I am now Annoyed [Re: Old oscilloscope help: ideas sought]

On 7/5/2006 at 4:10 AM der Mouse wrote: It sounds as if your assessment is correct. :( Since gas reference tubes like the OB2 do best when the supply voltage is substantially higer than the operating voltage of the tube, I'd say that the winding on the plates of the 5Y3 are probably more like 150-0-150 VRMS. So, across the plates you should see almost 300V RMS (or its scaled equivalent with your transformer-lamp setup). Your next logical step is to disconnect and remove the transformer. Rather than unsoldering it, I'm going to assume that this is like most old equipment and there's some slack in the leads. In order not to put too much strain on the sockets and components, I'd recommend that you clip the leads perhaps a half-inch away from their ends, tagging the "stubs" so you can see where the wires connect when it comes time to connect up a replacement. There is a very very slim chance that one of the lead wires has had its insulation degraded to the point that it's contacting the shell of the transformer and shorting things out. So after you get the transformer out of the scope, you may want to open it up (if it's a "clamshell") type and have a look. Make one final test on the liberated transformer and then go look for a replacement. Cheers, Chuck