Sansei Polaris

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Sansei Polaris

Post by Motorola man on Sat Jun 12, 2010 8:23 pm

I picked up a Sansei AM / FM plastic table radio a while back. It's a cheap early 1960s six tube, two diode Japanese set that came with a few gremlins. So far, I have not found a schematic so all the repairs that I've done to date are just educated guesses based on markings on the existing componants. I've replaced the electrolytics and a toasted resistor in the power supply section (the resistor was burned in two, so I just made my best guess on a replacement). The radio plays loud and clear on AM, but after an hour or more it suddenly loses signal. On the FM side, the lower frequencies are a little weak when the set is cold and the higher freqs are fine. After just a few minutes of warming up, starting with the lower freqs the progressing up, it begins to lose signal across the entire FM band. So, does anyone have a suggestion on where I can find any information on this model or where I should concentrate my efforts on the troubleshooting? Even being able to find a schematic for another make / model radio with the same tube line up might be helpful (17EW8, 12BE6, 12AC6, 2 ea. 12BA6 & 50EH5).
Thanks,
Dave
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Re: Sansei Polaris

Post by exray on Sat Jun 12, 2010 8:55 pm

I don't know which is the converter/oscillator tube in that lineup but my first thought would be to sub it with a known good one.

You might be able to find a similar schematic under the name of 'Rincan'. These sets tended to be somewhat generic in circuitry.

I know I have one of those schematics in my computer's bloated archive but dang if I can locate it now.
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Re: Sansei Polaris

Post by Bill Cahill on Sun Jun 13, 2010 1:34 am

The 17EW8 is the fm oscilator.
These early Japanese radios tend to use cpc baced paper capacitors, and, they are leaky, and, get worse with use.
I'd consider re capping it.
Also, you may still be low on power supply B+ voltage, causing your initial weak reception on fm.
Having a schematic would definately help....
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Re: Sansei Polaris

Post by Motorola man on Sun Jun 13, 2010 1:20 pm

No paper caps in this one, all ceramic disk. Low B+ may be a good possibility. Not sure if I have the correct value for the crispy capacitor, the new one is already discolored from heat.
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Re: Sansei Polaris

Post by Bill Cahill on Sun Jun 13, 2010 2:37 pm

Sounds like you put too low a voltage cap in it.
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Re: Sansei Polaris

Post by denver on Sun Jun 13, 2010 6:22 pm

Is this your sethttp://www.radiomuseum.org/r/sansei_hi_mood.html When looking on info for this set drop the polaris It is a hi mood set. Very Happy
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Re: Sansei Polaris

Post by Motorola man on Sun Jun 13, 2010 10:54 pm

Not the same radio, the Hi Mood is a seven tube. That is the only other reference to a Sansei I've ever seen. The caps that I've replaced are rated at 450 volts, way higher than the factory caps. I'm going to try to get a few voltage measurements sometime this week, and maybe a few pictures too. Thanks everyone for the responses, I'll keep ya'll posted if I find anything. Keep the suggestions coming if ya'll have any other thoughts on this one.
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Re: Sansei Polaris

Post by denver on Sun Jun 13, 2010 11:09 pm

Ifound out model numbers are for year made 63 model 3ect. Also when i found other pics said made by afco sansei. For american companys.
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Re: Sansei Polaris

Post by denver on Mon Jun 14, 2010 3:29 pm

http://www.japanradiomuseum.jp/plastic.html
Might look through this site find your set.
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Re: Sansei Polaris

Post by denver on Mon Jun 14, 2010 3:33 pm

or herehttp://www.japanradiomuseum.jp/index-e.html
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Re: Sansei Polaris

Post by Motorola man on Fri Jun 18, 2010 8:52 pm

Looks like low B+ was my culprit. Started off at about 130 volts and slowly dropped to about 86 volts, that's when the FM would die. Still haven't found a schematic that uses the same tube line up as mine, so I did a little educated guessing and got it up to a stable 120 volts. It's been receiving perfectly for about two hours now, and on the lower end of the frequncy dial. Now on to the second question... I know that the 50EH5 tube normally runs pretty hot, but how hot is too hot? This thing is throwing off some serious BTUs.
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Re: Sansei Polaris

Post by exray on Sun Jun 20, 2010 12:54 am

yes, it will run hot. Can you cook with it? That would be about right. Its not going to run as cool as the 12v tubes in the circuit.

Best way to evaluate 'heat' concerns is to check the grid bias and make sure its working within its published parameters. Bad coupling cap, for example, can goof up the bias and make it run hotter than normal..
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Re: Sansei Polaris

Post by denver on Sun Jun 20, 2010 1:49 pm

http://tubedata.itchurch.org/sheets/093/5/50EH5.pdf
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Re: Sansei Polaris

Post by Motorola man on Sun Jun 20, 2010 11:17 pm

Forget the campfire, going to roast my marshmallows over the radio. Might make a good space heater this winter.
Developed a new problem last night... played fine for about 8 hours. I turned it off for a while and when I turned it back on, the volume was way too high. After about 5 minutes it returned to normal and played fine again. Time to break out the freeze spray and find my culprit.
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Re: Sansei Polaris

Post by sprman on Mon Jun 21, 2010 9:00 pm

Take a look at what each tube is runing voltage wise..Then look at max tube data voltages from data sheets.That should let you know if each tube is runing at right voltages..Wonder if you IF cand have silver mica caps in them that are going bad?Good luck with it..Sprman : )

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