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Old 16th Jul 2010, 12:09 pm   #121
oldticktock
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Default Re: GEC BT1156 First Light & Vidor CN4216

Ok

having a thick moment, I cannot find R89, I'm so hoping it's not in the sealed tuner unit. Ah ha hidden blighter emerges from behind card
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Old 16th Jul 2010, 1:22 pm   #122
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Default Re: GEC BT1156 First Light & Vidor CN4216

I have height control

Still some issues though, the squiggle on the top is there, I guess that will go with time like last night we shall see.

I have taken photos of the rheo travel

1st pic is removed R90
2nd pic is new R90 hard wired in , quite happy with that
3rd pic is at min setting (when I had the Squiggle)
4th pic is mid setting (as it is now)
5th pic is max setting (when I had the Squiggle)


I cannot explain this to well so here goes.

It's almost like when you advance past the middle optimum point it's sort of like the top most section folds on itself and the circle extends at the bottom


Edit:
The top squiggle has now gone
A1 volts 318V
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Old 16th Jul 2010, 1:35 pm   #123
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Default Re: GEC BT1156 First Light & Vidor CN4216

latest, I guess the reduced EHT & HT are responsible for the rest.
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Old 16th Jul 2010, 1:44 pm   #124
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Default Re: GEC BT1156 First Light & Vidor CN4216

Measure the HT rails and compare with the diagram. Are they low?

Try replacing V12 and look at R89. Measure the voltages on the valves and compare them with the sheet.

Cheers,

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Old 16th Jul 2010, 1:48 pm   #125
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Default Re: GEC BT1156 First Light & Vidor CN4216

Hi Steve,

Boost should be 520V I have 390V
A1 should be around 400v I have 318V
EHT should be 13-14kV I have 8-9KV

At the begining of this set I measured the HT at the metal rectifier it was around 187V and should be 205V
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Old 16th Jul 2010, 1:54 pm   #126
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Default Re: GEC BT1156 First Light & Vidor CN4216

No spare 30P12's so swapped V13 to V12 and......................
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Old 16th Jul 2010, 2:08 pm   #127
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Default Re: GEC BT1156 First Light & Vidor CN4216

Oh good well you're almost there. The linearity is out somewhat - called Vertical Form on this set. Change C99, C101 and then try setting it up with the two controls. Might also be worth looking at R98.

Cheers,

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Old 16th Jul 2010, 2:14 pm   #128
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Default Re: GEC BT1156 First Light & Vidor CN4216

I will have a look at them but they are all new yellow 630V axials.

Can you explain something to me, How is this set is producing a picture with half the EHT missing I just measured it at 7.4kV it should be around 13-14kV. It's blown a way a myth I had that low EHT and as low as this, would result in no picture or very little in the way of picture.
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Old 16th Jul 2010, 2:25 pm   #129
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Default Re: GEC BT1156 First Light & Vidor CN4216

I've just made a correction up above. Should be R98.

I rarely even measure EHT. Mind you I am a coward...

But it does depend on the measuring equipment. EHT and A1 are derived from the line transformer which does not run at 50 or 100Hz, but 10.125 kHz. So the equipment may not measure it right.

Get the frame right and then we'll look at the HT as the width seems a bit low. Might be me - often it is.

There's a saying in some circles - your test equipment only misleads you when you believe it 100%

Cheers,

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Old 16th Jul 2010, 2:30 pm   #130
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Default Re: GEC BT1156 First Light & Vidor CN4216

OK, I did'nt know that, cheers

My EHT meter is a honking one though with an industrial probe, I've verified it with Malc Scotts both read the same.

I guess at this stage of my development I believe what they tell me
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Old 16th Jul 2010, 2:37 pm   #131
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Default Re: GEC BT1156 First Light & Vidor CN4216

R98 measures 70K, well within 20% caps are fine

can I ask are we trying to fill the entire screen? or sort out the vertical form I can try adjusting the vertical trimmer
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Old 16th Jul 2010, 2:44 pm   #132
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Default Re: GEC BT1156 First Light & Vidor CN4216

Use the trimmers - see if the top will come out. It seems to be folded in which is wrong.

Cheers,

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Old 16th Jul 2010, 2:52 pm   #133
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Default Re: GEC BT1156 First Light & Vidor CN4216

Ok two controls, I adjusted the vertical form R96 and the form height R97. This brought it all together.

It seems when the set get's first powered on the squiggle at the top cannot be removed by line hold, once it's warmed up a bit i can adjust it out.

Chris
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Old 16th Jul 2010, 2:59 pm   #134
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Default Re: GEC BT1156 First Light & Vidor CN4216

Looking good that. Now for the low HT. Have you changed the silicon diode, and can you put the HT side of the set up?

Cheers,

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Old 16th Jul 2010, 3:04 pm   #135
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Default Re: GEC BT1156 First Light & Vidor CN4216

I think I should probably do the IN4007 now

http://www.oldticktocks.co.uk/gecht.jpg
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Old 16th Jul 2010, 3:30 pm   #136
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Default Re: GEC BT1156 First Light & Vidor CN4216

In place of MR3. Check R137 and R138 aren't high. If they are, a 50 Ohm wirewound will do nicely in place of them both.

Cheers,

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Old 16th Jul 2010, 3:43 pm   #137
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Default Re: GEC BT1156 First Light & Vidor CN4216

Are you taking the photos in a mirror or are the line scan coils connected back to front ? and could this affect anything ?

Peter
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Old 16th Jul 2010, 3:55 pm   #138
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Default Re: GEC BT1156 First Light & Vidor CN4216

Righty O'

Looks like someone has been here before me again.......................

It will just take me a while to get my head around what someone has done with the added dropper plug-ins.

Edit:

I was waiting for someone to notice that and comment , yep mirror.
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Old 16th Jul 2010, 4:18 pm   #139
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Default Re: GEC BT1156 First Light & Vidor CN4216

Find and change the diode. I think you have the details for this. Then see what it's like for HT. If it's OK now then leave the resistors alone. Why do extra work you don't need to.

If it is still low, then trace the path back from the diode. If there is only one resistor, it should be 50 Ohms. (Well, 49 to be precise. 50 will do admirably.)

Might be worth cleaning the On/Off section of the switch too.

Peter : It's through a mirror, but it shouldn't really matter.

Cheers,

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Old 16th Jul 2010, 4:26 pm   #140
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Default Re: GEC BT1156 First Light & Vidor CN4216

I thought the only diodes were MR1 (GEX34) sound interference limiter & MR2 (GEX35) vision demodulator. Is MR3 HT Rectifier not a diode? am I going mad or are Metal rectifiers also known as diodes...... I bet i'm being dopey again
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