[Kenwood] ASTRON RS-35M - FOUND it!

[Kenneth G. Gordon]

OK. Here's the deal. This MAY NOT be related to your problem, but you may wish to check 
it anyway.

According to Astron, there are two components associated with the LM-723 which may be 
causing trouble: these are C-3, which is connected to pin 15 of the LM-723. It is 0.01 mfd at 
50 volts. Remove this cap in every case.

Secondly, already silkscreened onto the board is R-3X, but it may or may not be installed.

If it is not installed or if it is the incorrect value, it should be 5K ohms at 1/2 watt.

Install that.

What happens when R-3X is missing is that at the upper limit of current capability, there is 
too much hysterisis in the system and it shuts down. This MAY be related to your issue.

On one end, R-3X connects to pin 2 of the LM-723 and goes to common on the other.

Lastly, there was a problem common to all of the Astron power supplies I worked on (this 
was back in December of 2005, BTW) in that the output connectors may be missing their 
flat-washers, and maybe even their lock washers. In attempting to tighten the output 
connectors, one can instead loosen the entire bolt associated with that connector. This 
causes a large voltage drop at the output connector which then causes the supply to lose 
control.

I had to replace the LM-723 in at least one of the supplies I worked on as the original one 
would not regulate properly.

I used an LM-723CN, a military grade unit, which has much "tighter" specifications than 
some of Astron's originals.

One of the 35A power supplies I repaired then showed 13.72 volts at no load, and 13.80 
volts at a load of 35 amps.

Anyway, let me know if this helps or not.

Ken W7EKB

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