Magnavox 153B Hepplewhite.

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Magnavox 153B Hepplewhite.

Post by 75X11 on Fri Dec 11, 2015 11:11 am

Well, it's here.  I had been concerned that it was set up for AM and Shortwave without FM.   The former owner brought in the record case that sat atop it and the problem was solved.  It is a disguised FM tuner.  The turntable is a truly trashed Webcor unit.  This is not too much of a concern as the drawer will offer plenty of room to secrete my laptop music library. The former owner was kind enough to bring the unit up to me because I started some antibiotic eye drops yesterday and I have had an allergic reaction to them and my eyes feel like two ____holes in a snowbank. Nothing but luck.  I gave him my spare restored 75X11 radio and he was quite pleased with it.  





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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Fri Dec 11, 2015 11:20 am

That FM tuner appears to be a genuine Magnavox factory accessory.  Notice the printing on the dial.  That is quite the find.  If you want a record player, may I suggest finding a stereo Collaro changer from the tube days, bridge it for mono and use it that way.  They are plentiful and will work on newer stereo records.  Either the newer "Micromatics" or the older Conquest models work about the same.  They are somewhat cantankerous to service, but once you have them right, they are amazing changers, built like a tank.  You have a handsome instrument there, 75.  I wish you the best of luck with it.

I have the service literature for the Collaro changers here in my files, if that will help any. When I get a Magnavox instrument, I give it a good bath in Go-Jo hand cleaner, the kind with no pumice. Then I go over it with Old English furniture polish. Then, if all the flea bites are not gone, I get a touch-up pen from Home Depot in the appropriate finish and touch up remaining spots. Magnavox finishes are extremely tough. One has to be pretty beat up to be really beyond help and requiring refinishing. My frau has been trying to burn the finish off the Imperial for a couple of years with her fake ceramic Christmas tree with no luck so far. Rolling Eyes

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sat Dec 12, 2015 10:41 am

I think I can afford to wait a while for getting a changer for it. The drawer will be a nice hidey hole for my 300 album changer, My NC610 Compaq laptop. The Riders library does have a file for the A and B receiver models but not for the CR198C that is in this unit. They have nothing on the CR192 FM converter. There is about a 1-1/2" scratched hole in the receiver side speaker cone. I think I ought to be able to mend that. It still has its loop antenna. My eyes are slowly recovering The drops contained a penicillin like material that I'm allergic to. They got my eyes and a couple of sinuses.
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Re: Magnavox 153B Hepplewhite.

Post by Bill Cahill on Sat Dec 12, 2015 1:12 pm

Looked familiar. I have a CR-198C in my book case style cabinet. Two twelve inch speakers. Chassis is virtually the same as the 198B.
I had to use that schematic to rebuild mine.
Puts out twenty watts of audio. Excellent bass, treble, and, reception is fantastic. My problem Is I have to adjust the high end of a m oscillator, and, you get your pick of adjustments on top of the chassis.
I have to replace my bad crystal cartridge. I had rats many years ago, and, they ruined original record changer. I had to find an original replacement. That was slightly tough. My case needs work, and, though playing, my eye tube isn't indicating. It's bright, but, doesn't move. The 1meg resistor is bad, and, I think it's in the eye socket. That chassis is a good player.

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sat Dec 12, 2015 2:07 pm

That's good to know. I do read what you say, too. Very Happy
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Sat Dec 12, 2015 2:14 pm

FM drift is an issue in the stereo instruments. Do the mono instruments have this issue? Discriminator alignment is said to improve matters. Antenna strength is important.

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Re: Magnavox 153B Hepplewhite.

Post by Bill Cahill on Sat Dec 12, 2015 2:35 pm

Well, the fm in my 1947 3 way entertainment center is stable. Haven't noticed any drifting. Surprising. It uses a 6J6 f m oscillator, and, that tube does like to drift.

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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Sat Dec 12, 2015 2:45 pm

The stereo ones sure do! The fix is tinkering with discriminator alignment, I am told. A more practical, for me at least, cure is an FM Multiplex adapter. Also the FM oscillator tube is uber-critical. I replace the 6EA8 with a 6GH8A for whatever reason. It seems to work better. I don't yet have a mono Magnavox. I may consider getting one. Room is the issue for me.

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sat Dec 12, 2015 7:09 pm

Bill, are there many differences in the parts list for the customary replacements in the receiver? I want to start working up a list of what I will need to get the capacitors taken care of.
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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sun Dec 13, 2015 2:31 pm

Removed the receiver and removed and marked the tubes. gave the chassis a good dusting. The tuning cap is mighty clean. Gave its contacts a clean, the cap a workout and lubed the mechanical linkages.removed the heavy rust spots and cleaned the pots. Cleaned and tested the tubes. The IF amp 6SK7 is failed. The rest test well.
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Sun Dec 13, 2015 8:02 pm

Have you fired it up yet to see what works?

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sun Dec 13, 2015 10:49 pm

I'll do the caps first. I have to order some and it looks like the gent with the emerald '58 Chevy is out til the 19th. So I'll get out the speakers and work up a patch in the meantime.
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Re: Magnavox 153B Hepplewhite.

