Hi all,
I have just picked up a faulty CUB monitor which I am hoping to repair. It was suffering from vertical collapse, so I downloaded the schematics and found one of the capacitors to be a likely cause. I took this out and tested it and yes it was dead. At this point I found this is a fairly common fault and quite often takes the resistor with it so I checked that and yes it was dead also.
At this point I was feeling fairly confident, so replaced the capacitor, and put a standard resistor in as a test as I don't have any fusible ones here.
Powered it up and got full vertical deflection so started a little mini celebration![:D]( "Very Happy")
Next I wanted to test the image, so connected it up to my BBC. At this point I got a sort of very squiggly image for a couple of seconds and then my resistor let out the magic smoke so I immediately powered it off.
I took it back over to my bench replaced the resistor and powered it back on with nothing connected and immediately the resistor gave way again.
With the resistor removed, the set works fine but with no vertical deflection as would be expected.
So I assumed a short somewhere on that part of the circuit. So I made a list of all the resistors and capacitors. I then went through and tested all the capacitors on that part of the circuit by removing them from the board and testing. Each one tested fine. I tested a whole bunch of resistors too but I need to go back and check them again if anyone thinks one of them could be the issue.
At the moment I am wondering if there is something wrong with the TDA1170 as that is the only part I can't test easily. But I don't know what symptoms they can cause on failure.
Has anyone had a similar issue with these monitors? Any ideas on what other parts I could test? Could any other part of the monitor cause high current draw on the vertical deflection circuit or is it pretty much isolated?
Any help would be greatly appreciated.
Thanks, Matt.
I have just picked up a faulty CUB monitor which I am hoping to repair. It was suffering from vertical collapse, so I downloaded the schematics and found one of the capacitors to be a likely cause. I took this out and tested it and yes it was dead. At this point I found this is a fairly common fault and quite often takes the resistor with it so I checked that and yes it was dead also.
At this point I was feeling fairly confident, so replaced the capacitor, and put a standard resistor in as a test as I don't have any fusible ones here.
Powered it up and got full vertical deflection so started a little mini celebration
Next I wanted to test the image, so connected it up to my BBC. At this point I got a sort of very squiggly image for a couple of seconds and then my resistor let out the magic smoke so I immediately powered it off.
I took it back over to my bench replaced the resistor and powered it back on with nothing connected and immediately the resistor gave way again.
With the resistor removed, the set works fine but with no vertical deflection as would be expected.
So I assumed a short somewhere on that part of the circuit. So I made a list of all the resistors and capacitors. I then went through and tested all the capacitors on that part of the circuit by removing them from the board and testing. Each one tested fine. I tested a whole bunch of resistors too but I need to go back and check them again if anyone thinks one of them could be the issue.
At the moment I am wondering if there is something wrong with the TDA1170 as that is the only part I can't test easily. But I don't know what symptoms they can cause on failure.
Has anyone had a similar issue with these monitors? Any ideas on what other parts I could test? Could any other part of the monitor cause high current draw on the vertical deflection circuit or is it pretty much isolated?
Any help would be greatly appreciated.
Thanks, Matt.
Statistics: Posted by Croccy22 — Wed Apr 23, 2025 6:58 pm