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  #1  
Old 05-02-2017, 11:34 PM
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Emerson 609 projection TV

So, I'm chugging along, replacing electrolytic and paper caps in a 1949 Emerson 609 projection TV (on the left):



In addition to the usual wax paper caps, I see about a dozen of these little guys in white cases (ceramic or porcelain?). Some have wax gooping out the ends.



They have values (1500pf) in the mica range, the kind of thing I'd normally leave alone during the first pass.

Are these paper caps in sheep's clothing, or something more reliable? I would rather not shotgun parts unnecessarily.

Thanks!

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  #2  
Old 05-02-2017, 11:44 PM
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Suspect caps; at the very least check a few by lifting one leg and testing it at/near rated voltage.

Plan on replacing them in any case. I'm even finding "normal" mica caps that are shot in '46 to '50 era sets.
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Old 05-03-2017, 01:31 AM
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For what it's worth, they're described as "ceramic" in the Rider's parts list, although I guess that could mean garbage paper dielectric inside a ceramic tube.

All (14!) of them occur in the audio & video IF sections, where they are used for bypass, AGC filtering, and decoupling, according to Sams. Examples: C6/C8, C10/C11, and C13/C14 in this schematic snip:

http://antiqueradio.org/art/Emerson6...io-VideoIF.jpg

I'm usually loath to replace a dozen of anything in the video IF, because . . . alignment.

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Last edited by Phil Nelson; 05-03-2017 at 01:36 AM.
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Old 05-03-2017, 02:31 AM
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I think you'd better leave them alone. Even if they're paper types, the leakage should be insignificant with such small values.
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Old 05-03-2017, 09:40 AM
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Quote:
Originally Posted by Gleb View Post
I think you'd better leave them alone. Even if they're paper types, the leakage should be insignificant with such small values.
That may be the case with Russian made paper caps, but American made paper caps (and many Japanese caps) are crap...I've seen plenty of papers in that value range nearly dead shorted or leaking heavily even below 50V.
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Old 05-03-2017, 09:58 AM
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I can see "HI-Q" printed on the side. All the vintage caps I've encountered that look like that have been true ceramic and just fine. I'd leave them alone.
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Old 05-03-2017, 12:34 PM
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At that point in time I don't believe the state of the art even allowed winding paper caps that small? Well maybe, but they'd of been too expensive for consumer electronics.
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Old 05-03-2017, 01:08 PM
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Thanks, I'll leave 'em in peace for now.

These caps are definitely smaller than any of the TV's paper caps in that general range (.001, .003).

Phil Nelson

Last edited by Phil Nelson; 05-03-2017 at 02:23 PM.
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Old 05-03-2017, 02:34 PM
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I've found those in other sets and left them alone, they don't seem to be troublesome.

I suppose you could replace one and bust it open to see what it is inside.
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  #10  
Old 05-03-2017, 08:22 PM
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Here's the ceramic cap next to the smallest paper cap in this TV:



My Dumont RA-102 has a number of ceramic caps about the same size as these, but they have a different profile, more like a dogbone style resistor, and no wax dripping out the ends.

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Old 05-06-2017, 09:26 PM
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I see those all the time, and I've always left them alone.

In 30 plus vintage TV restorations I might have replaced one, and I didn't have to.
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  #12  
Old 05-09-2017, 08:24 PM
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After replacing the factory-installed electrolytic and paper caps on my Emerson 609, I'm looking at this big .25-mfd paper cap, evidently added by some sloppy repairman:



The cap isn't shown in either Riders or Sams. It's hard to trace things in this messy chassis full of long, wandering leads. But as near as I can make out, the guy wired this new cap in parallel with the Horizontal Size adjuster coil (L-8 in Riders):



Any ideas as to why someone would add this? Tacking stuff onto a width coil suggests an attempt to get more (or less?) width, at first glance . . . .

I normally remove mods and restore things to match the schematic, especially messy work like this, on the theory that the repairman was attempting a quick fix for some symptom that will be cured by the time I'm done recapping, etc. But if someone thinks this is a great improvement, I suppose I could try a new .25 cap there.

You can read the full schematic here:

http://antiqueradio.org/art/Emerson6...maticSmall.jpg

Regards,

Phil Nelson
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  #13  
Old 05-09-2017, 09:43 PM
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That is a width mod. I've seen .05 uF caps occasionally attached to RCA KCS-20 flybacks to fix a width issue.
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  #14  
Old 05-10-2017, 06:02 PM
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OK, that rogue cap is gone.

In preparation for powering up, I checked out the five-element ballast (Emerson # 397023). Most of the elements test bad. There's a lot of corrosion where the elements join the pin leads. Even if I could coax it back into life, this doesn't seem like a good bet for long-term reliability:





I found an eBay supplier with a Clarostat ballast, so let's hope that one works. Can't wait!

Phil Nelson
Phil's Old Radios
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Last edited by Phil Nelson; 05-19-2017 at 02:25 AM.
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  #15  
Old 05-20-2017, 02:05 AM
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It's alive!



OK, that looks underwhelming, but it's exciting to me. After replacing the ballast and doing, well, a bunch of other stuff, tonight I saw the first coherent image on the Emerson's little 3NP4 CRT. (That's the Xfinity cable TV guide screen, in case you're wondering).

With the chassis spread all over the workbench, there's nothing to project on (the ceiling's much too far away to focus). So peering slantwise down into the Protelgram optic box is the only way to see what's happening.

This set had more problems than I had noticed at first, including an under-chassis meltdown that burned everything around the sockets of the vertical and 1st video IF tubes. But now, the vertical & horizontal are stable, brightness & contrast work as advertised, and the audio is excellent.

There's more checking and tweaking to do, but it's always fun to see the first signs of life.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Last edited by Phil Nelson; 05-20-2017 at 02:21 AM.
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