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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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7th Sep 2017, 3:43 pm | #21 |
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Re: Vintage switched mode power supplies
That is quite amazing!
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7th Sep 2017, 3:53 pm | #22 |
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Re: Vintage switched mode power supplies
Likewise. The famous 'chopper' power supply! The idea was totally alien to me at the time and it caused some serious willies among myself and my fellow engineers.
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7th Sep 2017, 4:12 pm | #23 |
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Re: Vintage switched mode power supplies
Just had a look at the schematic for that and I'd be afraid of it! It's back to the old "stick beeswax in the grub screw holes to stop getting electrocuted" territory
Here for ref: https://www.radios-tv.co.uk/wp-conte...brc3k35k-4.jpg |
7th Sep 2017, 4:49 pm | #24 |
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Re: Vintage switched mode power supplies
The export version of the Thorn 3000 PSU did use a double wound mains transformer.
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7th Sep 2017, 5:32 pm | #25 |
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Re: Vintage switched mode power supplies
I seem to remember a Pye switch mode in-vehicle charger in the early eighties. I think the switch mode bit was to step up the 12 volts to maybe a higher voltage battery for a portable? I can't remember exactly but it wasn't easy to fix. Also Motorola made a 30A 12V power supply that was used on main site equipment which looked to me as if it was designed in the mid to late seventies. This had a conventional mains transformer and rectifier, but the regulation was by a couple of massive power transistors switched with a variable mark space. When under heavy load they used to audibly scream. When first switched on you could hear the oscillator start at low frequency then rise up as the regulator took over. It was always a good sign when you powered everything back up and could hear the whistling. Very reliable but it looked a bit lashed up inside. If the crowbar protection triggered they used to make a bit of a pop as the big fuse blew.
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7th Sep 2017, 5:40 pm | #26 | |
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Re: Vintage switched mode power supplies
Quote:
Is this switch-mode? I'd argue not. I bet the UL84's are working in Class C (the anode circuit is tuned) rather than Class D or E, thus not dissipationless. But interesting all the same! |
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7th Sep 2017, 5:43 pm | #27 |
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Re: Vintage switched mode power supplies
Apart from a lesson in how NOT to draw a circuit diagram, this looks like a self-oscillating push-pull converter, with regulation achieved by a linear regulator controlling the push-pull stage's input voltage. So again, not switch-mode, but I can imagine it would be easier to shield and filter than a PWM switching thing.
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7th Sep 2017, 6:44 pm | #28 |
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Re: Vintage switched mode power supplies
I suppose 50's car radio vibrators were switch mode...literally.
The american space programme of mercury-gemini-apollo used switch mode power supplies in the spacecraft though I dont have many details.
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7th Sep 2017, 7:18 pm | #29 |
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Re: Vintage switched mode power supplies
You could say they are switching, yes. And they also have lossless snubbing by virtue of a tuned transformer winding and associated capacitor which acts to reverse the voltage during the vibrator's dead time.
But they key thing that they don't do is regulate. A modern SMPS adjusts its output by controlling the switch 'on' and 'off' times, giving continuous adjustment of output, without any dissipation (save for the losses introduced by the non-idealness of the circuit elements). |
7th Sep 2017, 7:55 pm | #30 |
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Re: Vintage switched mode power supplies
I used to have a Marconi H2900 receiver. A very early 1970s state-of-the-art HF rx developed in the late sixties. It had a switch-mode PSU regulated by pulse-width modulation.
Everything was in compartments in an immense cast chassis. No linear regs, if I remember, just huge amounts of filtering. David
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7th Sep 2017, 7:58 pm | #31 |
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Re: Vintage switched mode power supplies
Syclops...Not that early but anyone remember them
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7th Sep 2017, 8:18 pm | #32 |
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Re: Vintage switched mode power supplies
Interesting switch regulator circuit using a cold cathode trigger tube in Contamination Meter No.1. dated early to mid 1950's. The tube operates as a relaxation oscillator and switches to discharge C3. It was designed to regulate the battery supply over a fairly wide range.
Rich
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7th Sep 2017, 8:33 pm | #33 |
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Re: Vintage switched mode power supplies
The first one I came across was in the HP 5830A and 5840A gas chromatographs, the 5830 being introduced in 1974 amd HP's first processor-controlled GC. While most repairs were board swap, we had to repair these supplies down to component level in the field. Fortunately, by the time I was trained on them in 1979, the failure modes were fairly well known. The SMPS boards were huge and very complex by today's standards. There's an article about the 5840 here, if anyone is curious about what a gas chromatograph is:
http://www.hpl.hp.com/hpjournal/pdfs...Fs/1976-04.pdf |
7th Sep 2017, 10:29 pm | #34 |
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Re: Vintage switched mode power supplies
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7th Sep 2017, 10:54 pm | #35 |
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Re: Vintage switched mode power supplies
The EHT supply in Tektronix 500 series scopes must be a contender. It uses a valve oscillator driving a transformer at 20khz or so, and definitely regulates. From memory, it uses the screen grid for feedback. The design dares from at least the model 535 in the mid 1950s, and possibly earlier.
