[TenTec] [TenTec_Eagle] Eagle and Astron, update

[José Félix Ballester]

All,
Evidently after all is said and done many problems with Astron supplies boil down to a “good” LM723 voltage regulator.  Mine seems to have a good one and works like a charm.
73 de Pepe WP3HW.   


On Mar 21, 2014, at 11:08 PM, Bob McGraw - K4TAX <RMcGraw at Blomand.net> wrote:

It is a DC regulator circuit voltage bump cause by slow response of the LM723.  The OVP circuit is working very fast and catches the spike on the DC and thus quenches the supply output.  After I found a "good" LM723 all issues were resolved.   There is a good MOV across the AC line after the switch.
 
73
Bob, K4TAX
 
 
 
 
----- Original Message -----
From: José Félix Ballester
To: TenTec_Eagle at yahoogroups.com ; Bob McGraw - K4TAX
Sent: Friday, March 21, 2014 10:03 PM
Subject: Re: [TenTec_Eagle] Eagle and Astron, update

A good working MOV across the 120 V line installed after the turn on switch is bound to help in the described situation.   Some Astron schematics show it in the circuit.

73, Pepe WP3HW


On Mar 21, 2014, at 9:29 PM, Bob McGraw - K4TAX <RMcGraw at Blomand.net> wrote:



It is not an over current issue.  It is an over voltage issue as the result of hysterisis.
 
From my earlier findings and post:
<snip>
 I found the turn-on current surge of the caps charging in the radio may cause the Astron voltage to momentarily drop.  The supply attempts to compensate for this voltage drop and in doing so, the supply pushes the voltage up to compensate for the momentary voltage drop.  Unfortunately the voltage recovery process seems slowed and thus I find allows the voltage to momentarily exceed 16.6 volts.  At that time the Over Voltage Protection activates and shuts down the supply. 
<snip>
 
Nothing said or found about overcurrent shutdown.
 
73
Bob, K4TAX
 
 
----- Original Message -----
From: Jim - N4ST
To: TenTec_Eagle at yahoogroups.com
Sent: Friday, March 21, 2014 7:50 PM
Subject: RE: [TenTec_Eagle] Eagle and Astron, update

The bad Astron supplies I had, had no resistor installed in the "select at
test" position. Made me wonder if the supply passed the test without being
trimmed, or if it had not been tested at all.
(FWIW, I did tack a resistor in there that should have raised the
overcurrent kickout to ~70 amps, but it still would not power up my Omni
VII.)

_________
73,
Jim – N4ST

From: TenTec_Eagle at yahoogroups.com [mailto:TenTec_Eagle at yahoogroups.com] On
Behalf Of Bob McGraw - K4TAX
Sent: Friday, March 21, 2014 20:00
To: TenTec_Eagle at yahoogroups.com
Subject: Re: [TenTec_Eagle] Eagle and Astron, update

  
After spending some 3 hrs with the Astron linear supplies this afternoon, I
came to the conclusion "its the 723 regulator IC's".  I went through all in
my shop inventory, a total of 10 pcs.    I checked each supply with
different 723 devices.   Clearly there was a measurable difference in the
dynamic regulation  of the supplies depending solely on the specific 723
installed.  Some better, some worse.   From the 10 pcs of 723's, there were
3 different brands an those were different date codes.  I was not able to
correlate any specific brand nor date code as being more or less
problematic.  I ended up choosing a chip that worked best for the given
supply.  I did note there is one resistor across a diode that, according to
the schematic, is a "select at test" value.  I didn't bother to tamper with
the value.  In my case the power up surge issue was resolved by "selecting"
the best 723 for the job.
 
 
 
73
Bob, K4TAX




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