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 Post subject: Help with Zenith 6-S-238 radio
PostPosted: Nov Thu 09, 2017 1:52 pm 
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Joined: Jan Sat 24, 2015 8:01 pm
Posts: 20
Location: Virginia Beach, VA.
Hi all,
Been a long time lurker, much knowledge here. I need a little help, as I'm still learning, on a the schematic here: http://www.nostalgiaair.org/PagesByMode ... 025211.pdf

I'm I reading this right? The Power transformer is two 322 HV lines totaling 644 volts, and the filament voltage is 6.1 volts..?


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 Post subject: Re: Help with Zenith 6-S-238 radio
PostPosted: Nov Thu 09, 2017 3:07 pm 
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Joined: Jul Mon 26, 2010 8:30 pm
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Location: Annapolis, MD
Filament is right---the tubes are 6.3 volts nominal, but 6.1 is fine

At the rectifier, pins 3 and 5 are the unrectified AC voltage. The 322 is the raw DC at the cathode.

And Welcome to the forum!!

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 Post subject: Re: Help with Zenith 6-S-238 radio
PostPosted: Nov Thu 09, 2017 3:15 pm 
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Joined: Mar Sat 14, 2009 5:56 pm
Posts: 3873
Location: RI, 02885
These would be minimum load requirements on the power transformer: 5V@2A, 6.3V@2A and 600 - 650VCT@120ma.
6.3V@3A would be better for tube filaments.
You could post a WTB on ARF for a direct replacement.
Include the original transformer part number.

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Last edited by Bugman on Nov Thu 09, 2017 3:18 pm, edited 1 time in total.

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 Post subject: Re: Help with Zenith 6-S-238 radio
PostPosted: Nov Thu 09, 2017 3:17 pm 
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Joined: Jan Mon 16, 2012 4:15 pm
Posts: 3612
Location: Near Brandon, Iowa
That's what the Riders "socket voltage" data table indicates. These were allegedly actual voltages measured at the respective tube sockets under the conditions given. They will be close to, but not exactly the same, as the voltages measured at the transformer. This is due to resistive loss in the heater bus between the transformer and the tubes; and also due to the presence of a resistor stack between chassis ground and the center tap of the HV winding which drops some voltage across itself.

The relatively low-impedance voltmeter used to take these readings would also contribute a tiny bit to the observed values; but not much since the voltage sources are themselves fairly low impedance.

The rated values of the transformer at full load for these two windings are probably 6.3 V and 350 V (phase end to center tap). These are (roughly) RMS values, not peak. If you measured these points your results would vary by a proportional amount that your household voltage differs from 117VAC.

The B+ bus (filtered DC) will be around 250V after the 40V forward drop in the rectifier tube and the 60V voltage drop in the speaker field winding are accounted for.


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 Post subject: Re: Help with Zenith 6-S-238 radio
PostPosted: Nov Thu 09, 2017 3:34 pm 
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Joined: Jan Sat 24, 2015 8:01 pm
Posts: 20
Location: Virginia Beach, VA.
Pixellany, Thank you for the welcome! Its a great forum here.

Bugman, I'll do that. If I can't find a zenith replacement, should I look for one or have a PT made that is 5V@2A, 6.3V@2A and 600 - 650VCT@120ma. Would I request it as such..?

lorenz200, thank you. Good info. You guys are great.


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 Post subject: Re: Help with Zenith 6-S-238 radio
PostPosted: Nov Thu 09, 2017 5:53 pm 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 2947
Location: Mountains of Mourne. Ireland.
Re: Power transformer 95-450
viewtopic.php?p=1851304#p1851304

Greg.


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 Post subject: Re: Help with Zenith 6-S-238 radio
PostPosted: Nov Thu 09, 2017 6:24 pm 
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Joined: Jan Sat 24, 2015 8:01 pm
Posts: 20
Location: Virginia Beach, VA.
Greg,
Thanks! Great info. The part number on mine is 95-415 P, Chassis 5638.


Last edited by Flash on Nov Fri 10, 2017 2:18 pm, edited 2 times in total.

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 Post subject: Re: Help with Zenith 6-S-238 radio
PostPosted: Nov Thu 09, 2017 6:39 pm 
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Joined: Mar Sat 14, 2009 5:56 pm
Posts: 3873
Location: RI, 02885
Try posting here on ARF for Zenith power transformer # 95-415 in the Classified section. List the model numbers and chassis number that use the transformer for members that may have a parts chassis on hand.

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I'm not a hoarder, I'm a caretaker of scarce commodities


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 Post subject: Re: Help with Zenith 6-S-238 radio
PostPosted: Nov Fri 10, 2017 2:23 pm 
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Joined: Jan Sat 24, 2015 8:01 pm
Posts: 20
Location: Virginia Beach, VA.
Done. Thank you.

From the thread posted above about the 6s229, he ended up going with Hammond 272DX, am I right that it would be a direct wire-in, no added resistors, etc.? I would still add a fuse, of course.

https://www.mouser.com/ProductDetail/Ha ... yw8RI4qw==


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 Post subject: Re: Help with Zenith 6-S-238 radio
PostPosted: Dec Wed 06, 2017 12:02 am 
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Joined: Jan Sat 24, 2015 8:01 pm
Posts: 20
Location: Virginia Beach, VA.
Well, a awesome member here, Madrad, found a Zenith transformer for me that was an exact match. He even tested and labeled the leads before sending it to me. It made for a easy and seamless install. This is a great forum with great people.
Thank you, all. :D


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