[Elecraft] Astron RS-35M - Problem Related to RF !!!

[Sandy W5TVW]

The Astron supplies are notorious for shutting down if a little
RF gets into the "crowbar" circuitry!  Follow all the usual
supression techniques.  There is a digest somewhere about this
but I can't pull it up on my computer.  I might have seen it
while doing a "google" search.  I did some bypassing in my 35 amp
supply.  Commercially, we also used Ferrite RFI suppressors
on the power cable and output cables (the plastic encased
"clamp around" variety) That helped the problem.
73,
Sandy W5TVW 
----- Original Message ----- 
From: <lbailey@aep.com>
To: <elecraft@mailman.qth.net>
Sent: Tuesday, March 16, 2004 9:12 PM
Subject: [Elecraft] Astron RS-35M - Problem Related to RF !!!


| Looks like the problem is RF.  I put a dummy load on the rig & the power 
| supply works fine.....delivers 16 amps on CW key-down.  I discovered the 
| problem when I was operating 40 meters, so today, I checked out 75 mtr. & 
| 20 mtr. & the rig works fine.  Power supply still shuts down on 40 meters 
| so I will make the RF mods I have found & see how that works.
| 
| No problem on my K2 but my TS 440S shuts power supply down.  I'm in the 
| final stages of finishing up the KPA100 so I'm stopping to fix the PS 
| before proceeding.  (Antenna is a G5RV)  Wish I had the K2/100 ready to go 
| so I could see if it has the same problem.
| 
| (RF mod - .001 microfarad cap across pins 2 & 3 on LM-723 per KB7KBT)
| 
| UPDATE ON RF MOD...
| WHOOPS....Still not fixed.....
| 
| Looks like I'm gonna have to do more than just adding the 0.001 capacitor. 
|  Since this PS has been mated with the RS-35M for some time, I suspect 
| that my G5RV antenna is acting up or the antenna tuner in the TS-440s has 
| a problem.  I did check my antenna about 2 weeks ago & I was alarmed at 
| the degree of corrosion on the twin lead bolted connection to coax/balun 
| connector.  Think I'd better redo that connection & wrap it with duct seal 
| to keep the mosture out.
| 
| Guess another easy options are to relocate the power supply to the floor. 
| Also rig is not grounded.
| 
| 
| 
| 
| 
| >>>>>>>>>>>Earlier Note Below<<<<<<<<<<<<
| ================================================================= 
| My K2 power supply, Astron RS-35M, will put out low amperage...~2.5 
| amps...to drive my K2, but when higher amperage is req'd for my TS440s & 
| my almost finished KPA100, the output voltage goes to "0."  When I cycle 
| the on-off switch, the voltage comes back up but still limited amp 
| capability.  Receive works fine on the TS440s but when I key the mike, the 
| rig goes dead & the voltmeter on the RS-35M reads "zero." 
| 
| Output voltage under low current demand......14.1 VDC & 0.77 mVAC ripple 
| with Fluke 867B 
| Output voltage after high current demand.......0.8 VDC & 0.6 mVAC ripple 
| 
| History...this power supply is about 15-20 years old & all I've done is 
| tweak the output voltage via R5 up to 14.1 volts so that I would have 
| ample charging voltage on the K2 battery.....I did this tweak about 2 yr. 
| ago.  (This power supply stays on continuously) 
| ================================================================ 
| 
| I have replaced the LM723 & lowered the supply voltage to 13.6 v but to no 
| avail. 
| 
| 
| Lynn Bailey, P.E.
| Mgr - AEP Mtr Service - Corpus 
| AEP-Central & North Texas
| 361/880-6303 - wk
|      8-730-6303 - Audinet
|  361/816-6737 - cell
|  877/634-5107 - EasyFAX
| e-mail:  lbailey@aep.com
| 
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