27th Apr 2018, 3:18 pm | #121 |
Octode
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Most likely a capacitor letting go somewhere.
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27th Apr 2018, 9:51 pm | #122 |
Hexode
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Well I have ordered replacements for those 2 hunts caps as well as a new boost cap with a higher voltage rating
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27th Apr 2018, 10:51 pm | #123 | |
Octode
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Quote:
Have you measured the value of the 22 Ohm cathode resistor? Have you replaced the grid coupling cap (C105) to the 30P4? I still feel it would be worth trying a new 30P4, after all, the voltage readings would suggest it could be very low emission or faulty. At least it would eliminate that. Also the U191, although I don't think that is the problem but worth substituting just to prove the point. My best guess though is still something to do with the width, linearity or scan coils. I would thoroughly check the wiring and continuity of all these items. You may need to disconnect them to do that. I still at this stage do not think it's the LOPT!! Good luck and keep at it! Cheers Nick |
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27th Apr 2018, 11:00 pm | #124 |
Dekatron
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
1100 man wrote: "I still at this stage do not think it's the LOPT!!"
I've never replaced a line output transformer in these receivers because of winding failure. A PL36 can be used to replace the 30P4, the only modification is to remove the components anchored to pin 1. Pin 1 is an internal connection in the PL36. Is the line frequency correct? DFWB. Last edited by FERNSEH; 27th Apr 2018 at 11:07 pm. |
27th Apr 2018, 11:14 pm | #125 |
Hexode
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Hi, I'll see if I can get hold of a 30P4 and U191 valve. I'll get the 22ohm resistor and continuity of the coils measured tomorrow and I replaced C105 when I replaced the other higher value caps.
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1st May 2018, 9:20 pm | #126 |
Hexode
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Right, R101 is within tolerance, the continuity of the scan coils are fine as are the width and linearity coils although I can't 100% guarantee it since a simple multimeter can't detect a shorted coil...
I have replaced C92 and C103 and upgraded C98 to a 1000V cap but still V13 doesn't light. I'm waiting for replacements for V15 and V16 to arrive, should be here tomorrow - Peter |
3rd May 2018, 6:50 pm | #127 |
Hexode
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Newsflash! After replacing V15 and V16, The U26 is now lighting and the whine from the LOPT seems a lot louder which is a good sign.
Now the good news is out of the way, onto the bad news. Either the LOPT or the U26 are not behaving as it should, The video should explain it better than I can. https://youtu.be/Ze-Bh18yqQY During the test, the brightness control was turned down to the minimum and this was actually the second time powering it up, the first time there was a longer delay from the U26 lighting to the arcing being present. However I am now at the point where I have to discharge the CRT before handling it or the chassis so I got to be extra carefull from here on out. Feeling hopeful though. Oh and the modulator box is back from the french polishers and looks rather good! |
3rd May 2018, 7:07 pm | #128 |
Dekatron
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Try fitting the old heater winding back in it, the properties of its insulation will be better suited, centre it on the limb as well.
Lawrence. |
3rd May 2018, 7:34 pm | #129 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Reckon there's some EHT there now
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3rd May 2018, 7:48 pm | #130 |
Octode
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Hi Peter,
That looks much more sensible! Undoubtedly, the arcing is from the new heater winding which will be at EHT potential. As Lawrence said, putting the old one back may be the best way to go. The incorrect voltages were tending to indicate a low emission or faulty 30P4 but after the roasting the U191 had that may not have been so good either! Once you have sorted the arcing, re- measure the HT & Boost voltages. Also the screen voltage on the 30P4. The HT should have come down to about 200V due to the extra load and the screen should also be much lower. The boost should also have come up to 400V or so. Progress at last:- but you've a way to go yet! Cheers Nick |
3rd May 2018, 8:53 pm | #131 |
Hexode
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Well here it is, the first light! Picture tube looks very healthy.
Reusing the old winding did the trick - good thing I didn't chuck it away. However I did notice when switching it off that the screen flashed very bright for a split second. Is this normal or should I be concerned? Anyway I'll get the measurements taken soon Peter |
4th May 2018, 4:55 pm | #132 |
Hexode
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
HT Voltage = About 210VDC
Boost Voltage = About 400VDC PL36 Screen = About 140V There's a right ominous fizzing noise coming from what I think is the EHT rectifier, should this be happening? https://youtu.be/rQB_mWr5Jm8 Sounds worse in person than on camera Peter |
4th May 2018, 4:59 pm | #133 |
Dekatron
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Sounds like line rattle/whistle to me...magnetostriction. Try prodding various bits (LOP stage inductors) with a plastic knitting needle.
