CurtPalme.com Home Theater Forum

[mp20748]

[stridsvognen]

I think its possible, but dificoult to calibrate it to measure perfect, but it just dont look perfect to me.. Needs to much signal correction. and a non moddet Card can be calibrated almost to perfection without messing with the signal.

[jbmeyer13]

[mp20748]

[dvh99]

the line disappeared with me after removing u106 from the chain.

[mp20748]

[dvh99]

been working fine for months and it was a 10 minute job so why wouldn`t it be sensible?

[stridsvognen]

[Nashou66]

I just tried a variation of the line fix. I was told it was part of the X hatch pattern that of the internal video.

So I thought why turn off all the menu's with removing U106 and just turn Off the X hatch pattern!!

So I found the trace on the bottom of the CLM cut it and put a switch on that line. It is pin 19 from U108.

That goes into U106. Well it did shut off the X hatch patterns including the DOT pattern but the line remained.

So I don't think its the X hatch pattern causing this from the CLM.

I also tried to just shut the power to CL415 on the 02 Vim, it is the RGB quad op amp for the INT Vid. Same thing, Line remained.
So it got me thinking maybe its something with the power supply etc. I aded a 100uf cap to the positive side of the CL415 op amp and the line got brighter!! Strange.

So next thing I'll try is to just shut of either of the two Chips in the X hatch Generator. it might not be the Specific X hatch pattern but the other related signals associated with it.

nashou

[Nashou66]

Ok so I read back over the entire thread or most of the pertinent parts.

Here is my understanding of the problem in summary.

The Issue with the Resistor mod is that it raises the Black level of the internal video which is always there even when the external video is selected. In having the internal video on and the resistor mod in place the black pedestal level of the int vid is elevated and over rides the black pedestal of the ext vid causing the observed elevated level of the video on the screen.

So with no resistor mod the black pedestal of the internal video is black( 0 v ) or Blacker than Black ( -120mv ) according to the Service manual. This allows good black pedestal for the source Video however the faint line is there on some not all Vims.

So the question is Where does this line come from?

Some say its the vim others the CLM Or is it both depending on configuration and or build dates of the Vim and CLM.


My theory as to why some see the line others do not.

I have to agree with Mike that the line must come from a signal off the CLM. But which one for certain?

Why do some vims show the faint line and others do not that do not have the faint line TB applied?
My theory is that some of the parts on the said vims may work better than other vims. Id start with the DC restore chips, the DS5401's and the CL 415's and their associated decoupling caps etc. It might be possible that one or more of these components keep the line out of the final video and or they allow the elevated pedastal of the internal video to not be so overpowering, for example the MC 3404 DC restore chip brings the pedestal back down to where it should be at the Vim
which does not wash out the Internal video.


So which parts of my theory can be ruled out?

I refer back to this part of the service manual



That signal is where Mike said to remove the three resistors on the CLM, 205,206 and 208 I believe . Mike what happened when you removed these?

You posted to remove them and showed the picture but then did not make any comments afterwards and I think your post got lost and forgotten.

I think this might be the right direction but lets move back to where this wave form coms from, the DPB two signals and the VBLANK
signal. So what happened when you removed those three resistors?

Athansios

[jbmeyer13]

Hey Mike,

Can you provide an update on this?

[mp20748]

[jbmeyer13]

Does this remove the internal menu's and if so how are you currently switching them on/off? Barclay's idea would be nice if it can be implemented.

[mp20748]

[barclay66]

Hi,

I made it!
The mod only needs seven resistors and is controllable via the volume control on the remote (setting is saved per predefined channel in the channel list). Please see the attached schematic and the picture of my result. I know, it's not a beauty, but I was interested in its functionality first.
The mod takes advantage of the unused OP-Amp inside U15 and delivers its controllable voltages to U15 (what a coincidence!). As the D/A converter for the volume voltage (U10, delivers 0 ... 2.5V) is nearby, everything can be built around U15. Make sure to cut the traces at pins 12/13/14 first!

The OP-Amp is used as a voltage level shifter. R1/R2 determine the bias and R4 determines the gain. Using a OP-Amp calculator I determined that with a gain of 4 and the bias voltage of 1.6667V I could "convert" the input voltage of 0 ... 2.5V to the desired -5 ... +5V.
Of course the calculator assumes an ideal OP-Amp and the result was more like -3.9 ... +3.9V. Playing around carefully with the values of the above mentioned resistors should make the full swing possible (if necessary).

A look at the board picture reveals that I didn't have a 3K3 resistor at hand. Therefore You can see 2K2 and 1K1 in series.

Regards,
barclay66

[mp20748]

GREAT JOB..

..and using that fourth OP amp in U15 was pure genius.

[Nashou66]

Cool, Jorge. I'll have to try it. I have tons of SMD resistors I might be able to use with some fly wires etc.

The Yellow wire is the 2.5 volt volume reference I assume.

And the top of R5 is the VDD correct?

Nashou

[stridsvognen]

That looks nice..

[barclay66]

[barclay66]