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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Thu 14, 2017 6:43 pm 
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Location: Palos Verdes, CA
Al,
Both of my Zenith Royal 800s still have their original GE 121-27 transistors installed for the AF amplifier. I tried a Raytheon CK721 and a GE 2N190 transistor in the Zenith 800, and they both worked well. I saw some 2N190 transistors for sale on eBay, along with the NTE 102 transistors, which should also work. - Mark


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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Thu 14, 2017 7:40 pm 
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al puggy wrote:
From ground (chassis) to C of 2N190 blue wire from transformer I should get 850ohms? I disconnected c20 and took out transistor and it reads open. Could it be open transformer?

Sure sounds like it, and if so we could now be getting into the unobtainium realm, unless there's a readily available sub. First though, reflow the solder at the five transformer PCB connections, and then measure the primary again.

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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Thu 14, 2017 8:30 pm 
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I disconnected blue wire from transformer, and checked it from ground, and it is open. I hooked up a transformer of 500ohms in its place, and she still is dead, but my voltages on transistor are now correct.


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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Thu 14, 2017 8:38 pm 
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Al,
There is a Thordarson TR-7 transformer for sale on eBay, which is the correct part of the Zenith Royal 800:

https://www.ebay.com/itm/Lot-of-3-NOS-T ... SwZW5aLbqx

Mark


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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Thu 14, 2017 10:42 pm 
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al puggy wrote:
I disconnected blue wire from transformer, and checked it from ground, and it is open. I hooked up a transformer of 500ohms in its place, and she still is dead, but my voltages on transistor are now correct.

So it looks like the transformer is the culprit. How did you connect the other transformer? If you merely connected it to the primary points, and left the original connected at the secondary, there would be no flux interaction, and of course it wouldn't work AFA developing sound.
One test you might try is connecting a battery powered audio amp to the collector of the driver, and circuit ground, to see if you get signal. If not, try connecting to the base.

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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Fri 15, 2017 4:00 am 
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Location: new hyde park ny usa
I am getting strong signal through the 2 2N187's.......weak signal through 2N190.....and nothing after that.


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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Fri 15, 2017 4:21 am 
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OK, I presume you are injecting an audio signal at the output, and working your way toward the front end of the receiver. If the audio transformer's primary is truly open, I'm surprised that you get any signal at their connections.

My suggestion was to test the circuit at the base and collector of the 2N190 by connecting an amplifier, to see if you get signal from the set's front end.

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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Fri 15, 2017 6:40 pm 
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Yes, I am using audio out from battery radio. I am getting a very faint signal from C&B of 2N190. Since I am getting strong signal from the outputs, and they are before suspect transformer, Do you think new transformer will solve our problems? As Mark sent, there is a TR-7 on ebay that fits our bill. Thanks AL


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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Fri 15, 2017 8:22 pm 
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She wants twenty bucks + shipping for three transformers, and you only need the one. Maybe message her and make an offer just for the TR-7, or ask her what she wants just for it alone.

I've been trying to encourage you to check for signal from the antenna to the base of the audio driver, to make sure it's there, and that there aren't any other problems, before investing $ in the audio section.

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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Sat 16, 2017 2:35 am 
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I am trying to negotiate for the TR-7. Since that open transformer is the cause of the high voltage on the 2N190, I would have to get that before going further. I do not get any signal from antenna to base of audio driver. You are right...this is turning into expensive repair! I hope it works out in the end.......Thanks AL


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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Sat 16, 2017 5:59 am 
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I looked for eBay sales and found two; one from 2016, and one from this year, so that is an indication of rarity. They each sold in the $230 range; one worked and the other was untested.
I think that regardless of whatever level of work or money you put into the set, you can't get hurt.

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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Sat 16, 2017 6:51 am 
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Wow. I wonder what my Magnavox AM-2 transistor radio might fetch as it's in cosmetically fine shape, and it's working.


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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Sat 16, 2017 7:01 am 
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Nowhere near what the Zenith's went for. I sold a couple of AM-2's a few years back; they fetched more than the AM-5's, but not by a ton. You can find them on eBay from time to time, unlike the Zenith 800.

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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Sat 16, 2017 6:52 pm 
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Good news....I managed to get the TR-7 transformer for $9. I ordered it today.....Will post results when I put it in radio...AL


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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Sat 23, 2017 3:49 am 
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New transformer installed (perfect fit).....radio working loud and clear...tracks stations very well too. My only problem is the back cover...it don't fit on correctly. I have read that this is common problem with the 800. Is there anything I could do? I will post pics soon. Thanks AL


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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Sat 23, 2017 4:24 am 
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Hey Al,

Great news---glad you have it working !

Hopefully someone will have an idea about the cover...

John


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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Sat 23, 2017 4:42 am 
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What he said ^. And you have now troubleshot to component level, so you be a tech! :wink:

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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Sat 23, 2017 5:33 am 
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Thanks John......I heard about using heat gun to mold fit, but would not know how to do that.....AL


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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Dec Sat 23, 2017 5:59 am 
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Location: Palos Verdes, CA
Al,
Good to hear that you got your Zenith 800 working! It is common with Zenith 800s that the cases get warped when they were stored upright as the radio is so heavy and the plastic case is relatively thin. Both of the cases of my Zenith 800s are warped and I've decided not to try and fix them. - Mark


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 Post subject: Re: Zenith Royal 800...Dead
PostPosted: Jan Mon 15, 2018 10:07 pm 
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Location: new hyde park ny usa
I changed all caps, including .1's...she is loud and tracks stations well.....but The sound quality is a bit 'tinny'


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