hallicrafters s-38b coaxial connection

[kc2etm]

Hi im trying to find out if i can add an so-239 to my s38b it has the power cord fix where hot is to the switch
and netraul is to the chassis but i still get a volt reading to the chassis of about 67 volts also same reading to the ground connections of the antenna jack so needles to say if install a panel mount so-239 as soon as the coax ground touchs its gonna go pow is there another way of doing this isolating the jack etc i just want to use this as a reciver with my viking 2 rather then using my ft-950
thanks
fred
kc2etm

[kc2etm]

Update i tested from the ground of my coax
to where the netraul hits the radio i get
300 volts this coax is connected to the vikings
t r switch could there be voltage on the ground from
the viking 2

[Pete, WA2CWA]

If I had to use this type of receiver (AC/DC) in my operating position, and I would have to be desperate, I would use an AC isolation transformer with it.

[N0WEK]

A couple of things come to mind...

When you did the power cord fix, it seems that you didn't use a three prong cord with ground or you wouldn't have any potential to ground on the case.

When you did the power cord fix, did you change the bypass caps that usually go to ground from the line in most of those rigs, they are probably leaky. If you had used a grounded cord the leak would be going to ground, and in the worst case, would be pulling the fuse. You did use a fuse, didn't you?

I would look to see if the transmitter is on the other side of your power, in that case, if both cases were hot you could have as much as 250 VAC between cases.

My guess is that you didn't use a grounded cord on the transmitter either and that neither the receiver or transmitter are connected to your station RF ground.

All dangerous stuff. Fix that and you will probably solve the problem and a few others in the bargain.

Greg

[KA8WTK]

The schematics I have DO NOT show one side of the line cord attached to the chassis directly. The only connection between the line cord and the chassis on a "B" model is through a 0.1 mfd capacitor.
Please re-check what you have done before something unfortunate happens.
Also, the advice about an isolation transformer is very good to follow. I own one of each s-38 model and consider an isolation transformer a "must".

Bill KA8WTK

[WQ9E]

The old advice is ground is the first lead to be connected and the last to be disconnected and that is particularly good advice given some of the "modifications" that have been done to rigs over the years.

Also make sure there is a proper sized fuse in the appropriate holder.

If your Viking 2 has the original Johnson power plug (fuses in each lead) you should seriously consider replacing it.  The neutral lead should never be fused but it is when these plugs are used.  I would suggest putting a 3 wire grounded cord on the Viking and either drill a hole for a fuseholder or install an inline fuse under chassis if you don't want any additional holes in the rig.  The fuse should be in the hot (AKA load and generally black colored lead).  The white neutral lead should never have a fuse. 

I bought a DX-100 that had a 3 wire cord with fuses in all three leads-I have no idea what the previous owner was thinking.  A friend recently bought a transmitter with a paper clip replacing a blown fuse.   You never know what was done to the rig before you bought it so check it out carefully.

So, use an isolation transformer for the S-38B.  It has low current draw so a small and inexpensive one will be fine.  I used to use some little Hitachi units from Fair Radio but I don't see them listed on their website anymore.

Then put a proper 3 wire cord on the Viking 2.  Make sure everything is grounded together and enjoy a long and shock free radio experience.

[W3RSW]

I agree with the 3 wire update to all older AC/DC sets.

Many of the all American five had a 0.1uf and a 1 meg. resistor resistor from line to chassis as well a a common DC ground buss unconnected to chassis.

Yeah, I'd use Pete's isolation transformer advise if you do nothing else.

[The Slab Bacon]

Yea, but the question still remains................. Why in the hell would you want to use an S-38B as your station receiver??   

[kc2etm]

The only reason i was going to use it
is because i had it laying around and i dont want
to usevmy new rigs with it the cheapest
thing i have is the ft-950 i been using with it
someone gave me a s-20r thats at least
a little better so s-38 is going back to
the parts pile anybody have a decent
print of alignment caps layout the ones i
found on the net are not legible
thanks
fred

[WD8BIL]

The scizo shows 2 grounds. A chassis ground and a CABINET ground. The .1uf 400v caps is between them.

The CABINET ground is earth ground. The green wire in the power cord.

[WA1GFZ]

V2 also has caps on both sides of the line to ground so you might want to ground the chassis or get bit. 3 wire cord is the first thing you want to do.

[KA8WTK]

The schematics I have DO NOT show one side of the line cord attached to the chassis directly.

I stand corrected! I was looking at the wrong model!
The "hot" (switched side) of the line is, in fact, conncected to the chassis. This was bothering me today at work so when I got home I pulled the "B" aprt to take alook inside. That cap shown from the line (hot) to the cabinet is located in one front corner and connects from the chassis to the cabinet via one of the slide switch mounts.
Forgive my gut reaction post.
Now, to your original question about a SO-239 connector. With the line cord attached to the chassis, you couldn't mount the SO-239 on the chassis. The easiest thing to do is connect the "A2" terminal to the "G" terminal then use a short piece of coax from A2/G and A1 to the SO-239. The braid of the coax to the A2/G terminal. You will find that even the "G" terminal isn't really a chassis ground but has a cap between the terminal and ground so you don't ground the line (110v). With this type of wiring, a 3 wire cord is out of the question. The best bet for safety is still an isolation transformer.
For alingment, the BAMA has a clear copy of the manual and schematic. http://bama.edebris.com/manuals/hallicra/s38b/  You will need the Lizardtech DjVu reader to view the schematic. If you can't download it, let me know and I will send the pages to you.
You don't need to give up on the S-38 just yet.

Bill KA8WTK

Almost forgot! Make sure that the rubber grommets that keep the cabinet insulated from chassis are in good shape or the cabinet will become "hot" like the chassis.

[KA8WTK]

Here is a link for the DjVu viewer.

http://www.caminova.net/en/downloads/download.aspx?id=1

[The Slab Bacon]

The only reason i was going to use it
is because i had it laying around and i dont want
to usevmy new rigs with it the cheapest
thing i have is the ft-950 i been using with it
someone gave me a s-20r thats at least
a little better so s-38 is going back to
the parts pile anybody have a decent
print of alignment caps layout the ones i
found on the net are not legible
thanks
fred

Ah, yes an S-20R Champion of the sky!! Next thing you'll be listening for "that little voice in the wilderness" Like Irb!  

If you are serious about AM (or ham radio in general) you really need to have a descent receiver, and a real signal or you will definately get trampled by the jammers, qwermers, and slopbuckets!!

Now, thatz quite a message!!