11th May 2018, 10:26 pm | #161 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Hi Peter, Well done for getting this far, I have been watching this with great interest. Thanks to forum members for helping bring this restoration to life. Norman
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11th May 2018, 11:08 pm | #162 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Hi Andy and Norman thanks for the words of encouragement, You were right about the aurora converter, absolute miracle piece of technology!
I'll look out for the oscillator tomorrow and see if I can improve the picture. Peter |
12th May 2018, 9:01 am | #163 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
The tube certainly looks good, it really helps in diagnosis to have a testcard on screen. Once you have the line timebase running at the correct speed, the remaining problems should be straightforward.
Mark |
12th May 2018, 1:02 pm | #164 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
What would be the problem with the line oscillator which I guess is V18 (6/30L2)?
Should I check the resistors around it have not gone high and see if C111 needs replacement? Peter |
12th May 2018, 1:56 pm | #165 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Well, done, won't be long before you're posting the perfect test card. Get your freeview box ready as well!!
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12th May 2018, 2:12 pm | #166 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Peter,
C111 is 680pF and almost certainly wont need replacement, C113,C114 which are wax paper do need to go. Also C107 which is a 16uF electrolytic is usually bad. Is the line hold at one end of its travel to get the picture you have at the moment. Also to check is R79 4.7k, R120 2.2M, R114 120K. These are a bit all over the place but have proved out of spec in sets I have looked at.
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Stephen _________"It`s only an old telly" ___ Last edited by Freya; 12th May 2018 at 2:26 pm. |
12th May 2018, 3:13 pm | #167 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Hi Stephen, I replaced C113 and C114 and C107 at the start so they should be fine. R120 and R114 measure fine although R79 is the Metrosil VDR for the EHT line which I'm told the set works perfectly without.
Peter |
12th May 2018, 4:07 pm | #168 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
First lets establish if the line is running at the wrong speed....does the line hold control operate OK? Freya asked if the line hold control was at the extreme end of its travel...is it? If not can you adjust the line speed OK? One thing at a time!
The pictures you posted earlier suggest that perhaps the picture is 'floating' across the screen...is it?
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12th May 2018, 4:09 pm | #169 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Another video clip with sound might help, with sound I mean no sound out of the loudspeaker but sound on the video so's the line whistle might be heard.
Lawrence. Last edited by ms660; 12th May 2018 at 4:19 pm. |
12th May 2018, 5:24 pm | #170 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Sorry about R97, I was transposing across sheets. Its should have been R103 4.7k
This will not affect the line speed issue though.
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Stephen _________"It`s only an old telly" ___ |
12th May 2018, 8:01 pm | #171 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
I guess I was running ahead a bit, Line hold works fine and yes it is turned hard right to get a suitable picture. The picture is static on the screen.
This should explain it better https://youtu.be/SIOwP0swIUI Peter |
12th May 2018, 8:16 pm | #172 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Yep, way to slow (low pitch whistle) might be worth checking the anode and cathode voltages on the DC amplifier and osc with the line hold control turned fully the other way (higher pitched whistle) and checking the components around there such as R119, R112 and any other suspects.
Lawrence. Last edited by ms660; 12th May 2018 at 8:43 pm. Reason: addition...another addition |
12th May 2018, 8:37 pm | #173 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
As a quick alternative, try swapping V10 and V18 over to see if the situation changes, I also suspect as Lawrence suggests that the issue is resistor based.
The two 220k resistors R121,R122 on V19 flywheel discriminator need to be reasonably matched also.
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Stephen _________"It`s only an old telly" ___ Last edited by Freya; 12th May 2018 at 8:43 pm. |
12th May 2018, 10:36 pm | #174 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
R103 measures 5.2K, slightly higher than it should be, not sure what you would say but I'd say it's alright.
R119 is spot on R112 measures higher than it should, it's harder to read the logarithmic scale on my multimeter but it looks like around 350-400K Here's the readings for V18 with horizontal hold turned hard left: anode 1 (pin 6) - 120V (causes screen to flicker when measuring) - Should be 115V cathode 1 (pin 8) - 0.8V - Should be 0 - 1.4V anode 2 (pin 1) - 40V - Should be 100V cathode 2 (pin 3) - 7.5V - 4.5V Looking like the problem lies in and around V18B R121 and R122 are correct and identical I swapped the 2 valves over and it did make a difference but not a good one! The image on the left is with the valves in their original positions and the horiz hold turned hard right. The image on the right is with the valves swapped and the horiz hold roughly in the middle (would not reproduce a signal in any other position) Interestingly someone somewhere down the line has put a red dot on top of V18, must have marked it out for something but not sure what Peter |
12th May 2018, 10:40 pm | #175 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Line whistle should be at 10.125khz. Yours is way too low and would account for the lack of width since the line output valve is not being driven correctly. As others have said, you need to check resistors in the line oscillator stage. You might need a new ECC804 (6/30L2). Easy to obtain one of these but I can let you have a new one for cost of postage.
I would suggest that R112 is probably critical....300K is not in the standard resistor range....270K or 330K would be 'standard'. Therefore if 300K has been used, it's probably a 5% (gold band) type which means that 350 - 400K is way off the mark. You can either order a 300K or if you have enough 270K or 330K resistors you can select from a batch to find one close the 5% required (300K + or - 15K).
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12th May 2018, 11:14 pm | #176 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
The flywheel diodes are in an EB91 double diode valve (V19)? Try swapping this with another EB91...if the diodes are unbalanced it will affect the line hold.....easy one to try first.
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13th May 2018, 7:55 am | #177 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
For some reason I have lots of 300k 1 watt 5% Piher resistors, happy to post a few.
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Stephen _________"It`s only an old telly" ___ |
13th May 2018, 8:39 am | #178 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
The reason I think that R112 may require further investigation is because many years ago I was having trouble with the line hold of a particular receiver (back in the early 70's but I can't remember the TV). There was a 91K 5% (another odd value) which had risen to 105K, being used which we didn't have. I used a 100K which actually measured 98K which I thought was 'near enough'. The line lock was right at one end and only just locking...in the end we bought a pack of 91K 5% from our local supplier....result? Perfect lock. Why some of these circuits are so critical I have no idea but there we have it. If that 300K is really measuring 350 - 400K then it could well be causing a problem. Manufacturers won't use 5% resistors unless they have to and it's likely that the 300K is a 5% type.
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13th May 2018, 9:16 am | #179 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
Switching V19 with another 6D2 causes the same effect as switching the 6/30L2's around, causes a darker, mirrored image when the horiz hold is around the middle.
Seems like the current valve configuration is the best I can get it at the moment. I did however order a NOS 6/30L2 yesterday so that will probably help. What I'm going to do is borrow my friend's digital multimeter today and take some more accurate readings of all the resistors around the timebase circuits. If R112 still measures bad then I'll be happy to buy some, Stephen. Peter |
13th May 2018, 9:33 am | #180 |
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Re: First TV Project - Ekco TCG316 - Any Advice Appreciated
That is a good move. A digital meter although not absolutely essential (we managed for years without them) will give a much better result than an 'approximation' which you are getting at the moment.
The new 6/30L2 may help as well. I have actually found EB91's (6D2) to be very good little valves and seldom give problems. However in a line flywheel circuit where more critical balancing of the diodes is desirable you may well find another valve here may work wonders.
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