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Symphonic TV/VCR problems (potentially loose yoke)...

Nigel Goodwin

Super Moderator
Most Helpful Member
All 'modern' CRT sets, with the exception of Sony Trinitron use PIL (Precision In Line) tubes, and the scan coils are permanently bonded to the CRT neck, I've never seen a PIL tube where the scan coils came loose. Likewise, the CRT adjustments are permanently glued in place during manufacture, and so don't tend to come loose either.

By far the most likely reason is the posistor, a device that degausses the CRT every time it's turned on from cold. These usually consist of two thermistors, one PTC and one NTC, and a common fault is that one of them cracks in half, causing the CRT to become magnetised.

So you might need to replace the posistor - or it could even be a dry joint where the posistor is soldered in the board.
 

SatireOfComedy

New Member
All 'modern' CRT sets, with the exception of Sony Trinitron use PIL (Precision In Line) tubes, and the scan coils are permanently bonded to the CRT neck, I've never seen a PIL tube where the scan coils came loose. Likewise, the CRT adjustments are permanently glued in place during manufacture, and so don't tend to come loose either.

By far the most likely reason is the posistor, a device that degausses the CRT every time it's turned on from cold. These usually consist of two thermistors, one PTC and one NTC, and a common fault is that one of them cracks in half, causing the CRT to become magnetised.

So you might need to replace the posistor - or it could even be a dry joint where the posistor is soldered in the board.
Thank you, so it would be a huge waste of money to buy a degaussing coil when it’s an internal problem?
How much would it cost to have a professional do it, or should I do myself?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Thank you, so it would be a huge waste of money to buy a degaussing coil when it’s an internal problem?
If the posistor is cracked an external deguass 'may' cure, but probably only temporarily.

How much would it cost to have a professional do it, or should I do myself?
It's an easy part to change, if you can source one? - most CRT spares were binned years ago. It's only a ten minute job, so not too dear to have done professionally, again if you can find someone who has one.
 

Les Jones

Well-Known Member
Most Helpful Member
Just as a matter of interest CPC stock one type of posistor. I have only had to replace one so I don't know if there are many different types but I imagine there must be different types to suit 120 or 240 volt mains, This is a link to the one CPC stsock.

Les.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Just as a matter of interest CPC stock one type of posistor. I have only had to replace one so I don't know if there are many different types but I imagine there must be different types to suit 120 or 240 volt mains, This is a link to the one CPC stsock.
There were basically three types in Europe - two three pin types (both usually white), and one two pin (usually black) - at least those were the three we used to keep in stock.
 

unclejed613

Well-Known Member
Most Helpful Member
also, if you have stereo speakers on either side of the TV, move them further away from the TV, as speaker magnets can cause this.... but you probably do have a bad thermistor in addition to the speaker magnets being too close...
 

SatireOfComedy

New Member
also, if you have stereo speakers on either side of the TV, move them further away from the TV, as speaker magnets can cause this.... but you probably do have a bad thermistor in addition to the speaker magnets being too close...
Wait so now it is the thermistor?
 

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