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7th Sep 2017, 11:20 pm | #36 | |
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Re: Vintage switched mode power supplies
Quote:
When I restore/repair the Lucas RB106 regulators I always add a snubber diode to the field circuit, without it the voltage can peak to about -70V when the contact opens and the arcing is objectionable for long term reliability. I have also added transistor assistance to the contact. I have a large number of articles on these regulators, and electronic replacements, on my www.worldphaco.net website, how to repair & modify the RB106 regulators and how to make electronic replacements. Also there, is currently the only published design of a "Dynamo & Alternator Emulator" which emulates the electromagnetic properties of a dynamo so that variable frequency regulators can be designed and tested say in a Spice simulation. These early types have an operating frequency that depends on the parameters of the machine. Later when LRC (Load Response Control) was required, these parameters became unimportant and the switching went to a fixed frequency PWM controller instead. As a thought experiment, I wondered if it would have been possible for Lucas to have built an effective transistorized equivalent of the common RB106 regulator in the early 1960's. So I selected parts from that era and built a regulator which exactly emulates the features of Lucas's compensated RB106,You can see the switching waveform across the field coil at the end, the article is here, sorry about the crazy long link: http://nebula.wsimg.com/16f83c1c70ef...&alloworigin=1 My formal replacement for Lucas's RB106 is in this article; I worked on the design for some years to make sure it was rugged enough for the application. There are many versions out there now but they contain fragile IC's and electrolytic caps and don't do well under the bonnet in the heat and electrically hostile environment. This article also explains the two forms of compensation that exist in Lucas's design and contain the equations for their regulator which were resolved using a specially built test machine: http://nebula.wsimg.com/f167bd9d35e5...&alloworigin=1 |
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7th Sep 2017, 11:27 pm | #37 |
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Re: Vintage switched mode power supplies
Found a reference to transistor DC/DC converters from 1960: https://ia800706.us.archive.org/35/i...s1stEd1960.pdf
See chapter 26. |
8th Sep 2017, 1:09 am | #38 |
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Re: Vintage switched mode power supplies
What a wonderful manual, thank you very much for posting that. I have not seen that one before.
On page 139 is has one of my favorite amplifier circuits using an EF98 and a germanium power transistor and a 25:1 inter-stage transformer. The thing I have always liked about this design (despite the poor efficiency), it has an input impedance of 10 meg Ohm an output impedance of 3 Ohm, substantial power gain and it only has the two active devices. It took my fancy so much that it inspired me to build an entire radio using the EF98 and the OC16 as the output. I have a circuit somewhere in a vintage Philips manual with a single ended switch mode supply, that I think used an OC77 and the date of it was around 1959 I think, so the switchmode concept goes way back. There is also another type of switchmode supply used in aircraft, the Exciter. Initially these had a vibrating reed, but later they went to gas discharge tube. I could find so little information on these (partly because the designs are often proprietary and potted in rubber or resin) that I did up an article on how they work. I had a company in Shenzen make some GDT's for my experiments and I got a few GDT's from defunct exciters. The article is is here: http://www.worldphaco.com/uploads/GA...R_EXCITERS.pdf |
8th Sep 2017, 11:07 am | #39 |
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Re: Vintage switched mode power supplies
The mid-1960s all-transistor Racal RA217 communications receiver uses a SMPS (the switching component being a single NKT404 germanium transistor; another NKT404 is used - strapped as a power-diode - in the DC input to provide reverse-polarity protection).
The 'switcher' allows the entire radio to be run safely off a wide range of low-DC voltages while the supply to the radio's internals is regulated, smooth and stable . Just as important this makes the negative/positive-earth or floating-supply issue totally irrelevant because the SMPS provides full DC isolation between the supply and the radio's real workings. The power-supply also caters for AC supplies: when running on AC the output from the mains transformer is rectified, half-heartedly-smoothed, and fed to the switcher's input. |
8th Sep 2017, 1:50 pm | #40 | ||
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Re: Vintage switched mode power supplies
Quote:
The section on DC-DC converters is good, switching techniques to get voltage step-up. Although, there's no PWM so everything is unregulated. Quote:
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