OSSC and PC engine Issue [Solved]

[mimylovesjapan]

Hello everyone !

I have an issue with my OSSC and my PC engine.
Here some informations :

– OSSC is with the last firmware.
– OSSC working perfectly with all my other game systems.
– PC-Engine : the PC-engine is starting at 60.05Hz, then lose signal sometimes. After swaping many times the AV1, AV2, AV3, it changes sometimes to 60.01Hz or 59.94Hz. More stable in 59.94, but coming back to 60.05 automaticly...
-I use a PC engine modified in Japan (interface unit) by this store : https://page.auctions.yahoo.co.jp/jp/auction/d337601049 , because I live in Japan.
The site says this is a RGB, C-SYNC modification.
RGB cable was furnished with. It’s a japanese cable.

I asked to the OSSC forum. They said it is maybe a bad modding. But they couldn't help me more...

Where should I start ?
- other OSSC setting ?
- changing the cable ?
- open the interface and do something inside ?

[ASDR]

I think opening it up and taking pictures the experts here can look at is probably a good first step. Might also make sense to take a peek at the connections in the DIN connector / SCART/JP21 head of the cable.

I think most people who get into this hobby have been burned by shitty mod work. I mean you're not able to do it yourself, how can you judge the work of others. I now of course refuse to do business with any person that does not show their work. I don't require things to be some kind of Voultar style soldering art, but I need to have a look to see if the quality of the soldering, wire routing, components chosen, hookup points etc. look sensible.

If you post some pictures of the mod you've received you'd help the people here help you and hopefully future potential customers of that shop can have a look at what you've gotten and decide if they'd be happy with it.

[mimylovesjapan]

Thank you very much for your reply !
Then I will try to upload pictures soon ! (maybe tomorrow, if I can find a crew driver fitting the interface)

[mimylovesjapan]

OK ! I had a screw driver, same I used for my S famicom games !
Here are some pictures :

Front picture of the mod :


Back picture : (the black plastic isolant is sticken on circuits...)


Wires from the PC engine port :

[ASDR]

Curious what you'll find

So, many basic / old PCE RGB mods just keep using the existing sync-on-composite as sync for their RGB mod, which is perfectly fine. They just get RGB from the graphics chip or expansion connector and attenuate / buffer it and that's that. The fancier modern ones, like the one Voultar sells, use a 4 channel amp and also output proper buffered and attenuated csync. Even better. You're modder claims you have a csync mod, so there might be a number of things going wrong here. Just connecting csync straight from the expansion connector is not the proper thing to do and causes issues. I've also seen people claim that the csync from some PC Engines is wonky anyway. Some tried to generate csync from HVsync and screwed it up (SSDS3) and I've heard stories of people putting sync strippers in their RGB mod (ugh). And wire shielding/gauge and RGB amp placement can matter.

So in your IFU there's going to be an RGB amp board that gets R, G, B, sync, Vcc and Gnd somewhere from the board and then outputs RGBS to your DIN plug. Just take a picture where you can clearly see the board and where its ins and outs go.

There are some OSSC settings you can try, but I'd first have a look at the mod work to make sure there isn't something terribly wrong electrically. I've never done an IFU RGB mod, but hopefully somebody else can chime in if there isn't some immediately obvious issue.

[mimylovesjapan]

Thank you for your reply !
The RGB amp Board seems to be the little brown circuit in the center.
The RGBC wires from PC engine are connected to this board. Then the board send the signal to the port out.
Ground (black wires ?) are directly connected to the port out.

[ASDR]

Allright, pictures



The board seems like it uses a 3 channel RGB amp and it doesn't hook up to the csync pin on the expansion connector, just drawing RGB, Gnd and Vcc. Also looks quite different from the design used in mine, I'm pretty sure there are some 220uF (?) caps supposed to be on the output side :/ I can't really tell where the DIN connector gets its sync from, probably just re-uses the composite video. So I think this isn't a csync mod or not a proper one because of the 3 channel amp.

