[GreenKeys] constant current

[Ralph Mowery]

----- Original Message ----- 
From: "WB6BLV" <wb6blv at inreach.com>
To: <GreenKeys at mailman.qth.net>
Sent: Tuesday, January 23, 2007 3:37 PM
Subject: [GreenKeys] constant current


> NOTE- heat sink the MJE340
>
> Will Rogers said something like 'common sense is not all that common' 
> ...
> I am living proof, having smoked my share of 340s!
>
> John
>
>
The MJE340 does not need a heatsink IF it is used as Hoff designed it.  The 
device will be either full on or full off.  If fully turned on it will 
dissiapate very little power.

If used in a circuit that does not turn it full on or fully off (using it as 
an element in a constant current supply)  the dissiapation goes way up and 
you need a good heatsink.

I could not locate a MJE340 when I built a ST-6 and used a very small 
transistor similar to a 2n3904 in physical size but rated for 200 volts.  It 
ran for several years before I quit using the st-6 copy.