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 Post subject: Zenith Royal 3000-1 dead
PostPosted: Jul Sat 30, 2011 12:39 am 
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Location: Cedartown,Ga. USA
My 3000 only makes a little static when I turn the band switch.I tried cleaning it not much difference. I tried bending the leads on the transistors too. Any ideas? I'm kinda new on the transistor radios! Radio looks good on inside, has not worked since I had it!


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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Jul Sat 30, 2011 7:22 am 
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Location: Dallas, TX - in the city but with bobcats and coyotes
Look here for service info:http://www.transoceanic.nostalgiaair.org/3000.htm

If you have a volt meter, measure the voltages at the test points shown in the service info (look for a little chart with the "good" voltage readings). Post your measured voltages here.
Also, see if the oscillator works:
Set it to AM broadcast band and turn on a good, working, AM radio placed next to it. Tune the good radio to a quiet spot near the middle of the band and listen to it as you tune the radio under test (your 3000-1) up and down the band. If the TO's local oscillator is working reasonably well, you should hear the good radio squeal as you tune the TO's oscillater to a frequency about 455KHz away from wherever the good radio is tuned.
Also, does the FM work?
If you wire up an external supply it needs to be "tip" negative and NO GREATER than a measured 12 Volt supply. A 12v "wall wart" may put out well over 12v with the low current draw of the 3000-1.

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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Jul Sat 30, 2011 11:11 am 
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Thanks Mescalero! The radio is dead on FM also, just hear a slight crackling when I turn the band selector. I wll do the tests you mentioned and post results later!


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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Jul Sat 30, 2011 1:49 pm 
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no osscillation! can you tell me the value needed of capacitor in picture(blue) This one was cracked and i could not read it. I may have used the wrong one(not too good on the schematics yet) It is just right of the volume control. I checked voltages fm pretty close but am off on most.
FM 1= 1.07 2=.91 3=.91 4=.001 5=.44 6=.47 7=.60
AM 1=1.59 2=2.99 3=3.02 4=30.6 5=9,4 6=5.9 7=4.9
all negative values
Could that cap be it?
Thanks


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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Jul Sat 30, 2011 2:42 pm 
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Location: Dallas, TX - in the city but with bobcats and coyotes
I'll get to opening mine in a while to check cap value and polarity. I'll also dig up my schematics and look at your voltage measurements. Please give me a while because my leg is not fully healed after surgery. In the meantime, maybe another forum member can "step" in. :lol:

Edit - I take it that TP4 in AM is 3.06, not 30.6.

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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Jul Sat 30, 2011 3:41 pm 
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Have you replaced the paper cap "C5"? It should be located near the #121-351 AM mixer transistor.

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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Jul Sat 30, 2011 5:41 pm 
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Regarding the cap in your photo; please trace the wires connected to it until you come to something that can be identified on the schematic. I now see that I (apparently) would need to pull my chassis to get a visual on 'er. I'm not wanting to do that. :wink:
It is pretty obvious to me, from voltage readings, that your radio's C5 is probably a dead short. Let's get that out of the way, double-check your electrolytic's value and polarity, and then re-measure voltages at the test points. If you have a film cap that would be my recommendation for replacing C5 (the paper cap).
Bit by bit, we should be able to get it patched up. You'll "love" this radio. Mine lives on my bedside table and is playing some Eric Burden and War right now. 8)

BTW, if you forget which way a polarized cap was in circuit, a voltmeter will show you which end is more negative than the other.

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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Jul Sat 30, 2011 9:44 pm 
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The only paper cap I see is a yellow one .1 mfd 50 volt. It does not show a dead short. When I touch the end of it I hear a loud buzz. This would not be an electrolytic, correct?
Thanks very much for your help!


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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Jul Sat 30, 2011 11:37 pm 
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The capacitor in the picture has the black speaker wire coming off of it. I still can't be sure if it's correct!


