Oops, missed a vital word. I'm sure there is nothing on the timebase that could cause.....
John.
When I read about the lost frame, I dismissed the idea that a wire could have broken off.... that would be too simple wouldn't it. 🤢
Just goes to show how the mind can leap into the technical abyss and miss the simple things.
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![20210517 211119[1]](https://www.radios-tv.co.uk/wp-content/uploads/wpforo/attachments/884/9012-202105172111191.jpg "20210517 211119[1]")
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OK back to where I was about four hours ago, time to map the vision IF transistors
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Well I was about to map the transistors, however when I touched the probe to TR2142 base the screen lights up with snow and audio and buzzing, take the probe off, and it returns to a blank raster. Nothing to tune but thought it might be a clue. Anyway map time.
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Coupling via the scope probe makes it come to life !
Interesting that, because it could rule out anything after that stage.
To understand the black art of electronics is to understand witchcraft. Andrew.
| Transistor | Function | Emitter | Base | Collector |
| TR2140 | ||||
| TR2141 | ||||
| TR2142 | 1st Vision IF | 4.7V | 5.5V | 12.1V |
| TR2143 | 2nd Vision IF | 4.7V | 5.5V | 12.3V |
| TR2144 | Lum Phase Splitter | 588mV | 37mV | 16.5V |
| TR2145 | Lum agc amp | 34mV | 1.2V | 13.5 |
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Transistor Function Emitter Base Collector TR2145 Lum agc amp 34mV 1.2V 13.5
Hang on a minute... how have you got over a volt between base and emitter, yet the transistor appears to be off?
Does not compute; remember, a silicon transistor normally only has 6-700mV between base and emitter to turn it fully on.
I say "test it"...
Transistor tested OK replaced just in case, same readings
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That is doing this simple soul's nut in.
Glad you too, as my misery loves company, I'm at my wits end with this bloody TV.
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So you're getting noise if you probe T2143 base, what about at T2142 base?
John.
So you're getting noise if you probe T2143 base
No I said when I probe TR2142 base
when I touched the probe to TR2142 base the screen lights up with snow and audio and buzzing, take the probe off, and it returns to a blank raster
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If I touch the meter probe to TR2143 base the same thing happens but at a lower level compared to TR2142 base
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Well it sounds like there is IF activity, tuner or it's supply?
John.
Still using the 3k its got 12V
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Just speculation, but let's say it is oscillating and by touching the probe it decouples... is that a train of thought worth investigating?
To understand the black art of electronics is to understand witchcraft. Andrew.
I'll try the G6's tuner
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Its back and we're on the G6 tuner. What's confusing is there's no snow in between tuning on the band. Screen is still an unlocked mess.
![20210517 224308[1]](https://www.radios-tv.co.uk/wp-content/uploads/wpforo/attachments/884/9013-202105172243081.jpg "20210517 224308[1]")
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OK, this was the best I could get, then all of a sudden a whoosing sound, EHT goes down to 5K and the ISO/TX started humming like a mad thing. Powered off quickly. Either the transformers gone or the Tripler, the transformer looks OK so my money is on it killed the Universal tripler.
I think I'm at the point with this TV now, after almost 5 months, It just isn't worth the hassle, got really close though, almost a resurrection.
![20210517 225025[1]](https://www.radios-tv.co.uk/wp-content/uploads/wpforo/attachments/884/9014-202105172250251.jpg "20210517 225025[1]")
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