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 Post subject: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 4:45 am 
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Location: Wheeling, WV
This zenith recently had a original black beauty burst so I decided to recap most of the caps. Only the ones not changed are the electrolytics, one paper, one Black plastic cap, and two Black beauties that are on the tone control(I think). I powered it up and everything seemed to be working fine again. I let the set sit for a few hours and I tried it again...now it is not receiving any stations. If I turn the volume up completely I can hear a lite buzz in the speaker so I guess the audio stage is still good. I believe this kinda happened before I replaced caps but I barely used the set before this.


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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 5:56 am 
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Is this on BC or all bands?

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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 5:58 am 
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cameronw wrote:
Only the ones not changed are the electrolytics, one paper, one Black plastic cap, and two Black beauties

Three guesses as to what your next move should be (first two guesses don't count) :wink:

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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 6:11 am 
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All bands are dead. I forgot to add I am in another location than where I worked on the set... but my other sets here are able to pick up stuff just fine. I tried the trick of having another set tuned to nothing and then tuning this g500 around that blank spot and I can here some reaction on my working set... so I guess its tuning okay. I just tried turning the set on and let it sit for a bit... I can now hear static over what I think would be stations but I can only hear it when I put my thumb on the antenna. I got no idea what is up here.


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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 6:26 am 
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Local oscillator not running.


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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 7:18 am 
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If this were my set, I'd do the following in the order listed:

(1) replace the filter electrolytic caps;
(2) get the tubes tested; and
(3) check the selenium rectifier circuitry for correct voltage output (assuming that the radio is being operated on line current, not a battery).

Filter electrolytics can short out nearly anytime, taking out the radio power. A bad tube is also a possibility. These tubes are direct-emitting (no cathode sleeve) but they still can be depleted to the point of failure, even if they "light up". Selenium rectifiers can fail suddenly (in which case no output voltage is produced) or they can fail gradually, becoming resistive internally and dropping excessive voltage across themselves to the point where the local oscillator can no longer operate (slow selenium failures are usually first noticed by the upper shortwave bands going "deaf").


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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 7:28 am 
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cameronw wrote:
I got no idea what is up here.

Apparently.
Replace the caps you didn't the first time and it should work.

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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 12:05 pm 
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I'm suspicious that ur 1L6 tube is no longer functioning. You'll need to check the voltages from the selenium rectifier to confirm. Be careful, this is a line operated set, and there is nothing between you and the powerline if you don't use an isolation transformer. the 1L6 should have about 1.4 volts across its filaments. If it does, it may just be worn out. a cheap sub is a 1R5, which should work on the BC band and the lower SW bands. I would suggest reading the H500 restoration by Badrestorer, http://www.renovatedradios.com/articleP ... nGuide.pdf, also on this site. The H500 is very similar to the G500 and his restoration is good reading as well as informative. You should be able to download a schematic online which will have expected voltages.. Good luck, they're grand old radios. ...and BTW replace those other caps first chance you get. You'll see how Badrestorer did it.


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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 5:21 pm 
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Leno Pederson wrote:
the 1L6 should have about 1.4 volts across its filaments.


Ill check these voltages. I do have the right caps on hand to replace the electrolytics.... but I always get confused when replacing them. I am pretty sure the negative side need to be connected to the can instead of ground. I have never stuffed a can before so I don't think I should on this set. From what I understand all the terminals are used on the can so I couldn't just use one of them.... I don't know where else I would put the negative sides if I can't use a terminal on it.

I will replace the other caps when I get them ordered.


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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 9:03 pm 
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It's always easiest to simply D/C the leads going to the vertical can's solder lugs, and tie the + side of discreet Electrolytic values to them, in accordance to the symbols denoting capacitance values.

In this case it looks like 4, from a cursory glance. Here's the print;

http://www.nostalgiaair.org/pagesbymode ... 025526.pdf

Note that the negatives tie to circuit B-, not the chassis. I would suggest locating R13 (330K) and tracing it to where it ties directly to the switch on the volume control. Use that as the B- point.

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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 9:13 pm 
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I tied the negative ends to these twisted sections on the bottom of the can which I figured was the bottom of the can. I have a am transmitter and it is able to pick that up but nothing else.


