Pre-war tv sets

[jshorva65]

Many of these gems were actually DELIBERATELY DESTROYED years ago because they were considered DANGEROUS. For those who don't know the background, pulse and rf supplies for high voltage were not developed until after the war. These pre-war sets used a second power transformer and usually a 2X2 rectifier with much larger filer capacitors to develop the 7.5kV second-anode voltage. These supplies were not energy-limited like the more modern flyback-pulse or rf oscillator supplies. These old supplies could easily continue producing high voltage at sufficient current to kill while loaded with 50K of body resistance. Body resistance normally presents such a heavy load on rf and flyback circuits to limit the output current to a level that will produce little more than a very unpleasant shock to a healthy adult (I still wouldn't recommend touching the hv circuits of a flyback or rf supply with power on and also recommend discharging the filter capacitor(s) before working on them. When restoring one of these pre-war gems, use extreme caution around the high-voltage supplies, never work near them with power applied and always discharge the filter before working on the hv circuitry.

John

[Dude111]

Thats insane!!

Anything is dangerous if not used properly and ANYTHING CAN BE SAFE IS USED CAFEFULLY!!

Heres some pics of pre-war sets

http://fernsehen.bplaced.net/ind_blau.html

And this one is amazing!!

http://www.myvintagetv.com/GE275.htm

My gosh,i wouldnt mind having that!!! (Are these in colour or BW?)

One thing i can say is: OLDER SETS ARE BETTER THAN WHATS OUT NOW!! (More stable and produce an even better picture!)

[kx250rider]

I hadn't heard of any official effort to destroy TVs with those power supplies... Is there an article on it? Hopefully, we're talking 50 years ago....

There were a few postwar sets with that type of HV supply; the DuMont RA101 and others with prewar carry-over designs. I have a great respect for that circuit, and treat it the same as I treat an exposed 480-volt 3 phase electric panel. Either one will kill you with no regrets. It's gruesome to read a coroners' report on someone who has been killed by a high voltage DC shock. In one I read, that the guy had leaned on a grounded object, and touched a 25KV DC supply of some sort. Ligaments in his arms exploded, and were torn away from the bones. The moral of the story is, pay the same attention to your surroundings and to what you're doing while working on one of those power supplies, as you would if you were driving a fully packed school bus on an icy highway in the fog!

Charles

[Steve McVoy]

I've never heard of a campaign to destroy sets in the U.S.

In England, there were apparently magazine articles about the subject, though I've never seen one. I've been told that a number of repair shops did destroy sets for that reason, but have no documentation of that.

[Eric H]

Off topic somewhat but I believe Wurlitzer had a campaign in the 40's to sell new Juke Boxes and destroy the old ones, there is film or pictures of this horror somewhere.

[ChrisW6ATV]

Just one time, I touched the output of a disconnected (from the CRT) and turned-on flyback/HV output. It was on a 23" B&W commercial video monitor. It kind of felt like getting hit by a truck.

After that, I REALLY got careful with monitors, connections, and power.

[ppppenguin]

Originally Posted by Steve McVoy

In England, there were apparently magazine articles about the subject, though I've never seen one. I've been told that a number of repair shops did destroy sets for that reason, but have no documentation of that.

I've never seen such an article in the UK but I've never really looked for one. These sets were known as "widow makers" here in the UK and I'm sure that too many TV techs died. I know people who have smashed up plenty of early TVs but this was because they were large lumps of useless junk.

Imagine 1955 and you're a TV dealer who has just taken a large pre-war TV in part-exchange for the latest 14" or 17" set. The new sets are giving big, bright pictures in small cabinets. Nobody is going to want a big, dim, unreliable pre-war set, even at a bargain price so it's going to get smashed up. Sounds unpleasant but that's real life.

[jshorva65]

As Steve, Charles, and others pointed out, there was no officially-documented, organized policy requiring or encouraging destruction of pre-WW2 sets in the US, however, the practice was encouraged somewhat by certain media in the UK. Yes, Charles, most of the deliberate acts of destruction occurred 50 or 60 years ago and were carried out largely under the same rationalizations used by repair shops of recent years whose policy was to place "abandoned" sets which were unlikely to sell as "refurbished" models out to the curb and "neck" their CRT's. At the time, the sets were literally considered "hazardous waste" to a degree. In rare cases, however, according to legend at least, a few shops recognized the future historical significance of very early sets and merely cut off their line cords or otherwise disabled them in some semi-permanent (reversible by someone who knew how) manner before placing them in long-term storage.

[Dude111]

Originally Posted by Eric H

Off topic somewhat but I believe Wurlitzer had a campaign in the 40's to sell new Juke Boxes and destroy the old ones, there is film or pictures of this horror somewhere.

They should do whatever they can DO PRESERVE THE OLDER ONES! (Quite better than the ones made now (Which are made with the cheapest garbage they can use to make them))