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Old 20th Jul 2007, 12:42 pm   #1
hairymike
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Default Advice for powering up a Ekco T.331

Hello. After a morning of surfing around the internet trying to find out about the Ekcovision T.331 television, I found this forum.

My friend's son is all into collecting antique televisions, radios and cinematic projectors. Recently he got his hands on one of these ekco tvs, and has been torturing his mum to let him turn it on. She is afraid that he's going to electrocute himself or fuse the house out, so up to this point she has refused.

I got talking to him a few nights ago and said I would do a little research and see what I can find out about it. I'm hoping one of you electronics gurus might be able to offer some advice.

I'll admit that I know very little of indepth electronics, but I have wired up numerous plugs and sockets (and put a computer together one time).

I was reading earlier that this model of tv did not use a transformer, and that the chasis has the neutral current connected to it. There are 2 prongs that stick out the back of the telly for connecting the mains to (looks quite dodgy to me). I was thinking about maybe connecting 2 sheathed connectors to these and just hooking straight into the mains. Then I read something about an isolating transformer - would one of these make the whole operation safer?

fyo, it also says on the back that the set accepts dc current.

So to round up,
1. should I get an isolating transformer?
2. are there any other things in the tv I should check or replace before I even think about turning it on?
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Old 20th Jul 2007, 12:51 pm   #2
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Default Re: Advice for powering up a Ekco T.331

You are very wise to take advice before powering it up.

I don't work on tellies, but as a general rule you shouldn't power up any piece of unrestored valve equipment without investigating the condition of components. It will almost certainly need lots of capacitors reforming or replacing - if this isn't done, not only will it not work, but it may suffer damage or even explode or burst into flames.

There are many helpful people on this forum who can give you detailed help, but if you have no electronics experience you will have your work cut out restoring this TV to a safe and usable condition.

Remember there are dangerous high voltages inside old TVs.

You will of course need a standards converter if you want to use a 405 line TV.

Good luck, Paul
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Old 20th Jul 2007, 12:52 pm   #3
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Default Re: Advice for powering up a Ekco T.331

Hello!

I'm afraid his mum is right! I'll let the TV experts explain why, and what he needs to do

Nick.
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Old 20th Jul 2007, 1:01 pm   #4
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Default Re: Advice for powering up a Ekco T.331

very quick replies there gents, many thanks
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Old 20th Jul 2007, 1:32 pm   #5
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Default Re: Advice for powering up a Ekco T.331

The set after it is restored will not work without a line standards converter . this converts the lines fro 625 to 405 lines and moderates the signal . The latest bit of clever modern kit to do this is the Aurora , It costa about £150 and has a built in testcard and sound whistle . The input can be then connected to anything that produces 625 lines , digi box dvd vcr etc .
But first the set needs all of the wax paper capacitors changed etc which someone else will explain to you .The chassis should be treated as live ,as it just may be depending on which way the socket is and it will produce very high voltages from parts inside while running
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Old 20th Jul 2007, 1:56 pm   #6
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Default Re: Advice for powering up a Ekco T.331

Hi, Mike. I don't think anyone on this forum would recommend you encourage a friends son to restore a vintage TV as they are extremely dangerous.
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Old 20th Jul 2007, 2:06 pm   #7
hairymike
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Default Re: Advice for powering up a Ekco T.331

Hi PJL,

I appreciate and thank you for your concern. My intention is to do this myself if at all possible / feasible. The young lad will be kept out of harms way.

At the moment though, I have to admit that I have my doubts. It is something that I would like to learn about, although I don't want to risk electrocuting myself either
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Old 20th Jul 2007, 2:19 pm   #8
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Default Re: Advice for powering up a Ekco T.331

Quote:
Originally Posted by hairymike View Post
At the moment though, I have to admit that I have my doubts. It is something that I would like to learn about, although I don't want to risk electrocuting myself either
If you are genuinely interested in repairing and restoring old valve equipment, your best bet would be to acquire a cheap 1950s valve radio and learn the ropes on that. These are inherently less dangerous than TVs, and the circuitry is simpler, but many of the issues are the same. There's quite a bit to learn though.

Suitable radios are often available from car boot sales for a few pounds. The ideal radio would be a big wooden LW/MW/SW set - the cosmetic condition doesn't matter.

There's lots of useful stuff about radio restoration here: http://www.vintage-radio.com/repair-...ion/index.html

Good luck, Paul
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Old 20th Jul 2007, 2:23 pm   #9
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Default Re: Advice for powering up a Ekco T.331

Even after replacing all the waxies I still introdude the mains very slowly & gently.
My method's pretty bizzarre, with the rectifier out I put a 15 Watt bulb in series with the mains to the thing, then another 15 Watt = 30 Watts, then another 15 Watt = 45 Watts etc, over several hours, this is to tease the thing back to life instead of just surprizing the hell out of it with the full goodness of the mains, after all, if you were sleeping quite happily for several decades and someone shouted in your ear, you'd be pretty upset !
Please also remember that these things generally have a 'mains tap' or adjustment in the back because the mains was different voltages in different areas, this also needs concideration.
But most importantly, be carefull, a shock from a vintage telly will really upset you ! ! !
Be warned ! ! !

