When did high-voltage transistors become common?...

[George Herold]

On Friday, August 14, 2020 at 5:23:26 AM UTC-4, piglet wrote:

Early 1970s , there was a short period around 1970 when TV sets were all solid state except for the horizontal drive!

piglet
(Using google groups on a phone while travelling in Africa)

Wow, look out there may be heffalumps!
George H.

 

[piglet]

Haha! Thanks George, my daughter is marrying a Zambian in Zambia. Have spied zebras and antelope but heffalump are elusive. Travelling during a pandemic is weird.

piglet

 

[Tabby]

On Friday, 14 August 2020 at 19:38:54 UTC+1, Pimpom wrote:

On 8/14/2020 4:08 PM, Michael Terrell wrote:
On Friday, August 14, 2020 at 5:23:26 AM UTC-4, piglet wrote:
Early 1970s , there was a short period around 1970 when TV sets were all solid state except for the horizontal drive!


Motorola\'s \'Quasar\' solid state color TVS came out in the late \'60. they only used a vacuum tube for the HV rectifier and the CRT. The audio output transistor was around 125VDC. It used an Allen Bradley carbon comp resistor for a fuse, Anything else wouldn\'t open in time to protect the output transformer.

My dad bought one of these TVs when they first came out. I still have it.

I heard that there was a period when car radios used tubes with
12V anode supply in the RF sections and transistors for AF
output. The purpose was to obviate the need for a vibrator to
generate a high voltage plate supply.

Yes. Car radios were initially all HT valve, then ponly the output valve needed HT, then 12v valves but an output transistor. My hybrid one proudly says \'transistor\' on it, well it does have one.


NT

 

[George Herold]

On Saturday, August 15, 2020 at 2:25:05 AM UTC-4, piglet wrote:

Haha! Thanks George, my daughter is marrying a Zambian in Zambia. Have spied zebras and antelope but heffalump are elusive. Travelling during a pandemic is weird.

piglet

Awesome! Some hope for grand kids to spoil then.
(Or perhaps you have \'em already?) My son has had a
girl friend for several years... which looks promising.
My daughter is more interested in other women, which doesn\'t
make kids impossible, but does need some external input.

George H.

 

[Chris]

On 08/15/20 01:28, John Larkin wrote:

On Fri, 14 Aug 2020 12:09:34 +0530, Pimpom<nobody@nowhere.com> wrote:

About 50 years ago, I was asked to make a high voltage constant
current supply for a medical research lab. The requirement was
600V at up to 30mA. I stacked two EL84 tubes in cascode (a 6L6GC
cost more and was less easily available). Television arrived here
in this remote place a decade later and I used TV FB transistors
in an apparatus for a local college.

Looking back on those times, I\'m wondering when high-voltage
power transistors first became common in the more advanced countries.

I found a really cool use for the c-b junction of a horizontal-output
transistor that accidentally had the ideal doping profile. It\'s not
made any more, of course.

My great little 3KV Bertan 215 bench power supply has one tube inside.
I bought a couple of spares.

Couple of tubes, (8068 from memeory) in my Fluke 415B high voltage psu,
Rest is solid state, other than a gas tube voltage reference. HP BWO
based sweepers and spectrum analysers used similar tubes for the hv sweep.

Also have a fluke 335 1000v voltage standard here that uses a huge
Westinghouse transistor in the series regulator. Bolt style package
base with 3 tag pins out the top...