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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Mon 10, 2021 3:31 am 
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Take out the batteries, and use your meter at the lowest resistance setting on the solder lugs of the switch, to see if contact is made when it's turned on. A few ohms of resistance is OK, but you want to see infinite when the switch is off, and a very small or no resistance when it's on.

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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Mon 10, 2021 3:47 am 
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Both negatives are to the left.


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Mon 10, 2021 9:08 pm 
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Joined: Mar Thu 04, 2021 2:18 am
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Location: New Hampshire
took readings of the control pot and here's what I got-
200-ohm setting- taken from the two yellow wires going to the solder lugs.
off- infinite
on- 0.06 ohms
so nothing really to worry about with the volume control, all seems good.

then I inspected my e-cap work, again all seemed good.

so I put the batteries in and there was the same "click", but as I tuned it I could hear very quiet static on one section and no noise whatsoever when I tuned back.
does contact cleaner make these tuning condensers scratchy too? if so a puff of it may have come up when I was cleaning the volume control pot. but even at full volume, it's barely noticeable.

not sure what to do next I don't think it's going to make any noise with the second radio test, so the transistors may be up next, if so I will need a schematic.

below are some well-needed "in progress pictures", sorry they're a bit blurry I am using my desktop camera.

henry


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Mon 10, 2021 11:32 pm 
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Location: Indianapolis, IN
Henry, that switch has two sections so you need to measure the red and white wire terminals also.

Do any of the tuning cap plates look shorted?

John


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Tue 11, 2021 6:17 am 
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whfh99 wrote:

not sure what to do next I don't think it's going to make any noise with the second radio test,

You don't know unless you try.

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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Tue 11, 2021 9:14 pm 
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Location: New Hampshire
Hey guys,
Measured The rest of the volume control pot, I got Infinite When the radio is turned off And 0.20 ohms When It was on. So it looks to be functioning fine.
Also took a look At the Tuning Capacitor And none Of the plates seemed to be touching.

I think you misunderstood Me when I said I didn't think any noise would come out of it When I was doing the Second radio test, I meant I didn't think Any noise would come out Of the zenith. I didn't understand it was supposed to come out of the other radio.

Anyways I tried it and There was Noticeable oscillation On my channel master Radio. So we can assume The oscillator is working.

Any suggestions on what to try next?
Henry

Oh and does anybody know Why the circuit board is green? Most of the radios I have worked on have Brown circuit boards.


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Tue 11, 2021 9:34 pm 
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Green was a common PCB color, as was brown.

Henry, now with a gazillion pages of help in your various radio repair endeavor threads, do you really need to ask what you should do next? Read all the help previously offered, my boy.

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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Tue 11, 2021 10:05 pm 
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Location: New Hampshire
yes, your right.
The next step would be to check for shorts or broken copper traces and after that, I would probably go to the transistors.
but I had another question about the circuit board; when I was replacing the electrolytic capacitors a copper trace came up, so I soldered it back to the green copper trace.
so my question is the green coating on the copper tracing conductive, meaning if a capacitor is soldered to it will the energy go thru?
also when working on my channel master somebody suggested doing this download/file.php?id=348982&mode=view
If I remember correctly it was to make sure the current was passing thru all of the radio, is there a way I could do this with a 6-volt radio?


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Tue 11, 2021 10:43 pm 
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To test if current is flowing through the capacitor, simply measure the voltage between the capacitor leads. If you see voltage it's passing current. Though this pic looks awkward, it's how to measure current. You simply put the meter in the circuit so the current must pass through it for the radio to work. Note it's hard for the negative side of the battery to make contact with the battery tab, but it works.


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Tue 11, 2021 10:50 pm 
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Joined: Oct Mon 26, 2009 10:02 pm
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Location: Indianapolis, IN
That green coating is an insulator and needs to be carefully scraped off to expose copper for soldering !