At this point maybe somebody more experienced than me hopefully chimes in, but the issues I can see are that this uses either no or improperly buffered csync, misses some AC coupling caps (?) and has generally a bit of janky look to it :/

edit:

Here's some proper boards, first three channel and then the Voultar csync variants:





At the very least you're missing some caps on the output, maybe they're in the cable?

[mimylovesjapan]

Thank you for your help !
I think, its is not the same scheme as your picture, as the Sync on mine is connected to the 5V on mine... or maybe the modder was taken the +5V to do something, and completly miss the Sync part.. or maybe it's taken from an other part of the interface ? I know nothing about PC engine... I wish someone can guide me step by step !

Edit : Yes, that's definitively strange... I will wait for help !
I have some basic skills in soldering, then I can maybe do it by myself (if someone give me the steps to follow !)

[ASDR]

If you have a multimeter just check which pin on the DIN socket is connected to the comp / sync pin of your SCART cable (20, IIRC) and then check in the IFU where that is connected. Probably just composite video.

[Kez]

Been a while since I opened one of these but it looks like the red, white and yellow wires are going to the connector for the RCA outputs. If it's hooked straight up to those, then the mod is simply using composite video for sync.

[ASDR]

Been a while since I opened one of these but it looks like the red, white and yellow wires are going to the connector for the RCA outputs. If it's hooked straight up to those, then the mod is simply using composite video for sync.

Yeah, suspecting that as well, especially since he neither has a 4 channel RGB amp nor does the csync on the expansion connector seem to be tapped. Any idea why he's having trouble with sync then? I mean the RGB amp seems very janky in both design and soldering, so I could see this having major picture problems but the OSSC can't even seem to get sync. The composite from the console should be good to go.

(Honestly, if this was my PCE, I'd just remove the mod and start over with a good amp from Voultar/mickcris/Tim Worthington/etc.)

[Kez]

Any idea why he's having trouble with sync then? I mean the RGB amp seems very janky in both design and soldering, so I could see this having major picture problems but the OSSC can't even seem to get sync. The composite from the console should be good to go.

Yup, I'm with you on this. Theoretically the composite video should work fine.. I am wondering if there is any trickery involved to live up to the "csync" sales pitch, like a sync stripper hidden somewhere (the SCART cable maybe?). Still I suspect even the composite video output from the PC-E is a little bit janky.. maybe try tweaking some of the sync settings in the OSSC - sync LPF in particular. I do think the best option long term would be to install a proper mod board that buffers csync.

[ASDR]

Yup, I'm with you on this. Theoretically the composite video should work fine.. I am wondering if there is any trickery involved to live up to the "csync" sales pitch, like a sync stripper hidden somewhere (the SCART cable maybe?). Still I suspect even the composite video output from the PC-E is a little bit janky.. maybe try tweaking some of the sync settings in the OSSC - sync LPF in particular. I do think the best option long term would be to install a proper mod board that buffers csync.

For what it's worth the OSSC never barked at the sync-on-composite from my CoreGrafx1, but then again there are so many revisions of the PCE, who knows what they changed. I agree doing a mod with proper csync probably has the best chance of fixing all issues. The Voultar board is quite simple to install in the IFU (https://voultar.com/index.php?route=pro ... duct_id=53). It's ten wires soldered to large pads, no SMD / fine-pitch chip legs. If you can solder at all, you can pull this off.

mimylovesjapan - You should have a look at your cable, both on the DIN and SCART ends. Maybe we'll indeed find a sync stripper and our missing AC coupling electrolytics A common mistake with the LM1881s I've seen in the field is forgetting the resistor on the sync line, so this cable might be blasting the OSSC with TTL sync.

The LPF should be set to the lowest frequency and some playing around with the sync options in general could yield a picture, but yeah, this likely requires some hardware fixes. Lesson learned, next time ask for pictures of the mod work!

[mimylovesjapan]

OK, then I should focus on buying this RGB amp ? But it doesn't says it's for a interface unit...

