Johnson 500 Help Please

[rich]

Hi
I have a Johnson 500 and Modulator/PS
I get arcking off the purple
plastic connector on back of Power supply.
It was changed with a new plug and also
where the plug connects to was changed.
I get less arcking now, only a few times a day.  And I did clean up the carbon where it arked.
Is there a update for changing the connection to something else?
Or is there something I can wrap around it to insulate the problem?
I sure get scared when I hear the arck. Don't want nothing to happen to this nice boatanchor.
Thanks for reading........Rich

[WV Hoopie]

Hi Rich,

Well now, the color at one time was blue. A different color though will not solve the issue. Thats the modulated B+ line going to the PA toob.

So, number one. The original items were tip plugs and tip jacks. I've replaced them on my Junkston "500" with the same style with no issues. The old ones had arcs and carbon tracks, no good. If yours are now scorched, money has it they will arc again. Could look and find the part numbers of what I purchased. The tip jack is recessed for the tip plug.

Number two. I use a cable clamp to prevent the tip plugs from backing out on the PS/Mod deck and the RF deck.

Number three. Check the air gaps of gap101 (1/8inch) and gap 301 (0.018 inch).

Original colors were blue, yellow, and red. Can't find the yellow tip plugs in quantities of less than a couple thousand. So I used some 3M yellow tape.

wd8kdg
Craig

[WQ9E]

Rich,

Also check your antenna switching if you are not using an electronic switch.  Make sure that your antenna relay is not making slower or breaking faster than the plate relay in your 500.  I know that for my Desk KW Johnson recommends using DC for the antenna relay with a small capacitor to create a slow relay release. 

I am also jealous of your having a 500 , I have wanted one since seeing the ad in an old copy of Radio TV News while studying for my novice in the early 1970's.  I did have its little brother (Valiant) as a novice.

73, Rodger WQ9E

[k7yoo]

This arcing is most likely the result of relay sequencing of both the HV relay and TR relay. Changing connectors will not solve the problem and mod transformer failure can occur if not addressed. Years ago K7CMS came up with a solution and I published it in Electric Radio. If you go to the archives of ER and look up Viking 500 articles you will find it. If you can't do this please send me your address and I will give you a copy of the mod sheet. The mod is simple and only involves the power supply unit. You may also consider replacing the weak HV connector with a HV BNC type. I did this on several of my 500's and they are much better than the cheezy plastic test prod pin jacks the EFJ used--and they will fit the hole without much trouble.
Skip
K7YOO

[rich]

Thanks for your help.
I'm very new to AM boatanchors.
Have alot to learn.
Rich

Rich,

Also check your antenna switching if you are not using an electronic switch.  Make sure that your antenna relay is not making slower or breaking faster than the plate relay in your 500.  I know that for my Desk KW Johnson recommends using DC for the antenna relay with a small capacitor to create a slow relay release. 

I am also jealous of your having a 500 , I have wanted one since seeing the ad in an old copy of Radio TV News while studying for my novice in the early 1970's.  I did have its little brother (Valiant) as a novice.

73, Rodger WQ9E

[W9LBB]

Hi
I have a Johnson 500 and Modulator/PS
I get arcking off the purple
plastic connector on back of Power supply.
It was changed with a new plug and also
where the plug connects to was changed.
I get less arcking now, only a few times a day.  And I did clean up the carbon where it arked.
Is there a update for changing the connection to something else?
Or is there something I can wrap around it to insulate the problem?
I sure get scared when I hear the arck. Don't want nothing to happen to this nice boatanchor.
Thanks for reading........Rich

Howdy!

I know exactly what you're talking about. IMHO the use of pin jacks to carry PA
B+ was a MAJOR blunder in the design of that rig! It's scary to look at, and when I
got hold of one of these rigs back in high school the arcing to the chassis was more
than evident, especially on the transmitter itself.

If I was to deal with a 500 today the FIRST thing I'd do is say "to HELL with the
authenticity, this box gets MODIFIED for safety", and those damned pin jacks would
be HISTORY.

What amazes me is that the pin jacks weren't mounted on an insulated subpanel; the
jack itself can carry the voltage and current involved with ease, but the arc path is
WAY too short!

I didn't have the rig long enough to make the mods...   I found the Johnson 500 to
be a VERY boring transmitter (aside from things flashing over on the rear apron), and
was somewhat dissapointed that tho the VFO said so, it WOULDN'T run on 160! So...
being young and stupid, I SCRAPPED the rig to use as parts for a homebrewed rig!

Seeing what a Johnson 500 goes for today, I'm STILL kickiing myself in the ass! ;o)

73's,

Mr. T., W9LBB