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Microvitec CUB showing horizontal line. Repairable?

Posted: Thu Mar 07, 2019 2:34 pm
by VectorEyes
Hi all,

I've got a Microvitec Cub which is externally in great condition, but shows only a single horizontal line in the middle of the screen. As I type (from a Beeb I have plugged in via RGB cable) I can see the brightness of parts of the line change as the letters appear, so it's clearly receiving the signal but not able to move the electron beam vertically away from the centre.

Is this something that can be 'easily' fixed, either by myself or perhaps at an ABUG meet or similar event? If not perhaps I should just sell it on for parts.

Re: Microvitec CUB showing horizontal line. Repairable?

Posted: Thu Mar 07, 2019 2:41 pm
by 1024MAK
It is most likely a fairly straightforward repair, common faults are either the vertical output transistor has failed or the large electrolytic output capacitor has failed.

Of course, as with anything, it could be something simple like a dry solder joint, or worse, such as a failed chip or the power supply to the vertical output stage has failed.

Do you have any experience of working on and repairing electronic systems? Are you aware of the high voltages inside a CRT display? What test gear do you have?

Mark

Re: Microvitec CUB showing horizontal line. Repairable?

Posted: Thu Mar 07, 2019 3:37 pm
by VectorEyes
Thanks Mark, appreciate your reply.

Do you have any experience of working on and repairing electronic systems?

I've recapped a bunch of PSUs and soldered a few things together (pin headers onto Raspberry Pis, etc) but that's about it.

Are you aware of the high voltages inside a CRT display?

Yes, which is what makes me somewhat nervous about attempting any kind of CRT repair!

What test gear do you have?

A reasonable digital multimeter, a cheap soldering iron... No oscilloscope or anything like that.