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Old 18th Apr 2018, 8:01 am   #61
Freya
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Your A1 boost voltage is too low, it should be around 410 volts.
I would stop component changes and wait until you can use a good signal to observe whats happening on the screen.
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Old 18th Apr 2018, 8:08 am   #62
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Too many components replaced without checking prior to initial switch on. We have been here many times on this Forum.

These Ekco models usually display visible results even with many faulty capacitors. Action can then be taken to repair the chassis by observing the results on the CRT.

I fear with so many components replaced, this thread will probably conclude with a 'man made' fault, either an incorrect component fitted or a wrong connection.

There is a set procedure that must be followed to resurrect these old receivers.

Good luck with it and I hope you get there eventually. Regards, John.
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Old 18th Apr 2018, 8:41 am   #63
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

You may find this list of some use. The last item on this thread lists most of the stock faults I encountered when servicing these receivers back in the 1960's.

https://www.vintage-radio.net/forum/...ight=Ekco+T331

Some other interesting threads listed on the archive: Page 11, T283. Page 13, 'Rogers dream chassis'. Page 13 again, 'The Ekco is here!' Page 14, Ekco T331. Page 18, 'Advice on powering up an Ekco T331'.

I hope these notes will help. John.
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Old 18th Apr 2018, 7:13 pm   #64
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Wish I had read those thread sooner, I think I've messed up in a big way. What I can do is double check the connections of the capacitors I have replaced against the circuit diagram although since I have confirmed that the record player and FM receiver work, is it safe to rule out those areas on the circuit? I haven't replaced any of the small value caps (under 0.01uF) I counted the number of caps I replaced and it comes to 31 out of the 137 in the set, I don't plan on replacing any more.

What would be your best recommendation at the moment, John?

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Old 18th Apr 2018, 7:54 pm   #65
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

I think your plan of attack is a good one. First of all you need to check what you have replaced against the circuit diagram. Copy the circuit and check the circuit location of each component you have replaced. Mark it with a high lighter pen when you are certain it is correct.

The power supply sounds OK as you have sound from the the record player. You need to work on the line timebase first. When this is working correctly things will start to drop into place.

These have probably been mentioned in the past but I would suggest you check the boost capacitor wiring, the coupling capacitor to pin 5 of the 30P4 [via a 1k ohm grid stopper] This is first moves. Check the voltage to pin 10 of the CRT A1. 350V DC at this point should give a bright picture.

I doubt if the 30P4 is faulty but of course that is possible. The U26 heater in the centre of the anode 'bell' should be visible quite plainly in subdued light. The metal rectifer is an AUTOMAT, again incredibly reliable.

As a quick test you can link a shorting wire from the CRT cathode pin 11 to the grid pin 2. This should give some sort of screen illumination and give a clue as to the missing link.

Please don't think I am being offhand about your progress so far. A lot of Forum guys have done the same as you and all have succeeded in the end. It's a learning curve and after 60 years I am still learning. John.

PS Notes reprinted to save searching. Some items mentioned may not apply to your particular chassis.

1 Mains fuse blown. .1uf across mains switch S/C
'Trombone' radio/TV change over switch burnt.
The PY32/33 heater will be O/C.
2 Weak frame sync. D2 frame clipper diode O/C. It looks like a very fat
resistor. Any diode can be used as a replacement.
[1N4001]
3 No line timebase.
U191 boost diode glowing red plus general overheating.
Line linearity coil has slipped down its former and
shorted to chassis. Warm with a hot air gun and
slide it back up.
4 Picture enlarges when brightness turned up.
U26 EHT rectifier.
5 Picture has ragged edges that decrease when brightness is reduced.
U26 EHT rectifier.
6 Slow frame warm up. Lacking in height and bottom cramp.
30PL1 frame output valve.
7 Picture lacks general overall contrast and tends to go negative when contrast control is turned up. Brightness and sync good.
Vision detector diode mounted on top of final
vision I.F. transformer leaking.
This is accessible from the top after
removing the spring clip and sliding the top off
the final vision I.F. transformer.
8 No or very weak signals.
30L1 [PCC84] or 30C1 [PCF80] low emission or
U/S.
9 Sweet sickly smell, frying sound, ragged picture and maybe smoke..
Line output transformer case [Perspex] breaking
down between anode and cathode connections of
original U25 wired in EHT rectifier.
Replace case with one made of paxolin. [easy]
10 Sound on vision dependant on VOLUME setting.
Combined frame output cathode decoupling cap 500uf and I.F. H.T decoupler 16uf. [They are both in the same can!]
I see from your pictures that yours has been replaced with the later type and appears to be in very good condition. If you have to clean the chassis, use a 1/2" paint brush and a vacuum cleaner. Take great care of fine wires around the LOPT.

Additional faults due to age that did not occur when these sets were in normal service.

1 No control of contrast.
.1uf capacitor INSIDE tuner, large wax type.
This decouples AGC line.
2 All frame faults. Wax capacitors.

3 Line timebase faults.
Wax capacitors......
4 Weak sound Screen decoupling capacitors in I.F. strip .001uf

5 Unstable vision, patterning etc
As above.
That's about it. Very reliable sets. Mazda CRM172 tube fairs quite well.
Cracking picture. Rock solid sync. Mazda valves have very long life.
They went to Mullard for the H.T. rectifier PY32/33. For some reason Mazda had big problems producing a decent rectifier, odd really as its a basic valve to make. This prompted makers that were signed to Mazda to seek a reliable valve from another source...The screen can be cleaned from the front by sliding out the bottom strip and removing screws.
Well that's all I can recall. I'll probably be shot down in flames when you discover a fault I have never had.......

