Test data from working design

updated Monday, August 14, 2000 pstewart@gwi.net

Julie Porter Gets Cybermaxx LCD Up and Running
Julie S. Porter got her LCDs working over the weekend, sending email on Monday, April 4th that she had gotten a test pattern displayed stably on the screens.

We will be posting a full account of Julie's tests here, as time allows. In brief, the tests went like this: Both I and Julie were unable to get the IR3y05 to put out RGB with the proper DC offset of 7 volts from system ground, while running the chip at VCC2 = 12 volts. RGB DC offset (video center voltage) sagged to between 5 and 6 volts. Since the LCD's COM voltage is defined as RGB DC Offset minus 1.7 +/- 0.2 volts, Julie adjusted COM lower as well. Presto: Video appeared on the LCD screen.

Along the way, Julie collected oscilloscope pictures of various test points i the working system. You can see them below. More commentary on these and other data from the tests will be posted, again as time allows.

Our next test will run the IR3y05 at 13.75 volts or so, on the assumption that this will give a better RGB DC offset (with pin 28 of the IR3y05 disconnected, it should be VCC2 / 2).

Julie's test rig combined an IR3y05 on one board with an MN83803AL on another. She used the Nuts'n'Volts NTSC color bar generator, built around the Harris/Intersil CD22402 sync generator chip and the Motorola MC13077 NTSC video encoder chip-- hence the references below to the CD22402, used for a number of purposes in our tests.

You can see her results at
MN83803AL close-up
working LCD close-up!
working LCD & test rig (including several revisions of the driver circuit, and test pattern generator)
working LCD & test rig, showing whole bench setup

Julie Porter provides screen shots from her oscilloscope, showing circuit performance in the test rig:

These are the best photos of the lot.

Blue channel, input to LCD (top) and pin 13 of CD22402 (bottom).
This is blue channel after the 100 ohm resistor at I think 20us/div. (might have been 10) it is set to 5V per division. The bottom trace is the output of pin 13 of the CD22402, It is a negative trigger. LCCom seems to flatline about the same place as the tops of the lower wave about the same distance below the 5V graticule.

Blue Channel, Trigger at Pin 15, Start of FRP
Blue channel this time with the trigger at pin 15 the start of frame pulse. I think I was at .2ms/div. Also at 5/div.

IR3y05 pin 20 output to Pin 6 of MN83803AL
output of pin 20 at the base of the wire from princess sharp to pin 6 of prince Albert. Scale should be the same as 9,and 10. Each pulse is the hsync. The line across the ground is the ground reference from the Harris board. Since the trigger is 1/30 of a second no trigger is seen on the display.

18 & 19
output between pins 18 and 19 I think the settings were the same as for photo 8. I might have had this as far up as .1ms/ div

Here are some shots from the first set. The second set was to improve focus.

18 & 19
A wider 20us/div take on the output from 18/19 combo. This was before I moved the second trace to mark ground. ground is at the same place as on the other photos. (3 divisions under the center graticule.)

HPulse
A shot of one of the Hpulse lines, same scales I think.

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