Lawrence. Last edited by ms660; 4th May 2018 at 5:27 pm. Reason: clarification |
4th May 2018, 10:18 pm | #134 |
Octode
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Hi Peter,
Voltages look much more sensible now- and the boost is pretty much spot on. Also looks like you have plenty of brightness on the CRT as well which is good. It does sound like EHT leakage to me (corona discharge) and is a very common problem. When you turn the brightness down, the EHT will rise, so the noise should get worse. Conversely, at full brightness, the EHT will drop and the noise should reduce. If indeed it is EHT leakage. The HT is still on the high side at 210V. It should be 195V. This will tend to give higher EHT which will make the problem worse. Out of interest, is the metal rectifier for the HT still in circuit or has it been replaced with a diode? All surfaces near anything at EHT potential need to be very clean- gunge tends to be conductive! The EHT cap on the tube is another common source of leakage and is worth cleaning. Sharp solder points also promote leakage. If it is as bad as it sounds, you should be able to see it in a darkened room. You will also get an ozone smell which is quite distinctive. Make sure before removing or touching the EHT cap or EHT rectifier after the set is switched off, that the CRT is discharged. If the set has been turned off with the brightness turned down, it will retain nearly full EHT charge. Even if a bright screen was displayed before switch off, enough charge will remain to give you a bit of a bite! Good progress though, Cheers Nick Last edited by 1100 man; 4th May 2018 at 10:22 pm. Reason: more text added |
4th May 2018, 11:00 pm | #135 |
Hexode
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Hi Nick, yes correct, the sound reduces the brighter you make the screen.
The circuit still has the original metal rectifier I have not replaced it. There is a corona ring around the inside of the U26 when operating what I'll do is give the area around the U26 a good cleaning with meths and cotton buds and try neaten up the soldering I did on the LOPT Peter |
5th May 2018, 7:27 am | #136 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Some good progress.
The raster is well off centre but is easily corrected with the shift adjustment on the focus assembly. You will have to watch that discharge carefully. If it is around the U26 anode anti corona cup it may well be an early sign that the LOPT case is breaking down. If it's just conductive muck your cleaning will solve the problem. Solder joints around the U26 need to be round and smooth, no 'spikes'. You need a signal to aid fault finding from now on. John. |
5th May 2018, 7:35 am | #137 |
Dekatron
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Anywhere there is EHT you need neat rounded solder joints particularly around the EHT rec.
Make sure the EHT is discharged (two large insulated screwdrivers was the common method...one blade under the EHT cap and another to short this to a convenient chassis point....be prepared for a sizeable crack as it discharges...). Remove the EHT cap and thoroughly clean with meths or similar and while it's off, check the condition of the contacts...clean it well. A smear of anti-corona grease is very effective or vaseline if you don't have anything else helps to keep the moisture out. Next clean the connector button on the CRT itself but make sure you discharge the button again....the CRT outer coating, the glass and the internal silvering form a very efficient capacitor and it will 'recover' some of it's charge so a quick discharge will ensure that is doesn't 'bite'. Some engineers would connect a shorting link from the button to chassis while working on it but I never found it necessary. Thoroughly clean the area around the button with meths or similar. Next I would remove the EHT rec and clean the area around the transformer where it sits and make sure any soldered connections were neat and rounded. A corona glow inside the EHT rec is not so unusual and is probably OK. You'll know if there is a problem with the valve....! Corona discharge was a very common problem back in 'the day' and was mainly caused by dampness or dust or a combination of both.
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5th May 2018, 9:44 am | #138 | |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Quote:
EDIT: Just plugged a speaker amp into the PC....can hear it now!....yes, EHT corona, dark room. Lawrence. |
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6th May 2018, 11:51 am | #139 | |
Hexode
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Quote:
I do have another problem though, I can't seem to adjust the width of the raster, the focus control and picture width control do nothing to change the width. The height control works no problem. Peter |
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6th May 2018, 1:29 pm | #140 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
The oscillators are free running and the frequency will impact the EHT voltage. You really need a picture before you can make further progress.
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