CurtPalme.com Home Theater Forum

[Nashou66]

I have been modding my old Vim as some of you know from the marquee maintenance group purchase thread. It has been going great .... but last night I added inductors to the 5 volt rails and changed the value (lowered) to some of the caps i changed. I also did some CLM cap changes but ruled that out as the problem so far.
This is the problem. when i have no input selected or on and am just scrolling through the patterns with the # key on the screen where it should be all black the red tube is on and fairly bright(lights up the screen). I changed the video cable from red to green and it follows to the green tube so G2 is not the problem. I inspected the board under the magnifying glass and thought i saw a small thread of solder across two of the pins on the first op amp . removed it and plugged it all back in and fired it up. it was gone but just till the marquee warmed up after about 3-5 minutes and you could see the intensity increasing as the projector warmed up. I'm wondering if I had some loose solder and it may have shorted out one of the op amps? The pin where the ultra fine thread of solder was on pin 3 and 4 the In+ and the -v pins. I'm not sure if it was solder because it was so fine could have been a fiber.

For those techies out there, would the op amp still pass the signal if those two pins where shorted out and even after i removed that hair of solder across them?

Now when a signal is present on the moome card I have no issues. the picture is the same and no red increase in colors. and when i go into the # button while the image looks fine with no red increase.

Looking over the schematics tells me that the cap changes i made are no where near the video signal line.

Any ideas where to look is helpful. besides changing the op amps I plan to do that.

Athanasios

[9kids]

What happens when there is no External input and no menus or internal pattens selected. I guess that still produces internal video from the "no H-Sync" and "No V-sync" popup boxs. What happens when you select different internal frequencies? You might try just external H & V sync and no RGB and see what happens or just disconect external red and see what happens. If it only happens when there is no external Red input then it does sound like a problem with the op amp. I would think that if there is no external Sync that the analog switch signal V-SEL would keep the Internal video selected all the time (but that is a wild guess). If it is suposed to keep internal video selected all the time then the problem could be in the analog switch. I am no techy, and I have only just stated looking at the VIM design, so I really have no idea what I am talking about.

Good luck

[Nashou66]

[Nashou66]

Ok I cleaned the board with denatured alcohol let it dry inspected it again and tried one more time. Now the red full fiels lights up with no input connected and not pressing the # key its red when the no sync green text comes up. I connect a source to the moome card and the image is fine with no red added ,so this" always on" does not come through to the video signal. I went through the test patterns on my Lumagen and i see the same there. grey step patterns as they should be. It seems like if there is no video signal going through the board that its allowing a G2 signal to get to the red tube. Is that the Blanking or Clamp or something like that. I have to look at the service manual again.

Athanasios

[9kids]

The more I think about it, the more I think it is related to the op amp and not the switch. I don't have any idea the state of the switch when there is no external signal. If you apply an external signal and just leave the red off then you know the state of the switch. It will be connected to the external op amp. With no red signal to the op amp it should not be outputting anything, so if it happens with external signal on but no red, then it must be related to the op amp.

[9kids]

You posted while I was typing. So no problems with external signal and no red connected. I was thinking that the problem was with the external op amp when no red signal was applied. But that test seem to say no. Maybe something related to sync and clamping?

[9kids]

Just to rule out the CLM mods you did, you might want to swap in your other VIM and make sure it is not the CLM.

[9kids]

You have mentioned a moome card a few times. What happens when you select the RGBHV input on the VIM with no signal? Maybe the moome card is sending something strange on red when there is no signal.

[Nashou66]

Well I figured it out with your help 9Kids. it was a loose resistor wire to the SD5401 chip. That chip does the switching of the internal and external Video. on the old vimes it was an added resistor to pin 8 on the newer vims its built into the PCB. This is the green channel but same resistors are on all chips.





Thanks for your help


Athanasios

[9kids]

Well done