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 Zenith model T825 AM/FM

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so-tingly
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Join date : 2023-05-09

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PostSubject: Re: Zenith model T825 AM/FM   Zenith model T825 AM/FM I_icon_minitimeDecember 6th 2023, 7:03 pm

I have done the smaller type IF cans, not easy to do.
These cans are about the same size as the regular cans. More room the play around in. 
The mica are shaped like disks. Not east to remove but do-able. 
On the under side where the connections are soldered, it shows 4 connections for the coils but on the inside there are 5 connections. According to the schematic the fifth wire is connected to one of the 4 other connections.
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Cliff Jones
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Join date : 2010-11-22

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PostSubject: Re: Zenith model T825 AM/FM   Zenith model T825 AM/FM I_icon_minitimeDecember 5th 2023, 10:35 pm

I haven't done a replacement as such, but I read several have instructions showing the same issue. Some on YouTube.
Type in this phrase, and you will get a lot of links.

“Silver migration repair on the I.F. cans in a tube radio”
----------------------------------------------------------------
Another link here --not always a I.F. Can

Static from mica cap

https://www.youtube.com/watch?v=-xASXPmxTOc

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so-tingly
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PostSubject: Re: Zenith model T825 AM/FM   Zenith model T825 AM/FM I_icon_minitimeDecember 3rd 2023, 5:26 pm

My model has or had the selenium rectifier. replaced it with a diode and a step down resistor.
This one I got a few years back and shot gunned it. I'm surprised I got it to work.
Well, the FM did work BUT I found out the cans have SMD. AM is very weak until I put my finger on the center grid of the air cap. Comes in strong whenever I do that. The AM band and now the FM band is showing signs of SMD, crackling popping, the works. I took one apart to find I was right. 
I've never worked on one of these before but I'm guessing I have to replace the mica with pf caps like one would use on the smaller IF cans.
Please let me know if I'm right.
Thanks
PS again I tried to upload the pics but it refuses to upload.
I'm thinking this site doesn't like me.
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Cliff Jones
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Cliff Jones


Join date : 2010-11-22

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PostSubject: Re: Zenith model T825 AM/FM   Zenith model T825 AM/FM I_icon_minitimeDecember 3rd 2023, 10:27 am

Note: on the bottom left, there are 5 diode symbols that represent a copper or Selenium rectifier.
You may find a chassis that's the same, but a different radio model number with voltages printed, and realize also that it's an RCA or Hazeltine copy that Manufacturers use with permission to manufacture. So there are many different-branded radios using the same design.

https://en.wikipedia.org/wiki/Hazeltine_Corporation

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so-tingly
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PostSubject: Re: Zenith model T825 AM/FM   Zenith model T825 AM/FM I_icon_minitimeNovember 29th 2023, 5:47 pm

Finally figured out a way to change the files to be able to post. It took multiple steps to do it.Zenith model T825 AM/FM Schema10
Zenith model T825 AM/FM If_can10
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so-tingly
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PostSubject: Switch works   Zenith model T825 AM/FM I_icon_minitimeNovember 29th 2023, 11:27 am

The band selector does work. Confirmed when I got a weak signal. No stations just and odd signal my other radios have between stations. Now again to find out why no stations come through. I ran into this problem before but can't recall how I fixed it.
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so-tingly
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PostSubject: Zenith model T825 AM/FM   Zenith model T825 AM/FM I_icon_minitimeNovember 29th 2023, 7:11 am

Zenith model T825 AM/FM 20231115
Well again... I apologize. I wasn't able to upload the schematic. 
Reason? I don't have permission and it won't accept a web capture. So this sucks. I could take a picture and upload that but the quality would be worst than the original.
Any who... The pilot light won't turn on even if the tubes do. I don't see it on the schematic so I don't know where it's supposed to connect.
I got the FM to work great.... 3 bad tubes. 
Am on the other hand... All I get is static and a soft hiss. 
I can't test for voltages because the schematic I have doesn't show them. It's also kinda blurry. It's the only schematic I could find and it's from Beitmans. No parts list... so I'm very limited on what I have for references. Very frustrating for me and you.
Paper and filter caps replaced. All bad resistors as well. It is very tight under the chassis.
I believe the selector switch is asl follows....
FM... FM Automatic Frequency Control... Standard Broadcast = AM?
The band switch seems to be working. I've sprayed electronics cleaner on all controls, everything moves smoothly.
It had a massive hum , found out it was the tone control quite filthy.
What am I missing?
Any help would be appreciated.
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PostSubject: Re: Zenith model T825 AM/FM   Zenith model T825 AM/FM I_icon_minitime

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