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Old 22nd Feb 2024, 2:36 pm   #1
SpaffyJ
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Default Philips Discoverer - Distorted Image/ misaligned image

Hi everyone,

I have an issue with my crt, there is a green line running through the display and when I boot up a console it looks distorted along the same line and misaligned.

I've seen on another closed thread here that the problem could be due to a crack on the GR 1 chassis' PCB along the line output transformer which may have cut one or more of the copper tracks...

But to be honest I have no idea what I'm looking at and don't want to take it apart without some sort of informed help. I am friends with a decent solderer and can likely get it fixed if that is the issue but guidance would be very welcome!

Thanks
SpaffyJ
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Old 22nd Feb 2024, 5:44 pm   #2
slidertogrid
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Default Re: Philips Discoverer - Distorted Image/ misaligned image

Hi Welcome to the forum! You may find that you don't have a fault just that the TV is not 'liking' the signal from the console. In the first instance try tuning it into another signal source if you can. A VCR with RF out would be ideal. Not many Freeview or DVD players have RF out, just passthrough of aerial signal.

Without getting too technical it may be that a slight adjustment to the Line hold control will lock the picture I have found this on some sets. They are OK on a signal but need a small 'tweak' on a games console.

The line hold control will be a small somewhat delicate pre-set control and if it is not labelled Line hold look for a symbol of a screen with leaning TV letters within it.
Be very careful with the back off as high voltages are present and the neck of the CRT is very thin and vulnerable when the back is off.
There are a couple of capacitors that cause hold and Sync problems on this chassis. C2523 and C2501 according the the GR1 fault guide but try the other suggestions first.
Good luck !
Rich.

Edit: The line hold control (Philips call it Horz freq)is R3049 and should be located somewhere near the Chip/IC TDA8305
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Last edited by slidertogrid; 22nd Feb 2024 at 5:57 pm. Reason: added info
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Old 23rd Feb 2024, 2:21 pm   #3
Maarten
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Default Re: Philips Discoverer - Distorted Image/ misaligned image

On a hunch, are you trying to feed an NTSC signal into the TV?

However there might be a problem without signal as well, pointing to another problem. I don't see a green line. Do you mean the darker slightly off to the left vertical column?

It could be a problem with a distorted sandcastle signal. I don't have the schematic handy right now.
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Old 23rd Feb 2024, 3:47 pm   #4
marceljack
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Default Re: Philips Discoverer - Distorted Image/ misaligned image

Quote:
Originally Posted by Maarten View Post
I don't see a green line.
Yes, there is one very fine green vertical line on the third picture (like it happens on LCD screens when some vertical driver transistor is always on).
But this is a CRT, so it cannot be a problem of the display, it's probably a synchronous disturbance of the signal.
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Old 23rd Feb 2024, 3:51 pm   #5
Maarten
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Default Re: Philips Discoverer - Distorted Image/ misaligned image

I see it now. In the same place as the dark bar in the noise picture. Very strange. It's perfectly timed horizontally, hence my idea that the sandcastle pulse might be disturbed somehow. I've seen black vertical lines come from a feedback resistor from the horizontal circuit that had gone open.
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Old 23rd Feb 2024, 8:52 pm   #6
Bobdger
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Default Re: Philips Discoverer - Distorted Image/ misaligned image

Is the set in search mode,green line which goes across the screen as the tuner searches for new channels. Bob
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Old 23rd Feb 2024, 9:12 pm   #7
marceljack
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Default Re: Philips Discoverer - Distorted Image/ misaligned image

Quote:
Originally Posted by Bobdger View Post
Is the set in search mode,green line which goes across the screen as the tuner searches for new channels. Bob
Is it not the so-called "ligne magique" (magic line) which was present on some La Radiotechnique (Philips France) TVs of the 70s ?
This line appeared when the drawer of the preset potmeters was open and it was used as a tuning indicator: in order to obtain optimal tuning the line had to be as far right as possible.
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Old 23rd Feb 2024, 10:42 pm   #8
Maarten
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Default Re: Philips Discoverer - Distorted Image/ misaligned image

I seem to remember that the GR1-AX already had a more advanced on screen display. Though given that the line is green, it could be some problem with the microncontroller putting out some strange signal on the blanking and OSD outputs.
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