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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 4:59 am 
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Location: Tulsa area
Read some where you could use electric box as ground, doesn't seem to good an idea? What do you think?
Will try to put up long ant. in the attic soon. Have picked up Cuba on my Admiral 195 11S on an old dish line not used with new dish.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 5:03 am 
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Others can weigh in with their experiences, but I've never noticed a difference in reception with a ground wire connected to my various S-38s.

If you're asking about whether there is an electrical issue, no there is not, as long as you don't have a hot chassis (in which case connecting this to ground would definitely displease the gods of electricity).

-Bryan


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 5:25 am 
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Earth ground wire on S38 is independent of the chassis. Primary of coils only. I do have a .01 in series with the ground wire. Stations come in without the ground but sensitivity and selective improves with earth ground. Also static is way less with good real earth ground. The same seems to hold true on my SX models.
Did you know you can use your phone wire as an antenna ? Wrap your phone wire into a loop. about 5 turns or better around your hand. Wrap another wire around the loop more turns the better making a loose coupling. Connect one end to antenna screw other end open ended. Phone line does not need to be active for this to work. Static free good for long distance reception. Also works on radios with built in loops. A few turns of the open ended wire wrapped around the loop antenna. Wakes up an average AA5 or AA6 even better.


Last edited by thunderbird281 on Dec Sat 08, 2018 5:39 am, edited 1 time in total.

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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 5:35 am 
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Thunderbird, I'm not sure that I'm following you. The ground lug "G" of the S-38s connects directly to the chassis. Do you recommend connecting an earth ground to the "A2" antenna lug (the other side of the RF coils from the A1 antenna input) and removed the nominal jumper from that connects the "G" to the "A2" terminals?

-Bryan


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 5:47 am 
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Well yes. Earth ground to point 12 on the input coils, not the chassis. Remove jumper of course. I should have made the clear.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 5:50 am 
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Gotcha. Makes perfect sense, and I'll give it a try.

-Bryan


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 6:37 pm 
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The terminal G should not be a direct connection to the chassis. Should be a .01 capacitor from G terminal then to chassis. My chassis has the neutral wire connected to chassis. However I still use the A2 terminal for earth ground with jumper open. If that .01 should short out there goes your antenna coils. Path is though the heaters.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 8:17 pm 
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It sounds like you might indeed have a model with the hot chassis. Which model do you have? My S-38C and S-38D both have the "G" connection direct to the chassis, both in real life and in the schematic. No 0.01 uF capacitor.

Here is the schematic for the S-38C:
http://www.nostalgiaair.org/pagesbymode ... 008865.pdf

And here's a screenshot of the appropriate portion of the only schematic that I have for my S-38D:
Attachment:
Screen Shot S-38D antenna section.png
Screen Shot S-38D antenna section.png [ 100.54 KiB | Viewed 434 times ]


Note that the "G" terminal is to the chassis ground, and one of my AC lines (on both my S-38C and S-38D) is connected to the B- "ground" which is not connected to the chassis (except through a 470K resistor and a 0.05 uF safety cap). I.e., not a hot chassis.

-Bryan


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 9:06 pm 
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I have the original S38 with 6 tubes and pitch control. The G screw is not to chassis ground goes thought a .01 cap first. I see your S38C is different but still can use earth ground on G. I still play it safe and open the jumper and earth ground A2.

http://www.nostalgiaair.org/Resources/862/M0008862.htm <===S38 original


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 9:14 pm 
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Thanks, Thunderbird. I tried your suggestion about connecting an earth ground to terminal G and removing the jumper, and the stations did come in louder. Unfortunately, so did the background noise, so it ended up being a wash. Could be my location.

-Bryan


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 9:51 pm 
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The line in is not connected to the chassis on the S-38D. Note there are chassis symbols which look like a rake and the B- circuit which looks like an upside down christmas tree, this is where the line in is connected. And yes the antenna ground is connected to the chassis, not the B-

Dave


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sun 09, 2018 12:26 am 
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Good deal then. Looks like all models of the S38 series can have an earth ground to G with jumper wire connected to A2 & G. You open the link from G to A2 for installing a doublet antenna to A1 and A2 and still have an earth ground to G. Old Rad Lab try keeping the jumper in place and connect the earth ground to G and A2. See if that works the best. On my S38 the static is reduced to a minimum with earth ground. The S38 does have an ANL too. I just uses one diode section of the 12SQ7 BFO switched to pin 5 of the 35L6. I think you can have an switched ANL too if you use one of the diode sections in your 12SQ7. I see that both diodes are connected together so you can open one anode side and use that diode (switched) to have ANL.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sun 09, 2018 1:12 am 
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Decided to try my radio today after getting dial cord on and working. I just replaced the caps I was sent in the kit and didn't change power cord placement as shown by S-38D guy. New robber feet and two rubber grommets. Powder up the radio and light bulb lit then seemed to dim some but slowly got bright. The tubes started to glow but 35Z5 GT was slow to glow but got very bright at the top, mesh type filament, maybe 30 to 40 sec. later. there was no sound at all but it didn't smoke or smell. So I put it all back in the case and then looked at the back panel and thought, seems I remember a switch in the back. Yes, the speaker/phones, darn I had it on phones. Fired it back up and it made noise but tuner wouldn't work with it in the case. Seemed to close to front. Took it out and picked up a few stations but still need to work on turning cord.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sun 09, 2018 1:27 am 
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steve5542 wrote:
Took it out and picked up a few stations but still need to work on turning cord.


Progress! :D

For Dave and Thunderbird, yes, good points. This all does seem consistent with the S-38, S-38A, and S-38B having a hot chassis (unless modified), but starting with the S-38C, the chassis was the RF ground but not the line (B-) ground. Please do correct me if I have this wrong.

-Bryan


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sun 09, 2018 2:10 am 
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That's correct Old Rad Lab. Try again with the jumper in place. Connect earth ground to G & A2. With the jumper open and G to earth ground your antenna coils are open ended. Won't work that way. Coils need a return line.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sun 09, 2018 9:05 pm 
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Is it normal for the 35Z5 GT to glow very bright at the top? Looks like mesh type filament, maybe 1/8 inch at the top. Thanks


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sun 09, 2018 9:21 pm 
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The heater should glow a bright orange. It's a 35 volt tube. Be sure you have a dial light working too. Dial light uses the heater tap on 35Z5. Without a dial light the tube will glow bright and burn out real soon.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sun 09, 2018 9:33 pm 
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Ok thanks. The dial bulb is working fine. The radio is just tight in cabinet and dial cords won't turn right.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Mon 10, 2018 12:24 am 
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The dial cords are simple in the S38's. May have weak spring tension that will cause a slip. Try cutting off a turn or two from the spring. That should make the dial cord more tight. You can also make your own non-slip by melting a blob of solder on a glass dish. Crunch up the rosin with a small screw driver. Add a drop or two of alcohol. crunch up the rosin in the alcohol until it dissolves. Use Q-tip in the solution and add that to the dial cord. Let dry. Add more is need be. Should not slip anymore.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Mon 10, 2018 2:03 am 
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To make sure that the glowing 35Z5 rectifier tube isn't because of excessive plate current, you could measure the DC voltages (referenced to the B- line) at the positive leads of C14B (red wire), C14C (yellow), and C14D (yellow). These voltages should be about 113, 95, and 85 VDC, respectively. If they are significantly lower, you have a problem and you'd want to resolve that before powering up again.

-Bryan


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