Philco 48-700 on Ebay

[John Folsom]

A Philco 48-700, next best thing to pa pre-war TV.


http://cgi.ebay.com/Vintage-1948-Phi...QQcmdZViewItem

[Bill Cahill]

Nice toy.......

[John Folsom]

Very nice, and VERY heavy.

[Bob E.]

Are those Loktal tubes?

--Bob

[jpdylon]

Originally Posted by Bob E.

Are those Loktal tubes?

--Bob

Indeed they are. I'm not sure why the loktal tubes came about, they didn't really help with space constraints any.

[Bob E.]

The reason I asked is that I have limited shelf-space for our tubes, and was going to leave out the Loktals in our inventory, figuring they were not too useful to many restorers. I wasn't aware that there were classic televisions that used them, I thought they were mainly used in military radios and such. I believe they came about for ruggedized installations near the end of WWII (they "locked" in place with a snap ring that fit into the groove on the center locator). There were lots of them released to the surplus market and lend-lease projects after the end of the war, which makes the timing about right for the subject-line television. Maybe Philco got a deal on those tubes!

--Bob

[Eric H]

Philco used a lot of them at least as late as 1950.
Their sets used a hodge podge of tube types in that era, very possible they were using up left overs.

[Don Lindsly]

Loctal tubes were originally conceived for car radios. Cars of the 30s and 40s rode pretty rough and tubes would occasionally work loose.

Loctals are also more reliable and cheaper to manufacture since the tube pin extends directly through the glass envelope. There is no additional plug threading and soldering operation. Later they were phased into other products as well. It also gave Philco and Sylvania a differentiated product since RCA was marketing metal tubes at the time.

Don

[Eric H]

Getting back to this set, I would love to have it but would hate to have it shipped!

Is the seller correct about the CRT being a 7GP4? how does it differ from the 7JP4?

[David Roper]

Lower maximum/ideal second anode voltage. The 48-700 has a TT-5esque single transformer for deriving both B+ and high voltage directly from the AC line. It's been a while since I peeked at the Rider's for this set, but HV secondary is something like 2500 volts.

[John Folsom]

In addition to the 60 cycle HV supply, (an electric chair...one should use great caution when working on it), and lost of loctal tubes, (which Philco invented), the design also features an eight position tuner with AFT (automatic fine tuning). A control voltage from the audio discriminator is fed back to the tuner oscillator to keep reception centered on the audio carrier. This feature was not much used by other manufactures until much later. One of my favorite 7" sets.

[doug621ts]

Concerning this set, the wooden trim around the screen warp and break being thin wood so if it was in any enviromemt other than being stored inside a home. I had purchased one on ebay without asking about this and to my disappoinment the trim was warped and cracked and loose in many spots, not easy to repair without replacing the wood all together. The set on ebay appears to been in a garage or basement so buyer beware! Neat set and crude with the brute force high voltage!

[rld-tv01]

Another one (48-700) in Lodi California.

http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA%3AIT&rd=1

[David Roper]

none of the vacuum tubes are broken (This should make the search for new ones easier)

Hmm.

Hmmm.


I think I know what he means . . . no, maybe not. I've gotta go sit down and figure this out.

[rld-tv01]

Quote:
none of the vacuum tubes are broken (This should make the search for new ones easier)

Years ago there used to be tube testers in drug stores. This was for an average person without electronic skills could take in a tube and test it. If it tested bad you would buy a tube and replace it yourself.