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 Post subject: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 12:03 am 
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Joined: Nov Sun 16, 2014 7:08 pm
Posts: 43
Location: Tulsa area
Got new rubber feet and (2) grommet for one tuning cap and hope the other grommet will fit the switch panel. Picked up kit with all the caps from Hayseed Hamfest and looks just right. Being new to doing it myself, watched Gene re cap two radios for me and 40 years ago put togother a Heathkit and Ico (seems like it was an I co) transceiver. Read S-38 guys how to for a S-38D and printed out stuff I thought I would need.
The 20, 60 and 2 40 MFF came in a tube like whats on it now so no need to use 4 prong terminal strip. I didn't get a square special .022 mdf safety cap, it's just one of three standard .022 cap 630V. Will that be ok? The one that's there is different than the other caps that look like they need replaced. It's a red Tiny Chief PJ6S2 .02 MDF 600 VDC, does it need to be replaced with a regular .022 cap 630V?
S-38 guy says to add 2 lug terminal strip for power cord (and where to run wires), but my power cord is on 35Z5 GT pin 2 and 6, is it ok to leave it there? Would the polarized side of the polarized plug go to pin 2?
Very new and only have a volt meter. Thanks


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 12:23 am 
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Location: La Mesa Califonia
The filter capacitor you have sounds to be new old stock. It's very old and by now is dry and leaky. Should use new individual filter capacitors. The polarized side (wide blade) will be going to pin 2 of the 35Z5. Hot side to switch.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 12:44 am 
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Joined: Feb Sat 10, 2018 4:58 pm
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Location: Livermore, CA
Funny you should ask about the S-38D as I just finished aligning mine this afternoon. A good radio for getting some practice on, albeit a modest performer. It sounds like you have found the website for the S-38 Guy, and his warnings about the hot chassis of the Hallicrafters S-38 series.

However, I have heard conflicting stories about which S-38 models came from the factory with a hot chassis, and which models were designed with a common B- line connected to the 120 VAC, but not a direct AC line connection to the chassis (assuming all capacitors between B- and the chassis are OK). I have both an S-38C and an S-38D, and neither of them had a hot chassis and with no evidence that they had ever been "fixed", and in fact I read somewhere that the S-38C and later models did not have a hot chassis.

So, definitely best to figure out whether you have a hot chassis or not, and if anyone else on this forum knows definitively about the S-38D (and S-38C and S-38E), PLEASE step forward.

Also, a 0.02 uF safety cap is the preferred option as these are designed to fail open rather than fail as a short, definitely a good idea when you have these going from 120 VAC to the chassis. Your 0.022 uF 630v cap will work, but if it were me doing this, I'd use a safety cap.

Another website you could take a look at is at: http://www.geojohn.org/Radios/MyRadios/Safety.html

-Bryan


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 12:55 am 
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Location: Mpls, Minnesota
thunderbird281 wrote:
The filter capacitor you have sounds to be new old stock. It's very old and by now is dry and leaky. Should use new individual filter capacitors. The polarized side (wide blade) will be going to pin 2 of the 35Z5. Hot side to switch.

Hayseed makes these capacitors, they are new not old stock. As far as a polarized cord it is better to use a non polarized cord as you can reverse the plug for better reception.

Dave


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 1:07 am 
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thunderbird281 wrote:
The filter capacitor you have sounds to be new old stock. It's very old and by now is dry and leaky. Should use new individual filter capacitors. The polarized side (wide blade) will be going to pin 2 of the 35Z5. Hot side to switch.
Hayseed Hamfest specializes in building new caps for restoration. The kit is one stop shopping to get the job done...

In some instances having the ability to reverse the power plug will improve reception. A polarized cord will prevent this.

Chas

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First they ignore you, then they laugh at you, then they fight you, then you win.
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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 1:47 am 
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I don't have a schematic for an S-38, but if it's wired like most other transformerless sets, a polarized plug will do no good. That's because the switch is in the "ground" lead of the cord. So if the set is plugged in one way, the B- (chassis or floating ground) will be grounded when the set is on but "hot" when it is off, the current path being through the tube heaters. If the plug is reversed, it will be "hot" when on and grounded when off. The set can be rewired to fix this, but if all the insulation between the circuits and the cabinet is good, it isn't necessary.

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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 3:11 am 
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Joined: Nov Sun 16, 2014 7:08 pm
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Location: Tulsa area
Thanks for all the information, guess I do need to get the 0.02 uF safety cap. Just went out today to get the cord, maybe ground off the wide sides of the plug then check for best reception when done and still be able to tell which lug of plug is ground.
Where's the best place to get the 0.02 uF safety cap in the US? Didn't see one at Hayseed.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 4:03 am 
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Joined: Nov Sun 16, 2014 7:08 pm
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Location: Tulsa area
S-38 guy has moved the power cord location and sent other wire from on/off switch to pin 2 of rectifier with AC. Pin 2 also has one side of .022 mdf Y safety cap. Any need of safety cap if not changing power cord from Pin 2 and 6 of tube?