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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 9:26 pm 
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Also I am working on this set in a rural area and the only other set I got here really can’t pick up anything but I figured this set would be more sensitive. I am moving from my dorm to here to work on it so I keep moving place to place.... sorry. It’s picking up my transmitter just fine but I can’t even hear any other stations


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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 10:42 pm 
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I would suggest using your meter to see if there is zero resistance between where you tied the grounds to, and the switch lug tied to R13.

AFA reception, see what your car radio can pick up on the AM band, to use as a standard. If it gets at least a few stations, then the Zenith has a front end problem if it only gets your in house transmitter.

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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 11:16 pm 
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It’s picking up my transmitter just fine but I can’t even hear any other stations.

Where is the transmitter? In the room where your working or in another?
I’m assuming your antenna is plugged into the extension cable and then into the chassis.
I’m asking because a TO will not pickup a station without a good antenna where as other radios will. Now if the transmitter is close by, your radio just might work if it’s close enough. I also had a problem on a G500 where just twisting the antenna by it’s self, with two hands would make or break a bad connection inside the oval antenna. Worked fine on the bench, but not when it was in the cabinet and the antenna snapped into the front door.

Freeman


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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sun 17, 2019 11:39 pm 
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My transmitter is right next to the set. It comes in just fine. The set appears to be a little more alive after changing the electrolytics. I get a little buzz now when turning the set up. It isn't that loud so I'd say its normal.... unless I put the electrolytics in wrong. I am just using the antenna in the set... the other set I have here I can barley hear one station... but Ill try the car. I had the set in town where one station should come in very well but yesterday is was still deaf... I will try to use it when I get it in town with the changed electrolytics.


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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Mon 18, 2019 1:12 am 
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cameronw wrote:
unless I put the electrolytics in wrong.

Did you do what I suggested in my last post, to verify that they were installed correctly as to the negative leads?

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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Mon 18, 2019 1:22 am 
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fifties wrote:
Did you do what I suggested in my last post, to verify that they were installed correctly as to the negative leads?


I did not and I will when I'm at my bench again. I tied the negative leads to the 3 or 4 outer leads on the can... the twisted ones. If I am correct the four inner leads are the positive ends for each of the four caps and then the other outer leads are there to hold the can in place.... so tying the new negative leads to them would be correct. The sound appeared to be a little louder and now having an audible buzz when the volume is turned up.


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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Mon 18, 2019 6:12 am 
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cameronw wrote:
fifties wrote:
Did you do what I suggested in my last post, to verify that they were installed correctly as to the negative leads?


I did not and I will when I'm at my bench again. I tied the negative leads to the 3 or 4 outer leads on the can... the twisted ones. If I am correct the four inner leads are the positive ends for each of the four caps and then the other outer leads are there to hold the can in place.... so tying the new negative leads to them would be correct. The sound appeared to be a little louder and now having an audible buzz when the volume is turned up.

Use your meter to determine if there is resistance between the lugs you tied the negative leads to, and the chassis. If there is either zero, or very little (the resistance in the meter leads, 1-3 ohms), locate an outer can terminal that does have resistance to the chassis, and use that instead. The can would have one or more solder terminals isolated from the chassis, for circuit ground.

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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sat 23, 2019 4:51 am 
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fifties wrote:
Use your meter to determine if there is resistance between the lugs you tied the negative leads to, and the chassis. If there is either zero, or very little (the resistance in the meter leads, 1-3 ohms), locate an outer can terminal that does have resistance to the chassis, and use that instead. The can would have one or more solder terminals isolated from the chassis, for circuit ground.


I got about 350k on the two outer terminals I used for electrolytics. I am in strong station area now and its louder than ever. I have replaced every cap but tone ones. It is receiving all the stations I should get here but the dial is off where the stations should be. The spacing of the stations is fine but are off probably an inch on the dial... for the station that is at 1290 the dial shows 1390. I guess just moving the pointer would probably do it but before I do I'd like to know if something else would cause this.
Thanks so far!


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 Post subject: Re: Zenith G500 Stopped receiving stations
PostPosted: Nov Sat 23, 2019 5:02 am 
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Glad to hear that you have it working well. I would first suggest tuning the set to 1600 Kc, and adjusting the tuner oscillator trimmer to place a station near or at that frequency. If there is a station at 1580, for example, have it locate just below 1600 on the dial. If you have a generator, of course, that would be more exacting.

Next, if the dial pointer is still off at about the same at each end of the dial, the easiest fix is as you've said, to simply move the pointer. Sometimes it's a balance between both ends, so it may not alight perfectly, but be close throughout.

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