The voltage on the G2 is too high.
The R053 22M workaround seems to be working around. However I don't like procedures which are only compromise of the circuit.
There is a RGB preamp MC13289 in the F99 chassis. The voltage measurement on the pin 18 (BRT) is 0V (should be 1V). I've checked this pin (unsoldered) and it is absolutely open (to ground and +12V). I can't find any aplication of the MC13289 in the WEB, but I guess the pin 18 is something like the reference. I'm going to change the MC13289 next week.

I agree there is a problem in the circuit but not with the pre-amp as you suggest, as the video is AC coupled to the cathodes and any DC eerors on the ouput of this IC would not be passed to the cathodes.

You hit the problem when you said the G2 is too high, if you measure the voltage you will find it way above what is printed on the circuit diagrams.

The fault is in the G2/control circuits study the circuit hard and check all measurments then find the faulty component and let us all know the answer.

I do not have a unit here or the time to sort this one out, all the Sony models with this sort of G2 control suffer from this problem.

By the way please dont take this as though I am criticising you I would welcome some other eyes to look at this one.

Rich

Thanks Richard B for your reply. I'm happy to see any opinion, cause opinions usually help to resolve failures.

There is a triple RGB output from the Pre-Amp MC13289, which is AC coupled to cathodes, as you said. However there are also 3 outputs signals R BKG, G BKG, B BKG from the MC13289. These signals are DC coupled to cathodes (through an IC H8D2972 and diodes) and they're Cut-Off Control, in fact. The lowest voltage maesurement of cathodes controlled by the RBG BKGs should be about 100V. In my unit this voltafe is about 80V. This is why the black level on the screen is so high.

Let's look at the circuit. The G2 voltage is controlled by the differential amplifier NJM 2904. In my opinion high voltage on the G2 is caused by too high voltage from the MC 13289 (pin 5 of the NJM2904). By the way, there is a mistake on my schematic diagram(Sony diagram), because pin5 is (+) and pin6 is (-), in fact.

Could anyone give me a link to the MC13289 data sheet?

Hi sorry yes you are correct.

What is the DC levels out of 30,31 & 32 of the MC13289.

Rich

Hi Rich,
I'm sure voltage measurements are higher then mentioned on the schematic diagram. I don't remember the value at the moment and I'll give you exact measurements next day.

Hi,
The voltage measurement on each of the R,B,G BKGs is slightly lower.
Now I have full details of voltage measurements. You can find some of them below.
Warm up time: 20 minutes, followed by Restore function
Signal source: 100% EBU Colour Bars
Voltmeter: Fluke 189, Input Impedance 10MOhm
Units: V
Measurements are made in the following order : dark(bright minimum), normal(bright 31%), bright1(bright maximum), contrast always 85%.

MC13289
7. (+12): 11.8 ; 11.8 ; 11.8
8. (V8 REF): 7.9 ; 7.9 ; 7.9
9. (GND) : 0 ; 0 ; 0
17. (ABL) : 2.95 ; 2.95 ; 1.51
18. (BRT) : 0.00 ; 0.00 ; 0.00
20. (R OUT) : 2.26 ; 2.43 ; 2.43
23. (G OUT) : 2.20 ; 2.36 ; 2.36
27. (B OUT) : 2.20 ; 2.35 ; 2.35
29. (G2) : 2.34 ; 2.34 ; 2.34
30. (R BKG) : 3.25 ; 2.99 ; 2.40
31. (G BKG) : 3.15 ; 2.94 ; 2.46
32. (B BKG) : 3.45 ; 3.23 ; 2.72

NJM 2904
5. (+) : 2.66 ; 2.66 ; 2.66
6. (-) : 2.82 ; 2.78 ; 2.76
7. (OUT) : 8.55 ; 8.54 ; 8.54

Collector
Q001 (G2): 637.6 ; 637.6 ; 637.5

Probably cut-off points on cathodes are too low because of RGB BKGs on the MC12389. So, I guess the MC12389 is failed.

I can see why you want the data sheet, I have been unable to find it thus far but will continue to look.

Rich