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eHam Forums => Mods And Repairs => Topic started by: KM4IY on January 04, 2013, 06:07:48 AM



Title: astron 35A powersupply curiosity
Post by: KM4IY on January 04, 2013, 06:07:48 AM
i have 3 power supplies in my station, an Astron RS-50M, a Kenwood KPS-12, and an Astron RS-35A.

they do a great job with all my gear, with the exception of the 35A when i key my Ameritron 811H, the 35A shuts down.

perhaps RF is backing into it? but i'm wondering why the other power supplies aren't reacting the same way.

in my defense, i've been almost totally inactive for the past several years, i don't remember how many, but i find i've forgotten more than i think i ever knew... so this is puzzling to me...

suggestions?


Title: RE: astron 35A powersupply curiosity
Post by: AA4PB on January 04, 2013, 06:38:09 AM
Try a 0.01uF ceramic disk capacitor directly across the 12V + and - terminals on the power supply.


Title: RE: astron 35A powersupply curiosity
Post by: KA4POL on January 04, 2013, 07:08:14 AM
You could put ferrite chokes around the cables to protect against RF.


Title: RE: astron 35A powersupply curiosity
Post by: K8AXW on January 04, 2013, 10:09:21 AM
4IY:  Some Astrons are susceptible to high RF fields.  Suggestions by other here should be tried.

There is a fantastic article available which includes specific solutions for this very problem.  Unfortunately, I don't have it available at the moment. 

I suggest you Google your problem.  I'm confident you'll find this information.  In the meantime, I'll try to find it.



Title: RE: astron 35A powersupply curiosity
Post by: KA4POL on January 04, 2013, 10:41:52 AM
It should be interesting to see if the supply also fails when using a dummy load for the antenna. At least you can exclude the antenna if it still does.


Title: RE: astron 35A powersupply curiosity
Post by: KK5JY on January 04, 2013, 02:20:18 PM
There is a very nice site documenting many years of knowledge and experience regarding the Astron linear supplies used for amateur radio (mostly repeater sites).

http://www.repeater-builder.com/astron/astron-index.html (http://www.repeater-builder.com/astron/astron-index.html)

I remember seeing several notes there describing RFI issues and fixes.


Title: RE: astron 35A powersupply curiosity
Post by: KB4QAA on January 05, 2013, 01:16:01 PM
https://comm.capnhq.gov/comm/ntc/rs35amod.cfm

Here is a link to the CAP communications website, with a fix for RS-35A's that were shutting down under heavy load.


Title: RE: astron 35A powersupply curiosity
Post by: AC2EU on January 06, 2013, 08:31:14 AM
https://comm.capnhq.gov/comm/ntc/rs35amod.cfm

Here is a link to the CAP communications website, with a fix for RS-35A's that were shutting down under heavy load.

In this case the load does not seem to be the problem, but some kind of RF feedback into the reg circuit. ( The Ameriton has it's own supply).
Running a  turn or two of the power leads through a "clip-on" ferrite cylinder and a maybe even a .05 ceramic across the terminals should help as already suggested.

That being said, I suspect that that you don't have proper shack grounding either. Each device should have it's own ground ( not in tandem or Daisey-chained!!!) to the master bussbar, then the bussbar is strapped to a nearby earth ground. All of the above should be as short as possible.

You may have a very high SWR on the antenna side ( even if you tuner can tune it) causing the RF kickback.
What kind of antenna are you using?

Jim
AC2EU


Title: RE: astron 35A powersupply curiosity
Post by: W9CW on January 07, 2013, 09:21:11 AM
I second the motion to read the info available on the repeater-builder.com website. 

Astron has made running changes on the design of the RS-35 series, in addition to their other supplies, and sometimes it's hit and miss.  Not to open Pandora's Box here... as there is a continual debate, including on the repeater-builder.com website, as to the technical pros and cons of bonding the negative post of the 13.8VDC output to the supply's chassis ground.  Most technically-astute hams, including the aforementioned website, state unequivocally that the negative post should not be tied to the power supply's chassis ground.  Nevertheless, rumors have it that Astron tied the negative post to chassis ground to eliminate RFI effects upon the voltage regulator IC. 

Open up your supply and look to see if there's a jumper from the negative post to chassis ground.  If indeed Astron added this jumper to theoretically reduce or eliminate regulator RFI problems, they didn't implement it very well.  The "grounding jumper wire" from the negative post is tied to a point on the bottom of the supply's chassis through a star washer, but the chassis is painted and most of these jumpers do not effectively ground the negative output post.

The best solution is to investigate any source of RFI problems induced by your antenna or inadequate station grounding (not from a DC perspective, rather from a RF perspective).  Remember, a DC ground and a RF ground are entirely different animals...

Best of luck.

73
Don W9CW