[Tim]

Hi all.


The day after I picked up a Philips PM3240 to cure my working 'scope deficiency, I was given one of these today, discovered while tidying a friends loft. One minute one is scopeless, and then suddenly they're knee deep!
He said it didn't work, so I got it.
It didn't power on, but that was due to a bad connection in the mains fuse holder.
When powered up it ran( actually very well) for about an hour before the trace disappeared.
(This was down to a blown fuse for the 20 volt supply feeding the EHT module, in turn caused by a shorted oscillator transistor(BFY51). Transistor replaced and now trace again, and stable current on the 20 volt feed of about 260mA. )
Before it did so, I noticed some strange behaviour. First the traces were pulsing in brightness alternately, which got worse until the solid trace became a series of dashes(but perhaps blanks or gaps)?)
The period of the blanks is variable with the timebase setting, but is not triggerable upon, and affects both traces.
Initially I thought that this might have been related to the loss of trace, but I don't think it is, and merely occurred at about the same time.
I did manage to get some pictures.
No funny noises or smells.


Any one out there who is familiar with this beastie, have any idea where I should start looking please.
I'm inclined to investigate the Bright up/ z mod circuits with a can of freezer spray as it seems to be temperature related, but after that it's the long way round.