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Old 13th May 2018, 9:51 am   #181
Freya
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Just to highlight the possible differences with analogue and digital measuring of resistors, this is a 300k measured bang on with the fluke digital. The Analogue Taylor 131 has been accurately set.
Yes, the orange band looks very brown and threw me for a second thinking it was 100k
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Old 13th May 2018, 5:57 pm   #182
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Took a good hour but here are the timebase resistor readings. Most of them are way out of tolerance and will probably need replacing.

I also managed to find someone a few miles from me who has some NOS 6D2 valves so I'll go pick them up tomorrow after work.

Peter
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Old 13th May 2018, 7:10 pm   #183
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Have you replaced C107?
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Old 13th May 2018, 7:18 pm   #184
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Aye
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Old 13th May 2018, 7:36 pm   #185
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Hi .

I would change R112 first, rather than blanket change the other resistors. Yes, they are out of tolerance, but not quite so critical. Out of interest, have you checked the 1k hold control, too?


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Old 13th May 2018, 8:21 pm   #186
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Quote:
Originally Posted by thermionic View Post
I would change R112 first, rather than blanket change the other resistors. Yes, they are out of tolerance, but not quite so critical.
Absolutely agree with that! R112 has to be the first one to change. It is the most critical and will have the most effect. Most of the others will not have so much/any effect.

If C117 and C118 (both 0.002uF) are paper or moldseal types then they should also be changed. Why?, because they are in the feedback circuit to the 6D2 flywheel discriminator diodes.
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Old 13th May 2018, 8:32 pm   #187
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

It's a long time since I worked on these old flywheel sync jobs, I'm wondering if the line osc would normally run at the correct speed if the grid of the DC amplifier was shorted to chassis, might help to break any chicken or egg wonderings.

Lawrence.
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Old 13th May 2018, 8:34 pm   #188
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Last time I tried that (with an Ultra) the oscillator ran at a very low speed and the LOP valve was very unhappy!
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Old 13th May 2018, 8:35 pm   #189
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

That's that then.

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Old 13th May 2018, 10:53 pm   #190
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

It's alright I've ordered replacements for all the resistors with modern 1% tol ones cause they're cheap as chips and it'll be handy to have them on stock if anything happens in the future, I'll do what you said though and just replace R112 initially and see what happens.

I've also ordered replacements for C117 and C118.

Quote:
Originally Posted by thermionic View Post
Out of interest, have you checked the 1k hold control, too?
VR5 was a bit all over the place when I first measured it but a few squirts of contact cleaner and it's behaving like new, thought I gave all the pots a good cleaning when I replaced the caps a month ago but obviously not!

Don't know if I mentioned it before but the corona ring around V13 has gone so that's good news

Peter
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Old 14th May 2018, 7:39 am   #191
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Of course you probably realise that you don't need 1% resistors for any valve equipment. Most manufacturers used 20% where they could (which was in most places) and 10% in other. 5% types were pretty rare.

With the exception of R112, most of the other resistors are within 10 - 20% of their nominal value and even if they are slightly out, they are not sufficiently out to cause major/any problems. You'll probably find that most of them are 20% (no tolerance band) with a few 10% (silver band).
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Old 15th May 2018, 5:06 pm   #192
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Big thanks to Freya for supplying replacement 300K resistors, unfortunately it doesn't seem to have made much difference to the picture, it has however created an unwanted side effect of having the horizontal hold suddenly go out of focus without me even touching it causing me to have to reset it, you can also hear the pitch of the LOPT change when this happens, completely unsure why this is happening.

Peter
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Old 15th May 2018, 5:47 pm   #193
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Sounds like a component is breaking down further, can you post a picture of the components around the line oscillator, especially C111 680pF that's usually ok.
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Old 15th May 2018, 6:20 pm   #194
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Here, the mica capacitors don't look like there's anything wrong with them although you may see different.

I tried replacing the 6D2 valve but it made no difference.

The rest of the resistors should be arriving tomorrow I guess the first thing to try then would be to replace R121 and R122 and possibly R103?
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Old 15th May 2018, 6:35 pm   #195
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

I spy Four capacitors that still need changing in picture 3, not had a look to see what they are for yet though.
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Old 15th May 2018, 6:39 pm   #196
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

haha That waxxy TCC and 350DC70C have been ""skillfully"" restuffed when I did the other capacitors but yes the other 2 do need doing and I have the replacements on the table right next to me!

Peter
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Old 15th May 2018, 6:43 pm   #197
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Sneaky , I like your style.

Edit,

that Hunts 0.002uf C117and C118 is part of the flywheel sync and if even partially short will be the cause of your problem.
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Old 15th May 2018, 6:44 pm   #198
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

What is that nasty-looking 500V silver cap (looks like a polarised 'metalmite'). 2nd picture shows it top right, 3rd picture shows it centre right. They are polarised in the sense that the outer foil is marked negative and the inner foil is marked positive. Basically they are just paper caps but some circuits take advantage of the fact that when the outer foil is at chassis potential and it forms a screen around the inner foil reducing hum. Just replace it with an ordinary polyester.

They are well past their prime by now.
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Old 15th May 2018, 6:52 pm   #199
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

One of those must be C105 which could definitely cause trouble.
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Old 15th May 2018, 7:07 pm   #200
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Default Re: First TV Project - Ekco TCG316 - Any Advice Appreciated

Well I replaced those 2 caps with 0.0022 630V poly caps and what a difference! It's still not perfect but as Lennon would say, it's getting better all the time.
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