First TV without PwrTransformer?

[dieseljeep]

Originally Posted by jr_tech

I remember the model 606 with 5 25Z6 rectifiers for B+, but didn't they use a transformer for the 6.3 volt heaters?

jr

Our first family TV was the 12" version of that chassis, a later run.
It had two larger selenium rectifiers and two smaller ones. It had two B+ supplies, stacked to provide 390 volts for the vertical sweep. It had a mess of electrolytics, where the five 25Z6's were originally and a ballast tube.
The transformer was rather large and only furnished the 6 volts, for the heaters and a separate 5 volt winding, for the 5V4 damper.
It always amazed me, that they went through all that trouble, instead of just using a regular transformer and vacuum tube rectifier.

[dieseljeep]

Originally Posted by Tom Albrecht

Indeed. Most 7" electrostatic sets did not have a power transformer. The exceptions were cases that did, like the Admiral 7" set. And the stream of transformerless sets never stopped. Early Emerson 10" sets included transformerless designs.

I was surprised to see the 7" Emerson Electrostatic set, using only a 140 volt B+ supply.
It was interesting to see how they could do it and everyone else had to use a doubler.
I'm sure, they considered DC operation, as well.

[NewVista]

Originally Posted by peter scott

British ...AC/DC doesn't really arrive until about 1949.

Peter

Thanks for that info, was curious about this. The British really embraced this idea early on, not sure if it was because of aggressive price competition or the challenge of an elegant engineering solution?

[peter scott]

I think it would be simply the cost reduction of not supplying a beefy mains transformer.

Peter

[Electronic M]

IIRC the Britts have 240VAC service so I have to imagine that (at least for radios) it had to be a challenge getting the tube heaters to sum up to that voltage.

[peter scott]

Yes, transformerless valve (tube) radios in the UK were pretty horrible things with large resistive droppers throwing away heat. Capacitive droppers are a possibility but were probably not favoured again on cost grounds.

Peter

[dieseljeep]

Originally Posted by peter scott

Yes, transformerless valve (tube) radios in the UK were pretty horrible things with large resistive droppers throwing away heat. Capacitive droppers are a possibility but were probably not favoured again on cost grounds.

Peter

The AC-DC sets built in the US, weren't only built for cost reasons, but there was a lot of DC districts in the larger cities.
Philco built a few, strictly 110 volt DC sets, in the early 30's. They used paper power supply caps, in case it was connected reverse polarity.
BTW, didn't Britain have DC districts in some of the larger cities, as well.

[peter scott]

Yes, leaving aside industrial supplies it seems that there were still a few areas with DC supplies right into the 1960s.

http://www.vintage-radio.net/forum/s...ad.php?t=41380

Peter

[dieseljeep]

Originally Posted by peter scott

Yes, leaving aside industrial supplies it seems that there were still a few areas with DC supplies right into the 1960s.

http://www.vintage-radio.net/forum/s...ad.php?t=41380

Peter

I was reading some information on early British television, at the website, "405 alive".
I never realized that, there was such a thing as a TRF television set. I know the US, had some entry-level sets, but never a TRF design.

[ppppenguin]

Quite a few early British TVs were TRF. There was only 1 TV channel and no immediate prospect of more so a fixed tuned TRF was a simple and economical approach. TRF designs continued to appear until around 1952, with different models being sold in different regions which used different channels for the BBC service.

AFAIK the first British set without a mains transformer was the Pye B18T from July 1948: http://www.thevalvepage.com/tvmanu/pye/body_pye.htm this was also the first Briitish set to employ flyback EHT. It was also a TRF.

[peter scott]

Both Jeffrey and I are owners of early British TRF sets. The TRF section is very obvious when you remove the back of these sets.

Peter

[NewVista]

Originally Posted by ppppenguin

...Pye B18T from July 1948: http://www.thevalvepage.com/tvmanu/pye/body_pye.htm...

Good informative link, their W.W. Ad (below pictures) claims it was the first with direct-to-AC power.
There would be no turning back now, other manufacturers would have to follow!

The British had now found a way to reduce the price of television sets!
They had found two ways, the other was to quote the price in Guineas!

[NewVista]

Vacuum tube design minimalism reaches its apotheosis with the GE Porta-Color. Even the Japanese couldn't beat it on price - and they had a similar vertically-integrated large corporation model to GE.

Kuba says "we can make money in Europe with this TV". Their version has a single diode to obtain required B+ from 220vAC, add a few more diodes for Simple-PAL, bringing affordability to the marketplace.

[NewVista]

Just 8 years after GE ceased production of the profitable Porta-Color, they sold all GE & RCA TV business to the French who believed they make money building TVs in the US - second guessing Jack Welch of GE? How'd it go? The French Co's stock 'TCH' went from €600 down to €1. A bigger crash than even the high flying Northern Telecom of Canada.