Recently picked up a 62x13u. all caps replaced once before i got it. I replaced them again. When i turn on the radio it sounds good for a couple of minutes then it is so garbled or there is no noise. I can't find a loose connection but i will try again. Maybe i will resolder the caps.

Any info is apperciated, Thanks for your help
JK

:Recently picked up a 62x13u. all caps replaced once before i got it. I replaced them again. When i turn on the radio it sounds good for a couple of minutes then it is so garbled or there is no noise. I can't find a loose connection but i will try again. Maybe i will resolder the caps.
:
:Any info is apperciated, Thanks for your help
:JK

Assuming all tubes are good, sounds possible it could be a component changing value after warmup - a stunt sometimes pulled by resistors. A quickie check to see if any resistors are discolored from heat sometimes makes for a quick ID of the problem but other times you may need to simply go through and check to see if all resistor values are within design specs.

replaced all electrolytic caps and paper ones. None of the resistors look burned. Did find a couple of loose connections. Now the radio works okay for a while then its garbled and then clear once again. it does this repeatedly. Tunning is sharp and clear and very sensitive, i pick up stations my little homemade transistor can't.

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That’s one nice little unit that you have your self., a full house tube complement and even with the desirable RF front end stage, only being topped with utilization of another variable tuning condenser section devoted to the plate circuit tuning of the RF amp stage.
Using just only what information that you have provided…I interpret your description as saying that there is an onset of audio distortion , progressively getting worse after thermal warmup. If that was my set to troubleshoot….
I would start by seeing that there is not a gassy 35C5 audio output tube involved. Then after experiencing the distortion onset, I would take my trusty ¼ in nut driver that I have a 3 inch length of rubber heater tubing installed within its shaft center area. Then I would place stabilizing downward thumb pressure atop each tubes evacuation tit and then enact some healthy buffered taps on the sides of each of the tubes progressively to confirm no loose tube support infrastructure or loose floating contaminants/slag/crud/bad internal spot weld that could be thermally activating. If all passes the tappa-tappa-tappa tests .I think that I would then be taking/logging down voltage readings on 1st grid, cathode, screen and plate voltages (with the volume an minimum for that one measurement) and the companion audio preamp/driver stage on its equally applicable G1,K and P. Taking the readings quickly , before approaching that trouble time threshold.
(That may take two attempts, with cool own time in between)
Then after warm up, when the trouble onsets, do a voltage check again to see what voltages are shifting. With particular consideration to the 1st grid’s voltage swinging more positive , with the coincident reduction of plate voltage. The troublesome audio out’s 1st grid coupling capacitor seems to be a composite feature within a PC couplate (C7)_ and , probably, the couplate was never touched…but the good thing is that their ceramic construction is VERY reliable compared to the typical utilization of a std paper cap in that application.
Now should that problem be RF related with a complete loss of audio and had the audio section passed I would move on to monitor the highest level of the AVC developed for the set, which would be at the top/high end terminal of the volume control.
That way you would have a very sensitive monitoring point of all of the frontal RF circuitry performance of the set. The developed AVC voltage will shift upon a frontal RF gain malfunction or its abrupt failure.
Component checking of higher value resistors with a controlled mid level heated air flow from a blow dryer. Then the reversal cooling procedure with a drop of liquid CO2 from an inverted “Can of Air” .
Feedback time pls.

73’s de Edd

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:Recently picked up a 62x13u. all caps replaced once before i got it. I replaced them again. When i turn on the radio it sounds good for a couple of minutes then it is so garbled or there is no noise. I can't find a loose connection but i will try again. Maybe i will resolder the caps.
:
:Any info is apperciated, Thanks for your help
:JK

:Recently picked up a 62x13u. all caps replaced once before i got it. I replaced them again. When i turn on the radio it sounds good for a couple of minutes then it is so garbled or there is no noise. I can't find a loose connection but i will try again. Maybe i will resolder the caps.
:
:Any info is apperciated, Thanks for your help
:JK
JK: I think your problem is in the heater of the 35C5 output tube. It is opening after warmup causing the set to gradually "fade" and garble. I believe in mesurements. Connect an AC voltmeter across pins 3 &4 of the 35C5 and monitor the voltage. When your set starts to fade I think you will notice the voltage immediately increase --probably to 120 volts. Replace the tube. The "C5" audio output tubes are notorious for this.

The 35c5 has a blueish green deposite in side the tube where ever there is a hole in the outer metal tube. The 35W4 also has some white particles in the bottom of the tube. Is one or both of these my problems? If so where is a good place to by tubes, i buy my caps and other stuff from Ocean State Electronics, they have every thing except tubes.

:The 35c5 has a blueish green deposite in side the tube where ever there is a hole in the outer metal tube. The 35W4 also has some white particles in the bottom of the tube. Is one or both of these my problems? If so where is a good place to by tubes, i buy my caps and other stuff from Ocean State Electronics, they have every thing except tubes.

JK....
Don't know where you live but I buy my tubes from Mark Oppat (Antique Radio Supply) in Michigan. He is a hobbyist like you and I and has VERY reasonable prices. Contact him at moppat@comcast.net
Just tell him what you need and he will take care of you.

Dennis Wess

does this discoloration signify a gassy tube or something else? Is this the source of my problem. The radio works fine for a while then the noise starts then its okay for a while then it does it again, i can still hear the station in the back ground though the static really drowns it out. Also a 12ba6 has replaced a 12bd6, is there any difference between the two? I am researching to understand what all the numbers mean. I am finding the values for the tubes at http://www.nj7p.org/Tube.php
I'm still pretty new to tubes. I only work on this stuff as a hobby when i have time. Want to get this thing working good before i leave for school.

Hi

12BA6 & 12BD6 are interchangeable. 12BD6 has a higher cutoff voltage which means little except in a car radio with a lot of ign noise.

Could you be receiving outside interference? If not how about silver migration of mica caps built into IF Transformers? This usually causes a crackle.

Norm

:does this discoloration signify a gassy tube or something else? Is this the source of my problem. The radio works fine for a while then the noise starts then its okay for a while then it does it again, i can still hear the station in the back ground though the static really drowns it out. Also a 12ba6 has replaced a 12bd6, is there any difference between the two? I am researching to understand what all the numbers mean. I am finding the values for the tubes at http://www.nj7p.org/Tube.php
:I'm still pretty new to tubes. I only work on this stuff as a hobby when i have time. Want to get this thing working good before i leave for school.

Yeah the sound is more of a crackle. Interference it possible. tried turning off all florecent lights and motors. crackling is still there.

:Yeah the sound is more of a crackle. Interference it possible. tried turning off all florecent lights and motors. crackling is still there.
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A..haa,,,the plot thickens with more exacting feed back info. A usefull adjacent test aid would be a shirt pocket size 9V batt powered AM radio. To initially set aside to the RotoMola to see if the noise is present on bnoth receivers. Or if the inteference is internally generated from the Motorola,the ferrite bar antenna of the pocket radio could be used with its directional pick up nulling being used for probing within the radio. This is particularly helpfull on a breaking down of an IF xformers caps. Probing right up next to their terminals.
73's de Edd

Thanks for all of your help everyone. I replaced a couple of resistors, and one of the transformers. Works pretty good. Thanks again for all of the great help.

Jeremy