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#436
04-30-2004, 07:20 PM
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#437
05-01-2004, 12:08 AM
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I'm not sure by any means, but given the fact that only one switch was used in these sets as the TV/phono selector, and the TV came on immediately after switching back to TV mode from phono or radio, I would think all tube filaments remained on when the set was being used as a phono amplifier or when the radio tuner was on. However, the circuit was probably arranged to open the B+ lines to the video and RF tubes, leaving the filaments on, during such operation. The sets I've seen with phono inputs usually used a push-pull, rotary or slide switch on the front panel in this position. For TV/radio/phono, however, most if not all sets used a rotary switch on the audio control panel (I have never seen or even heard of any American-made 3-way console which used any other arrangement, including push button switches, for mode selection). The arrangement you mention, using either a separate high-current switch for the filaments ganged with the B+ switch or a separate switched filament supply for the RF and video tubes, would have been, IMO, unnecessarily complex and would have added a certain percentage more to the cost of the set, not to mention being wasteful of power, also as you mentioned.
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Jeff, WB8NHV Collecting, restoring and enjoying vintage Zenith radios since 2002 Zenith. Gone, but not forgotten.
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#438
05-01-2004, 10:06 PM
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I took a closer look at the Silvertone I have and it, too, has that switch. Seems like an odd place to put it. The Transvision I have is similiar in that you can tune it from tv to fm (or aircraft band) and the picture tube will come and go as you tune. (I forget how exactly its switched) That type of back/forth switch is kinda neat; its used on a Philco I have with factory UHF-turn the channel knob one way and you stay on VHF, turn it to the UHF setting then backwards and it switches bands. Kinda like switching an old car into overdrive!
Regarding the Silvertone,the cabinet is a natural for doors, mine looks like it has room for them, but no sign that it ever had them. That set is really oversized-the chassis is huge, especially compared to its contemperaries. The set is something like 27" square, not counting crt cap, and the chassis uses most of that floor space, plus is extra deep. Meanwhile, the Motorola has a chassis smaller than many old radios.
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Bryan
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#439
05-01-2004, 10:40 PM
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Most 3-way units had completely separate power supplies for the TV and radio/phono sections, especially separate-chassis arrangements like the RCA 730TV1 and 730TV2. The master on/off was usually part of the volume control or sometimes the tone control. The primary circuit of the power transformer on the audio chassis was connected so that the master on/off alone would control it. The TV chassis' power switch was ganged to the mode switch such that the tv power transformer primary was shunted across the audio power transformer's primary in television mode. Many radio/TV combo units left the heaters energized but switched the B+. Some compact and low-priced models merely cut the drive for the sweep circuits and biased the sweep output tubes to cutoff (thus killing HV and blanking the raster) such that the mode switch handled only grid-circuit currents, eliminating the need for high-current switch contacts. Certainly it was a waste of power and tube life, but it could be accomplished with cheap parts and the power company and service shops got plenty of business ... all those extra watthours and replacing weak tubes.
Last edited by jshorva65; 05-01-2004 at 10:43 PM.
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#440
05-07-2004, 09:01 AM
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Here's my contribution. Got w-a-y too many sets after 20-some years of collecting and three moves, but here's a pic of the wretched centerpiece of my collection, in all it's "before" glory. I've had this set for 13 years and assumed I'd never get it done 'cause I'd never find a picture tube so it has just sat around.
Due to the extraordinarily kind assistance of Dave Johnson and Steve McVoy I now have a good 12AP4. The cabinet is currently undergoing restoration and if things go accoding to my usual thoughtful pace ("I think I'll have another beer instead of replacing those caps!"), I'll have the electronics done sometime within the next 13 years! Last edited by Dave S; 05-07-2004 at 04:44 PM.
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#441
05-07-2004, 09:03 AM
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Hey, I'm new here... Still gotta get the hang of handling pictures. Here's the set:
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#442
05-07-2004, 10:28 AM
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Neat-o set, classic early Moderne styling. That's pre-war isn't it?
Anthony
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#443
05-07-2004, 12:08 PM
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Aah, yes I also neglected to ID the set for you. It is an RCA TRK-12 from 1939. This is by far the most common of the remaining prewar sets but I feel very fortunate to have found one. The styling is classic industrial design of the era. There's lots of info available on the web about designer John Vassos if you're interested.
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#444
05-07-2004, 12:12 PM
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Vassos you say? Sounds Croatian to me, kinda like a certain Serbo-Croat we both admire.
  Anthony
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#449
09-02-2004, 07:22 PM
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Here's a shot of my latest projection set (#10).
It's an RCA 648PTK from 1947. I picked this up from the original owners' son, it was kept in the main house and looks like new, but not working. He told me that it was operating until the early 60's then got to expensive to keep getting it repaired. A new 5AZP4 CRT was installed in 1958. Chuck
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www.myvintagetv.com Learn from the mistakes of others - You can't live long enough to make them all yourself.
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#450
09-05-2004, 06:54 PM
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1948 Admiral Bakelite
So how many of these are there out there? I've counted three so far on this thread.
Mine gets sound, the cabinet is OK, but the set is unrestored. It's another project for another day, but I know the picture tube works. I bought it a few months back at an antique show in New Harmony, Ind.
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