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Old 7th Aug 2017, 6:32 pm   #1
MartinMarris
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Default Can I run A UK 1950s Set On 60Hz Mains?

I have decided I would like to restore a 405-line set from the 1950s.

There are a couple of 405-line UK sets from the 1950s available on eBay in the USA, which is where I currently live. They are not cheap, but it would be even more expensive (and problematic) to try to import one from the UK.

I have two questions:

(1) Stepping up the local 117VAC to 240V is easy, but changing the frequency from 60Hz to 50Hz is harder. However, solutions do exist (see http://tinyurl.com/y924gk66; or I might even be able to homebrew something like this) and I assume that a 50Hz supply is absolutely necessary? I do realise that until the 1960s, UK sets were mains-synchronized and I supposed could even get damaged by the higher U.S. frequency. The antique TV museum in Ohio has a whole section devoted to UK sets, I suppose I could ask them what they do....

(2) The two sets I am eyeing, which are currently available here in the U.S., are a KB FV30H (http://tinyurl.com/yajebb3r) and a Murphy 998T (http://tinyurl.com/ybbpptag). They are both in good cosmetic condition but the electronics are anyone's guess. I am leaning toward the Murphy, for nostalgia's sake (in 1970s while at school in the UK I restored a broken 1950s Murphy, or perhaps a Pye, I cannot remember for sure). However my general impression from reading many forum posts here is that the KB might have a better picture, once restored.

I have a workshop with basic test equipment (VOM, VTVM, RF and AF signal generators and a rather dodgy 'scope, all from the 1950s; and basic metalworking and woodworking tools plus a drill press). I don't currently have a method to measure EHT: what do y'all recommend?

I don't yet have an Aurora but have been in touch with the manufacturer and can purchase the basic 625-to-405 single-conversion model when needed.

Not totally sure whether I will actually take the plunge into 405-line set restoration yet (it may have to wait until I am in the UK at some future time) but not harm in exploring the possibilities....
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Old 7th Aug 2017, 7:44 pm   #2
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

The only practical solution I can think of short of a comprehensive rebuild is to find a 50Hz mains supply. You could use a 220/240V UPS or some sort of inverter solution. It would be possible to rewire the heater chain to use 117V 60Hz, which would reduce the 50Hz load, but that would wreck the originality of the set.

I agree it would be worth contacting the Ohio museum for advice, as they have probably had to address these issues, and there's no point in re-inventing the wheel.
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Old 7th Aug 2017, 8:02 pm   #3
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

Can't see why a 50hz TV can't run on 60hz, the timebases will lock to the signal sync.

Lawrence
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Old 7th Aug 2017, 8:07 pm   #4
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

I think the Murphy you refer to is a FERGUSON/THORN 998T. This has nothing to do with Murphy so if you are thinking of restoring as a Murphy it would not fit the bill.
The 998T is simply a first class and simple receiver that had a reliability factor that was very hard to equal and would make a great restoration project. The Mullard valves and MW31-16/74 picture tube are very reliable as is the flyback transformer.

The KB is more American in style with USA type octal valves and a number of B7G 6AM6/8D3 in the RF section. The Brimar/Cintel tube is difficult to replace being an odd shape with high EHT [10kv] It certainly works well.

Both models should perform OK with 117v 60hz mains without modification other than a step up transformer of course. Good luck with your eventual acquisition. Plenty of help on here. John
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Old 7th Aug 2017, 8:08 pm   #5
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

I would have thought it should work on 60Hz as it's just an ac/dc supply. Although the transmitted frame rate in the UK was aligned to the mains frequency, there is nothing in a 405 set that uses the 50Hz. You would need a suitable signal source such as an Aurora 405 converter.
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Old 7th Aug 2017, 8:08 pm   #6
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

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Originally Posted by MartinMarris View Post
and a Murphy 998T (http://tinyurl.com/ybbpptag).
Of course I meant to say *Ferguson* 998T (not Murphy)!
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Old 7th Aug 2017, 9:05 pm   #7
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

In the attached extract from an early 1950's Bush leaflet it is explicitly stated that Bush TVs will work on AC mains 40 - 60 Hz, as well as DC.

My KB and Murphy leaflets of the 1950's do not state the AC frequency range. Bush seems to have been the only company to explicitly provide this information. I did find one with a KB FV 30, but don't have any with the Murphy model.
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Old 7th Aug 2017, 9:16 pm   #8
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

As stated in #5 frame was locked to mains at source ie studio/tx and no use was generally made of mains in set other than for power (I believe that one or two very early sets did use mains for frame lock) - however sets were designed to work in an environment where broadcasters system was mains locked and performance of 1950s sets used asynchronously can be unpredictable - indifferent synch separator and interlace performance etc - I would strongly advise against using an inverter (other than one producing a perfect sine wave - rare, expensive and, quite frankly, not worth the bother - better to try set on 60Hz power - it will, most certainly, work & deal with issues as they arise

Hope this helps
Regards to all
John
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Old 7th Aug 2017, 9:17 pm   #9
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

The benefit of mains-locked TV signals was that any picture variation due to power supply ripple would be stationary and a lot less noticeable than moving patterns.

