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Old 6th Jun 2012, 3:34 pm   #1
Mikey405
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Default Repairing a 14" Philips Tea-Chest

Hi all.

Over the weekend a mate of mine Tony (a member of this forum) came round and badgered me into getting my finger out and repairing an old Philips 1446U TV from 1954 that I’d had lying around for the best part of 17 years. I say “repair” rather than “restore” because there was so little (technically) to do to get it working. The set, an astonishingly plain but somehow quite endearing monstrosity, hadn’t been powered up once since I got the old thing many many years ago.

In the best tradition of things around here we decided not to plug the set straight in but to use a toaster as some kind of protection (what protection?) against short circuits. On powering the set up and waiting a good few minutes a faint line whistle was heard and some slight scratching noises from the loudspeaker. After some time had passed (not really very long actually) we decided to throw caution to the wind and plug the old girl into the full force of the mains. Faint line whistle and no picture at all. Hmm.

“Okay”, we thought, “let’s put a signal into the aerial socket to see if we get any picture or sound now”. So, on stringing an aerial lead from the bench to my big cabinet containing the Aurora, a loud yelp and a sudden spasm up my arm after touching the metal cabinet told me that something was not quite right. It turned out that somebody had once changed the mains lead but they’d connected the live (red) wire to the chassis – this combined with a very leaky capacitor between the aerial socket and the chassis had led to there being a nasty charge on the aerial socket outer, and my cabinet, being earthed, made quite a nice path to deck through my body.

After rewiring the mains lead and replacing the leaky cap there was still no picture. On checking the EHT, it appeared a little bit low but not so low that a picture shouldn’t have been displayed. We then started prodding around the tube base to see what was there. Around 700V on the A1 and pretty normal readings on the control grid and cathode (I can’t remember what they were, but Tony, a much cleverer and more resourceful chap than me, said they were fine). We even shorted the cathode to the control grid and got nothing at all on the screen.

Okay, perhaps the ion-trap was set incorrectly – It looked about right but we loosened it off and spun it around without any effect whatsoever – Not a glimmer on the screen. Surely the tube couldn’t be so duff that there was not even the slightest glimmer of a picture could it? After all it must have come out of somebody’s house – Would they have still been using it if the tube had gotten so bad that there was not even the faintest hint of a picture?

But then we thought – "Hmm. Perhaps there isn’t enough heater voltage for some reason". So we checked – and – there was only 4.5V instead of 6.3V. On disconnecting the heater connection to the tube and powering it via a separate power supply, a reasonably bright but very squashed picture was shown. However, a look at the current being drawn (450mA) revealed that the heater had an internal short somewhere.

Luckily I had kept a slightly tattier (but otherwise identical) spare set. After gingerly powering that set up too (not even through a toaster this time) there was a reasonably bright but, again, very squashed, picture. The chassis of the two sets were removed and the tubes duly swapped over. Putting both sets back together and powering up the original now revealed a fairly bright but still squashed picture.

Since we’d been working on the set upside down I decided to make sure the smoother capacitor was okay after its rather rude awakening. On touching it, it was pretty warm so we decided to re-form it. I’d been meaning to build a re-former for some time and I just happened to have all the parts (all 3 or 4 of them) to hand – a small 1:1 isolating transformer, a handful of medium to high value resistors and a load of croc clips. Everything in fact except a suitable diode. On rummaging through my collection of diodes, I picked out what I thought looked like a suitably beefy monster – I forget the number now – but we decided to look up the spec to make sure it was okay. Looking through my diode book, it only gave equivalents and checking the Interweb just revealed plenty of promises to data but very little actual data. All I got was “click here for datasheets” simply to be taken to another site with more “click here for datasheets” and so on. “Not to worry” I thought, “It looks pretty hefty so I’ll give it a shot anyway”. The diode was duly connected up to the transformer with an 8W 18K resistor, a multimeter measuring the voltage, and the capacitor to be re-formed. We then left it cooking nicely on the side and went back to the set.

We temporarily tacked a much smaller more modern cap in place of the old smoother and carried on with the repair. To cut a long story short, after deciding to not just do a blanket-change of all the black-wax-pitch Philips capacitors, every one we took out to check was duff – either incredibly leaky, low value or reading high value. In the end we decided that a blanket-change was what was actually required after all. And a blanket-change was what the set got. We’d been powering the set up after each few capacitors that we changed and the picture was getting better and better after each batch replaced in the line and frame sections. In the I.F. section though there was virtually no difference made to the picture or sound but at least it would be more reliable we decided.

After a couple of hours the voltage across the capacitor on our impromptu reformer had only risen to 30V (suspiciously exact in hindsight). The capacitor was also a bit warm but not alarmingly so. “What the hell”, we thought, “let’s give it something to think about” and bridged the 18K resistor with a big fat 10K. “Hmm. That’s odd” we thought after another while – the voltage is still stuck at 30V and the capacitor and resistors are getting warm. It wasn’t until we’d almost exploded the capacitor and burnt the house down with yet further smouldering resistors (I think this was a case of “It seemed like a good idea at the time”) that we decided enough was enough. A slightly more persistent search on the Interweb revealed that what we’d supposed was a big hefty power-diode was in fact a 30V zener diode! We then ripped the diode out and put in what we should have put in to start with – a plain old 1N4009. After a couple of hours with the new diode and the original high-value resistor, gradually working our way down to lower values, the capacitor had re-formed and was holding its charge nicely, none the worse for its terrifying ordeal.

The newly re-formed cap was then installed, the set boxed up, and, after a few tweaks here-and-there, the set was displaying a lovely picture. Not wonderfully bright, but still very watchable.

So, a couple of morals to this tale I think – First don’t assume the chassis you are working on is not live – even if the plug is wired correctly, and next – don’t assume that the aerial-isolator is actually isolated! As for the diode – I don’t think there’s any accounting for stupidity on this scale.

Thanks all.

Kind regards.

From Mike.
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Last edited by Mikey405; 6th Jun 2012 at 3:45 pm.
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Old 6th Jun 2012, 4:52 pm   #2
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Default Re: Repairing a 14" Philips Tea-Chest

I agree about this set having a certain charm, and an enjoyable tale too.

- Joe
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Old 6th Jun 2012, 5:17 pm   #3
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Default Re: Repairing a 14" Philips Tea-Chest

I can just imagine what was said regarding the incorrect diode!

Nice to see another of your long standing "to do" sets done so to speak and very nice it looks too. Anything need doing to the cabinet?
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Old 6th Jun 2012, 6:38 pm   #4
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Default Re: Repairing a 14" Philips Tea-Chest

Nice job Mike. These receivers are incredibly ugly but I suppose after a dozen 'Tinnies' anything can look beautiful. On the plus side they are incredibly reliable and being Philips give a grand stable picture.
I have a similar model, like yours repaired around 30 odd years ago and then simply cast aside as more attractive receivers came along. Maybe I'll get it out sometime..
That partial heater short was an ongoing problem with Mullard tubes from the 12" MW31-74 series right up to the last ion trap tubes the AW43-80 a period of over eight years. Simple to cure but they never did. Leaning the cabinet back and tapping the tube neck will cure it for a very short period but it proves the point. I have never heard of a BY127ZX30..Oh dear, what a stinker. All the best, John.
PS Tea chest, I like that. The cabinet is even lined with tinfoil!
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Old 6th Jun 2012, 7:51 pm   #5
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Default Re: Repairing a 14" Philips Tea-Chest

Nice results and I don't actually think that's a bad looking set! And I've not had any tinnies (yet)! Seem to remember seeing a photo of one of these in 'The Radiophile' not too long ago.

With that central control on the front, it's asking to be converted in to a 'mono-knob' version, now that would be a challenge, a few old bike brake cables, etc.

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Old 6th Jun 2012, 8:48 pm   #6
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Default Re: Repairing a 14" Philips Tea-Chest

Almost looks 'monitor style' that some manafacturers used to style TV's in the 80's,
Has the arm recovered Mike, or still feeling the jolt.
Regards, Alan, (stacman).
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Old 7th Jun 2012, 1:24 am   #7
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Default Re: Repairing a 14" Philips Tea-Chest

smashing stuff, great write up. Now when does the second /rougher set get its turn to shine?
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Old 7th Jun 2012, 4:12 pm   #8
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Default Re: Repairing a 14" Philips Tea-Chest

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Originally Posted by ThePillenwerfer View Post
I agree about this set having a certain charm, and an enjoyable tale too.

- Joe
Thanks Joe. I think I like the set now - It's certainly growing on me.
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Old 7th Jun 2012, 4:14 pm   #9
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Default Re: Repairing a 14" Philips Tea-Chest

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...and very nice it looks too. Anything need doing to the cabinet?
Hey Tas. Well the cabinet isn't too bad really - A few scratches and scrapes but generally it's pretty good. And "Topps" scratch-cover masks a multitude of different marks and scratches etc. And yes, it is pleasing that another "long-timer" has been sorted out at last.
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Old 7th Jun 2012, 4:19 pm   #10
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Default Re: Repairing a 14" Philips Tea-Chest

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Originally Posted by Heatercathodeshort View Post
Nice job Mike. These receivers are incredibly ugly but I suppose after a dozen 'Tinnies' anything can look beautiful. On the plus side they are incredibly reliable and being Philips give a grand stable picture.
I have a similar model, like yours repaired around 30 odd years ago and then simply cast aside as more attractive receivers came along. Maybe I'll get it out sometime..
Thanks John. Oh, I don't know about "incredibly ugly" - certainly no oil-painting but not that bad. Having said that I wonder what the designer was thinking when he came up with that shape. Perhaps he'd had a few tinnies himself the night before.

I think you ought to get yours sorted out as well John. They're definitely more interesting than plain old TV24s etc.
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Old 7th Jun 2012, 4:20 pm   #11
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Default Re: Repairing a 14" Philips Tea-Chest

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With that central control on the front, it's asking to be converted in to a 'mono-knob' version, now that would be a challenge, a few old bike brake cables, etc.
I'm not too sure about that Greg - Trying to work Volume, Brightness, Contrast, Width, Height, Vertical Hold, Horizontal Hold and Tuning into one control would be quite some feat of engineering I think.
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Old 7th Jun 2012, 4:23 pm   #12
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Default Re: Repairing a 14" Philips Tea-Chest

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Originally Posted by stacman View Post
Almost looks 'monitor style' that some manafacturers used to style TV's in the 80's,
Has the arm recovered Mike, or still feeling the jolt.
Regards, Alan, (stacman).
Yes, the arm has recovered fine thanks Alan. Although a strange side effect is that I still can't play the piano.
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Old 7th Jun 2012, 4:24 pm   #13
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Default Re: Repairing a 14" Philips Tea-Chest

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smashing stuff, great write up. Now when does the second /rougher set get its turn to shine?
Thanks Ben. Well, the other set has gone off to a mate of mine to be sorted out as well. It wasn't actually that bad - the chassis basically worked although the tube heater was of course duff. The cabinet wasn't as good as this one either and there were a few woodworm holes in the speaker-grille too. Hopefully one day it will live again though. Probably in another 17 years...
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Old 7th Jun 2012, 5:03 pm   #14
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Default Re: Repairing a 14" Philips Tea-Chest

Hi Mike,
I've come across these sets in the past and never bothered to actually acquire one because, well to be honest they ain't pretty, but I do know that they perform very well indeed.
The Philips 1446 and 1746 were disappearing fast when I entered the TV trade in 1960. Everyone wanted one of those new "slimline" TVs. Big boxy TVs became valueless.

DFWB.
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Old 8th Jun 2012, 7:53 am   #15
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Default Re: Repairing a 14" Philips Tea-Chest

A man after my own heart David. These young kids have no idea what a good telly should look like. [slobbering over TV22's]
The 1446 looks quite good in Mikes pictures but I still think it's an ugly duckling. Strange because Philips designed some of the best looking receivers. The previous 11/1200U series were very nice. The turret tuner was an after thought of course, the chassis being the twin design from the five channel period. They had to stick it somewhere but I'm not a fan of the 'Cyclops' look. Brilliant electronics of course from such a respected company. Regards, John.
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Old 8th Jun 2012, 7:43 pm   #16
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Default Re: Repairing a 14" Philips Tea-Chest

I don't know if it even crossed the mind of the stylist, but that single central knob suggests to me a set so stable that the only adjustment normally required would be channel selection. I rather like its clean, simple lines!
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Old 8th Jun 2012, 7:59 pm   #17
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Default Re: Repairing a 14" Philips Tea-Chest

I like it.
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