That didn't just happen, did my oscilloscope die!?!? How??? Repairable???? Answered
I went to my workbench today to discover that my BK Precision 30MHz analog scope has stopped working. Symptoms:
❶ Still shows a trace
❷ The trace does draw across the screen*
❸ The horizontal time base seems to work
❹ 10x horizontal magnification seems to work
❻ XY mode only draws in the X direction
❼ Waveforms do not show up, for either chA or chB
❽ Triggering seems to work (it causes the trace to draw more/less frequently. No vertical deflection)
❾ Vertical controls for both channels have stopped working
❿ Dual trace shows only one trace
⓫ I have not been able to do anything to make the trace move up and down, vertical deflection is definitely shot.
⓬ * When changing the timebase, I noticed that the length of the trace horizontally gets shorter, and when a signal is present, or the vertical position for the appropriate channel is twiddled, it becomes the right length, within certain ranges.
⓭ When I was reaching for a powerstrip to turn off power to the lab the previous night, I heard a loud buzz, similar to that of the degaussing on a old computer monitor, but louder. no sparks or anything were visible as I recall. scared the crap outta-me, and I could not figure out what had happened. First thought was that maybe somewhere there was a live mains exposed somewhere that had shorted to ground or neutral. That was quickly dismissed since nothing was exposed like that, and also it would have popped the circuit breaker, and instead would have sounded like a firecracker. This sounded more like a small transformer failing. Also the same day, I have been messing with a tesla coil circuit (my beefed up slayer exciter) and the probes were sitting here by not connected picking up interference. They were in 10X mode, I do not remember the volts per division, however. I do recall a trace being shown on the display the previous day.
With these symptoms, I think the issue has to do with the vertical control on the CRT, and perhaps another, separate issue with the horizontal time base control, or possibly triggering. I think I might do a teardown on it to see if there is anything obvious that has failed, such as a charred coil. Then I will need to figure out what had caused the issue.
It is obviously something gone horribly, horribly wrong with vertical deflection or something of the like. I will have a look at the schematic and see what I can learn about the operation of the scope. I am glad I do have the user manual and schematics, so it should be straightforward, it is a nearly 100% BJT design.
The scope was used and old, and lacked a lot of features, such as cursors and frequincy counters. Perhaps it is time for a digital upgrade anyway...