1952 Zenith Bugeye AM/FM Clock Radio

[vortalexfan]

Originally Posted by Electronic M

I'd remove or replace those line to chassis caps if you plan to have that radio plugged in unattended for any length of time...They are time bombs at this point in their lives.

I'd try variacing it the chassis out of the cabinet and see if it smokes again and where...If it does not smoke look at all the wiring on the chassis and clock and see if anything could be moved by flexing or bumping into something during installation in a way that could cause a short. Magic smoke can come from anywhere so finding the general vicinity of the source is key to diagnosis.

How would I variac the radio out of the cabinet? I can't run the radio outside the cabinet because of how the interlock plug is made on this radio.

Also I had figured out that the diode I wired into the radio to replace the selenium rectifier shorted because I wired it in backwards unintentionally because I was wiring it up how it was on the selenium rectifier which had the cathode marked with a (+) sign which made me think it was the anode side because of how it was marked.

But the only thing is that when I replaced and properly wired in properly, there was no audio but the tubes were lit.

What would be going on?

[init4fun]

Originally Posted by vortalexfan

How would I variac the radio out of the cabinet? I can't run the radio outside the cabinet because of how the interlock plug is made on this radio.

Also I had figured out that the diode I wired into the radio to replace the selenium rectifier shorted because I wired it in backwards unintentionally because I was wiring it up how it was on the selenium rectifier which had the cathode marked with a (+) sign which made me think it was the anode side because of how it was marked.

But the only thing is that when I replaced and properly wired in properly, there was no audio but the tubes were lit.

What would be going on?

Having the diode wired backwards could have damaged your electrolytic caps , but first things first there is usually a resistor between the rectifier and and the filter caps , that's the first check you should make and hopefully if that resistor smoked it saved your filter caps in the process .

Also , if at all possible when replacing a chassis mounted multi cap with single caps , it's best to mount a terminal strip and use that to install your new caps .

[vortalexfan]

Originally Posted by init4fun

Having the diode wired backwards could have damaged your electrolytic caps , but first things first there is usually a resistor between the rectifier and and the filter caps , that's the first check you should make and hopefully if that resistor smoked it saved your filter caps in the process .

Also , if at all possible when replacing a chassis mounted multi cap with single caps , it's best to mount a terminal strip and use that to install your new caps .

I didn't have a resistor in line with the diode on my radio... I just wired the diode straight up to the radio because I didn't realize you needed a resistor online with the diode, so yeah the capacitors are probably toast, but would that cause there to be no sound to come out of the speaker or the tubes not to light?

[init4fun]

Originally Posted by vortalexfan

But the only thing is that when I replaced and properly wired in properly, there was no audio but the tubes were lit.

Originally Posted by vortalexfan

I didn't have a resistor in line with the diode on my radio... I just wired the diode straight up to the radio because I didn't realize you needed a resistor online with the diode, so yeah the capacitors are probably toast, but would that cause there to be no sound to come out of the speaker or the tubes not to light?

Your sending contrary messages , in one post you say "No audio but the tubes were lit" and in this post you say "The tubes not to light?" , , , So , which is it , ARE the tubes lit or are they not ?

Now , to get down to the troubleshooting , we need to talk about troubleshooting itself and what it means to diagnose and repair vacuum tube circuit electrical failures . The "Shotgun" method of replacing parts on a vague "It could be this part" notion is not the right way to go . A LOT of perfectly good parts end up replaced that way at great cost till the bad part is finally changed by the luck of the draw . Yes indeed changing out the failure prone electrolytics was a good action , but now that you've had the episode of reverse polarity and have no sound the best course would be to start over completely .

Were this my situation to rectify I'd start by replacing the filter capacitors again because as Electronic M and I have said , they very well could be damaged . Consider mounting a terminal strip to the chassis and attaching the new caps to it as in my picture . I'd put the Selenium rectifier back in the circuit (polarized correctly or you'll REALLY learn what it means to "let the magic smoke out"* !!!!!) and then with a DC voltmeter on a scale of 300 volts or higher , and the schematic diagram , see exactly where B+ voltage actually is and isn't . This of course presumes that the tubes ARE lit and you have no sound . If the tubes aren't lit , start with an AC voltmeter on at least 200 volts scale and using your schematic follow the tube's heater AC path till the open is found .

A multimeter , a schematic , and about 5 minutes are all it should take you to diagnose this , once you replace the filter caps and put the rest of the circuit back to original status . Once you've got it running if you want to eliminate the Selenium rectifier , fine , but DO install the proper dropping resistor for the excess voltage of the silicon diode , circuits have "as designed" operating voltages for a reason , and especially in electronics "somewhat higher" is just about never equated with "better" .

