1952 Westinghouse Model H-378T5
 

Hello everyone, a week ago I received from a friend of mine from church a 1952 Westinghouse Model H-378T5 radio and when I got it home and tested it out it powered on perfectly without hum or anything and it still had all of its original Westinghouse branded vacuum tubes that still work perfectly, and what I find rather unusual about this unit is that the chassis is Bakelite and not metal or PCB like some units from that time period were.

Anyways I took the chassis out of the cabinet to further investigate how the Bakelite Chassis was put together, and when I popped the bottom cover off I noticed that the unit was still using its original filter caps for the power supply which kind of surprised be because of the fact that most of the time original 1950s vintage multisection e-caps are usually duds by now but not so in this old Westie, anyways another unusal thing I noticed is that there was one of those old black Bakelite coated paper caps with the 5 color-coded stripes on the outside inside the unit and the capacitor had at some point in time "vented" as part of the Bakelite coating on the capacitor was broken off and the paper and electrolyte insulation was exposed which I thought was rather weird because the radio still worked perfectly even with the "blown" capacitor in the circuit.

My question is, how is it possible for this radio to work flawlessly even with a "vented" coupling cap in circuit? Also what is it about this radio's power supply filter caps is making them still perform flawlessly after over 60 years (40 of those years spent in storage) especially considering that I have another radio that's one year older than this Westinghouse and its already on its third set of filter caps?

Ive seen old radios where old dried up electrolytics were left in the circuit when lazy repairmen bridged them with new parts. Problem is, as the old caps continue to deteriorate with age they could short out. Always best to remove the old part from the circuit even if it is left in for appearance.

I couldn't agree more, but what surprised me is that this radio is still running off of its original filter caps and its hum free yet.

The issue that has me thrown off is how the radio was able to work with the vented paper coupling cap still in the circuit...:scratch2:

Grab a schematic and a cap tester and see what that cap does and how it tests (we can't tell you exactly what is going on without that info). Odds are it is used for some menial filtering task that is non-essential...It probably shorted, drew enough current to vent and internally burn open one of the leads, and now sits there doing nothing since one of the leads is cut internally. I'd change that cap and any others like it...Bumblebee caps are nothing but trouble.

That's the thing I wasn't able to find a schematic for it so I guess I'm out of luck...

Also what's rather odd is that the cap that vented was the only as you call it "bumblebee cap" in the radio the only other cap in the radio besides the filter caps is a standard paper and wax capacitor made by Sprague, and it seems to be in pretty decent shape yet physically.

With that tube lineup, it's very likely that this schematic below is very close
http://www.wa2ise.com/aa5diaa.jpg
The blown cap may be the one across the rectifier, or maybe across the 120V powerline. You do want to replace it.

Close but no cigar, the radio in question has no pilot light, and only has 2 coupling capacitors, whereas the one in the schematic you posted shows a pilot light and at least 3 coupling capacitors of which none of them even close to the value listed on the paper cap that had the value listed on the capacitor case (which the paper cap that had the value listed in English was a .05 MFD 400 W.V.D.C. capacitor, and the one that was "blown" which used a colored pinstriping code was according to a capacitor color code chart I had used told me it was also a .05 MFD 400 WVDC capacitor but not sure how accurate it is) which is why it would be nice to have the actual schematic for the exact model I have.

For some reason Rider's had covered my 1951 Crosley 11-119U but for some reason they didn't cover the Westinghouse H-379T5-H-381T5 series of radios (which would of used the same chassis design) or any of the other H series radios made by Westinghouse for some reason...

What do the ends of the blown cap connect to?

Well it doesn't appear to be attached to anything critical in the radio (its not attached to any tube sockets or anything related to the power supply), its just attached to two metal "poles" which have other components attached to them of some sort (you can see for yourself in the photos I've uploaded) which might explain why the radio is still functional even with the "blown" capacitor in place still.

I suspect that blown capacitor is wired across the AC power line. It's purpose is to help filter out any interference that may be riding on the power line and it's very possible for the radio to work without it. This type of capacitor is known as a bumblebee and they were supposed to be an improvement over older style capacitors; but, they are in fact worse. I've seen lots of these used across the AC line and it's very common for them to blow apart when used in this application. For maximum safety, it should be replaced with an AC safety capacitor.

