Re: TDS754D CRT

 

Hello,

On late CRT TVs there was also cathode current measurement that could delay
the time to bring a picture up when the CRT was worn (Philips).

For whining sounds poke around with a chopstick at any ferrite core, the
most common cause is a loose core. Bad capacitors can be a cause too, not
limited to electrolytics.

Measuring ripple across electrolytics should give you a clue before
actually replacing them.
Beware of electrolytics in the flyback primary drive path.

Often a failing flyback will come with other symptoms: Heat, smells,
blooming picture or measurable oscillations on at least one winding.

Does this scope use the same CRT driver board as the TDS 544?

Paul



Le jeudi 5 janvier 2017, david.wilson92@... [TekScopes] <
TekScopes@...> a écrit :

I am debating with myself and I think I need your help.

This concerns the CRT and driver board. I'm about to removing this part
for inspection. Looking down from the top I don't notice anything broken or
burnt visually.

I read that a high pitch sound coming from the fly back transformer is a
indication that it is failing. I read that a dim crt usually means it is
getting tired, though sometimes it might be the driver board typically it
is the crt.

I read on a crt tv forum that a delay before a picture should already come
in is a indicator of a dried / bad capacitor. Recapping the board might fix
the delay before picture but it might not fix the wining sound or dim
picture I seem to have. When I recapped the TDS380 the picture was
noticeably sharper.

Since the display still works I could go ahead and recap it and get what I
can out of it. Maybe finding a decent CRT is really all I need to get
things going like new again. Maybe, don't know about the flyback.

Picture is stable by the way. Noticing no wobble or jitter.

So what is your take on the fly back transformer? Should I recap the board?

Thanks

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Posted by: david.wilson92@... <javascript:;>
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