Post by Bill Cahill on Mon Dec 14, 2015 12:26 pm

75X11 wrote:Bill, are there many differences in the parts list for the customary replacements in the receiver?  I want to start working up a list of what I will need to get the capacitors taken care of.

Not that I'm aware of. I don't have schematic on C. Only the B. But, it appears to be virtually the same with few, if any differences.

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Mon Dec 14, 2015 2:24 pm

The physical layout looks alike so far. I just got the CR192 service folder on Ebay.
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Re: Magnavox 153B Hepplewhite.

Post by Bill Cahill on Tue Dec 15, 2015 2:34 am

That one has some circuit differences..........

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sat Dec 19, 2015 11:07 pm

Now I am having my first problem in interpreting the parts layout as opposed to the as-built device.  The layout shows 12 600v .01uf molded paper capacitors and 1 600v .05uf molded paper capacitor.  In the attached photograph of the CR192 FM tuner you can see the large square caps going clockwise from the bottom near the 6SB7Y converter socket.  This is covered in Riders V.15, Pg. 15-51 to 53.   The problem is that there are more than the specified compliment of caps.  The ones you can see with the values given in orange digits are plain enough, but the others are color coded and I can not discern the colors nor make any sense of the coding, given the expected values in the compliment.  There are also a couple of changes to the as-built wiring with a couple of extra tie points with extra caps.  I don't know if the caps with color coding in the layout locations of the .01 uf caps are of that value.  I am assuming the cap with the color code facing the chassis at the full clockwise position, which is connected to a tie point adjacent to the discriminator transformer is the .05uf.  If anyone could help to set me straight on this, I'd appreciate it.



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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Sun Dec 20, 2015 12:38 am

Good old "Micamolds."  I dislike working with those.  I have trouble figuring out their coding.  What I do when I find those is to first take a series of detailed pictures of what is currently there.  Something good enough to refer to if step two messes me up.  Then I replace the Micamolds with modern caps at the location and value stated in the schematic.  My thinking is to correct discrepencies found to what the schematic diagram says should be there.  THEN if something does not work right, refer to the pictures and the schematic to try and figure out where the problem lies.  I don't know what else to tell you other than that.  I have never had a problem when I verified that the chassis was wired per the schematic. This issue is why I asked if you had powered the instrument up to see what worked and what didn't. This carefully done can answer some of these questions. If it basically worked, one could assume basically correct wiring, good transformers and "unobtaniums." Then if you run across something not wired like the schematic showed, you would have information to figure out which way to go. There is no right or wrong way, no "industry standard" to follow when messing with one of these things. You have to fly by the seat of your pants many times. I hope this helps a little. Smile


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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sun Dec 20, 2015 12:59 am

That is indeed the brand of the color coded caps. Even with that branding, would they be molded paper?
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Sun Dec 20, 2015 1:06 am

Yep.  Micamold is a brand, but I have heard that type of cap universally referred to as Micamold.  Like all gelatin desert is called Jello.  All refrigerant is called Freon.  They are paper caps, and are universally panned as being problematic due to time.  Something one replaces when one sees them.  I would be as concerned about the resistors as I would those caps.  I have seen more problems with resistors in Magnavox instruments than most anything I have ever worked with.  There is enough room under that chassis to roll around on a creeper while working on it.

It is not my intention to preach to the choir here, but it might be well to pay close attention to lead dress and component location, since you are working in the front end of the tuner.


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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Sun Dec 20, 2015 1:09 am

Ain't that sweet! Thanks, I reckon I'll start tomorrow.
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Sun Dec 20, 2015 1:14 am

Good luck, 75. You'll do fine. I'll be anxiously awaiting progress on your project.

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Re: Magnavox 153B Hepplewhite.

Post by Bill Cahill on Sun Dec 20, 2015 9:19 pm

They were called micamold. It's a mica body with paper cap inside. They are ALWAYS junk. They were one of the lowest grade caps made. Wax impregnated inside, and, out.
They are always shorted. No, a meter won't show the short.

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Re: Magnavox 153B Hepplewhite.

Post by 75X11 on Mon Dec 21, 2015 3:25 pm

I've replaced most of the paper capacitors in the CR192.  The only one shown in the layout to be of a different value from the ref. number 40 was the same value as the 40's.  I have a load of capacitors coming to finish the job and curiosity has prompted me to get a capacitor tester to at least get a approximate value, if not the dielectric strength of the old units.  I took pics of the position and type of each of the old components.  I also replaced a couple of resistors that crapped out during handling.  I also replaced the resistors for the indicator tube.
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Re: Magnavox 153B Hepplewhite.

Post by Wildcat445 on Mon Dec 21, 2015 10:02 pm

Sounds like you are making progress. Very Happy

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Re: Magnavox 153B Hepplewhite.

Post by Bill Cahill on Tue Dec 22, 2015 7:42 am

Capacitors change value when leaky.

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Re: Magnavox 153B Hepplewhite.

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