Tek RM17 repair updateOnly problem left is the trace moving up and down a bit. With now zero filtering on the voltage divider, plus crappy caps decoupling that pre-amp supply... no wonder. So I will replace these x3 10uF caps and I guess it should get rid of that problem !
OK so I did just that. Cobbled together a replacement C146 A/B/C 3 section cap, see how beautiful it is ? You are all jealous of my artistic talent, I know, I know...
Just looked at my stock of SMPS / 400V caps, found a few 10uF , spot on the value of the old caps, fantastic.
Here is a little video I made of what the calibrator signal looked like on the 10/20/50mV ranges, i.e when using the pre-amp.
trace randomly moves a bit up and down, plus regularly it gets wild and gets all scratchy/super noisy, as if there was a bad switch contact somewhere.
Also, big spikes on the trailing edges !
And of course the amplitude problem... but that has now been solved as we have seen.
Just in case, I put a plastic box no top of the caps.. safety first ! Then I power the scope up and... no explosion, good start. 10 seconds later... no smoke.... even better. 30 seconds later... a trace on the scope.... ohhhhhh.... 100% fixed ! No spikes anymore no the leading edges, zero vertical movement, zero scratchiness... just a nice rock solid, super stable, clean sharp square wave ! I like that a lot !
Just goes to show that even these 60+ year old antiques can still do great things... I can't get enough of the joy it brings me to see such an old scope display such small signal so cleanly, so sharply, so rock solid... it's not a toy, it's a proper piece of TE
So I think that's about wraps it up for this scope ! All fixed. Just need to order decent new caps and tidy up this hack, the button it up !
I can now resume work on the Rochar Nixie DMM