Morning fellas -

I've got an Emerson model 459 that plays fine for about 2 hours and then nothing. Power is still on, lights still on including the magic eye. No static. Just a couple clicks here and there when moving the dial. Tranformer and tubes checked good. Most caps have been replaced. If I let it cool down for a few hours it'll start playing again. Any idea what I should look at next?

Thanks,
Paul

Check your Main B+ voltage feed at startup, plus the other tube plate voltages..Then re-check when it stops playing. Could be a drifting resistor on the B+ legs, among other things. Could be a 'drifting' tube that stops working at it's specs in the rf/IF/audio section .

When it quits working, does the sound fade away or does it disappear abruptly, like flipping a switch?

Might be a capacitor leaking, but it usually doesn't take that long.

:When it quits working, does the sound fade away or does it disappear abruptly, like flipping a switch?
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:
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It quits suddenly like flipping a switch.

My guess is that you have a poor solder joint (or MUCH worse, a corroded coil wire) that is abruptly disconnecting when the ambient temp of the chassis reaches a certain point due to thermal expansion. You might remove the chassis and attempt to induce the failure by warming up the various parts with a heat gun. If you are able to localize the fault to a specific area, try to restore operation using Circuit Cooler spray or similar "freeze mist" product.

:My guess is that you have a poor solder joint (or MUCH worse, a corroded coil wire) that is abruptly disconnecting when the ambient temp of the chassis reaches a certain point due to thermal expansion. You might remove the chassis and attempt to induce the failure by warming up the various parts with a heat gun. If you are able to localize the fault to a specific area, try to restore operation using Circuit Cooler spray or similar "freeze mist" product.
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Had some time to look at this over the holiday's. Plenty of old wiring in the chassis. Insulation falling off both bulb wire so I replaced them. The 6UG magic bulb died during testing. Seemed a little weak to begin with. This was a flea market find and bought cheap. Unable to find schematics on it on Nostaligia Air. Wondering if this is a low production model just prior to WWII? I'm going to follow good suggestions here and continue to troubleshoot. Thanks all.

Hi Paul,
I have had the identical problem, twice. Both times it was a tube. The tube overheats then its emission drops. In both cases the onset is sudden.
Since it doesn't show up on a tube tester, the only way out of it is selective replacement of tubes. In one case the tube was the oscillator converter, in the other the IF amplifier tube. I recommend starting there.

All the best,

Bill Grimm

I would wait unit the radio stops playing, and then troubleshoot in a systematic manner. Check all voltages. I would work from back to front, but the other direction would be OK, too.

Even if one of us correctly guesses the cause, then you will still need to confirm the cause through troubleshooting - or else start throwing parts at it.

Hi Doug,
I share your dislike of throwing parts at a problem. This kind of problem can go away once you take the chassis out and it cools off.
On one I took the chassis out and wrapped it in towels to get the heat up. I then swapped out tubes. This was easy since I have spares around. In the end only the bad tube was replaced.

All the best,

Bill Grimm

Here's a question for Paul: when the radio stops playing, and the power is left on, does it start up again on its own? If not, pull the chassis, power it up, wait for it to quit, and troubleshoot.

But, if the radio starts up again on its own within a few minutes, there probably wouldn't be time to troubleshoot?

:Here's a question for Paul: when the radio stops playing, and the power is left on, does it start up again on its own? If not, pull the chassis, power it up, wait for it to quit, and troubleshoot.
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:But, if the radio starts up again on its own within a few minutes, there probably wouldn't be time to troubleshoot?
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It does not start playing on its own after it goes out. Stays very quiet with a click or two over the speaker. Starting to question the tubes myself but my tube tester went south on me.

OK, good. Then wait for the radio to quit playing, leave it powered up, and troubleshoot. Check all the voltages in a systematic manner.

If you have spare tubes, go ahead and replace them, one by one. But don't go buy new tubes or anything else based on a hunch. Look over this whole thread, and count the number of hunches, including mine. Forget guessing and troubleshoot in a systematic manner.

Start with the B+ voltages.

:Start with the B+ voltages.
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It now fails using a dim bulb tester. This was not the case earlier.

::Start with the B+ voltages.
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:It now fails using a dim bulb tester. This was not the case earlier.
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I've been unable to locate the schematics for this model. As others bave suggested I'd prefer to take a logical approach to this rather than just throw parts at it. I've also been told this is a somewhat rare model. A cbeap flea market find has turned into a restoration project. Not that I'm complaining.

Go back to my first post advice here. Get the voltmeter out...Fire up the radio and write down your B+ voltage at the rectifier, voltage divider resistors, and plates on the other tubes...Re-check those voltages every so often until you lose the sound, and see if any voltages are dropping off or changing drastically. This would be a good starting point. If that doesn't show anything, the make up a plan 'B'.

Hi Paul,
Any updates on this?

All the Best,

Bill Grimm

:Hi Paul,
: Any updates on this?
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:All the Best,
:
:Bill Grimm
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Howdy Bill -

I have not made much progress on this set. My 84 year old father has become very interested in the radio work I'm doing as it brings back many memories of his youth. I found a restorable Emerson table set that I'm recapping for him in time for a Christmas present and will then return to this 459 problem.

Thanks for asking.
Paul

Merry Christmas,
Bill

Hi

I agree. As tubes heat internal metal expands. If the radio pops off rather than slowly dies might be a cathode lead opening? The cathode is connected by a small ribbon or welded metal. As the filament heats this metal can open. When cool the tube will again operate.

This is fairly common and may happen the other way around as tubes heat. Nothing from a radio then all of a sudden pops on.

Norm

:Hi Paul,
: I have had the identical problem, twice. Both times it was a tube. The tube overheats then its emission drops. In both cases the onset is sudden.
: Since it doesn't show up on a tube tester, the only way out of it is selective replacement of tubes. In one case the tube was the oscillator converter, in the other the IF amplifier tube. I recommend starting there.
:
:All the best,
:
:Bill Grimm
: