Dear All,
I hope you will be able to help me to repair a breakdown that is most entirely my fault.
I was finishing to tune a PM3209 oscilloscope and was checking voltages after replacing a cap,
when my DMM probe occasioned some flash (spark ? ) in the vicinity of the neon bulb.
I must say it was quick and I do not know if it was a spark or a flash from the neon.
The result is that the focus was immediately destroyed and the trace of the screen becomes a big
fuzzy spot.
The focus setting of the front panel of the oscillo has now no effect on the setting.
Nevertheless, I was able to restore the focus to reasonable setting by using the focus
pot on the board that is visible in the picture (VR2011 on the schematics), but it is not perfect,
and the tuning from the front panel does not work.
The schematics for the 3209 is difficult to find on the WEB (I could not find it ), but I got the PM3208 service
manual which looks exactly the same, maybe with some minor changes.
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Philips/pm3208.pdfI attach here the part of the schematics.
My problem is that I really do not understand how the focus work, and what is the effect of the
front panel focus pot with respect to the one on the board (VR2011).
Any hint on where to search for a blown component would be useful.
PS : I still do not know how to insert a picture in the text. If anybody can tell me ....
Edit : I think I found the way to do it. Using the link of the image that has been already downloaded to the eevblog website.
Then blanks after "img " needs to be removed.
[img ]https://www.eevblog.com/forum/repair/focus-problem-on-a-pm3209-oscilloscope/?action=dlattach;attach=141893[/img ]