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Tue 11, 2021 11:57 pm 
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Joined: Mar Thu 04, 2021 2:18 am
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Location: New Hampshire
thanks, guys.
will measure voltages and re-do my recapping job tomorrow afternoon.

henry


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Thu 13, 2021 12:11 am 
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Location: New Hampshire
hello,
took off all the insulation from the copper traces and measured the current.
got around 3 volts on each side, so we know that's fine.
after re-doing my recapping job it stills makes a pop when turned on but makes a very quiet rushing-like sound barely noticeable even at full volume, I can hear it across the band.
but get this; when I bring it outside (out of my workshop) it doesn't make the noise, my guess is that it's using my soldering iron extension cord as a longer antenna. the sound gets louder when I touch the antenna also when I touch the tuning capacitor.

henry

p.s. also reheated the solder landings and checked for broken traces/shorts.
with no luck!


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Thu 13, 2021 12:41 pm 
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Joined: Mar Thu 04, 2021 2:18 am
Posts: 320
Location: New Hampshire
I am going to test the transistors next. (Unless theres anything else we could try)
For that I will need a schematic,
Anybody have a copy they could post?


Henry


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Thu 13, 2021 2:48 pm 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6920
Location: Indianapolis, IN
Henry,

Also possible that you might have a cracked PCB---examine it carefully with a bright light behind it.

Just extracted the factory Zenith service info from Beitmans---PM me an e-mail and I'll send it...

Then you can measure the voltages at transistors and report back...

John


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Thu 13, 2021 9:18 pm 
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Joined: Mar Thu 04, 2021 2:18 am
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Location: New Hampshire
Thanks, john.
Didn't look like the board was cracked anywhere.
Just sent a pm.

Henry


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Sun 16, 2021 10:36 pm 
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Location: New Hampshire
tested the voltages today using an electrolytic capacitor lead as my ground, nothing looked out of the ordinary, but I can post my results if you guys want.
though the 2 outputs schematic shows b-.14v e-0 c 3.0 and I get b-1.5 e-0 c-3.0 it may also be part of the fact that is it very difficult to test and my lead was shorting with another one.

however, I have an interesting story to tell you; thanks to zenith who put their transistors in the hardest-to-reach spots I had to get out my extended probes that go on my DMM leads. so anyway it was touching the gold cage type thing that holds in/protects all the plates on the tuning cap while it was touching a lead of the 2nd output transistor. I could hear loud static which sounded just like the am band! as I tuned around I could hear an extremely distorted wbz Boston weather report. it could barely be heard in all the static.
then I stopped shorting it together and it all stopped.
I have never had this happen before,
any thoughts on what it might be?

henry


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Mon 17, 2021 1:02 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6920
Location: Indianapolis, IN
Sounds like a bad ground to tuning cap !

Check the ground screws to tuner and make sure they're tight---also measure from tuner frame to ground with meter to make sure you have a good connection...

John


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Mon 17, 2021 1:45 am 
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Joined: Mar Thu 04, 2021 2:18 am
Posts: 320
Location: New Hampshire
Great!
By ground screws I assume you mean the screws on the tuning capacitor?
And by ground you mean what I was using to test the transistors, correct?

Thanks,
Henry


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Mon 17, 2021 4:49 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 6920
Location: Indianapolis, IN
Yes, the same ground which is connected to positive end of battery array and the screws which attach the tuning cap to PCB. Easy way to test first is to just use a wire connected to the ground and touch it securely to gold metal frame of tuner and see if it works or makes a difference...


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 Post subject: Re: Zenith royal 500E-1
PostPosted: May Mon 17, 2021 9:03 pm 
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Joined: Mar Thu 04, 2021 2:18 am
Posts: 320
Location: New Hampshire
John,
here are the results-
when a piece of wire was connected to the frame of the tuning capacitor & the + battery clip, it made the same noise as it did before lots of static but only this time there was no sign of a station broadcast. this tested at 0.62 volts on my meter.

when I put a piece of wire to the copper piece connecting the tuning cap to the PCB & the + battery clip it makes the same noise as before, static no stations.
this measured about 5.5 volts on my meter.

also tightened the screws that are on the tuning cap this did not seem to make a difference, was I supposed to tighten the ones that hold it on to the pcb?

thanks for the help,
henry


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