 setup in S77A?It came in two versions, 117Volt and 220Volt.There is some
> information hand written into one of the manuals I have however,the resistor
> values seem to be incorrect.
>
> Thanks,Brian G.
>
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