With a good power supply there should be no problem. As you'll need to use a transformer anyway, you could go for full-wave rectification and simultaneously reduce the ripple voltage and push up the beat frequency.

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Old 7th Aug 2017, 9:17 pm   #10
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

A BBC report of the reverse situation, I.e 525/60 tv on a 50hz supply, interesting read. Good smoothing of the DC supplies and little injection of the power frequency from other sources.

http://downloads.bbc.co.uk/rd/pubs/reports/1963-56.pdf

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Old 7th Aug 2017, 9:23 pm   #11
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

Quote:
Originally Posted by Radio Wrangler View Post
The benefit of mains-locked TV signals was that any picture variation due to power supply ripple would be stationary and a lot less noticeable than moving patterns.

David
One interesting effect of mains locked signal and poor smoothing was if the BBC and ITA locked on the opposite phase, it could affect vertical linearity, correct on one channel bad on the other.

BBC2 was not locked and this showed up poor smoothing when there was little effect on the 405 line system.

Frank
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Old 7th Aug 2017, 10:18 pm   #12
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

So 1950s TVs didn't use the local mains frequency as a reference at all? I'm genuinely surprised to learn that, as I was sure they did. Live and learn.
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Old 7th Aug 2017, 10:46 pm   #13
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

Just had another look at my 1950's leaflets. Most simply refer to AC mains (or AC and DC mains) without further details. The only other company that explicitly stated that their TVs were usable on other than 50 Hz mains, was RGD. Most were for 50 to 60 Hz, AC only, but the 6014T was suitable for 40 - 100 Hz AC or DC. Scans of my RGD TV leaflets, which are from the early 1950's, are available in the following thread

https://www.vintage-radio.net/forum/...d.php?t=137905

at posts #13 and #14.

There were still a number of public DC mains supplies (and non-50Hz AC mains supplies) in the 1950's. I don't know when the last one went, but I don't think my Uncle's DC mains in East London was changed to AC until the late 1950's. The many 1950's TVs that were designed to operate on both AC and DC, clearly couldn't use the mains as a reference.

Last edited by emeritus; 7th Aug 2017 at 11:08 pm.
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Old 7th Aug 2017, 10:48 pm   #14
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

You always got variation over where the stationary pattern sat because electrical power is distributed as a three phase group, and the feeds to single phase users like homes are distributed across the phases to keep the overall load reasonably balanced on the 3 phase equipment.

Whichever phase the BBC used, roughly one third of homes would be 120 degrees out, and another third would be 120 degrees out the other way.

With a large proportion of period tellies and radios being AC/DC with half-wave rectifiers, I wonder if some feeds were deliberately 180 degrees out to try to balance things and try to cancel DC components in transformers.

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Old 7th Aug 2017, 11:04 pm   #15
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

TV timebases locked to the received sync pulses from the transmission, a small change in mains frequency that the TV was powered from would have little effect on the picture if the HT reservoir/filter capacitors were up to spec, a small change in HT ripple voltage maybe but that's about all as far as I can remember.

A change in mains frequency might have affected a capacitor dropper TV that used the BRC 960 chassis.

Lawrence.

Last edited by ms660; 7th Aug 2017 at 11:09 pm.
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Old 7th Aug 2017, 11:55 pm   #16
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Arrow Re: Can I run A UK 1950s Set On 60Hz Mains?

Extracted from Wikipedia on this subject. (Slightly edited by me to improve readability):

Why 50 fields per second?
Since the mid-1930s, it has been standard practice to use a field frequency equal to the AC mains electric supply frequency (or a sub-multiple thereof) of 50 Hz in most countries (60 Hz in the Americas and some parts of Japan).
Reasons: First, because studio lighting generally uses alternating current lamps and if these were not synchronized with the field frequency, an unwelcome strobe effect could appear on TV pictures.
Secondly, the smoothing (filtering) of power supply circuits in early TV receivers was rather poor, and ripple superimposed on the DC could cause visual interference.
However, the main problem was the susceptibility of the electron beam in the CRT being deflected by stray magnetic fields from nearby transformers or motors. If the picture was locked to the mains frequency, this interference would at least be static on the screen and thus relatively unnoticeable.
The very earliest TV sets used a mains transformer; care had to be taken in its design to prevent the transformer's stray magnetic field from disturbing the electron beam in the CRT.

