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 Post subject: Re: My Next Project - 1951 Zenith H2445R Tennyson Porthole
PostPosted: Dec Thu 29, 2016 10:35 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1993
Location: Riverside, CA
Did I say Thursday or Friday of last week or this week :D ? I had planned on last week but with family visiting during the holiday's I did not find the time to test the flyback until today. According to my Eico 944 the flyback is good so I'm going to use a heat gun and gently remove as much of the old coating as possible and recoat with sensor safe RTV. I'll post a photo when done.

- Geoff


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 Post subject: Re: My Next Project - 1951 Zenith H2445R Tennyson Porthole
PostPosted: Dec Thu 29, 2016 10:36 pm 
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Posts: 1993
Location: Riverside, CA
Here are some photos of the inside of the yoke. Is there any good way to clean this or should I leave it as is?

Image

Image

Image

Image


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 Post subject: Re: My Next Project - 1951 Zenith H2445R Tennyson Porthole
PostPosted: Dec Fri 30, 2016 9:06 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5117
Location: Woodinville, WA USA
The yoke looks fine to me. If there's any loose dust in there, you can gently sweep it away with a soft brush.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html


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 Post subject: Re: My Next Project - 1951 Zenith H2445R Tennyson Porthole
PostPosted: Dec Fri 30, 2016 9:27 pm 
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Thanks Phil. I have some artist brushes I'll use to try and brush it clean. It's mostly just filled with dust.


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 Post subject: Re: My Next Project - 1951 Zenith H2445R Tennyson Porthole
PostPosted: Jan Tue 03, 2017 5:33 am 
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I spent some time over the holiday's cleaning the top of the chassis with isopropyl alcohol. There is a fair amount of rust that I'm going to have to address. I recoated the flyback with sensor safe RTV I picked up from Ace Hardware. It's supposed to be good up to 400F. I won't win any artist awards but it's recoated. As someone mentioned in another thread, it was like trying to frost cake, only worse! Now to place my capacitor order.

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 Post subject: Re: My Next Project - 1951 Zenith H2445R Tennyson Porthole
PostPosted: Jan Wed 11, 2017 2:34 am 
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While waiting for my electrolytic capacitor order I went through and started checking resistors last night. I checked about 30 of them and almost every single one was just out of tolerance. Looks like I’m going to have a fun job swapping them all out. Not to mention the tubular caps. I usually try to totally remove the component I am replacing but sometimes in cramped quarters I have wrapped pigtails on each end of the new component. Then cut out the old component, cleaned the remaining leads, slide the pigtails over the remaining leads, and solder in place. Quick and easy. Given the number of resistor and capacitor changes I will need to do I may end up using this method with all the components I replace. A lot of the lugs are small and have multiple leads and as mentioned in an earlier post, one of the lugs in the power supply just came clean off when I tried to unsolder all the leads to it. I want to avoid this again if at all possible. I plan on restuffing the e-cap cans.


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 Post subject: Re: My Next Project - 1951 Zenith H2445R Tennyson Porthole
PostPosted: Jan Fri 13, 2017 7:52 pm 
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I’ve finished checking about half of the resistors. Most of the resistors are out of tolerance. What is strange is that I’ve found 3 resistors so far that don’t match what the Photofact says should be there. There are a couple others but then in the notes section it states the correction for some models. Here are the 3 in question:

R24 is supposed to be 1,000 ohms (+/- 10%) but a 1,200 ohm resistor is installed. Measures 1,180 ohms.

R43 is supposed to be a 1M resistor (+/- 20%) but a 1.5M resistor is installed. Measures 1.42M.

R49 is supposed to be a 33K ohm resistor (+/- 10%) but a 30K resistor is installed. It’s in parallel with coil L17 so I can’t measure it without unsoldering one end.

For the value installed in R24 and R43 both are in tolerance and appear to be original. Should I leave these as is or install the value listed in the Photofact?

Here is a high resolution scan of the service information (600 dpi, 54MB):

https://drive.google.com/file/d/0BzQx4c ... sp=sharing


Last edited by Geoff on Jan Fri 13, 2017 8:20 pm, edited 1 time in total.

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 Post subject: Re: My Next Project - 1951 Zenith H2445R Tennyson Porthole
PostPosted: Jan Fri 13, 2017 7:53 pm 
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Posts: 1993
Location: Riverside, CA
I’ve been checking the capacitor types and identifying all the tubular that I will be swapping out. Looks like there are a lot of tubular ceramics. I’ve been cross-referencing the different part numbers from other listed manufacturer’s and have found that some are NPO type. I know what NPO’s are but was surprised that the NPO requirement was not listed in the Installation Notes. For example, C36 looks to be a tubular ceramic. The Aerovox equivalent is P/N SI6.8NPO. However, the Cornell-Dubilier P/N is 5W5Q1 which is a standard molded mica. I’ll leave the original in place when I begin to power it up but if I need to replace it should I use an NPO type or just a standard mica?

I wish there was a catalog of Zenith part numbers so I could look them up and see what type was originally installed. I’ve scoured the internet but to no avail.


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 Post subject: Re: My Next Project - 1951 Zenith H2445R Tennyson Porthole
PostPosted: Jan Fri 13, 2017 9:01 pm 
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Joined: May Fri 29, 2009 4:35 am
Posts: 1950
Location: Chicago, IL USA
Ceramic caps rarely go bad - especially the tubular type. I've never needed to replace one and I suggest you leave the originals alone. They very likely found the a vreplacement cap from each parts vendor that was closest to the original specs. Cornell-Dubilier might not have made NP0 ceramic caps in that value.


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 Post subject: Re: My Next Project - 1951 Zenith H2445R Tennyson Porthole
PostPosted: Jan Thu 19, 2017 9:04 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1993
Location: Riverside, CA
I finished checking all the resistors, except for the ones in the RF Tuner. I have always read that these should be left alone and only replaced if there is a problem that is traced back to particular resistors in that area (same with the caps).

I measured 99 resistors in all and 53 were bad. A failure rate of 53.5%. I have most of the resistors in stock but had to order some odd value and high wattage resistors from Just Radios. I also order replacements for all the tubular caps. I received my electrolytic cap order last week and will start restuffing the cans shortly.

I'll post again once the electrolytics, tubular caps, and out of tolerance resistors are replaced. It's going to take awhile :D .

- Geoff


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