Regards

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Old 20th Jul 2007, 2:27 pm   #10
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Default Re: Advice for powering up a Ekco T.331

If you want to restore this set, you need basic tools, a Variac is a good idea, and above all some prior knowledge.

It's a good idea to get some knowledge on radios first. And then TV sets..

www.oldtellys.co.uk

All you need to know about old tellies but were afraid to ask. Read that lot and come back.

Cheers,

Steve P
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Old 20th Jul 2007, 4:03 pm   #11
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Default Re: Advice for powering up a Ekco T.331

Basically, you should consider this old TV very dangerous if switched on in its present condition, both from the electric shock and the fire hazard point of view.

Also bear in mind that if damaged the picture tube can 'implode' (this effectively means explode) - it goes off like a small bomb, with glass flying everywhere including into peoples' faces.

My advice for now is to put this TV aside, that is until you have gained enough knowledge to fully understand the risks and have a go. Then, you'll enjoy a really great hobby along with the reward of being able to watch a vintage-style picture at the end.

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Old 20th Jul 2007, 4:13 pm   #12
hairymike
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Default Re: Advice for powering up a Ekco T.331

Thanks for the replies. Rest assured, the set will remain switched off for now.

Like you said, trying something like a lower voltage old radio sounds like a very good idea.

It looks like theres a lot of useful information on your website Dr-Watts. I'll have a good read through that this evening.

Thanks and Regards,
Mike
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Old 20th Jul 2007, 7:59 pm   #13
hairymike
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Default Re: Advice for powering up a Ekco T.331

I should have credited Steve P for the website I was reading and typing too quickly there.

My friends son actually has a working vintage radio (not sure which make). I think the only thing wrong with it is a hole in the speaker.

Very useful information all round though guys. Thanks, I will keep you up to date on any progress
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Old 20th Jul 2007, 8:33 pm   #14
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Default Re: Advice for powering up a Ekco T.331

Hello Mike,
I agree with everything said by Forum members. It would take many pages to talk you through the information required. The Ekco T331 is the rarer version of the T330 as it has F.M. radio included. It dates from 1958/59.
Fine receivers and very reliable.
Just to prove you can get them working, I have taken a few pictures from the screen of my T330 a few moments ago. My T331 operates very well too. I have set the focus on the set slightly off its best setting to limit strobing effects with digital cameras. Feel free to ask any questions. Regards, John.
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Old 21st Jul 2007, 8:49 am   #15
hairymike
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Default Re: Advice for powering up a Ekco T.331

Hello Heatercathodeshort.

That is very exciting to hear that you have a working set. Thanks for attaching those pictures - looks exactly the same as this set.

From the oldtellys website, I gather that the starting point is to get the service manual and wiring schematics. Then replace the HT smoothing cans, wax paper capacitors and grid coupling capacitors (is this the same for vintage radios?). Remove all the valves and apply the mains gently using a variac, looking for signs of smoke, overheating etc. If all is well, refit all valves except for the EHT rectifier valve and reapply the mains with the variac - checking that all valves light up. If any don't light up or light up too brightly, recheck the smoothing cans. If all is well then refit the EHT rectifier valve and see if there is any picture.

I gather this is rather simplified, and there is still some jargon that I am struggling with. I think for now, I will see if I can get my hands on the manual and schematics. I might see if I can have a go at replacing some of the wax paper capacitors on the vintage radio and see how that goes.

It does sound as though I would need a lot of equipment to do this. From what I can see on that website, I'd be needing a variac (is this the isolating transformer?) a multimeter an oscilloscope and a signal converter (to see the picture).

Have I missed anything here?
Thanks
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Old 21st Jul 2007, 9:46 am   #16
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Default Re: Advice for powering up a Ekco T.331

Quote:
Originally Posted by hairymike View Post
It does sound as though I would need a lot of equipment to do this. From what I can see on that website, I'd be needing a variac (is this the isolating transformer?) a multimeter an oscilloscope and a signal converter (to see the picture).
A variac is not an isolating transformer. Despite what some of the old hands say, you really must use an isolating transformer or an RCD. Opinions differ as to which is safer. At least with an RCD if you touch any dangerously live part it will cut off the mains immediately. You can often use a lamp limiter instead of a variac. This is just a 100W or 150W bulb in series with the mains supply to the set. You don't get the fine control of a variac but it can prevent all sorts of tragedies. It is also possible to run up the heater chain at full power and use the lamp limiter purely in the HT supply.

A multimeter is essential. A 'scope is useful but not essential. I wouldn't be wthout one but the guys who serviced these sets in real life would rarely even have access to one. You can get as far as lighting up the screen with a blank raster without having a source of 405 pictures.