[ASDR]

OK, then I should focus on buying this RGB amp ? But it doesn't says it's for a interface unit...

These kinds of amps take R, G, B, sync & power and output RGBS suitable for any standard RGB SCART device. These signals are available on every type of PC engine. You can tap RGB & sync directly from the graphics chip or at the expansion connector of any console that has one. They're then obviously also available on the other side on any device that plugs into the expansion connector like an IFU. Heck, people put RGB mods in a Tennokoe 2, here: http://retrostuff.org/2018/01/04/tennokoe-2-rgb-output/. With analog signals it's generally better to be as close to the source as possible so the preferred way is probably to hook up the amp directly to the graphics chip, but you can also get good results by tapping RGBS from the expansion connector on the IFU side. You'll then have to route the RGBS from the amp to your DIN connector and make sure you have a cable correctly putting the audio and video coming from the console on the pins of the SCART plug. I'd be suspicious of the cable you got from your modder, definitively make a visual & multimeter inspection of it. I use a cable from RGC for my RGB modded PCE, very happy with it (https://www.retrogamingcables.co.uk/pc- ... o-av-cable).

[fernan1234]

I got an IFU (as well as other stuff) from that same Yahoo auctions seller. He also sells, or at least used to, on eBay. He probably has varying quality in his work. I got burned with a CD-ROM2 unit from him, but the RGB-modded IFU worked fine when I used it for a while with an OSSC, and with a cable other than the one he supplies, one from RA (BTW, the pinout he used for RGB is not the standard, I found out the hard way but luckily got the cable rewired by RA).

I did hook up the IFU through a good quality SCART switch though, so that may have helped with sync issues latent in his mod work, if there are any. If you have a SCART switch that you can put in between I'd say give it a try to see if it makes a difference.

Edit: I should say that I do think the video and audio quality, at least from the unit I got, is quite good.

[ASDR]

I think most SCART switches would either be an additional source of problems or do nothing at all, but a gScart could help. It has a fairly unique sync processing and IIRC they also contain a distribution amplifier, so maybe that also helps. Generally speaking, the OSSC is a highly tolerant device with a fair bit of control offered, so you should be able to make it work with one if the output of your mod is salvageable at all.

[Mobiusstriptech]

You have a myriad of issues with that mod unfortunately. Namely as someone pointed out the lack of AC coupling capacitors. However the attenuation is also wrong and you are lacking a proper sync signal. Your best bet would be to have someone replace that with a good quality circuit that does all of those things for you. You already have a DIN socket so it's mostly a matter of swapping out the board for a new one and fixing up any possible poor connections. I believe if you do this, you would have something that performs quite well and you would be pleased with the results.

[mimylovesjapan]

Thank you everyone for your help !
What version of the RGB amp do you recommand me, Mobiusstriptech ?

[thebigcheese]

I'm not sure what become of it, but I know Voultar was working on a version specifically designed for the IFU. He might have just made it an open source design, I'm not sure, but that's the one I'd go with. Otherwise, either his RGB mod or the Mickris board are both high quality (I think the picture above of the Mickris board is my CoreGrafx, actually ).

[ASDR]

I'm not sure what become of it, but I know Voultar was working on a version specifically designed for the IFU. He might have just made it an open source design, I'm not sure, but that's the one I'd go with. Otherwise, either his RGB mod or the Mickris board are both high quality (I think the picture above of the Mickris board is my CoreGrafx, actually ).

https://twitter.com/voultar/status/9748 ... 57?lang=en

Hm, I guess there wasn't enough interest for it to be on sale? In any case, I think the only difference is that the installation is a bit easier and cleaner because it uses the N64 style where it directly solders to the pins of the connector, just on the input side this time.

[Mobiusstriptech]

The IFU board hasn't been released. It is different than the standard DuoRGB-X board. The IFU technically needs a slightly modified circuit due to the additional interference in it. He is still going to release it as a purchasable unit. I have seen the boards already but they aren't available publicly yet.

