Sony Monitor SCC-L22D-A (Dell) G2 Voltage ?

[Bill S.]

Can anyone tell me what the G2 voltage is supposed to be on a
Sony SCC-L22D-A monitor? This one has gotten extremely bright
with retrace lines. I don't have schematics, but I can see
that the G2 is a regulated voltage, unlike most units.

I determined by clipping resistors into the feedback string
that the regulator is functioning, and an 8.2M across the
top 10M makes it work so good that I am almost tempted to
just leave it that way. But something has obviously changed.
Bias and gain settings in the color menu look reasonable.
Is there maybe a Zener reference that has gone South?

Anyway, if I knew what the G2 voltage is supposed to be, it
would be helpful in determining whether this circuit is the
problem or I need to chase other things down.

TIA

 

[JANA]

There is normaly a pot to adjust the G2 voltage. Look on the back of the HV
multiplier. The pot is usually marked Screen, or G2, or Bias. '

In a dimly lit room, turn down the G2 bias to just slightly past the point
where the retrace lines have disappeared. This should be the correct range
for most CRT's.

If you find the main brightness control lacks proper range after adjusting
the G2 bias, then look for the CRT beam biases or the master bias to correct
for this. This is for the electron-gun grid cathode bias, not the G2 bias.

--

JANA
_____


Can anyone tell me what the G2 voltage is supposed to be on a
Sony SCC-L22D-A monitor? This one has gotten extremely bright
with retrace lines. I don't have schematics, but I can see
that the G2 is a regulated voltage, unlike most units.

I determined by clipping resistors into the feedback string
that the regulator is functioning, and an 8.2M across the
top 10M makes it work so good that I am almost tempted to
just leave it that way. But something has obviously changed.
Bias and gain settings in the color menu look reasonable.
Is there maybe a Zener reference that has gone South?

Anyway, if I knew what the G2 voltage is supposed to be, it
would be helpful in determining whether this circuit is the
problem or I need to chase other things down.

TIA

 

[Bill S.]

There is normaly a pot to adjust the G2 voltage. Look on the back of the HV
multiplier. The pot is usually marked Screen, or G2, or Bias. '

This is not your run-of-the-mill TV set. It's a high end dual focus
trinitron. The two pots on the IFT are both focus voltages. G2 is
controlled by a shunt regulator. If there is any G2 adjustment, it
must be from a service menu which I currently don't know how to get
into.

In a dimly lit room, turn down the G2 bias to just slightly past the point
where the retrace lines have disappeared. This should be the correct range
for most CRT's.

I have effectively done this by altering the regulator feedback as
I described, but I worry about how stable this might be since
something has apparently drifted since it left the factory, and it
doesn't really address the issue of why this now needs to be done.
And the change I had to make was on the order of 25%, which is
large enough in itself to be cause for wonder...

 

[Adrian C]

This is not your run-of-the-mill TV set. It's a high end dual focus
trinitron. The two pots on the IFT are both focus voltages. G2 is
controlled by a shunt regulator. If there is any G2 adjustment, it
must be from a service menu which I currently don't know how to get
into.

The service manual is at
<http://www.eserviceinfo.com/download.php?fileid=18433>
3 part tar archive.

It covers

CPD-E500 (US/Canada) Chassis No, SCC-L22P-A
&
CPD-E500E (AEP) Chassis No, SCC-L22N-A

(At a guess SCC-L22D-A could mean OEM'd to Dell)