HP 8399-xxx B/W monitor repair
[Document Version: 1.00]
[Last Updated: Jul_15_1993]
Author: Mike Thomas
Date: 15 Jul 1993
The black and white displays were built by PHILIPS in Canada. The plant
there has been shut down, when I last enquired with Philips re: purchasing
spare parts, I was informed that they did not want to support anymore
new customers for this product line. Philips makes the new HP b/w monitors
too, but it looks as if everything is manufactured in Taiwan.
You can also get a list of technical info for the color and monochrome
monitors, part of the Sync-On-Green (33KB) FAQ.
All of these tips apply only for the 8399-XXX series of monitors.
EXERCISE CAUTION WHEN WORKING ON MONITORS, THE MONO MONITOR HAS 18KV
GOING TO THE CRT. Let your techs show you the ropes on monitor repairs,
if you're going to be messing around with any live equipment. Be
especially careful when doing focus adjustments, aside from personal
risk you can smoke your board.
You may get
if you don't read these Notes on Safety V1.00 (7KB)
- Screen wrap problem or the horizontal width has grown too large and
the screen appears to be wrapping back around on itself. Replace
C205 and C206 on deflection board, 10 ufd/50V, electrolytic caps.
(Actually only one of these is causing the problem, but I'm too
lazy--change both) Cost: $0.12 per cap.
- Screen is shrinking from both sides. Change C161, 100 ufd/63V,
electrolytic cap near bottom right of deflection board. Cost: $1.00.
- Characters seem to be wiggling or vibrating. Change C101, 10 ufd/50V,
electrolytic cap, upper left quarter of deflection board. Cost: $0.12.
- On all white displays or on white backgrounds there appear bright
horizontal streaks. Replaced C315, 100 ufd/25V, electrolytic cap,
just below C101. Cost: $0.75.
- Top of display appears to losing a few lines of text sort of gradually
getting darker on top few lines. Replace C318, 4.7 ufd/100V, electrolytic
cap located left center on deflection board. Cost: $1.00.
- Display is too large vertically and cannot adjust in. Replace C310,
0.01 ufd/63V, P.S. cap, aluminum colored just above IC301.
- If the display is too dim and after adjusting brightness it is
out-of-focus, you can try the focus adjustment, but if that doesn't really
work well enough you will need to replace the CRT. This is not that
difficult, takes about 45 minutes, costs: $125.00. I use the on-line
diagnostic "/systest/grtest" to perform focus adjustments. Just enter
ad (adjustments) at the grtest prompt and select test 13. Save all
of the magnets from any scrapped monitor yokes, you'll need them to
adjust display geometry with the new CRT's.
- Also save your old flyback transformers on any scrapped displays,
flybacks cause several different problems: Squeals no picture and
a 'jittery' display are both flyback problems. The key to flyback
jitter is when the display shrinks or jerks both top, bottom and
both sides simutaneously. Another flyback problem is a slow
expansion and contraction of the display, some of my customers tell
me that it's 'breathing'.
- As far as adjusting focus goes, the pot labeled 'DYN FOC HOR' adjusts
the focus on the far right and left side of the screen. It also
balances the focus between these sides, so be sure to check both
left and right sides when adjusting this pot. The pot labeled
'DYN FOC VERT' just adjusts the focus for the top and bottom of the
display. I usually can't get perfect focus on the very top of the
display, especially at this site where the brightness has to be
turned up especially high. If no matter what you do with the focus
pots does not work, you might try playing with the 'focus phase' adj.
Focus phase is controlled by the coil with the adjustable core in the
center of the board. The way I play with it is to turn the main
focus pot, R431, to midrange and do the same for the two dynamic
focus pots. I then adjust focus phase for good focus in the center
of the display, then go through the normal focus adjustments, i.e.
turn R431 for best focus overall then adjust dynamic for sides and
top and bottom.
Pin 1 - ECL Video
Pin 2 - No connection
Pin 3 - Horizontal sync
Pin 4 - Vertical sync
Pin 5 - No connection
Pin 6 - ECL Video
Pin 7 - Video Shield
Pin 8 - Horizontal Sync Return
Pin 9 - Outer Shield Chassis