Finally please remember that these sets are potentially dangerous, especially if you don't fully understand them. It's great that you're helping a young friend like this. If he has access to the internet it would be good for him to join the forum in person. Then he will be able to ask questions directly. He probably won't be the youngest person in the forum!
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Old 21st Jul 2007, 10:56 am   #17
hairymike
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Default Re: Advice for powering up a Ekco T.331

Hi Jeff, an RCD sounds familiar.. thats a kind of trip switch isn't it? (I think I had one fitted to my fusebox recently) The lamp limiter definately sounds a lot more cost effective than a variac.

My friend's son (scott) doesn't have a computer in the house at the moment and is on his summer holidays, but I might see he can go around to the library and get online there. It would be nice to involve him in this as he is mad keen. I'd need to be 100% sure that there is no chance of him getting injured.

When (and if) the time comes to turn the tv on, it will be sitting in the back yard and I will be flipping the switch with a long stick (standing around the corner from it). I understand that there can be 6kV (6000 volts) inside one of these things.. and that the charge sometimes doesn't disipate properly once turned off. Is this true?

Many thanks
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Old 21st Jul 2007, 11:15 am   #18
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Default Re: Advice for powering up a Ekco T.331

RCD (Residual current device) often called a tripswitch. Not to confused with MCB (miniature circuit breaker) often used instead of fuses in the house "fusebox". You can identify an RCD since it will always have a "test" button" Use a plug-in one if you are in any way unsure whether the sockets in the house are protected by one at the fusebox.

Strange as it may sound, the EHT (6kV or more) on this sort of set is not the most dangerous thing in the set. The reason is that there's very little current available. Mains is *much* more dangerous, so is the HT at 200V-300V since there is lots of current available. Old saying: It's the volts that jolts, it's the mils (milliamps) that kills. Absolutely true. There are some early TVs that have their EHT derived from a big mains transformer. These were sometimes known as "widow makers" in the trade. Unless you have a dodgy heart most shocks aren't going to endanger you unless the surprise causes you fall off the ladder or impale yourself on a sharp object.

Charges can persist in a TV (or radio) long after the mains is turned off. Not usually anything too harmful unless the surprise makes you jump and smash the neck of the tube and get glass fragments stuck in you. I once got a nasty surprise from an old PC. The mains input filter had retained a charge and I got a belt from the pins of the mains plug after I had unplugged it. Almost dropped the computer
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Old 21st Jul 2007, 11:47 am   #19
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Default Re: Advice for powering up a Ekco T.331

Hello Mike,
First the advice from Jeffrey holds good as it always does. You will need to know the hazards involved in repairing Ac/dc equipment. If you have radio restoration experience in this direction this should not be a problem as its almost identical to television receiver practise. If in doubt, seek our advice and don't proceed until you are happy about it.
The Ekco T330 series will not produce any fireworks generally. You will need a circuit diagram to locate the capacitor connected across the set side of the on/off switch. Its usually mounted behind the mains dropper but its position varied. Snip this out of circuit, it has nothing to do with the sets operation and if faulty. [guaranteed] tends to 'pop' in a rather spectacular manner and can scare the unwary. Its not dangerous and at the worst is just a pop and a blown mains fuse. Next take a good look at the condition of the top of the perspex line output transformer CASE. If it looks burnt and has a sickly 'sweet' smell it will require renovating. A replacement paxolin case can be made up and substituted for the old paxolin one. The transformer windings never fail and the transformer comes apart easily. Take care with the fine wires. The main electrolytic should be ok unless the chassis shows signs of rust, my hatred! Whatever you do don't start replacing components wholesale. True the wax capacitors will no doubt need replacement but it needs to be done in an orderly manner. I would suggest replacing the boost capacitor connected between the boost H.T. rail and the main H.T. line, snip the capacitor off mentioned earlier and apply mains through a lamp for starters. If the chassis is clean You may well get some results when the mains is slowly increased, Use a 150watt lamp in series with the mains to start and then put another one in parallel if nothing appears to generate some sparks. I would be far more dare devil but I can't advise you to follow my bad methods learnt through years of repairing these receivers.....
The Mazda CRM173 holds up well. The nearest Mullard equivalent is the MW43-80. These are simply cracking sets and I wish you were a bit closer as I would love to have a go at it! I have no doubt you will get it working. Deal with each section of the set in turn switching on after EVERY replacement.
Paul no doubt has the circuit available on this site. [top of page] but if you have any problems I can photo copy mine and get it to you. Good luck with the set. Regards John.
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Old 21st Jul 2007, 12:40 pm   #20
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Default Re: Advice for powering up a Ekco T.331

It may sound like a mutual fan club but please read John's (heatercathodeshort) advice carefully. He's mended more TVs than most of us have had hot dinners. He's a particular fan of Ekco designs too. I'm a mere amateur in these matters. I design stuff for a living, John mends stuff> They're two very different skills; being good at one doesn't mean you're good at the other.
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