If you want something now, then I would just go with the DuoRGB-X. It handles CSync properly and doesn't have the issues that the Mickcris amps have with channel 4 driving signal into ground. Also Mickcris stopped selling those amps long ago. So you would need someone to build it for you anyway.

[thebigcheese]

The IFU board hasn't been released. It is different than the standard DuoRGB-X board. The IFU technically needs a slightly modified circuit due to the additional interference in it. He is still going to release it as a purchasable unit. I have seen the boards already but they aren't available publicly yet.

If you want something now, then I would just go with the DuoRGB-X. It handles CSync properly and doesn't have the issues that the Mickcris amps have with channel 4 driving signal into ground. Also Mickcris stopped selling those amps long ago. So you would need someone to build it for you anyway.

Console 5 sells the Mickris boards. Out of curiosity, what does that issue cause and is there a fix? I've got one in my Core Grafx and would love to know. Sorry to hijack...

[fernan1234]

More solutions for the IFU would be nice. It just looks so sick with all the modules. It would hurt to have to go with any kind of Duo, which kinda look like an old kitchen appliance.

[thebigcheese]

More solutions for the IFU would be nice. It just looks so sick with all the modules. It would hurt to have to go with any kind of Duo, which kinda look like an old kitchen appliance.

I think most people just mod the main console. CoreGrafx doesn't require any drilling/cutting, for example, so it's less intrusive. Plus then you have the flexibility of using just the console or the console + IFU. So that is my personal preference In this case, OP already has the IFU modded, so it makes more sense to do it there.

[Mobiusstriptech]

The IFU board hasn't been released. It is different than the standard DuoRGB-X board. The IFU technically needs a slightly modified circuit due to the additional interference in it. He is still going to release it as a purchasable unit. I have seen the boards already but they aren't available publicly yet.

If you want something now, then I would just go with the DuoRGB-X. It handles CSync properly and doesn't have the issues that the Mickcris amps have with channel 4 driving signal into ground. Also Mickcris stopped selling those amps long ago. So you would need someone to build it for you anyway.

Console 5 sells the Mickris boards. Out of curiosity, what does that issue cause and is there a fix? I've got one in my Core Grafx and would love to know. Sorry to hijack...

Console5 hasn't sold the mickcris board in a long time. You just need to cut off or lift the output pin for channel 4 to correct it. Basically it will cause the chip to heat up and could potentially cause a premature failure.

[fernan1234]

More solutions for the IFU would be nice. It just looks so sick with all the modules. It would hurt to have to go with any kind of Duo, which kinda look like an old kitchen appliance.

I think most people just mod the main console. CoreGrafx doesn't require any drilling/cutting, for example, so it's less intrusive. Plus then you have the flexibility of using just the console or the console + IFU. So that is my personal preference In this case, OP already has the IFU modded, so it makes more sense to do it there.

Right, I should actually go this route and have the old RGB mod that my PCE console has, which unfortunately was also done by this Japanese modder, and get it replaced with one of the recommended amps. In this setup extra RCA cables from the IFU are needed for CD audio, but I guess that's no big deal.

[thebigcheese]

Console5 hasn't sold the mickcris board in a long time. You just need to cut off or lift the output pin for channel 4 to correct it. Basically it will cause the chip to heat up and could potentially cause a premature failure.

I just bought mine from them last year... Don't have pre-assembled ones in stock, but the kits are still around: https://console5.com/store/kits/rgb/pce-rgb.html. Anyway, I'll have a check and see what's going on with mine. They do list that as "important note #2" on the product page.

[Mobiusstriptech]

That kit is a totally different amp. It's a 7316 based kit and not a 7374. The 7316 would not have the issue that the 7374 kits will. Namely because the 7316 is a 3 channel amp and not a 4 channel.

[mimylovesjapan]

Thank you Mobius !
Do you have any idea when the IFU version would be release ?
I can wait for month, but if it takes years, then I will go for a DuoRGB-X.