Sears 4587 glowing 5Y3

1/9/2013 6:39:29 PMDaveF

I recapped the electrolytics and a few of the many other paper caps on this chassis, which now plays pretty good. I notice that the rectifier glows more than I think it should. Is there some how a short that is causing this? I have not left the radio on for more than about 10 minutes for fear of issues.

1/9/2013 7:50:48 PMLou

You may still have a leaky electrolytic.

I would disconnect the electrolytic caps one by one and reenergize the set. I know you will get hum but you will be able to tell by the color of the rectifier ( NO COLOR )which one is the culprit.

Lou

1/9/2013 9:02:54 PMWALTER FROEHLICH

HI:

IF YOU MEAN THE FILAMENT.

MEASURE THE AC FILAMENT VOLTAGE ACROSS PINS 2 & 8.IT SHOULD BE 5.0 VOLTS AC.

BE CAREFUL AS THERE IS HIGH DC VOLTAGE FROM THOSE PINS TO GROUND.

WALTER-W2WIQ

:You may still have a leaky electrolytic.
:
:I would disconnect the electrolytic caps one by one and reenergize the set. I know you will get hum but you will be able to tell by the color of the rectifier ( NO COLOR )which one is the culprit.
:
:Lou
:
:
::I recapped the electrolytics and a few of the many other paper caps on this chassis, which now plays pretty good. I notice that the rectifier glows more than I think it should. Is there some how a short that is causing this? I have not left the radio on for more than about 10 minutes for fear of issues.
::
:
:

1/9/2013 9:21:47 PMNorm Leal

Agree with WALTER but you don't want any glow on the plates. If plates have glow keep the radio off or power transformer will be damaged.

Norm

:
:HI:
:
:IF YOU MEAN THE FILAMENT.
:
:MEASURE THE AC FILAMENT VOLTAGE ACROSS PINS 2 & 8.IT SHOULD BE 5.0 VOLTS AC.
:
:BE CAREFUL AS THERE IS HIGH DC VOLTAGE FROM THOSE PINS TO GROUND.
:
:WALTER-W2WIQ
:
:
:
:
:
:
:
::You may still have a leaky electrolytic.
::
::I would disconnect the electrolytic caps one by one and reenergize the set. I know you will get hum but you will be able to tell by the color of the rectifier ( NO COLOR )which one is the culprit.
::
::Lou
::
::
:::I recapped the electrolytics and a few of the many other paper caps on this chassis, which now plays pretty good. I notice that the rectifier glows more than I think it should. Is there some how a short that is causing this? I have not left the radio on for more than about 10 minutes for fear of issues.
:::
::
::
:
:

1/9/2013 10:04:28 PMJohn K

I copied this from another site, a post by Ron. Might help you ID the source of the bright glow. As the others said, a shorting cap could cause excess current thru the diode's plate.
"There are two parts to the 5Y3 that can get red. The heater inside the plates should glow orange-red. When cold, the plates of the 5Y3 are black or silver, and should remain so when hot. If the plates glow red, that means that the tube is being asked to supply much more current than it is designed for.

The heaters of the 5Y3, but not the plates would be the bright red item. The heaters (or filaments) look like narrow ribbons, about the width of a piece of string. They can normally be seen from the top. The heater voltage on the 5Y3 can be easily checked, and should be five volts AC." That voltage can be measured with the tube out of the socket.

You could rig up a temporary rectifier using 2 silicon diodes i place of the tube. I would do this if you can't locate the problem right away. Remember tho that those diodes will be carrying lethal voltages on their exposed leads.

:Hi
:
: Agree with WALTER but you don't want any glow on the plates. If plates have glow keep the radio off or power transformer will be damaged.
:
: Norm
:
::
::HI:
::
::IF YOU MEAN THE FILAMENT.
::
::MEASURE THE AC FILAMENT VOLTAGE ACROSS PINS 2 & 8.IT SHOULD BE 5.0 VOLTS AC.
::
::BE CAREFUL AS THERE IS HIGH DC VOLTAGE FROM THOSE PINS TO GROUND.
::
::WALTER-W2WIQ
::
::
::
::
::
::
::
:::You may still have a leaky electrolytic.
:::
:::I would disconnect the electrolytic caps one by one and reenergize the set. I know you will get hum but you will be able to tell by the color of the rectifier ( NO COLOR )which one is the culprit.
:::
:::Lou
:::
:::
::::I recapped the electrolytics and a few of the many other paper caps on this chassis, which now plays pretty good. I notice that the rectifier glows more than I think it should. Is there some how a short that is causing this? I have not left the radio on for more than about 10 minutes for fear of issues.
::::
:::
:::
::
::
:
:

