Zenith 5K03 on the bench

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Zenith 5K03 on the bench

Post by Greg Davis on Sat Sep 13, 2014 1:09 pm

I decided to see if I could be successful at restoring one of the better bakelite shelled radios I own.  Now that I have some of the smaller capacitor values and a boatload of tubes to work with, the time just seems right.  Here's what I'm starting with:







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Re: Zenith 5K03 on the bench

Post by Greg Davis on Sat Sep 13, 2014 1:36 pm

Here are the caps I am most concerned about.  The first two are marked Zenith 22-829 .05MFD 200VDC.




The next one is marked 22-3


The last one is marked RMC .01HD
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Re: Zenith 5K03 on the bench

Post by Bill Cahill on Sat Sep 13, 2014 2:54 pm

You must totally rebuild the radio for it to work reliably. Replace all paper capacitors, including that green bakelite cornel Dublier. It's paper inside. Also, your electrolytics.

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Re: Zenith 5K03 on the bench

Post by Greg Davis on Sat Sep 13, 2014 3:07 pm

Thanks, Bill. I appreciate the guidance.
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Re: Zenith 5K03 on the bench

Post by Dr. Radio on Sat Sep 13, 2014 10:09 pm

Greg,

Zenith's are great performers. In addition to what Bill said, also replace those "disk" capacitors. Typically ceramic disk capacitors are very reliable, however, those "waxy" disk caps are something Zenith built in-house and are prone to leakage. Not very good quality units.

You may run into the dreaded "silver mica disease" with those style of IF cans, but you won't know till you go over with your 're-capping'.

Be sure to ask if you need any guidance. I'm the clock-radio guy. Smile
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Re: Zenith 5K03 on the bench

Post by Greg Davis on Sun Sep 14, 2014 11:13 am

Thanks!
One thing I could use an assist with is translating the Zenith code for that ceramic marked 22-3.  What would be a suitable replacement?

And for the one marked RMC .01HD, as well...
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Re: Zenith 5K03 on the bench

Post by Wildcat445 on Sun Sep 14, 2014 7:29 pm

Those components should be on the schematic and identifiable that way. Good luck.

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Re: Zenith 5K03 on the bench

Post by 75X11 on Sun Sep 14, 2014 7:35 pm

Those poor ol' caps look like orange push-ups that got dropped on the ground.
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Re: Zenith 5K03 on the bench

Post by Dr. Radio on Sun Sep 14, 2014 11:38 pm

Greg Davis wrote:Thanks!
One thing I could use an assist with is translating the Zenith code for that ceramic marked 22-3.  What would be a suitable replacement?

And for the one marked RMC .01HD, as well...

22-3 was Zenith's nomenclature for a .01 uF cap. No voltage specified---they were usually found in coupling circuitry, so 200 volts would do, but personally would use at least 400 volt caps to err on the side of caution.

The RMC unit should be able to be interpreted literally--.01 uF. Same on the voltage rating, but since I don't have the schematic or the physical layout in front of me I can't tell you what exact rating you should be using or style (like a safety cap for chassis coupling or across the line).
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Re: Zenith 5K03 on the bench

Post by Guest on Mon Sep 15, 2014 9:48 am

I like Zenith radio's. Isn't that the model which has been nick named "owl eyes"?

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Re: Zenith 5K03 on the bench

Post by Greg Davis on Mon Sep 15, 2014 9:51 am

Seems an appropriate nickname, to be sure. Wink
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Re: Zenith 5K03 on the bench

Post by 75X11 on Mon Sep 15, 2014 4:12 pm

It looks like it will make a nice finished unit.
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Re: Zenith 5K03 on the bench

Post by Greg Davis on Fri Sep 19, 2014 10:46 am

I know it seems like I'm not doing anything... but the truth is I have already replaced the "orange push up" caps, as well as the Doublier and the 22-3.  That leaves the RMC and, interestingly, a component called M1 that seems to be a mix of a capacitor and a resistor (4 pins coming out of a flat rectangular ceramic piece).

I'm moving very slowly on this because it's my first time through this process and I don't have the comfort of familiarity with the process.  One of the things I find most challenging right now is getting the desoldering tool positioned to be useful, or failing that, removing a pin that has been wrapped through a hole in the socket and soldered, using only a soldering iron and a pair of needle nose pliers to remove it.

Anyway, all seems to be going well, more or less.  yesterday I noticed that one of the resistors had worked loose, probably as a result of my ham handed efforts.  I soldered it back into place, but didn't think to check it before doing so.  I'm thinking I should replace all the resistors anyway.

I still have no idea if any of the current tubes are good.  I did check my gigantic hoard of tubes and found replacements for all of the ones in the set, but as we noted before it is likely that all the replacement tubes are bad at the outset.  Still, it's a fun project.

- Greg
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Re: Zenith 5K03 on the bench

Post by Wildcat445 on Fri Sep 19, 2014 12:57 pm

I have the Deluxe version of that radio, with a 6 tube chassis. It is a pretty good performer for a clock radio.

