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THE AM BULLETIN BOARD => Technical Forum => Topic started by: rich on April 13, 2006, 09:26:04 AM



Title: Johnson 500 Arcking inside PS
Post by: rich on April 13, 2006, 09:26:04 AM
Hi
I fixed the problem arcking on the HV pin on rear of power supply.
Now the only problem seems to be when I unkey it I will get a loud arck like fire cracker noise in power supply. Not everytime I unkey, It could do it the first Time I unkey or hours later. Usually once or twice during a few hours use.
It does'nt seem to do it when talking, Just when I unkey.
Like I said not all the time, just once or twice within a few hours use.
I think I saw it come from the static bleeder in power supply.
Thanks for reading and any help would be great.
Rich


Title: Re: Johnson 500 Arcking inside PS
Post by: WV Hoopie on April 13, 2006, 11:45:00 AM
Hello Rich,

Check out page 28 of the operation manual. Under Arc Gap Adjustments: "When the high voltage is turned on and off there may be a brief arc." I don't like loud arcs!

I lost my mod transformer a few days ago and don't have a warm fuzzy feeling about arcing today. So, I'm waiting for the circuit description/modification from Skip, K7YOO.

We might have a relay sequencing issue, on unkeying the "500" in the AM mode, RY303 must open first -  then RY302. Both have DC coils energized by the bias supply. Looking at the schematic there is NO capacitor across the coil of RY302. RY302 should be a slow release relay. I don't know how this is achieved, mechanical friction and or electrical design? 

Not a good answer, just food for thought.

73's
wd8kdg
Craig


Title: Re: Johnson 500 Arcking inside PS
Post by: rich on April 13, 2006, 01:21:19 PM
Hi Craig
But it does'nt do it everytime I unkey, Just once or so in a few hours use?
You still think that may be it?
Thanks..Rich


Hello Rich,

Check out page 28 of the operation manual. Under Arc Gap Adjustments: "When the high voltage is turned on and off there may be a brief arc." I don't like loud arcs!

I lost my mod transformer a few days ago and don't have a warm fuzzy feeling about arcing today. So, I'm waiting for the circuit description/modification from Skip, K7YOO.

We might have a relay sequencing issue, on unkeying the "500" in the AM mode, RY303 must open first -  then RY302. Both have DC coils energized by the bias supply. Looking at the schematic there is NO capacitor across the coil of RY302. RY302 should be a slow release relay. I don't know how this is achieved, mechanical friction and or electrical design? 

Not a good answer, just food for thought.

73's
wd8kdg
Craig


Title: Re: Johnson 500 Arcking inside PS
Post by: WV Hoopie on April 13, 2006, 05:27:32 PM
Clue-less on this end. Mine would arc at GAP301 once in a blue moon, only on unkeying. :-\ I think the gap, GAP101, in the RF deck zapped once in a year and a half, now that was impressive, loud.

Need someone with relay experience to chime-in and tell all there is to know about RY302 in the Junkston "500".

wd8kdg
craig
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