1/10/2013 6:14:34 AMLewis

:I copied this from another site, a post by Ron. Might help you ID the source of the bright glow. As the others said, a shorting cap could cause excess current thru the diode's plate.
:"There are two parts to the 5Y3 that can get red. The heater inside the plates should glow orange-red. When cold, the plates of the 5Y3 are black or silver, and should remain so when hot. If the plates glow red, that means that the tube is being asked to supply much more current than it is designed for.
:
:The heaters of the 5Y3, but not the plates would be the bright red item. The heaters (or filaments) look like narrow ribbons, about the width of a piece of string. They can normally be seen from the top. The heater voltage on the 5Y3 can be easily checked, and should be five volts AC." That voltage can be measured with the tube out of the socket.
:
:You could rig up a temporary rectifier using 2 silicon diodes i place of the tube. I would do this if you can't locate the problem right away. Remember tho that those diodes will be carrying lethal voltages on their exposed leads.
:
:
:
::Hi
::
:: Agree with WALTER but you don't want any glow on the plates. If plates have glow keep the radio off or power transformer will be damaged.
::
:: Norm
::
:::
:::HI:
:::
:::IF YOU MEAN THE FILAMENT.
:::
:::MEASURE THE AC FILAMENT VOLTAGE ACROSS PINS 2 & 8.IT SHOULD BE 5.0 VOLTS AC.
:::
:::BE CAREFUL AS THERE IS HIGH DC VOLTAGE FROM THOSE PINS TO GROUND.
:::
:::WALTER-W2WIQ
:::
:::
:::
:::
:::
:::
:::
::::You may still have a leaky electrolytic.
::::
::::I would disconnect the electrolytic caps one by one and reenergize the set. I know you will get hum but you will be able to tell by the color of the rectifier ( NO COLOR )which one is the culprit.
::::
::::Lou
::::
::::
:::::I recapped the electrolytics and a few of the many other paper caps on this chassis, which now plays pretty good. I notice that the rectifier glows more than I think it should. Is there some how a short that is causing this? I have not left the radio on for more than about 10 minutes for fear of issues.

Be sure you have installed the caps with the correct polarity. I don't mean to insult your intelligence, but everyone has either done it or will do it someday.
Lewis
:::::
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::::
:::
:::
::
::
:
:

1/10/2013 8:21:50 AMdave F

::I copied this from another site, a post by Ron. Might help you ID the source of the bright glow. As the others said, a shorting cap could cause excess current thru the diode's plate.
::"There are two parts to the 5Y3 that can get red. The heater inside the plates should glow orange-red. When cold, the plates of the 5Y3 are black or silver, and should remain so when hot. If the plates glow red, that means that the tube is being asked to supply much more current than it is designed for.
::
::The heaters of the 5Y3, but not the plates would be the bright red item. The heaters (or filaments) look like narrow ribbons, about the width of a piece of string. They can normally be seen from the top. The heater voltage on the 5Y3 can be easily checked, and should be five volts AC." That voltage can be measured with the tube out of the socket.
::
::You could rig up a temporary rectifier using 2 silicon diodes i place of the tube. I would do this if you can't locate the problem right away. Remember tho that those diodes will be carrying lethal voltages on their exposed leads.
::
::
::
:::Hi
:::
::: Agree with WALTER but you don't want any glow on the plates. If plates have glow keep the radio off or power transformer will be damaged.
:::
::: Norm
:::
::::
::::HI:
::::
::::IF YOU MEAN THE FILAMENT.
::::
::::MEASURE THE AC FILAMENT VOLTAGE ACROSS PINS 2 & 8.IT SHOULD BE 5.0 VOLTS AC.
::::
::::BE CAREFUL AS THERE IS HIGH DC VOLTAGE FROM THOSE PINS TO GROUND.
::::
::::WALTER-W2WIQ
::::
::::
::::
::::
::::
::::
::::
:::::You may still have a leaky electrolytic.
:::::
:::::I would disconnect the electrolytic caps one by one and reenergize the set. I know you will get hum but you will be able to tell by the color of the rectifier ( NO COLOR )which one is the culprit.
:::::
:::::Lou
:::::
:::::
::::::I recapped the electrolytics and a few of the many other paper caps on this chassis, which now plays pretty good. I notice that the rectifier glows more than I think it should. Is there some how a short that is causing this? I have not left the radio on for more than about 10 minutes for fear of issues.
:
:
:
:Be sure you have installed the caps with the correct polarity. I don't mean to insult your intelligence, but everyone has either done it or will do it someday.
:Lewis
::::::
:::::
:::::
::::
::::
:::
:::
::
::
:
:
It is definitely a glowing plate problem. I have quite a few more caps to replace, and one of the resistors in the electrolytic area is suspect since the insulation is flaked off of this large resistor. I will finish the capping first and see what happens. Thanks for all your suggestions.

