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

[Jim W7RY]

Be really careful of counterfeit parts that are on EBay. I would not buy 
anything like this from eBay. And absolutely DO NOT buy components from 
sellers off shore on EBay.

73
Jim W7RY


-----Original Message----- 
From: Kenneth G. Gordon
Sent: Friday, November 11, 2016 3:23 PM
To: kenwood at mailman.qth.net ; Tim Billingsley
Subject: Re: [Kenwood] ASTRON RS-35M - FOUND it!

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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