Some years back,I worked in a place that fixed Hearing Testing equipment.
One such model had a 10" BW raster display (Picture Monitor) on it,with a habit of losing most of its vertical scans..
The standard procedure was to send it to the USA,where they sent us an exchange unit,fixed ours,& put it into stock for the next "punter".
We had no schematics so it was easiest to do this,pay $A1200 a time,which was passed on to the customer,& get on with the more specialist stuff.
All was well,until the folks in the USA informed us that they were not continuing this service,so we had to "pony up" considerably more for a new Monitor.
We,& the custome, said 'EEK!" & pushed the job to "the back of the shelf"!
I had recently worked at a TV Studio,among other things,fixing Picture Monitors,so I decided to take a look at it.
It had an uncanny resemblance to an Electrohome Monitor,but the big Horiz/Vertical "jungle" IC had the part number sanded off.
After borrowing an Electrohome 10" BW monitor manual from my old work,a few minutes checking verified that it was the same circuit.(Different PCB,though).
In the "E/homes" an underrated diode in the vertical circuit often caused the fault,& so it was in this case.
A new,better diode out of the parts store & the vertical scans were back to normal.
A few manhours & a $1.00 diode--a lot cheaper than even the old exchange service.
I photocopied the E/home schematic & pasted it,plus some relevant info into the Hearing equipment manual,for others.