1/14/2013 12:24:06 AMThomas Dermody

If a resistor is flaking (paint), something else is overheating it (likely capacitor).

Paper capacitors do become leaky with age. Be especially aware of any caps that connect from B+ to B- or from a plate or screen grid to B-.

2/1/2013 10:48:35 PMTom McHenry

:::I copied this from another site, a post by Ron. Might help you ID the source of the bright glow. As the others said, a shorting cap could cause excess current thru the diode's plate.
:::"There are two parts to the 5Y3 that can get red. The heater inside the plates should glow orange-red. When cold, the plates of the 5Y3 are black or silver, and should remain so when hot. If the plates glow red, that means that the tube is being asked to supply much more current than it is designed for.
:::
:::The heaters of the 5Y3, but not the plates would be the bright red item. The heaters (or filaments) look like narrow ribbons, about the width of a piece of string. They can normally be seen from the top. The heater voltage on the 5Y3 can be easily checked, and should be five volts AC." That voltage can be measured with the tube out of the socket.
:::
:::You could rig up a temporary rectifier using 2 silicon diodes i place of the tube. I would do this if you can't locate the problem right away. Remember tho that those diodes will be carrying lethal voltages on their exposed leads.
:::
:::
:::
::::Hi
::::
:::: Agree with WALTER but you don't want any glow on the plates. If plates have glow keep the radio off or power transformer will be damaged.
::::
:::: Norm
::::
:::::
:::::HI:
:::::
:::::IF YOU MEAN THE FILAMENT.
:::::
:::::MEASURE THE AC FILAMENT VOLTAGE ACROSS PINS 2 & 8.IT SHOULD BE 5.0 VOLTS AC.
:::::
:::::BE CAREFUL AS THERE IS HIGH DC VOLTAGE FROM THOSE PINS TO GROUND.
:::::
:::::WALTER-W2WIQ
:::::
:::::
:::::
:::::
:::::
:::::
:::::
::::::You may still have a leaky electrolytic.
::::::
::::::I would disconnect the electrolytic caps one by one and reenergize the set. I know you will get hum but you will be able to tell by the color of the rectifier ( NO COLOR )which one is the culprit.
::::::
::::::Lou
::::::
::::::
:::::::I recapped the electrolytics and a few of the many other paper caps on this chassis, which now plays pretty good. I notice that the rectifier glows more than I think it should. Is there some how a short that is causing this? I have not left the radio on for more than about 10 minutes for fear of issues.
::
::
::
::Be sure you have installed the caps with the correct polarity. I don't mean to insult your intelligence, but everyone has either done it or will do it someday.
::Lewis
:::::::
::::::
::::::
:::::
:::::
::::
::::
:::
:::
::
::
:It is definitely a glowing plate problem. I have quite a few more caps to replace, and one of the resistors in the electrolytic area is suspect since the insulation is flaked off of this large resistor. I will finish the capping first and see what happens. Thanks for all your suggestions.
:
Glowing plate= excess B+ current. Look for a leaky bypass cap that goes from B+ to ground. These bypass caps are intended to dump RF to ground before it gets onto the B+ bus and there could be several in this set. These caps can deteriorate and essentially become resistors between ground and B+. A HF bypass cap is frequently used on the plate of the audio output stage and this can short, also, causing excessive current from the rectifier, possibly even burning open the primary winding of the output transformer.

1/14/2013 11:57:25 PMSeth hardsocg

:I recapped the electrolytics and a few of the many other paper caps on this chassis, which now plays pretty good. I notice that the rectifier glows more than I think it should. Is there some how a short that is causing this? I have not left the radio on for more than about 10 minutes for fear of issues.
:you should make sure your wires are dressed so nothing is touching also you may have a bad resistor and make sure all of the caPs are replaced and connected properly. Good luck.

2/3/2013 6:21:27 PMPeter G. Balazsy

If you're just not sure about the red glow... you can disconnect the B+ lead completely from the rectifier's cathode and that will remove all loads.
If the tube glow looks the same.. then maybe it's just the filament you're seeing as glowing...

If the red glow stops when the B+ is disconnected.. then you do have a short in the B+ line.

Time then to remove each cap one by one in the supply.
Check all B+ loads one by one.

2/4/2013 9:16:00 PMHowell Q. Strye

:I recapped the electrolytics and a few of the many other paper caps on this chassis, which now plays pretty good. I notice that the rectifier glows more than I think it should. Is there some how a short that is causing this? I have not left the radio on for more than about 10 minutes for fear of issues.
: Is the tube glowing red? Any rectifier tube that glows red either has a short somewhere on the B+ line, or a partial short causing the tube to pass more current than it's designed to handle. Sounds like a leaky bypass cap on the B+ line.