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Re: Zenith 5K03 on the bench

Post by Dr. Radio on Fri Sep 19, 2014 4:25 pm

Greg Davis wrote:I know it seems like I'm not doing anything... but the truth is I have already replaced the "orange push up" caps, as well as the Doublier and the 22-3.  That leaves the RMC and, interestingly, a component called M1 that seems to be a mix of a capacitor and a resistor (4 pins coming out of a flat rectangular ceramic piece).

I'm moving very slowly on this because it's my first time through this process and I don't have the comfort of familiarity with the process.  One of the things I find most challenging right now is getting the desoldering tool positioned to be useful, or failing that, removing a pin that has been wrapped through a hole in the socket and soldered, using only a soldering iron and a pair of needle nose pliers to remove it.

Anyway, all seems to be going well, more or less.  yesterday I noticed that one of the resistors had worked loose, probably as a result of my ham handed efforts.  I soldered it back into place, but didn't think to check it before doing so.  I'm thinking I should replace all the resistors anyway.

I still have no idea if any of the current tubes are good.  I did check my gigantic hoard of tubes and found replacements for all of the ones in the set, but as we noted before it is likely that all the replacement tubes are bad at the outset.  Still, it's a fun project.

- Greg

Hi Greg,

Take your time, this ain't no race. Better that way then waste time trying to find the source of errors later.

Just leave "M1" alone. This is a component package, an early form of cost saving integration. Rarely do they fail, they can, but you just have resistors and capacitors inside for coupling.

You can replace all the resistors if you wish, but that's a bit extreme. As a general rule, take your meter probes and measure across each resistor in circuit. You should read the rated value or less. Reading higher means they have drifted up. Please be aware that old resistors without a tolerance band may be 20% higher or lower from the factory. Obviously too low of resistance (even with other components in parallel) need to be investigated as well.

Here's a tip for desoldering, heat up the tube socket connection or junction with your iron and then take needle nosed pliers and grab the leg or body of the component you are trying to remove and gently rock it back and forth. The solder softens and this action causes chunks of solder to fall away and make it easier to then do more precise clean-up/removal as you unbend the lead. Gently in stages is the key. Too much force and you'll break something you didn't want to replace.


If you want to take a break and work on the clock, here's my write-up on rotors:

http://prepostmodern.com/rotors/
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Re: Zenith 5K03 on the bench

Post by Greg Davis on Sat Sep 20, 2014 10:59 am

Thanks for the support, Dr. I'll follow your advice and leave M1 as it is, and test any resistors before replacing them.

I went ahead and replaced the RMC capacitor.  Here's the current state of the chassis.

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Re: Zenith 5K03 on the bench

Post by Greg Davis on Sun Sep 21, 2014 2:56 pm

I decided to hook it up for a test today. No sound at all.
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Re: Zenith 5K03 on the bench

Post by 75X11 on Sun Sep 21, 2014 3:21 pm

Here is another method for desoldering wrapped terminals. It gets a full contact on the wires wrapping the terminal and gets most of it.

http://www.tuberadioforum.com/t3702-a-mod-for-solder-sucker
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Re: Zenith 5K03 on the bench

Post by Dr. Radio on Mon Sep 22, 2014 9:35 pm

Greg Davis wrote:I decided to hook it up for a test today.  No sound at all.  

Okay Greg, let me dig up the schematic.

Have you tried anything?

The first step is carefully go over for mis-wires and poor solder junctions. Tubes test ok and in correct sockets?

Did you touch the "hot side" terminal of the volume pot to see if you get a loud hummmmm?
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Re: Zenith 5K03 on the bench

Post by Dr. Radio on Mon Sep 22, 2014 10:47 pm

You can touch the center (wiper terminal) of the volume pot too, in case something is loading down the hot/input side --the terminal that connects to the 2nd IF transformer.

I also sure hope you are using an isolation transformer with this one!
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Re: Zenith 5K03 on the bench

Post by Greg Davis on Tue Sep 23, 2014 9:16 am

Yesterday I did a little work and ran another test.  This time I got a solid, steady and loud hum from the speaker.  Didn't seem to matter where I set the volume control.  It had two settings... loud and louder.  I didn't think to check that all of the tubes were glowing, but I did particularly note that one was glowing.

As for messed up connections, if I did that the only one I could think of would be the loose resistor that I soldered into place.  I'll check the schematic and make sure I connected it correctly.
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Re: Zenith 5K03 on the bench

Post by Dr. Radio on Sat Sep 27, 2014 9:07 pm

Greg Davis wrote:Yesterday I did a little work and ran another test.  This time I got a solid, steady and loud hum from the speaker.  Didn't seem to matter where I set the volume control.  It had two settings... loud and louder.  I didn't think to check that all of the tubes were glowing, but I did particularly note that one was glowing.

As for messed up connections, if I did that the only one I could think of would be the loose resistor that I soldered into place.  I'll check the schematic and make sure I connected it correctly.


Hey Greg,

Sorry for the delay. I've been quite ill and didn't have a chance to respond.


Did you replace the electrolytic capacitors in this radio? Did you verify their connections (both B+ and B-) ?
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Re: Zenith 5K03 on the bench

Post by Greg Davis on Sat Sep 27, 2014 11:50 pm

That I did not do. Thanks for the reminder.
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