On Tuesday, July 11, 2017 at 11:38:23 AM UTC-4, rickman wrote:
wrote on 7/10/2017 10:25 PM:
On Monday, July 10, 2017 at 8:06:35 PM UTC-4, John-Del wrote:
On Monday, July 10, 2017 at 7:22:44 PM UTC-4, wrote:

just replaced the vertical deflection IC LA7851. same image, no better. regarding d360 possibly sagging, i did swap it with another on the board, and it was the same. i'll have to keep digging, but any help is appreciated.

thanks



Not much left...

Try warming up the board with a hair dryer on high or a heat gun on low and watch the picture as you do. I'd bet dollars to donuts at this point that the picture stretches out. You said you recapped the monitor but was this all the larger electros that are known to cause issues (like a kit) or *everything*. There are often low value electrolytics back at the signal generator side used for signal coupling that get juicy on the bottom and cause issue either from low esr (they can be juicy and still check OK) or from conductive contamination from the leaked electrolyte.

If the heat doesn't expose a lazy high esr coupling cap, then try washing the board with a suitable cleaner and acid brush, removing the "jungle" IC if need be but otherwise clean between all the leads.

well, im starting to think that its going into HV shutdown, and rather than shutting down, the half scan is how it was made to shutdown. still, doesnt shutdown usually not shut down the vertical scan ? i dont think anything on this unit is the usual. the manual for it is near useless, very little info. another thing, the schematic shows two pairs of jumpers, for 13 or 19 inch use. both pairs are jumped on this board, and the same board on ebay has both pairs jumped. its a hair puller. pin 13 on the 7851 is the x ray protection pin, and it needs to be a specific voltage or the chip shuts down. the manual says that, but doesnt say the voltage. im going to end up buying a chasssi, but i'd still like to know what the heck is wrong with mine.

If the high voltage section shuts down you would lose the brightness of the
electron beam, no? Sounds from your description the electron beam is
clearly visible when the deflection collapses.

--

Rick C

i put a probe on pin 4 of LA7851, the vertical deflector ic chip. its a pulse from the AFC terminal on the flyback. there is virtually no pulse, just a half volt . from the flyback afc terminal, i get a 90 volt shape that looks like a half rectified sine wave, just the top of the sine wave. 90 volt seems low. i think there has to be a pulse at pin 4 for the IC to operate. i bought a working chassis on ebay, and will check some pins outputs, i dont want to give up now.