At bases of q1001....4 there is only dc voltage.
Correct. The circled 4,2V and 3,1V on the schematic are the square wave voltage levels expected on the emitter. When U602 pin 20 is ECL high, the voltage should be 4,2V. When U602 pin 20 is ECL low, the voltage should be 3,1 Volts. A DMM cannot distinguish between the two and this is why I suspect these circled voltages may actually refer to waveform levels. It is not just a coincidence that the two voltages *are* ECL levels.
For clarity, CMOS logic low is zero to 1/3 Vdd and high is anything between 2/3 Vdd and Vdd.
TTL low is zero to +0,8 Volts and high is anything between +2,0 and +5 Volts.
ECL levels are as I explained previously.
When U602 pin 20 waveform is at an ECL low, the voltage level observed on the measuring scope should be 3,1V above the zero reference line. Similarly, the high portion of the waveform should be 4,2 Volts above the zero reference.
The objective is to measure the actual logic high and low levels, by counting divisions on the display, based on the number of divisions above zero reference, to the high and low portions of the gate waveform. With a vertical setting of 0,5 Volts/cm, 3,1 Volts would be 6,2 divisions above the zero reference on screen. If the probe being used is a 10x, then 0,5 Volts/cm is really 5 Volts/cm and 3,1 Volts would be 0,62 divisions.
At C and E is square wave. with peak-to-peak approx 0,1-0,2V depending which Q I am measuring.
If the total amplitude swing from high to low is only 0,1 to 0,2 Volts, then this is definitely a problem. The total amplitude should be 1,1 Volts. Q1001 through Q1004 are not being turned on by their corresponding gate signal. BJTs require about 0,65 Volts base-to-emitter minimum to turn on. 0,1 to 0,2 is inadequate.
The video of only Q1002 in circuit is half of what I expected. The RO intensity works and the other intensity controls have no effect.
The flicker is still present, but I am not ready to condemn U602 defective. Verifying the address timing is a challenging task. It would be nice find U602 is not being addressed correctly and failing to turn on its gate outputs when expected.
I have been studying the Readout System on sheet 9, looking for another possible cause. Waveforms 9A and 9B, /RO Blank and /RO Request, should be checked.
If you would like to take a break from this RO problem, here's something easy to address the channel 2 attenuator hybrid. Make up a chart of resistance measurements from AT117. No need to disconnect any leads.
pin 12 to pin 11
pin 11 to pin 9
pin 11 tp pin 1
pin 1 to pin 2
pin 9 to pins 8,10
pin 11 to pin 7
pin 7 to pin 6
pin 6 to pins 3,5
pin 4 to pins 3,5
Compare to AT127, to see if there are any significant differences.
Maybe your friend can smuggle his scope and your 2246 into the hospital?
Might make the time pass much more quickly.