* If you don't already know , an overloaded or shorted Selenium rectifier lets out a noxious smoke that smells like a bucket of rotten eggs X 10 , so make damn sure you polarize the Selenium rectifier correctly , and also using your ohm meter mode of your multimeter make sure that the new caps you install are wired correctly and aren't presenting any kind of short circuit to the rectifier BEFORE you power it on again .....

[init4fun]

Oh , and , Thanks to the schematic graciously provided by Jim , I can see that there is a resistor between the rectifier and the first filter cap . That resistor , R32 , which is a 22 ohm 1 watt , is very likely what made the smoke . I'd still change the caps , and then check R32 as you may well find it open (infinite ohms) . That is also the resistor you'd want to increase the resistance of if you do try again to install a silicon diode .

[Electronic M]

Originally Posted by init4fun

Oh , and , Thanks to the schematic graciously provided by Jim , I can see that there is a resistor between the rectifier and the first filter cap . That resistor , R32 , which is a 22 ohm 1 watt , is very likely what made the smoke . I'd still change the caps , and then check R32 as you may well find it open (infinite ohms) . That is also the resistor you'd want to increase the resistance of if you do try again to install a silicon diode .

IIRC from when I worked on mine that resistor looks like a thin mica cap. It was color-coded in dots...It may or may not be the same on your set depending on production run and any possible previous repair work.

[dieseljeep]

Originally Posted by Electronic M

IIRC from when I worked on mine that resistor looks like a thin mica cap. It was color-coded in dots...It may or may not be the same on your set depending on production run and any possible previous repair work.

I haven't seen one of those resistors in ages. The flat Micamold resistors. They're both 470 ohm, 2 watt resistors.
I had to take mine apart today. It's a 7X03 chassis with OEM part code dates from late 1955.
The under chassis view from the OP shows the band selector switch is mounted on an angle with some form of a universal joint, which I thought was rather novel. Mine is mounted straight.
I unsoldered all the leads going to the back to make it a little easier to work on. Of course I made a drawing where each one went.

[vortalexfan]

Originally Posted by init4fun

Your sending contrary messages , in one post you say "No audio but the tubes were lit" and in this post you say "The tubes not to light?" , , , So , which is it , ARE the tubes lit or are they not ?

Now , to get down to the troubleshooting , we need to talk about troubleshooting itself and what it means to diagnose and repair vacuum tube circuit electrical failures . The "Shotgun" method of replacing parts on a vague "It could be this part" notion is not the right way to go . A LOT of perfectly good parts end up replaced that way at great cost till the bad part is finally changed by the luck of the draw . Yes indeed changing out the failure prone electrolytics was a good action , but now that you've had the episode of reverse polarity and have no sound the best course would be to start over completely .

Were this my situation to rectify I'd start by replacing the filter capacitors again because as Electronic M and I have said , they very well could be damaged . Consider mounting a terminal strip to the chassis and attaching the new caps to it as in my picture . I'd put the Selenium rectifier back in the circuit (polarized correctly or you'll REALLY learn what it means to "let the magic smoke out"* !!!!!) and then with a DC voltmeter on a scale of 300 volts or higher , and the schematic diagram , see exactly where B+ voltage actually is and isn't . This of course presumes that the tubes ARE lit and you have no sound . If the tubes aren't lit , start with an AC voltmeter on at least 200 volts scale and using your schematic follow the tube's heater AC path till the open is found .

A multimeter , a schematic , and about 5 minutes are all it should take you to diagnose this , once you replace the filter caps and put the rest of the circuit back to original status . Once you've got it running if you want to eliminate the Selenium rectifier , fine , but DO install the proper dropping resistor for the excess voltage of the silicon diode , circuits have "as designed" operating voltages for a reason , and especially in electronics "somewhat higher" is just about never equated with "better" .

* If you don't already know , an overloaded or shorted Selenium rectifier lets out a noxious smoke that smells like a bucket of rotten eggs X 10 , so make damn sure you polarize the Selenium rectifier correctly , and also using your ohm meter mode of your multimeter make sure that the new caps you install are wired correctly and aren't presenting any kind of short circuit to the rectifier BEFORE you power it on again .....

No the tubes aren't glowing, what I thought was tubes glowing was actually the neon pilot lamp glowing.

As for the capacitors I ordered some new ones, and as for the selenium rectifier smell goes, I'm well aware what they smell like, that's why I wanted to eliminate it from the circuit so that it didn't have a chance to fail on me, and I did order a 47 ohm 2 watt resistor to install after the 1N4007 diode.

And I did use a terminal strip to install the electrolytic caps.

[jr_tech]

I would start by testing the tubes... the heaters are in series, so if one heater is open, none will light up.

jr

[vortalexfan]

Originally Posted by jr_tech

I would start by testing the tubes... the heaters are in series, so if one heater is open, none will light up.

jr

I did test the tubes that's the thing and they all tested good yet on my tube tester.

But they still don't glow.