I see, but when I looked at the area where the capacitor was wired in at, there wasn't any wires coming into that spot for the power cord the power cord just wires into one side of the power switch and the other side wires in to the power supply cap.

From what I saw when looking at the wiring of the capacitor again, one side of the capacitor is wired into the rectifier tube socket on either pin 2 or pin 6 (i'm not sure which pin it is as the sockets aren't marked and I don't know which way is which when counting a 7 pin tube socket from underneath) and the other side wires into a lone wiring pin that has nothing but bare wire running between it and some other wiring pins (which I suspect that these lone wiring pins are part of the grounding buss circuit since its a Bakelite chassis.) So I don't suspect that this capacitor is going across the AC Line, it must be part of the rectifier circuit some how but apparently not too critical of a part in the rectifier circuit...

That's pin 6. You count tube pins clockwise, starting at the gap. As you mention that there is no pilot light, usually pin 6 of the rectifier tube goes directly to the power line. The other side of the powerline usually goes thru a switch (usually part of the volume control), and then to the negative side of the filter cap and rest of the set. So that cap is across the powerline. You could just remove it and the set will still work. Or replace it with a modern "X rated" cap designed for the purpose, being across the powerline.

...and you can get an X2 cap from most junked PC power supplies. Your original is a .047uF, 400V, but all X2 caps are AC rated, either 250 or 275VAC.

Attached is the schematic for a Westy H-366T5, Sams 185. Your radio is in Sams 211 - I skip over it - 208-209-210-212...

ok, thanks, so why do you skip over the Sams folder No. 211, if you know its in there? Do you just not have that one or do you have something against that folder?

My Sams collection was the regional "library" of Sams. My dad, who had a shop, loaned out his older Sams to other shops and some individuals. It appears it was loaned out and not returned - 90% of the borrowers are now dead, so there's no recouping the missing stuff. Of consolation, I have two Sams 207 sets, and lots of other dupes.

Ah, I see. well I have a small Sams collection myself but it only covers a very small variety between 1946-1959 and that's about it I don't even remember all of the volumes it has in it without looking through it but I think no. 333 and 217 and 290, are just a few of the ones I have, they for some reason got only a select few volumes over the course of 13 years they didn't get all of them for some reason. I inherited mine from a flea market friend who got them from an estate sale and knew I liked monkeying around with old radios so he just gave them to me. :-)

I would clip the blown-up cap out and toss it.
Its original purpose was (ostensibly) to reduce any RF hash coming in via the power line.
But today with the maelstrom of broadband hash already in the air, any noise on the power line would pale to insignifigance.

Ok, so that would basically mean that without that capacitor this radio would them be a 1 capacitor equipped radios (not including the filter caps) which is kind of interesting because that's the first time I've ever come across a radio with so few capacitors in it.

Take a close look at the schematic PDF posted in post # 13... I suspect that your radio has a similar "couplate circuit" that contains several more capacitors and some resistors between the 12AV6 and the 50C5 (the dotted rectangle between the two tubes).

jr

Yeah, it has a ceramic disc capacitor in the circuit besides those two paper caps but the ceramic cap isn't going to be bad and besides I don't count ceramic disc capacitors when I'm referring to paper capacitors in these old radios.

Zenith made some later AA5 AM sets that had only ceramic caps...Only thing to go wrong on those aside from tubes is the lytic pair.

Yeah and on this one the electrolytics are still good surprisingly enough.

I actually took the liberty to taking OldCoot's advice and just snipping out the bumblebee cap and putting the radio back together and the radio still works fine but there is lots of RF Interference though that I noticed wasn't there before I took the blown Bumblebee Cap out (althouth the station I checked it with has a tendancy to get a little staticy in the evening so maybe that's what I was hearing.)

And I replied:
To which you replied:
No matter how you might *choose* to define it, the fact remains that the radio does, in fact have more than one capacitor.

jr

OK so then its a 2 capacitor radio then instead of a 3 capacitor radio (not counting the electrolytics), if that pleases the masses.
That's still the fewest capacitors I've seen in an AA5 circuit before. :scratch2: :yes: