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Old 24th Mar 2018, 4:49 pm   #21
Graham G3ZVT
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

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Originally Posted by 1100 man View Post
Many apologies, Graham, I forgot your excellent conversion method!! Out of interest, how easily obtainable is a suitable graphics card? I must say, that would make a very interesting project in itself: maybe I'll have to give it a go myself!
Sorry, just noticed this.

I recommend the ATI RADEON HD 2400 (PCI Express).
I paid £6 on Ebay, but I already had the Y splitter cable.

If you need the card + cable expect to pay about £10.
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Old 24th Mar 2018, 5:54 pm   #22
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

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Originally Posted by rambo1152 View Post
Search Ebay for "Inductor Shell Skeleton"
They are a former with a ferrite slug. Wind them with approx 20 SWG enamelled wire, close spaced.
Is there a certain number of times I need to wind the wire around the slug?
Also is the 1/4" referring to the ferrite core diameter or something else?

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Old 24th Mar 2018, 9:45 pm   #23
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

The number of turns is on the schematic you attached.
The first figure in each box relates to Channel 1, 4.5 turns, for both coils.
but the second figure is a little odd, because it is between Channel 4 & 5
I just noticed that.

The ferrite core will probably tune across two or three channels anyway.

I have tuned my modulator to Channel 2 because my Cossor TV almost certainly spent its life receiving Holme Moss signals which is correct for my area and yours too for BBC TV!

Incidentally I think I read that the MC1374 will not oscillate at BandIII frequencies, in other words CH5 and above on your set
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Old 24th Mar 2018, 10:58 pm   #24
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

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I agree about not testing the tube. I have found some commercial testers read low on mono tubes. the emission being much better than indicated.
I have cringed in the past when I have read threads where the tube has been boosted before a picture had been displayed. (I hasten to add this was on the other now closed forum not on here!)
Very tactfully put! but, yes, I'm guilty as charged I hadn't realised at the time that my newly acquired B&K tester read so low. Over the years, I'd got used to the emission readings on my home constructed one and what that meant in terms of actual pictures. Even the tube from my VT161, which is so bright it could be a projection tube, only reads half way into the green on the B&K!
I agree a much better approach in future will be to restore the chassis and see how the tube comes up after 10 hours of use. Only then will I consider giving it a clean!!

I dug out my TCG316 today which I haven't looked at for 10 years. It's been stored in a hideous, worm infested, damp chicken shed for that time since I moved house.
It had a good coating of mould on the cabinet, but inside there were no signs of worm holes. It has a Mazda CRM172 fitted and I remember it gave an excellent picture, so Mazda tubes are not all bad! It will need a proper restoration now before it's powered up again.
Looking at the circuit, it really was a 'no expense spared' design. It uses no less that 20 valves including the CRT and three solid state diodes so must have been an expensive set!
As you are planning to build your own modulator, I assume you are also going to try the PC standards conversion route? That will be interesting!
Best of luck with the restoration,
All the best
Nick.
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Old 25th Mar 2018, 12:01 am   #25
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

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Originally Posted by rambo1152 View Post
The number of turns is on the schematic you attached.
The first figure in each box relates to Channel 1, 4.5 turns, for both coils.
but the second figure is a little odd, because it is between Channel 4 & 5
I just noticed that.
Ah! I got confused I thought the diagram called for those ones with a screw on top and the number of turns was referring to the turns of the screw! All makes sense now

Quote:
Originally Posted by 1100 man View Post
As you are planning to build your own modulator, I assume you are also going to try the PC standards conversion route? That will be interesting!
Yes, I'm going to use Graham's graphics card method as well. Just waiting for the caps to arrive now, in the meantime I've been cleaning all the pots and sockets.

Peter
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Old 25th Mar 2018, 2:10 am   #26
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

According to the MC1374 information crystals can be used to replace the carrier oscillator coils.
Although designed for negative modulation NTSC and CCIR systems the MC1374 will work on positive modulation systems when the input video is inverted. The pre-set R30 across D2 must be adjusted for zero carrier at sync tips.

DFWB.
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Old 29th Mar 2018, 4:56 pm   #27
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Parts arrived today, I'll start replacing the necessary capacitors this weekend. Quick question though, without a rejuvinator, what's the best way to 'wake up' a tube? Do you just power it on normally for a few hours or is there a different method?
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Old 29th Mar 2018, 6:52 pm   #28
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

I just power up and if everything is fine it will slowly improve ,most times.
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Old 10th Apr 2018, 5:55 pm   #29
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Update: Right, all the bigger value caps have been replaced (0.01 and above), The tube has been removed and the face and lens been cleaned before being put back. The turntable mechanism and the cabinet wheels have been oiled and greased. The chassis has had a good clean and the valves and plugs have been removed and cleaned the sockets with super 10 as well as the pots and slide switch. I've got the 405 modulator built in solderless breadboard form and now I'm just waiting for the inductor skeletons and solderable breadboard to arrive from Chinaland. Home straight.
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Old 10th Apr 2018, 10:40 pm   #30
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

The set is more or less ready to power up for the first time. Are there any precautions or last minute checks to make besides the obvious?

