How to distinguish a failing CRT from other faulty components?

Thread Starter

Tom Vaughan-Mountford

Joined Dec 2, 2016
2
Hi everyone - first time newbie here! I've had an interest in electronics since I was a kid, but broke more stuff than I fixed. Now trying to make my interest of practical use...

I've acquired a broadcast video monitor, probably 30-35 years old, and I'd like to have a bash at tracing the fault and trying to repair it. However, the symptoms it's displaying, and it's age, make me think it has a failing CRT - and there's no way in hell I'm ever going to get it running again. I'm figuring it's either the tube that's about to fail, or a (potentially replaceable) component elsewhere. Check the video of the raster I put on YouTube, and let me know if I'd be better just scrapping this and finding a new project. Thanks.

 

AlbertHall

Joined Jun 4, 2014
10,231
The main failing of a CRT is gradually diminishing brightness but this one seems to be OK on that front.
The pulsing looks like a beat between the between the frame frequency and the mains. Check the ripple on the main PSU and if it is high then the smoothing capacitors will be low value and in need of replacement.
 

Thread Starter

Tom Vaughan-Mountford

Joined Dec 2, 2016
2
The main failing of a CRT is gradually diminishing brightness but this one seems to be OK on that front.
The pulsing looks like a beat between the between the frame frequency and the mains. Check the ripple on the main PSU and if it is high then the smoothing capacitors will be low value and in need of replacement.
Thanks so much Albert, that's a great steer! I'm also quite pleased that (even with my very limited knowledge) I'd put failing caps high on my list.
 
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