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 4:50 am 
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Joined: Feb Sat 10, 2018 4:58 pm
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Location: Livermore, CA
I believe we're talking about C27, the 0.02 uF capacitor that is essentially connected across the 120 VAC line inputs. Again, a safety cap is preferred for this, but a regular capacitor will work in this location. However, if in the future this regular capacitor happens to go bad and short, it would short the two AC lines together (not good).

-Bryan


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 6:31 am 
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Quote:
...Just went out today to get the cord, maybe ground off the wide sides of the plug then check for best reception when done and still be able to tell which lug of plug is ground...
Zip type power cord has an identifier molded stripe on the surface of one conductor, sometimes a colored thread in the copper or one conductor tinned. The identified conductor is the neutral, the wide blade.

Most metalized are self extinguishing in event of failure. However, common "replacement" metalized have a poor dv/dt rating. The metalizing will get literally blown away from spikes. Resulting intermittent noises in sensitive circuits and a reduction in capacity. That is why they should not be used as buffer caps,. I have also not used them in plate connected audio bypass, tone circuits either. Vulnerable to static crashes the can cutoff the output tube for an instant, then kick comes from the collapsing magnetic field in the output transformer.

The S38 is a great little radio for what it is, don't use it in the bathtub.

Chas

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"Gandhi"


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 6:44 pm 
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Joined: Nov Sun 16, 2014 7:08 pm
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Location: Tulsa area
Thanks for all the information but I think I will change all the caps with the ones in the kit for now and see how it works. Do have new insulated feet


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 7:31 pm 
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Joined: Nov Sun 16, 2014 7:08 pm
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Location: Tulsa area
Do the new caps have a +/- side? Read some where you could check with some sort of meter?


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 8:38 pm 
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Joined: Feb Sat 10, 2018 4:58 pm
Posts: 337
Location: Livermore, CA
The only capacitors in your set that are polarized (distinct plus and minus leads) are the four electrolytic capacitors C14A, B, C, and D. For those, connect them as per the schematic, with the negative lead to the B- bus, and positive leads to the appropriate points in the circuit. For all the other capacitors, they can be connected in either direction.

-Bryan


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 8:47 pm 
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Joined: Nov Sun 16, 2014 7:08 pm
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Location: Tulsa area
Thanks Bryan, I bet those 4 are in the Tube with 5 wires coming out. I'm set to start.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 9:10 pm 
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Joined: Feb Sat 10, 2018 4:58 pm
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Location: Livermore, CA
Yes, correct you are. The black lead would go to the B- bus, red and the two yellow leads at the appropriate points on the two resistors after the rectifier tube, and the blue wire goes to the cathode of the 50L6 tube.

-Bryan


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Fri 07, 2018 11:46 pm 
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Joined: Nov Sun 16, 2014 7:08 pm
Posts: 43
Location: Tulsa area
Got them replaced and wasn't to bad. Not as neat as I would like but for my first re cap ok I hope. I'll try to get my main man to look it over and bring it up slow and maybe fine tuning.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 12:25 am 
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Joined: Feb Sat 10, 2018 4:58 pm
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Location: Livermore, CA
Sounds like a plan. Note that Band 4 can be pretty weak in terms of reception on these radios, especially if the 12SA7 converter tube is weak. On mine, I get a smattering of stations between 13 and 18 MHz, but not much above that. On some of the S-38 radios that I've seen, the local oscillator peters out once you get into the top half of Band 4.

Time of day and atmospheric conditions make a big difference as to what you'll pick up on Bands 2-4. A good long antenna helps.

-Bryan


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 12:40 am 
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Location: La Mesa Califonia
Perk up your S38 by replacing the 12SK7 with a 12SG7. Has twice the gain. Makes a difference for long distance reception on both BC band and SW.


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 2:24 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Mpls, Minnesota
12SG7 is a semi-remote cutoff , the 12SK7 is a remote cutoff, I would think this would cause some problems with the AVC

Dave


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 Post subject: Re: Hallicrafters S-38D re cap
PostPosted: Dec Sat 08, 2018 4:20 am 
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Location: La Mesa Califonia
Yes I thought that too. Proves out it works great. On original S38 picked up Sacramento from San Diego. Cuba came in twice as strong. I do have a long outside wire and cold water pipe ground. Works great on "almost" any AA5.


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