The only changes I've made is the mains filter capacitor is now a 275V (2500V surge) X2 capacitor and the old blown soft blow fuses have been replaced with fast blow fuses. Does it make a difference or should I stick with soft blow ones?
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Old 10th Apr 2018, 11:33 pm   #31
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Hi,
I would stick with slow blow fuses. Fast types are liable to blow with the surge at switch on.
Before first power up after a rebuild, if I've not replaced the main high value electrolytics, I like to take each one up over a period of hours on a variac whilst monitoring the current through the cap. Only after I'm happy they won't go pop will I power up the set.
If I've replaced or reformed (and they have proved to be ok) the main electrolytics, then I just take a deep breath and hit the switch
After all, they are valves and don't suffer instant death like semiconductors can if something is wrong!
Mind you, by the time I get as far as applying power, I've already done enough work to a chassis to know that it will probably function at least basically.

If you haven't already done so, make sure that the chassis metalwork is connected to the Neutral of the mains lead!!

I wonder if your modulator will work?

Best of luck
Nick
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Old 11th Apr 2018, 2:58 pm   #32
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

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I wonder if your modulator will work?
And from me!
I take the view that those plastic solderless breadboards do have their uses, but this project is pushing their boundaries, to say the least.

Here is my current modulator.
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It works flawlessly, but admittedly is not a pretty sight, so, for that reason, and because I would like to release that 30 year old breadboard for the development of future projects, I have started to build a new one on this kind of project board.

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I am just waiting for a "round tuit", other things have jumped the queue, in particular the TV set that is to be fed by it has developed a fault.
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Old 11th Apr 2018, 6:02 pm   #33
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

I got one of these so I can just transfer each piece over from the plastic breadboard without having to rearrange everything haha
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Old 11th Apr 2018, 6:19 pm   #34
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Right then, I've powered up the telly for the first time with no bang or smoke so that's good. It's not much use testing the TV part yet since my modulator is still not complete but I tested the record player and it plays good, idler slips a bit but that can be easily fixed. Amazingly the original crystal cartridge in it still works, maybe the salty seaside air from where I got it from did the trick in preserving it.

However, the set does not pick up FM radio signals, admittedly I don't have an aerial plugged in the back of any kind but it's not even receiving static....cause for concern?
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Old 11th Apr 2018, 8:40 pm   #35
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

After making a makeshift aerial, it receives about half a dozen FM stations nice and clear. The flyback transformer is making a nice high pitched whine and I've got the picture tube to make a few short infrequent flashes of lines on random parts of the screen. Obviously the tube needs waking up and all the pots at the back of the set need adjusting once I bet the modulator built and can display a test card.

One question though, I know it's bad to leave a valve amplifier on without a signal but is this the same for a TV with no sound or image signal being inputted? Just wondering if it's okay to leave the set on to do its thing for an hour or two maybe it would improve the picture tube a bit.
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Old 11th Apr 2018, 9:32 pm   #36
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Hi,
I wouldn't worry too much about feeding signals in at this stage. There's a little way to go before you need to do that! The most important task is to ensure that the line stage is working correctly, then the frame stage and then to get a reasonable (but blank) raster on the screen.

The first thing to check is whether the heater is lit in the U26 EHT rectifier? This gives a fair indication as to what's going on in the line stage. Does the line hold control alter the frequency of the whistle? If it's going at roughly the right frequency, the whistle should be quite loud and extremely irritating!!
If the U26 is lit, does the brightness control have any effect? If you have EHT, you should be able to get a bright screen by turning up the brightness.

The line stage is the most critical part of the set and needs to be working properly before you can do much else! Don't just leave it running for ages at this stage until you know that is the case.

Edit: Just realised that it uses a U25 not a U26 EHT rectifier! The heater should still be just as visible though.

Cheers
Nick

Last edited by 1100 man; 11th Apr 2018 at 9:42 pm. Reason: extra text added
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Old 11th Apr 2018, 9:56 pm   #37
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

You were right the first time actually, mine uses a U26 that I replaced because the old one had its metal cap fallen off snapping the anode wire right at the glass tip. Checking again, no the U26 is not lighting, is the valve a dud or is something else wrong? I do have a few more spare. The brightness control does nothing but the horizontal hold does affect the frequency of the whistle
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Old 11th Apr 2018, 10:21 pm   #38
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Ah. My circuit shows it as a U25 which is a wire ended thing. Maybe they changed to the U26 at some point?
This valve is not part of the main heater chain due to the fact it should have 16Kv on it's cathode! The heater has it's own winding on the LOPT and gets it's power from the energy being transferred within the transformer. If the line stage is not working correctly, there will not be sufficient energy to light the heater.
This is a pretty common problem!

Do you have the circuit diagram? The next step will be to measure some voltages with the set running to find out what's going on. The info I have has a table giving voltage readings which is useful.

Has the boost capacitor (C90 0.5mfd on my circuit) been replaced?

Cheers
Nick
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Old 12th Apr 2018, 7:18 am   #39
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Yes I have the service sheets and my diagram shows it as a U25 too they must have changed it at some point, yes the boost capacitor will have been replaced. Is it a capacitor that has AC through it because if it does I'll have probably accidentally installed the max voltage rating equivalent in DC causing it to fall
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Old 12th Apr 2018, 11:05 am   #40
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Later factory supplied line output transformers were supplied with a Mazda U26 EHT rectifier in lieu of the original wired-in U25. Apart from the fact the U25 was considered an obsolescent valve the plug-in U26 valve was a much better replacement because there was always potential damage to the plastic transformer case during the soldering process of the wire ended U25.

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