American Television 2001A

20" screen, 1951
click on image to enlarge

This set was also advertised under the DeForest name (as in Lee) and possibly appeared under other badges as well.  The first bit of info I was able to gather on American TV is that it was based in Chicago and mostly manufactured sets for private rebranding.  I have since learned that American Television was headed up by mechanical TV pioneer U. A. Sanabria, whose Western Television had manufactured the Visionette, Empire State and other 45-line triple-interlace TV models back in the mechanical days. In the 50s, his sets were variously branded American, DeForest and DeForest-Sanabria. It must have been company policy to use whatever parts were onhand on any given day, as the printed tube location chart lists multiple possibilities for some sockets, while the designations for other sockets were crossed out and the substitutions written by hand.  It's still not correct...for example, no handwritten correction was made where the tube chart indicates there should be a 6AV5 horizontal out:  the tube in this set is a 6BG6.  On the plus side it's very solidly built and even features an auxiliary phono input complete with extra AC outlet.  So let's take a peek at the inside...

Whoa, look at the mounting of the 1B3!  It's wearing a humongous plate cap and partially sunk into the chassis,  very much echoing prewar TV construction practices.
Tube complement
 RF amp 1 6BC5 
mixer/osc 1 6J6 
 1st video IF 1 6CB6 
 2nd & 3rd video IF 2 6BC5 
 video detector  1N60crystal 
 video amplifier 1 6AC7 
 sound IF 1 6AU6 
 detector/amp 1 6T8 
 audio output 1 6K6GT (alternate:  6V6)
 sync seperator 1 6SN7GT  
 horizontal AFC 1 6AL5 
 horizontal osc 1 6SN7GT 
 horizontal output 1 6BG6G 
 damper 1 6W4GT 
 vertical osc/ouput 1 6BL7GTA 
 B+ rectifier 1 5U4G 
 HV rectifier 1 1B3GT 
Restoration notes

I learned a lot restoring this set.  I learned that circuits aren't necessarily eccentric just because they don't make sense to you at first glance.  I learned that reduced parts count doesn't necessarily equate with reduced performance.   But mostly I learned that there comes a time to declare a project done and move on to the next one....

This TV set entered my collection with the base already whacked off of the CRT (the cathode lead came off with it, snapped flush with the glass), a condition which kept it in the back of the to-be-restored queue until I acquired an 8" test CRT. I did not, however, acquire a schematic. Instead I traced out my own. In doing so I discovered just how unusual this set really is.

There are four distinct B+ lines, only one of which comes off the conventional source. It measures about 365 volts. There also is a 425 volt boost line--nothing unusual about that as it serves the vertical sweep section, except it also provides focus voltage for the CRT. Another source is the 150 volt line.  How I managed not to encounter stacked B+ prior to this TV is a wonderment in itself, but this circuit gave me fits wondering what's missing because (to someone who's never seen this arrangement) the line had no apparent source. But the fourth B+ line is really something else. Trace it back far enough and it does connect to the main B+ which accounts for it measuring within a couple volts of 365. But this fourth line, which provides most of the plate voltages, including audio and video output stages, first passes through the flyback and yoke.  So the process was: trace the circuit, rub my eyes in disbelief, confirm that what I drew is in fact how it's wired, move to next circuit, repeat.

The reason I felt it necessary to trace a complete schematic is simply that I suspected the set was incomplete.  There were several parts hanging loose and connected to nothing (seen at left) as well as evidence there had once been potentiometers mounted where there were now empty holes.  When I had traced everything out it was confirmed that it "could/would work" as drawn, so the extra hanging parts etc. will forever remain a mystery.

Unusual mating connectors were used extensively instead of conventional terminal strips. This was a poor choice, as the mating halves have developed intermittent connections over time, especially where high current filament lines are joined. I cannot guess what benefit the designers would have seen in using such connectors so perhaps--once again--it was a matter of using up hardware on hand. I was able to flow solder into the filament connections as these should have been solder joints in the first place, but subsequent attempts at this approach were not successful as the outside half simply didn't transfer heat to the inside.  The set occasionally acts up thanks to these iffy connection points, But when everything is working as it should it's an excellent performer.  Although tempermental, it saw four months of daily-driver use without needing further attention.  The set now sees only occasional use as a display piece, so I won't be taking any further action with the terminal boards unless it stops working.

The old CRT is still under vacuum and may well prove still good if ever the base can be successfully reattached.  In fact, for quite a while that seemed the only viable course of action.  Not only are replacement CRTs for 60-year-old sets not commonly available to say the least, this set's original CRT wasn't about to facilitate its replacement by revealing any markings whatsoever identifying its type.  The tube location chart is particularly confused on this point.  The crossed-out type is a magnetic focus tube, but so is the handwritten-correction type, despite somebody having written 'E-gun' (as in electrostatic focus), but upon closer inspection that too appears be be crossed out.

No matter what the chart said or the tube itself didn't say, the set has no focus coil and does have a lead for a focus electrode.  That meant the tube was really a 20HP4.  Thankfully, Moyer Electronics in New Jersey had a rebuilt 20HP4 in its seemingly limitless stock. 



To date I have found record of no other large-screen rectangular set driven by a 6BG6, which is a rebased 6L6G and mostly found in 10 and 12" round-tube sets made prior to 1950.  The sweep tube is apparently original to the set and hopefully will remain good for a long time:  through experiment I determined that the strange flyback circuit, which modulates B+ current drawn through the deflection coils to accomplish horizontal sweep, is very finicky and requires careful hand selection of output tube.  When the new CRT was installed there was insufficient width and the width control had little effect.  After swapping in several strong-testing tubes, all failed to operate properly in the set.  A small increase in the drive adjustment restored full sweep with the original output tube.




Here's a closeup of the American badge, visible on newspaper ads for this model--run under the De Forest name.

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