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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Jul Sun 31, 2011 3:27 am 
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I do recommend that you change the paper cap anyway if it is original. Even a fair amount of leakage from it would be unacceptable.
As for the electrolytic, the black speaker wire is probably chassis ground (positive in this radio). What does the other end tie to? The answer to that will tell you which cap it is on the schematic.

Edit -typo

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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Jul Sun 31, 2011 11:32 am 
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If the radio is positive ground do I ground the positive end of the electrolytic cap.?
Thanks! I will replace the paper cap when I find one and measure voltage again.


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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Jul Sun 31, 2011 12:57 pm 
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Technically, the cap polarity depends upon surrounding circuitry. That's why I suggested measuring the DC voltage across them to verify polarity. However, it is true that, in this radio, chassis ground is the most positive point in the circuit. So, yes, caps connected to chassis ground will have positive connected to said ground.

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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Aug Mon 01, 2011 9:38 pm 
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I was wrong about c5, I had the wrong place on the schematic! I removed the correct c5 and it was not shorted. I also found a disc cap very near c5 that looked melted and was not connected on one end! Could that be my problem? Can I replace c5 with one of those blue metallic caps( Radio Shack ) ? The disc cap looked like a factory error! I am getting better at the schematic! Lol Thanks


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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Aug Tue 02, 2011 1:48 am 
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Location: Dallas, TX - in the city but with bobcats and coyotes
Not sure what material/style of blue metallic caps RS is selling but I would use a film cap for C5. Audio quality would be best with film.

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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Aug Tue 02, 2011 1:59 pm 
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The problems I've seen with these T/O's are:

(1) Dried up audio coupling capacitors in the audio stages.

(2) Dirty bandswitch.

(3) Dead transistors in the IF and RF stages.

Everything else is mighty sturdy and unlikely to break.


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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Aug Tue 02, 2011 6:31 pm 
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Good points, and I'll recommend checking transistors for shorts after cap, C5 is known to be good. The only thing that "jumps out" at me that will cause high voltage at test point 3 & 4 (3.02 & 3.06v, respectively) is a badly leaking C5.
C5, 19, 31, 35, 56, 57, 58, 61 & 62 are all suspect in these. I changed all nine of these in my 3000-1 as it had obviously seen storage in a hot area at some point in its life. the vinyl was decidedly shrunken and the glue that held it to the case had run all over. In addition, the transistors can develop leakage and shorts that are bad enough to detect with a Volt meter.

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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Aug Wed 03, 2011 12:44 am 
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Thanks guys, I replaced C5 and here are the voltages
Fm 1=.65 AM. 1=1.19
2=.45. 2=.94
3=.41. 3=.46
4=0. 4=0
5=2.9. 5=9.5
6 =3.1 6=3.91
7=4.0. 7=103.7
Thanks! Not sure thought I heard very faint signal on FM


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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Aug Wed 03, 2011 1:11 am 
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Are there differences in the Zenith Schematic and the SAMs? C5 shows a . 1 mfd on Zenith and 10 Mfd on SAMs? I'm confused???


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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Aug Wed 03, 2011 8:08 am 
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I am referring to the Zenith schematic in the nostalgiaair.org link. I see the readings have changed. I will look at them in AM and see what I see next. I suspect that the next round will be checking transistors, one at a time, with the meter. If you want to read up on how to check germanium transistors with a meter, go for it. The transistor case/pin-out information is in the (Zenith) service info.

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 Post subject: Re: Zenith Royal 3000-1 dead
PostPosted: Aug Thu 04, 2011 4:55 am 
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Location: Dallas, TX - in the city but with bobcats and coyotes
TP7, AM mode - what is the reading?

Also, the IF and audio sections have voltage readings in tiny print on the schematic. Maybe the Sam's is easier to read. And yes, to answer your question, Sams drew their own schematics by dissecting perfectly good radios. So I've been told, the schematics are thus their intellectual property and they can then copyright and sell them. So the reference designators, such as "C5," are arbitrarily assigned.

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