Zenith 8Y02

4/11/2009 5:56:34 PMMmakazoo

Hey, all. Looking for some ideas about a problem with this radio. Sometimes (but not every time) after it has been on for a couple of minutes or longer, the volume will start to drop until there is just a hum. After a few minutes, the volume slowly comes back up and the radio plays normally. I was hoping that the problem would worsen so that it would be easier to locate. I hate intermittent problems like this. I have replaced various resistors, paper caps, and the electrolytics in previous repairs. Any thoughts about what to look at first? Mark from Kalamazoo

4/14/2009 4:03:14 PMMmakazoo

Now, come on you guys! someone must have some ideas about where to start looking. Anyone? Mark from Kalamazoo

:Hey, all. Looking for some ideas about a problem with this radio. Sometimes (but not every time) after it has been on for a couple of minutes or longer, the volume will start to drop until there is just a hum. After a few minutes, the volume slowly comes back up and the radio plays normally. I was hoping that the problem would worsen so that it would be easier to locate. I hate intermittent problems like this. I have replaced various resistors, paper caps, and the electrolytics in previous repairs. Any thoughts about what to look at first? Mark from Kalamazoo

4/14/2009 5:19:25 PMLewis L

:Now, come on you guys! someone must have some ideas about where to start looking. Anyone? Mark from Kalamazoo
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::Hey, all. Looking for some ideas about a problem with this radio. Sometimes (but not every time) after it has been on for a couple of minutes or longer, the volume will start to drop until there is just a hum. After a few minutes, the volume slowly comes back up and the radio plays normally. I was hoping that the problem would worsen so that it would be easier to locate. I hate intermittent problems like this. I have replaced various resistors, paper caps, and the electrolytics in previous repairs. Any thoughts about what to look at first? Mark from Kalamazoo

Mark:
Are you married? If so, does your wife have a hair dryer? Do you have a Radio Shack nearby? If so, do they have cooling spray? Assemble the preceeding while study the schematic and we'll get together later.
Lewis

4/14/2009 6:13:36 PMDoug Criner

I can't seem to locate the schematic. Can you link it to us? Or, describe the set's circuit and tube line-up.

When the volume drops, and then comes back up, does it then stay up? Or does it keep going through cycles?

It'll take a while, but you can monitor the plate and other voltages of each tube, and see if one of them drops when volume drops. I would start with the oscillator section and then the RF and IF sections. The audio section may be OK, since you hear hum when the volume drops.
Doug

::Now, come on you guys! someone must have some ideas about where to start looking. Anyone? Mark from Kalamazoo
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:::Hey, all. Looking for some ideas about a problem with this radio. Sometimes (but not every time) after it has been on for a couple of minutes or longer, the volume will start to drop until there is just a hum. After a few minutes, the volume slowly comes back up and the radio plays normally. I was hoping that the problem would worsen so that it would be easier to locate. I hate intermittent problems like this. I have replaced various resistors, paper caps, and the electrolytics in previous repairs. Any thoughts about what to look at first? Mark from Kalamazoo
:
:
:Mark:
:Are you married? If so, does your wife have a hair dryer? Do you have a Radio Shack nearby? If so, do they have cooling spray? Assemble the preceeding while study the schematic and we'll get together later.
:Lewis

4/14/2009 6:17:44 PMDoug Criner

Another thought. If you have a variac, try cranking it up a bit higher than the line voltage. That might make things heat up more, and cause the problem to persist longer and help with troubleshooting.

You have replaced the filter caps, right?
Doug

4/14/2009 6:26:02 PMLewis L

:Another thought. If you have a variac, try cranking it up a bit higher than the line voltage. That might make things heat up more, and cause the problem to persist longer and help with troubleshooting.
:
:You have replaced the filter caps, right?
:Doug

Yeah, I seem to recall that he did. I think the way to go is with heat and cold and let's see what develops. Oh, I can't find a schematic, either.

Lewis

4/14/2009 8:01:29 PMMmakazoo

Lewis: I can get the can of freeze spray and have access to hairdryer. Yes, electrolytics were replaced as part of an earlier repair. As far as I can tell, it goes through just one cycle of this problem and then works okay from then on. However, I haven't listened to it for more than an hour at a time. As far as finding the schematic, it is model Y832E and chassis 8Y02. I had to order the schematic - it is a Sam's Photofact. When I posted a problem with this set a while back, I think Edd found and posted a schematic. I will search for that. Mark from Kalamazoo

4/14/2009 8:08:26 PMMmakazoo

Here is the link to the previous posting about this radio with Edd's schematic -
http://www.nostalgiaair.org/forums/messages/262/m0060262.htm

4/18/2009 7:20:16 PMEdd

Sir Mark:

If that were my set to evaluate (and, snifff. . .alas. . .its not ) , again, I would be doing this:

Re Quote"

For a more exacting audio evaluation…pump one channel of a CD / DVD players audio into the phono input, or tie into the top of the vol-you-me control, should it not already have a phono input, as is shown on the back, but with this being the deluxe version, I think that it will. . . . .

" End Quote

Then you would be using the unit and
listening to it for that typical onset of failure time period, and that would give some degree of confirmation of the AUDIO section past the volume control and the power supply not being at fault.

BTW is this problem ocurring on BOTH AYE-EMM and EFF-EMM reception modes ?

73's de Edd
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ZENITH SCHEMATIC RESUBMISSION:

4/19/2009 8:42:41 PMMmakazoo

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:Sir Mark:
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:If that were my set to evaluate (and, snifff. . .alas. . .its not ) , again, I would be doing this:
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:Re Quote"
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:For a more exacting audio evaluation…pump one channel of a CD / DVD players audio into the phono input, or tie into the top of the vol-you-me control, should it not already have a phono input, as is shown on the back, but with this being the deluxe version, I think that it will. . . . .
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:Then you would be using the unit and
:listening to it for that typical onset of failure time period, and that would give some degree of confirmation of the AUDIO section past the volume control and the power supply not being at fault.
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:BTW is this problem ocurring on BOTH AYE-EMM and EFF-EMM reception modes ?

Edd: Yes, it's happening on both AM and FM. But, now it hasn't happened that last several times I have played it. Right now, it's been on for an hour without any problem. Arrgh. Yes, I thought about feeding another source in through the phono jack. With intermittent problems, I find I must just keeping playing the radio until it becomes a constant problem and thus easier to find. Mark from Kalamazoo
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