5bc3 why such a weird tube

[rcaman]

i have bought a few old zenith sets about 10 or 12 and a couple of motorola 19" tube hybrids. this one old zenith uses a 5bc3 for the low voltage rectifier why didn,t they use a 5u4 i have tons of those. the first 2 zenith 19" b&w came up with raster after a cap reform. i also ended up with a 22" zenith color tube type metal table set. there is still 2 consoles there that i didnt get 23" tube types. think i will get them if nothing but for the crt,s and chassis. on the 22" table top set the 6lb6 has cracked and gone to air and someone had pulled the high volt regulator tube it was laying inside and the green bellfuse was missing. i believe the regulator is a 6hv5. crt on green and red is like new blue is slow comming up but getting better on my sencore cr70 not going to rejuvinate it just yet. will post pics shortly. oh also got 4 nifty appliances from the early 1950,s 2 stoves and 2 ref. love the old appliance styling. havent got them home yet. heavy as hell. steve

[DavGoodlin]

I have a Philco 42-1009 that needs a 5Y4. No way do I have one! A quick check of my 1953 GE tube book reveals that the filament current and forward current is same as a 5Y3, so I will move two wires on the socket, because that's the ONLY difference.

Please post your appliance pics in the expeditions and passions. I will follow up with my two refrigerators 1953 Kelvinator (division of Nash Motors) and 1947 Westinghouse. Those old refrigerators use HALF the power than the 1996 and 1986 refrigerators we have. I proved it with a kWH meter.

[dieseljeep]

[QUOTE=DavGoodlin;3034663]I have a Philco 42-1009 that needs a 5Y4. No way do I have one! A quick check of my 1953 GE tube book reveals that the filament current and forward current is same as a 5Y3, so I will move two wires on the socket, because that's the ONLY difference.

In the 1938 model Philco's, the rectifier socket was on top of the transformer. It made the change a lot harder.

[dieseljeep]

[QUOTE=rcaman;3034647]i have bought a few old zenith sets about 10 or 12 and a couple of motorola 19" tube hybrids. this one old zenith uses a 5bc3 for the low voltage rectifier why didn,t they use a 5u4 i have tons of those.

That model Zenith you're working on is a real strange one. They only made one year of those. It has a 19" CRT with a large neck, which is the only set that ever used it.
At the time the set was built, Zenith also made 19" portables using a 3DG4 rectifier. Maybe they did that so the wrong tube couldn't be used.

[DavGoodlin]

Originally Posted by dieseljeep

In the 1938 model Philco's, the rectifier socket was on top of the transformer. It made the change a lot harder.

Fortunately the 42-1009 tube has a chassis socket. A friend has a 37-650 and that may be a case where a 5Y4 must be used. I hope that by not needlessly using a 5Y4, there will be more for others., they seem to be rare. Thanks for the heads up~!

[dieseljeep]

Zenith used the tube as well. The difference was, the socket didn't have all the contacts, so you couldn't rewire it for the 5Y3.
On a side note, I used to rewire the 6 volt GM radio's for a 6X5 instead of a 0Z4. They didn't have all the contacts either. I used to wrap a wire around the pin and solder it. I'd tell the owner not to try to remove the tube.

[peverett]

I have some Motorola 19 inch B&W portable sets. They loved using oddball tubes for some reason, not sure why(except maybe they got cheap prices on them). I also have some RCA sets of the same kind and of the same era, they tube line up is pretty standard, although with series string filiments.

[DavGoodlin]

Originally Posted by peverett

I have some Motorola 19 inch B&W portable sets. They loved using oddball tubes for some reason, not sure why(except maybe they got cheap prices on them). I also have some RCA sets of the same kind and of the same era, they tube line up is pretty standard, although with series string filiments.

Motorola seemed to use 6BL8's versus the 6GH8/6U8/6EA8. I wonder if there is an interesting story behind tube selection like patent infringements. etc?

[dieseljeep]

Originally Posted by DavGoodlin

Motorola seemed to use 6BL8's versus the 6GH8/6U8/6EA8. I wonder if there is an interesting story behind tube selection like patent infringements. etc?

Motorola used a lot of European type tubes in the early 60's. They also went back to 300ma heater strings, in a series parallel arrangement. Many of those tubes were sourced by Amperex. EIA 111.

[Einar72]

Okay, the 6BL8/ECF80 first. These tubes were cheaper than their U.S.- made counterparts like the 6U8/6KD8/6EA8/6GH8. Both Motorola and Fisher used those brown-painted imported resistors under the chassis back then as well. My Hallicrafters S-118 has two 6BL8/ECF80's marked on the tube chart. Moto, Philco and Magnavox all were sporting plenty of Japanese-made tubes "under the hood" come the end of the tube era.

I have a suspicion as to why Heathkit embraced the 6EA8 being that they were left "standing at the altar" in huge quantities by the major U.S TV makers once the cheaper-made 6GH8 came to town

The 5BC3 was a last gasp cost-reduction attempt for the 5U4/5Z3/5X4. The Novar-button based envelope was mucho cheaper as it eliminated the phenolic base with its pin-staking and bulb-cementing operations that cost extra $.

The 5Y4 (and its 5U4-thwarting cousin the 5X4) were a bold attempt by Philco and occasionally Zenith to force factory-service-dealer loyalty by being incompatible with the get-'em-anywhere 5Y3 and 5U4. Don't forget the 5Y3 crammed into a Philco Loktal package known as the 5AX4!

[dieseljeep]

If you look at all the Philco radios, built though the years, they never used metal tubes. The pre-war models used tube shield bases that would restrict the use of metal or bantam GT tubes. You see many 1937 and newer Philcos with the shield bases hacked away to use non-G tubes.

[N2IXK]

Strange that they would bother rebasing the 5U4 into a novar type. By the time the novar base was introduced, selenium and silicon diodes had already replaced tube LV rectifiers in most equipment.

An interesting tube, though. I had never heard of a 5BC3 before. Might have to snag one off eBay for my oddball tube collection.

[DavGoodlin]

Thanks Einar72 and Dieseljeep! I did get a 5Y4 for the Philco at Kutztown swap last week.

Just when you think you're the only one who wonders about these things, someone actually knows about them. Since I was old enough to pull them out, I accumulated so damn many tubes for TV and even tested most of them back when I had time.

I just wish I could do an ebay search for a TV SET without 90% of the listings being for tubes....

[peverett]

Philco did use some glass Octal type tubes in their radios following WWII. I have some of the "Hippo" models from this era. The tube line up varies from all loctal(The tube type Philco and Sylvania developed to combat the metal octal tubes), to loctal/octal, to loctal/miniature to loctal/octal/miniature.

I suspect this is due to tube availability issues at that time.

I have never seen a Philco radio with an original metal tube though. Philco seems to have used the loctal tubes exclusively in the sections of the radio that a metal tube would have been appropriate for(until miniatures took over).

[Reece]

Where height permits, on a difficult socket change, you can always make an adapter using an old tube base and a socket rewired to accommodate the alternate tube. That way if you ever get the original tube, it can quickly go back in.