That was the moment when the internal (high voltage) fuse decided it had enough. then the sparks started to fly between the CRT 4.5kV cable itself (through its insulation!!!) and. Using insulating liquid ('liquid insulating tape'), I made sure to cover these tiny bits.

But they started to form between the legs of the high voltage ceramic (metal film?) caps! The legs were originally insulated in most parts by some sleeves, but there were tiny exposed lengths just at the PCB connections. This helped - at least to eliminate sparks going there. the high voltage enclosure lid, as well as some plastic shields here and there - I found one loose inside not in its place and I can't find where it belongs), I thought of simply shielding/insulating between the PCB and enclosure. Since there were already some parts missing when I bought it (e.g. There is a distance of about 8-10mm between the PCB and the enclosure. When I powered up the oscilloscope for the first time after assembling it, the CRT came alive!īut there was a lot of sparks going between the 4.5kV CRT cable mount (solder) on a high voltage PCB and the internal high voltage enclosure (grounded). While working on the Power Supply board, I also discovered an internal fuse, which was blown.

I also labelled all the cables with the source and destination connectors numbers for a future reference. I managed to connect everything correctly (or at least as it was before I took it apart) with the help of the photos I was taking before each step of the way. I replaced ALL the electrolytic caps throughout the oscilloscope (what the heck - they were only 30 or so ), as most of them were old and this is the first thing which normally gives up the ghost, I was told. After all, 'if people made it, people can fix it' The oscilloscope had a blown fuse and I was told that prior to that the CRT lit up for a short while and then the fuse blew. I simply can't afford to spend $400+ on a new or used piece. I purchased very cheaply old oscilloscope Aaron BS-635 (also known as the later rebranded Hung Chang OS-635). This is my first post here (sorry for the long one) and I am rather a newbie to electronics, so please be patient with me.Īs one of my first projects, I picked a quite difficult one.

Hung chang os635 how to use it