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[PCE/TG-16|CD/SGX Discussion / RGBS Amped Core Grafx II - No sync on Sony PVM or 1084S]

Hi guys. Got a real head scratcher here. I recently obtained an RGB modded Core Grafx II system (not amped at the time). Despite the obvious dark colours, the image was otherwise fine on my Commodore 1084S monitor, but no sync on my Sony PVM (20M2DU). I understand the PVM likes a sync signal of at least 4V peak-to-peak and so I figured it must've just been a weak sync signal (I had this problem with my RGB N64 which had weak CSync, and tapping the luma pin solved that problem there) and so, went to work on making the PCE amp.

Having now built the amp precisely to the spec here: http://www.gamesx.com/grafx/pce_rgb.jpg, I first tested out the system on my LCD in the room where I work downstairs - success! Lovely rich colours and syncing just fine.


On my 1084S and PVM however, no sync - skewed image and fast rolling. It's worth adding that for both the PVM and 1084S I use an LM1881 sync-stripper - I doubt this should be an issue (and in the case of the 1084s, it is a requirement anyway) but I'm just making sure you know all the facts. I know the PVM can deal just fine without it, but it's built into the SCART-BNC converter I use and it's fine with a multitude of other consoles I use. I'm new to this modding stuff, and I've already blown a fuse on the PCE randomly switching out components so I figured I should do the sensible thing and get advice from the pros here. Many thanks in advance! If we can get things working, I shall reward with pretty photos, promise !

Edit: One more thing, I've modded using the EXT port method. I'm specifically getting my sync from pin 22C labelled "sync" funnily enough. Might it be worth trying one of the other pins (22A (Vid), 11B (HSn) etc)?

[PCE/TG-16|CD/SGX Discussion / Core Grafx II just died on me]

Hello all! I should probably introduce myself first. My name is scanline, I'm 26 and from the UK and a big fan of shmups - hence why I finally got myself a PC-Engine this week !! I should add, I'm also a fledgling modder.

I've been chuffed to bits with the little guy, and the seller on eBay I'd bought it from had also done an RGB mod which I thought was a bonus. However, when I got the unit I noticed it wasn't amped (and also wouldn't sync on my Sony PVM) so I figured I'd take things into my own hands and put together an amp, as per the recommended schematic which I've seen all around the web - http://www.gamesx.com/grafx/pce_rgb.jpg


Anyways, after a good couple of hour's careful soldering last night, I got the amp put together and it all seemed to work well on my LCD downstairs, but, still no sync on the PVM, shame. On the sync line of the amp, I had substituted the 300 ohm resistor connecting to the 5v line for a 330 ohm as this was the closest I had available. I figured maybe this was the problem and tried experimenting with some other resistors (75, 100, 400) to no avail.

I also tried removing the resistor altogether and that's when the system gave up giving me anything at all - no video, no sound, from any pins in the SCART lead on the multimeter even... it's a shame there's no power LED, but I'm guessing it's stone dead at this point. I obviously noticed the fuse while I was working on the system and so did the logical thing and checked it - seems perfectly intact and the multi meter registers a voltage through it when the power's plugged in (unless I'm checking it incorrectly). So, I guess my question is - can anyone suggest where I should go from here? Have I completely borked the system from simply removing that resistor connecting the transistor to the 5v line in the amp? I have at this point completely desoldered the amp and additional wiring from the EXT port and so we're back to a no-frills vanilla machine which should also eliminate any shorting concerns and still no dice - or so it would seem, I don't have a standard AV lead, but I'm still not getting a reading from the EXT pins, so that would lead me to assume it's still on the fritz.

I have to point out again that I am new to troubleshooting electronics so, please go easy on me guys, I'm still wet behind the ears !