Vectrex - No Sound or Picture but there is power.

About 3-4 years ago, my 1984-bought Vectrex ... uh ... bought it. Originally there was no sound or picture but the cathode bulb at the back of the CRT would glow. Now, it just sparks.

I'm not sure if this is an overvoltage issue or something more serious. I'm not that confident messing around with CRTs. I've checked the voltages going to the logic board and they all seem to be present, but a little off. For instance, I think it's something like 4.6v instead of 5v on one line at the logic board's power connector.

Anyone have any ideas as to what it might be and how to check it?

 

I would suggest not proceeding any further if you don't have an excellent knowledge of electronic principles and a background in television repair. You can receive a nasty, potentially fatal, whack if you don't know what you're doing.

Download the service manual and take it to a television engineer, or send it to a competent engineer familiar with the Vectrex.

Is the spark in the neck? It could be a cracked tube or a faulty LOPT. The television engineer would be able to diagnose.

 

What's a LOPT? Yeah, the spark is in the neck. I'm praying it's not a cracked tube. However, we have moved house quite a few times in recent years so there's every chance it got damaged in transit.

 

Yeah, take it to a TV repair shop! They'll have the equipment and knowledge to diagnose the fault. The line output transformer is what generates the high voltage needed by the CRT. There's also a 1,500V spark gap on the CRT.

A faulty LOPT could be equally terminal. I have a Vectrex sitting here waiting for a suitable donor to show up for certain parts... and there could be further issues once I replace them!

 

LOPT - line output transformer, also known as FBT - flyback transformer is a high voltage transformer which outputs several kilovolts - from 2-3kV for smaller (old car/battery powered TVs with very small screens or 80s-90s camcorder viewfinder CRTs) to 27kV for 20"+ tubes). If you don't know what you're doing, it's better not to mess with these - in rare cases jolt from those can stop your heart.