21-07-2020, 03:04 PM
(This post was last modified: 21-07-2020, 03:09 PM by ppppenguin.)
Rob has made a sensible decision to keep the Tek 935 and get rid of the older scopes. The 935 will do everything he needs to do with a scope and do it well too. I'd be perfectly happy with one for vintage radio and TV work. I have more advanced scopes because I'm doing professional design work. I sometimes look wistfully at the lovely Tek 547 with 1A4 plugin https://w140.com/tekwiki/wiki/547 that sits under my bench. Lovely instrument but almost never comes out to be used. Probably worth more stripped for valves (lots of ECC88) than as a scope. Would be sacrilege to do that.
As Mike has pointed out, the cathode(and grid) on most scopes is at a high -ve voltage. This is so the deflection plates can be at a sensible voltage, rather than a high +ve EHT. A few pre-war TVs with electrostatic tubes ran the deflection plates at +ve EHT so that the video could be coupled to the cathode or grid at a low voltage. It meant using 4 high voltage capacitors to couple the timebases to the deflection plates. OK in a TV with fixed timebase speeds, not OK in a scope.
Mike also mentioned adding a Y output socket. Some more sophisticated scopes such as Tek 24xx have a buffered Y2 output (Why Y2 and not Y1? I've no idea) . I often connect mine to a video monitor so I can see video that I'm probing. I lock the monitor to my lab SPG so there are no sync problems.
THose little bead tantalums can go bang with remarkable violence for their size. I've seen one hit the ceiling 6 feet above the bench.
As Mike has pointed out, the cathode(and grid) on most scopes is at a high -ve voltage. This is so the deflection plates can be at a sensible voltage, rather than a high +ve EHT. A few pre-war TVs with electrostatic tubes ran the deflection plates at +ve EHT so that the video could be coupled to the cathode or grid at a low voltage. It meant using 4 high voltage capacitors to couple the timebases to the deflection plates. OK in a TV with fixed timebase speeds, not OK in a scope.
Mike also mentioned adding a Y output socket. Some more sophisticated scopes such as Tek 24xx have a buffered Y2 output (Why Y2 and not Y1? I've no idea) . I often connect mine to a video monitor so I can see video that I'm probing. I lock the monitor to my lab SPG so there are no sync problems.
THose little bead tantalums can go bang with remarkable violence for their size. I've seen one hit the ceiling 6 feet above the bench.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
