ARRL

Secure Site Login

kg4msr

Joined: Fri, Aug 8th 2014, 13:19 Roles: N/A Moderates: N/A

Latest Topics

Topic Created Posts Views Last Activity
Power Supply Causing Dirty CW Signal? Sep 19th 2014, 03:59 3 1,379 on 23/9/14

Latest Posts

Topic Author Posted On
Power Supply Causing Dirty CW Signal? kg4msr on 23/9/14
Thanks for the reply Bob,

I called Astron and they promptly transferred me to a tech who, after hearing the problem described, recommended replacing C1 and C3.

Problem solved.
Power Supply Causing Dirty CW Signal? kg4msr on 19/9/14
Greetings,

I'm working on an Astron RS-35A linear power supply for a fellow ham. The power supply is said to be less than 10 years old.

He received a report of hum on his CW signal with a K3. I have confirmed the noise on CW only (no noticeable noise on SSB), using my FT-100D on his power supply. CW signal is clean with my power supply (new RS-35M).

Here's where I'm stumped:

Output voltage is 13.93 VDC, drops to 13.91 under full load (almost 20A). This is acceptable.

Ripple is less than 20mV peak to peak no load, increases to 30mV peak to peak under 20A load. Astron claims these supplies (new ones) get better than 5mV ripple at full load, but 30mV is still pretty good (or is 30mV horrible for CW?)

Floating/Grounding negative terminal makes no difference in ripple.

I could just 'shotgun' the supply, replace every electrolytic, 723, bridges, and pass transistors in it but I would like to know what is wrong and why. I'm not sure there is anything wrong with it... Or is there? Help!

Mike, KG4MSR

Back to Top