"If the picture was locked to the mains frequency". A comment, which to me, suggests that the field sync. pulses - as transmitted - were derived from the a.c. mains somewhere in the transmission path between camera and aerial. Hence, the receiver would not need to use the a.c. mains for its field sync. where that set was installed.

HTH,
Al.
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Old 8th Aug 2017, 3:02 am   #17
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

Thank you all.

Reading all of your suggestions, it seems that it would be worth trying to run the set on 60Hz. Among other things, the Ferguson 998T that I have my eyes on is early enough to be an AC/DC mains set. If it could work on DC it presumably did not need the 50Hz pulse from AC mains and can lock with whatever signal is fed to it (I am planning to obtain an Aurora). If a 240V/60Hz supply turns out not to work with such a set, I will rethink the issue.

As Heatercathodeshort points out, the 998T is a good "starter set" and I have found other threads on this forum with 998T restorations. Again, the U.S. eBay listing for the set I am eyeing is here: http://tinyurl.com/ybbpptag.

I wonder if people could weigh in on my question regarding how to measure EHT. "Back in the day" there were high-voltage probes for VOMs or VTVMs; and also stand-alone high-voltage meters (with a small meter built into the handle of the probe). I do have a whole suite of restored/rebuilt 1950s U.S. test gear, "Eico" brand. There are Eico high-voltage probes, but on reflection I think a modern solution might be wise, in the interest of stayin' alive -- i.e. to avoid any issues with rotting or degraded insulation in the vintage test equipment. In my ham radio homebrew work I've never worked with anything higher than about 800VDC.

(BTW I have already read the advice about working with high voltages on the "405 alive" website.)
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Old 8th Aug 2017, 12:19 pm   #18
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

Martin
Looking at the 2 sets you propose the Ferguson is an AC/DC set whereas the KB is an AC only set with an Autotransformer. Of the two the Ferguson would probably (all things being equal) would be the easier set to use. The autotransformer In the KB may not like 60Hz mains being either less efficient or overheating., with the Ferguson if I didn’t like 60hz (unlikely) you could always build a simple DC power supply and feed it from that.
With regard to your concern about measuring EHT I would leave that alone the EHT was not critical and if the set works Ok it is OK, trying to measure it can cause more problems and danger. If the EHT heater lights you can probably hear the whistle all should be well.
On the Aurora you propose 625 to 405, I assume you have a 625 line signal available otherwise you would need the more sophisticated multi standard which I believe covers 525 to 405 conversion.
Good luck Chris
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Old 8th Aug 2017, 12:57 pm   #19
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

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Originally Posted by chriswood1900 View Post
Of the two the Ferguson would probably (all things being equal) would be the easier set to use.
Thanks Chris, on balance I agree!

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Originally Posted by chriswood1900 View Post
Martin
If the EHT heater lights you can probably hear the whistle all should be well.
Good point. I am 60 years old but I should be able to hear a 10KHz whistle!

Quote:
Originally Posted by chriswood1900 View Post
Martin
On the Aurora you propose 625 to 405, I assume you have a 625 line signal available otherwise you would need the more sophisticated multi standard which I believe covers 525 to 405 conversion.
Unfortunately the Aurora supplier, here in the U.S., is "out of stock" of the multistandard converter (model WC-01), which is too bad. He is waiting for a reasonable bulk of orders (10 or more) before running up some more of them (he told me that the WC-01 was mostly purchased by museums). So I will probably be restricted to obtaining one of the single-standard models.

I have a multistandard Panasonic DVD player, playing into a multistandard Sony Bravia LCD set. My collection of DVDs is about two-thirds purchased in the U.S. and about one-third from Europe. Frankly I am not sure whether the DVD player is outputting 625 (PAL), 525 (NTSC) or something else altogether; there is no caption on the screen to indicate what the standard is and this is not something that I know very much about.

The DVD player is connected to the Sony TV with an HDMI cable and I have never had to worry about standards because the whole chain is multistandard. So this will require some research. Alternatively, I could just source a cheap additional DVD player from the UK and in that case I presumably would know for sure that I have a 625-line source.
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Old 8th Aug 2017, 1:01 pm   #20
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Default Re: Can I run A UK 1950s Set On 60Hz Mains?

At first I thought there would be no problem. But as Lawrence ms660 points out, a set with a capacitive dropper won't like 60Hz. The heaters will be over-run. You could drop the mains voltage a bit to compensate, for tryout purposes (worst-case will be that heater current is up by 16.7% so you'd need to drop the voltage by half of this, 8%. In practice, 5% drop should do the trick).

If there's an autotransformer, designed for 50Hz it won't mind at all running at 60Hz (will run slightly cooler in fact). But, if you watch a program at 50fps, there could well be the sort of effect that Al Skywave points out, a slight 10Hz wobble caused by the CRT beam being modulated by stray field from the transformer.
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