As a teenage hobbyist, I was delighted to acquire my first 'scope for free through a HAM friend (I also got a slightly odd PSU, an analogue meter and a transistor decade oscillator, but never mind those). Here it is running normally the day after I got it - the weird lines aren't the scope, that's my camera, since the waveform was rolling when I took the image.
Shortly after putting it into the cupboard with holes and ventilation in it that qualifies as a rack for me, the thing started acting up. The first time was when I was trying to trigger off a perfectly normal sine wave when testing an oscillator - as I adjusted the trigger level, there was a loud arc noise and for a split second, the trace jumped over to form a dot on the left side of the graticule. I promptly turned the scope off, but shortly afterwards had to leave the lab for the day and forgot entirely about what had happened. On switching the scope on again a couple of days later, without anything plugged in, it began to do the same thing again, getting faster, at which point I was pretty sure I was about to release the magic smoke and shut it off again. After being distracted from electronics for a month by a mixture of schoolwork and the horrific weather we have been having in the UK, I finally decided that I'd pop the cover on it today and see if any magic smoke was escaping - which brings me to the main part of this post.
On removing the cover from the scope (and being occasioned by an extremely inconveniently placed grounding wire!), I was greeted by this sight.
Firstly, just as an aside, the classic curved traces on the boards:
but, far more disconcertingly, this label:
and the insulator washers it refers to (both of those large caps have two, one on each leg). I decided to consult the forum for advice, as I am honestly not sure of the best way to approach beryllium oxide. Should I leave it be and just be extremely careful not to scratch or smash the insulators, or is it worth attempting to replace them with a modern alternative? I can provide further pictures if necessary, and I will resume trying to diagnose the scope once I've got this beryllia issue sorted out.