SE Labs Scope Repair

[Nick]

I would just use 3 1N4007 diodes in series for each one.

SCM30s are not ordinary diodes like the 1N400x series - they are unidirectional transient suppression devices which have specific breakdown characteristics - replacing with a string of 1N4007s would not work and would be unsafe as they would do nothing.

You should be able to use the cheap & common 1.5KE-series TVS diodes - do you have the schematic of the HV section that we can see so that we can suggest an alternative?

This is also a 30V, NOT a 3KV, device, so the common 1.5KE30A device would be fine - 33p ex-VAT from Farnell - http://uk.farnell.com/stmicroelectronics...dp/9884963

EDIT: Need to qualify this reply a bit - I suspect that these are TVS diodes, not ordinary ones, but until we have the schematic I reserve judgement!