[Milsurplus] Another GRC-9 battery idea

[Richard]

The schematic shows the bias battery, bypassed, in series with the 2M 
audio gain pot, thus there is no intentional battery load to ground.  I 
would expect much more than 20M leakage to ground. I have always used 
"N" cells from Radio Shack, but they're getting expensive and hard to 
find, and will use AAAA cells from a 9 volt battery in the future.  Bias 
batteries last a VERY long time.  I also installed a pin jack on the 
chassis to make it easy to measure battery voltage.

Early GRC-9's used a hard-wired bias battery, which was changed to a 
plastic-molded plug-in battery, probably mercury or hearing aid type, 
and good luck finding one.

Richard, AA1P


On 04/24/2017 07:26 PM, Hubert Miller wrote:
>
> Just thinking out loud here....
>
> Another possibility for the GRC-9 bias batt, that i might try:
>
> a 9 volt battery, with a voltage divider across it to deliver ½ the 
> voltage to the BA-1293/U minus terminal.
> My VOM sez 3Q4 grid to ground >20M ohm.  I’m thinking of maybe 
> resistors chosen to supply around 5 uA
>
> drain on the batt. The only lower limit on the current, i would think, 
> is the possible stray resistance to ground
>
> from the 3Q4 grid.  This would ensure long life, i think, plus being 
> very easy to change out, with a snap connector.
>
> I read that smoke alarms draw “about” 50-70 uA – nobody seemed to know 
> quite specifically – and those things’
>
> batts last a long time. There are also some batts specifically 
> advertised for smoke detector use – Duracell’s
>
> “10 Year Battery”.
>
> -Hue
>
>
>
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