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 Post subject: Matsushita 5S-15 (Help needed)
PostPosted: Nov Mon 27, 2017 4:34 am 
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Hi, this is my first post here. I have just a bought this radio. Status: power cord cut off, dust inside (of course), nothing seems burnt, insulation (cloth?) of part of the wire to output transformer broken off, parts all seem original.
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I failed to locate the schematic. Anybody can help with a schematic? Anybody know the history of this radio? It seems to be built befoe "National" was named.

The radio uses 6W-C5, UZ-6D6, 6Z-DH3A, 6Z-P1, KX-12F.

Thanks.


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 Post subject: Re: Matsushita 5S-15 (Help needed)
PostPosted: Nov Mon 27, 2017 8:27 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 11956
Location: San Jose, CA USA
Can you post a picture? Did you acquire the radio in Japan?

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Tom K6VL


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 Post subject: Re: Matsushita 5S-15 (Help needed)
PostPosted: Nov Thu 30, 2017 9:35 am 
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I am trying, trying and trying to attach some pics.


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 Post subject: Re: Matsushita 5S-15 (Help needed)
PostPosted: Nov Thu 30, 2017 9:41 am 
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Location: SoCal, 91387
Judging by the newspaper underneath it, I presume that you are in Japan? Regardless however, SOP is to first replace all the capacitors, and esp the Electrolytic's. You really don't need a print for that.

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 Post subject: Re: Matsushita 5S-15 (Help needed)
PostPosted: Nov Thu 30, 2017 7:34 pm 
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Joined: Jan Tue 31, 2012 1:55 am
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Location: Mountains of Mourne. Ireland.
The only published 5-tube schematics that I know of utilizing a 12F half-wave rectifier is...
the Yaou Radio Co. model 5NS-1 6W-C5 UZ-6D6 6Z-DH3A 6Z-P1 KX-12F
https://www.radiomuseum.org/r/gen_yao_ra_5ns_15_ns.html
Click on schematics to download.

1948 National Model 5S-15
http://www.japanradiomuseum.jp/11278.html

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Another radio with your complement (line-up) of tubes is...
Televian Radio Co. model Super 5S-14

12F
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Welcome aboard... :)
Greg.


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 Post subject: Re: Matsushita 5S-15 (Help needed)
PostPosted: Dec Fri 01, 2017 3:04 am 
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Joined: Nov Mon 27, 2017 4:18 am
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Thanks guys for the support and prompt response. Certainly, I will replace all the paper condensers and electrolyte caps.

Actually I do need a schematic to help me. The rectangular shape metal can next to the tunning cap is a multi unit cap and is labelled as a National Condenser. Strangely this one does not carry any engraved label with its details, or the paper(?) attached has fallen off? I need to judge from the schematic the values of the new cap's to stuff into the metal can.

I also found that the primary of the OPT is open. Too bad! Looks like somebody has previosuly attempted to solder some PVC wires to the secondary of the OPT trying perhaps to connect to some external speaker(?) and hope to revive the radio.

The power transformer seems OK. I will power it up over the weekend and see if it and the rectifier tube all work.

Will report progress later.


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 Post subject: Re: Matsushita 5S-15 (Help needed)
PostPosted: Dec Fri 01, 2017 9:34 am 
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Location: SoCal, 91387
I wouldn't power it up before changing at least the Electrolytic's; O/W you could end up frying the power transformer.

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 Post subject: Re: Matsushita 5S-15 (Help needed)
PostPosted: Dec Mon 04, 2017 8:25 am 
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Joined: Nov Mon 27, 2017 4:18 am
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You are right. Shoudn't power up without changing caps.

I have removed all tubes except the rectifier, disconnected the old filter caps, added a new (used) filter cap and fired up the radio.
The tube glowed nicely. The dc stood at ~340V. Transformer stayed cool.
I am happy. The transformer has no internal short, rectifier tube works.
So far so good. I figured out the values of the multiunit cap from the schematic.
I drilled out the guts of the old one and replace with 47+22+10+2.2uF 450V.
The pic below show the huge difference in size.
Interestingly, I tested the old caps with my multimeter and found the old caps still retain therir values after almost 70 years of use (storage?). Anyway, I replaced them to save me a time bomb.


Image


I have also replaced the OPT, and started to replace other caps. Still awaiting some parts.

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 Post subject: Re: Matsushita 5S-15 (Help needed)
PostPosted: Dec Mon 04, 2017 10:39 pm 
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Location: SoCal, 91387
CYI wrote:
added a new (used) filter cap

Not necessarily a good idea. Caps are cheap; I'd put in a brand new one. It doesn't matter that the replacement has been used, but rather the age of it. If you know that it's just a few years old, OK, but if there's any doubt, I'd replace it.
Quote:
Interestingly, I tested the old caps with my multimeter and found the old caps still retain therir values after almost 70 years of use (storage?)

That may be, but you can count on the fact that the Electrolyte has dried out, and in actual operation the caps will eventually fail.

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 Post subject: Re: Matsushita 5S-15 (Help needed)
PostPosted: Dec Tue 05, 2017 2:46 am 
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Joined: Nov Mon 27, 2017 4:18 am
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There is some misunderstanding. The "new (used) cap" was installed for the pupose of testing the power supply only. The permannent replacement caps are shown in the photo. They are all new.

I understand caps do dry out. When I pulled the guts out of the old rectangular condenser. The paper inside was not that "wet".


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 Post subject: Re: Matsushita 5S-15 (Help needed)
PostPosted: Dec Mon 11, 2017 2:57 am 
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Joined: Nov Mon 27, 2017 4:18 am
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I have finished recapping the radio. The radio fired up fine recieving stations. Will need to do a bit of tuning and fixing the scratchy volume.

I have pulled the old broken OPT apart and counted the turns to be roughly 4400 to 77.

Say if the old speaker is 4 ohm, the OPT primary will be 13 K ohm. It seems a bit high for the 6ZP1.

Any thought? Anybody like to have a guess of the impednece of the vintage speaker? Google does not give me any details of the speaker.

Right now, I am using the 7K and 4 ohm taps of the new OPT. It sounds OK.


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