[Heathkit] Astron power supply question???

[Kenneth G. Gordon]

> Picked up an Astron 35M power supply today.
> Before I hooked it up to rig I checked the output.
> It shows 13.97 volts steady for an hour.
> My question is should I open it up and set it to 13.80 as my other
> supply  shows or leave it alone.

Leave that alone. However, there are some OTHER things you may 
have to do to it.

Due to differences in the LM-723 voltage regulator chips, some Astron 
power supplies will "crowbar" to a very low voltage output if a sudden 
load is applied. This will make it LOOK like the supply has failed.

However, the real problem is that the components that set the 
"hysteresis" of the power supply do not match the VR chip 
characteristics.

The fix is quite simple: 1) remove C-3, a .01 mfd 50 VDC capacitor 
which is connected between pin 15 of the LM-723 and ground, and 2) 
add a 4.7 K resistor at the empty place on the circuit board labeled R-
3X.

I got this information from an engineer at Astron, and have used it with 
good effect on three Astron power supplies belonging to local radio club 
members.

Ken Gordon W7EKB