Sony Monitor KV-25xbr - Dim Picture from PC

[teetu]

- MOSTLY SOLVED!

- Anyone trying to google about the Sony KV-25XBR it is very easy to hook up (as pointed out at the neo geo forums).  It just requires RGB plus ground and sync.  From the PC you must take the H and V sync from the vga to the H-Sync pin on the sony. 

-  I made the very stupid mistake of incorrectly reading the 34 pin connector on the back of the Sony.  Pin 1 is bottom right and Pin 34 is upper left, so I assumed it was odd numbers in the right column and even in the left (isn't this the way most connectors are).  There was even a pinout posted somewhere that also had it listed as such: which ultimately led me on a wild goose chase trying to diagnose some huge problem that didn't exist.

-  But that is not the case: the right column of pins is 1-17 and the left is 18-34.  I only figured this out by taking the case off and looking at the backside of the pcb.

- Problem now is a dim picture from pc (see below!)

[lilshawn]

the 30 pin on this TV is meant to hook up a computer to it. this means the voltage level is supposed to be 0.7v peak to peak. there is no auto adjustment of the signal.

i have no idea exactly what you are hooking up to this monitor so i'll have to assume that the signal level is not what it's expecting. if it's an arcade PCB, you'll have to adjust the signal accordingly. composite sync levels on jamma are 0.3 volts (i beileve) which is probably why the video won't sync...because the TV is expecting a 0.7v signal level and i think the RGB is 5 volts p-p so you'll probably have to insert some resistors or pots to bring the levels down to a manageable level.

While i haven't dealt with this specific TV, i believe a circuit like this could help... http://www.ebay.com/itm/5-LOT-Old-CRT-to-New-LCD-Monitor-CGA-VGA-VIDEO-CONVERTER-Board-Arcade-8-Liner-/281224490577

[teetu]

Thanks for the reply!

I first tried hooking up a saturn, dreamcast, and then genesis.  The genesis gave picture that was most coherent, but still far from playable.

I then tried hooking it up directly to the VGA card per your suggestion but still didn't get a picture.  I'd get some red lines but nothing coherent.

I'll get a multimeter and try reading the levels- I have access to any resistors or other parts that may be needed.  The board you linked to is nice but kind of expensive if it doesn't end up helping me!

[lilshawn]

  i remember someone here had a TV with a DB25?? RGB video input that was having a similar issue and managed to get it going. i dont recall what though. (maybe a small resistor on the sync line?) It was about 2 years ago. the search is not liking me today.

[teetu]

No worries hopefully I can figure this out.  I was looking at that board you linked to on ebay, and it seems pretty simple with some trim pots.  What value trim pots do you think I should use? 

[lilshawn]

the ones on that board look like they might just be for the video signal (RGB) adjustment.

500 ohm pots they are.

still looking for that other thread... 

[teetu]

I finally got it to work!  It looks perfect with my saturn but the picture out of my video card is a bit dim (picture and brightness don't help much).  I tried plugging it into my jpac to boost the signal but I didn't get a picture.

I imagine this is true for sony pvms but I can't find any info.  Thanks for the help thus far!

[teetu]

Do I need to add resistors and caps possibly?

[lilshawn]

i'm not sure why you wouldn't get an image while using the jpac. it should get your image up brighter. perhaps you forgot to power the board.

some people have had some luck with inserting a resistor in line with the sync signal. not sure it will help in this case though.

some of these weird ass inputs can be really finicky. SCART is really notorious for being hard to hack into.

pots are to bring the signal level down. i think you may have to opposite issue (too low)

[teetu]

Yeah I don't know what the deal was because I reconnected everything and now its working through the Jpac. 

I connected the monitor to my super street fighter II PCB again and it was giving a dim image as before.  I added 220ohm resistors to the RGB lines and the picture looked near perfect.  I figured the jpac outputs at a similar level to the arcade pcb so I added 220 ohm resistors to the RGB lines and now the monitor gives a perfectly bright picture from the VGA card (similar to what I was getting out of the sega saturn)!

I have just two questions left because I don't want to be inadvertently hurting the monitor in the long term:

1) Do I also need to add a resistor to the sync line?  If the RGB was too strong coming out of the jpac, does that mean the sync is boosted too high as well?

2) I used a 220 ohm resistor because that was one of the few values I had lying around.  How can I determine what value resistor would be best to use?  Again, the picture is perfectly bright but I'm afraid of it being too strong perhaps.  Would I be better off putting 500 ohm pots in and adjusting it manually, or should I use an ohm meter to determine the level and then find the appropriate resistor?

If it sounds like I'm being over cautious its because it's incredibly hard to find a suitable CRT in my area- and this Sony KV-XBR25 gives the most beautiful picture I've seen at standard res!

[lilshawn]

if it syncs okay, i'd leave it alone.

if it's having troubles picking it up (comes up scrambled for a bit when first connected or randomly drops the sync for brief 1/2 seconds), maybe add the resistor.