The L7 uses a 75K pot in series with a 22K resistor. The L4B is 100K with no series resistor. I think your resistor change is still a good idea. Adding a TVS diode with a breakdown rating greater than the maximum voltage expected across the pot might not be a bad idea. Maybe add a picofuse to open the path if the TVS diode shorts. Or maybe I am overthinking this. :)
On Tue, 24 Dec 2024 15:16:25 +0000 (UTC)
"Evan via groups.io" <k9sqg@...> wrote:
As a side note with an unclear memory, the ALC circuit in the L4B is different than the one in the L7. ?Failure of that 5K 7 watt resistor (which should be replaced with a 10-20 watt style) will result in a failure of the ALC pot in the L4B; the L7 circuit is different and might not be as sensitive to failure. ?I've replaced L4B pots which are sometimes hard to ?find due to ?the pot having an on/off switch. ?The L7 ?pot is somewhat standard.
--
73
-Jim
NU0C
Jim Shorney