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Old 19th Apr 2018, 9:36 pm   #66
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Hi again John, I have double checked the connections of my capacitor replacements and everything seems to be in order. So judging by your notes the problem may lie with either the line linearity coil or the 1000pF caps on the if strip?

I'm quite disadvantaged at the fact that I have no test gear except a simple multimeter.
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Old 20th Apr 2018, 7:58 am   #67
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

The line lin coil is the next thing to check, its not always obvious that's its slipped down. I tend to use a hairdryer to heat the coil then slide it back up, usually about 1/2 inch. Don't forget to tape it in position or it will just go back again.
Leave the IF strip until the timebases are sorted, use the test John described shorting the crt cathode to grid to show first light.
One they are done then move onto the IF strip which can be trickier, capacitors must be done one at a time observing the changes each time. (this is only needed if there are brown crunchy hunts capacitors fitted, there could be a few standard wax paper in the sound side) picture would help deicide.
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Old 20th Apr 2018, 11:29 am   #68
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Good advice there from Stephen. I would tend to get a controllable raster before tackling the IF circuits.

You need to get the EHT working close to spec together with a reasonably shaped raster. Once you have done this the CRT display will give away it's secrets and the displayed results will lead you to a systematic fault tracing method.

This series of Ekco models usually give some sort of glimmer on the screen even when the circuits are well out of line due to faulty components. If the line lin coil has slipped down it's former and shorted to chassis the U191 anode will glow a dull red. I think the lack/weak EHT is a simple one yet to be discovered. John.
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Old 20th Apr 2018, 6:45 pm   #69
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

I've had a look at the linearity coil and it hasn't slipped down, I still slid it up a little precisely in the centre just to be sure but continuity tests confirm it isn't shorting. The coil was surrounded by what I think is beeswax but it basically crumbled away so I left it off. It was a bit too fiddly for my massive fingers to secure it with tape so I put a tiny dab of the infamous hot glue to secure it.

I did notice a loose wire connected to R92 although it looks more like a thin strand of wire with some tubing over it compared to a proper wire.

I also tried shorting the cathode and grid on the CRT but of course nothing happens because, well, the EHT rectifier is still not lighting!

Peter
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Old 20th Apr 2018, 6:56 pm   #70
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Check to see if you have line drive on the grid of the 30P4, it should be about -25 to -35
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Old 20th Apr 2018, 7:05 pm   #71
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Hi Stephen, I actually checked that before and was getting around -23V

Peter
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Old 20th Apr 2018, 7:14 pm   #72
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Starting to look like the line output transformer might be no good.
Can you draw a spark from the top cap of the 30P4.
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Old 20th Apr 2018, 7:18 pm   #73
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Would I do that by putting one end of a clip over the top cap and holding the other end just above the metal chassis?
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Old 20th Apr 2018, 7:26 pm   #74
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

I attach a clip to the chassis then touch other end on valve cap
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Old 20th Apr 2018, 7:42 pm   #75
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

..in fact if the line stage is working, all you need to do is hold an insulated screwdriver just above the top-cap of the 30P4...you should be able to see a small spark.
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Old 20th Apr 2018, 7:51 pm   #76
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Oh it's sparking alright

Take a look
https://youtu.be/pDnab9pR6-E
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Old 20th Apr 2018, 9:51 pm   #77
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

This is odd. Are you sure the top of the line output transformer case has not become conductive? Is there a sweet slightly sickly smell around the line output area? Check carefully around the U26 anode connection for discoloration of the 'plastic' material.

Remove the U26 and check for EHT at the anode connection by holding a plastic insulated screwdriver very close to the anode connection on the LOPT case. Do not short it to chassis!

A spark about a 1/4" should be easily drawn to the blade.

I suspect either a shorted or otherwise faulty EHT rectifier U26. A conductive transformer case. [Top section] or very unlikely a rotten EHT rectifier socket or internal heater dropper resistor. [A short length of resistance wire] These faults only if a healthy spark can be obtained from the anode connection of the transformer.
A few pictures will help greatly. John.
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Old 20th Apr 2018, 10:36 pm   #78
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

The anode connection on the transformer case looks normal to me, you can be the judge of that with the photo though.

I gave it a good sniffing over and can't smell anything out of the blue except that 1950s electronics smell that's present throughout the entire set!...Or should I be sniffing it when it's on?

I tried using the other U26 valve I have which is also brand new and boxed and still no difference. I think the probability of them both being faulty is out of the question.

Before I do the EHT anode test can I just confirm that I'll just hold a plain old plastic handled screwdriver with nothing connected to it? Having one hand behind my back won't be a bad idea either.
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Old 20th Apr 2018, 10:40 pm   #79
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Here's one of the whole area the valve sits.
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Old 20th Apr 2018, 10:46 pm   #80
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Quote:
Originally Posted by Vakito227 View Post
Oh it's sparking alright

Take a look
https://youtu.be/pDnab9pR6-E
Hi Peter,
By the look of your video, you have taken a wire from the top cap of the 30P4 and are shorting it direct to chassis?
All you are doing is directly shorting the HT from the anode of the valve to ground via the line output transformer and efficiency diode which is very unkind to both of them!!
What you are trying to test for is RF energy at the anode of the valve. As Sideband said earlier, you take an INSULATED screwdriver and hold it a few mm away from the top cap. If sufficient RF energy is there, you will see a fat, sizzling spark continuously. Don't short it to chassis or connect the screwdriver to anything else. Also don't touch the top cap with your fingers!
I suspect, however, you will see nothing at all as I still don't think there is much energy being transferred to the LOPT.

By following the circuit diagram, carefully check all the wiring & connections between the LOPT, width coils & line scan coils. Also check the continuity of all these items.

Cheers
Nick
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