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Other Crashing(?) white PC Engine.

relo999

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I recently got a Super System 3, that seemed to work great up until I used for an extended period of time (+-30~60 minutes) after which it outright crashed the game or rebooted the game being played out of no where. This didn't happen with my everdrive before.

Went to the Terraonion forums to get technical support as it seemed to be a problem with the Super system 3. And was told either the PSU is going bad or the system, and tried a different PSU only to blow the fuse. (both where megadrive model 1 PSU's)

So I thought, based on what I was told, that the system is going bad and so and replaced all caps, installed a fuse holder and a new fuse, removed the old RGB mod I did ages ago and replaced the 7805. Which is how I got to my current problem, it crashes to a black screen after a minute or 2 of use.
To be more specific, on turning it one it get a screen that for a few seconds is a bit whobbley on sync (on my CM8833, fine on my LCD but probably a load more filtering happening there). After a few seconds I get a stable image. And after about 2-ish minutes it seems to completely lose sync for a second and after get a black screen.
Once that has happened I only get a black screen when I turn it on again for about +-1 hour. After which the cycle can be gone through again.

After seeing that I check all soldered connections both visually and with a multimeter, and everything seems to be fine. I also redone the RGB mod to isolate the console from the Super System 3, but still the same issue.

What could be the issue and how can I fix this?
 

Trimesh

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OK, given those symptoms the first thing I would check is to see if the 5V regulator is getting excessively hot, since it sounds very much like an overload on the 5V rail, and the 1 hour recovery time is when it's cooling down.

Have a look at the areas of the board you worked on and check for shorts.
 

relo999

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The 7805 does get very hot after some use always has after some use. So I checked the PSU's voltage output and it's 14.5V rather than the 10V as advertised. So I wouldn't be surprised if it was the heat, especially with that heatsink the PC engine has being build for 9V.

I seemed to have fixed the whole "black out/weird sync" issue by giving it a good clean, so probably a short somewhere due to flux/dust. But I'm back now at the old issue of random reboots and crashes. Which happens more frequently now, though that might be because I didn't solder the screw to the heatsink to the board (otherwise it near impossible to replace) and the heatsink getting so hot you can cool an egg on it.

During testing the PSU that broke the fuse earlier killed yet another fuse so I'm not using that PSU anymore. And I've ordered a regulated 9V PSU which would at least half the heat output on the voltage in on the 7805.

(if that 9V PSU fixes the issue I want to replace the 7805 with some other part, no clue about a good 7805 replacement though)
 

Trimesh

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Yeah, if your supply is outputting that high a voltage the regulator is going to get very hot and might well shut down. Using a lower voltage AC adapter sounds like a very good idea.

You could also use one of the drop-in 7805 replacement switching regulators like this:


They run much cooler and don't suffer from the "more dissipation as the input voltage goes up" problem.
 

takeshi385

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I’ve heard switching regulators can create video noise if not properly filtered. Also as a tip when I replaced my regulator in my pc engine I had to use hot air to assist. I don’t know if this is factory, but the screw was solder to the board. Between, ground plane and heat sink, I had a heck of a time desoldering that screw. Used a texas instruments 7805 as a replacement.
 

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The solder on the screw is a factory implementation. They changed it to a washer and nut on the Core Grafx making it much easier to replace the voltage regulator.
 

relo999

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Bit of an update, 7805 was indeed hell to remove. But yesterday got the new regulated 9V PSU, still have the same issue. But reading a comment from Bart_simpson on Assembler (RIP) it might be the quality of the caps used. As the caps I currently use are all cheap SD Samwha's rather the high end ruby and nichicon's that are normally in the PC engine. And random resets seem to be related to the caps.
 

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I've never found it necessary to replace the capacitors in an original PC Engine.
 

Trimesh

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I’ve heard switching regulators can create video noise if not properly filtered. Also as a tip when I replaced my regulator in my pc engine I had to use hot air to assist. I don’t know if this is factory, but the screw was solder to the board. Between, ground plane and heat sink, I had a heck of a time desoldering that screw. Used a texas instruments 7805 as a replacement.

The ones that are designed as drop-in replacements for 3-terminal linear regulators have output noise that's of the same order as the parts they replace. Some of the old low-frequency switching regulators were pretty bad, but this hasn't been an issue for years.

Bit of an update, 7805 was indeed hell to remove. But yesterday got the new regulated 9V PSU, still have the same issue. But reading a comment from Bart_simpson on Assembler (RIP) it might be the quality of the caps used. As the caps I currently use are all cheap SD Samwha's rather the high end ruby and nichicon's that are normally in the PC engine. And random resets seem to be related to the caps.

I very much doubt that's your problem. First of all, Samwha caps are perfectly OK and secondly even the cheapest caps from some 3rd tier vendor will meet their spec - the difference is that if they are rated for 2000 hours @ 105c to 70% of nominal capacitance then they will probably last 2500 hours while something like a Nichicon might last 4000-5000 hours to the same endpoint.
 

relo999

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Than the question becomes, why are there random resets and on CD games glitches? And why have they gotten worse with the new caps even when the 7805 is still rather cold and with a 9V regulated PSU?
 

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Run your PCE open and measure output voltage on 7805 under the load. If it's getting way below 5v, then it can be a problem. Like 4.75v is fine, 4.1 or below will lead to glitches. Also if you have a scope check for your PSU output shape, some PSUs can generate too much noise.

Also carefully check everything for cold solder joints and dirty/oxidized contacts, reflow joints and clean contacts if needed.
 

relo999

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7805 under load gives between 4.99 and 5.02V.

That said, I stopped the frequent resets/glitches and haven't tested enough to see if the earlier +- half and hour to an hour long and then resets are gone as I can now easily play Galaga 90 for some 10 minutes without a reset happening. I seem to have fixed the issue of the 1 minute resets by removing a wire I use to give the 7805's screw a better anchor (not necessary). What's weird though is testing the voltage, specifically touching the ground with the ground probe resets the console.

Also runs a lot cooler now with a 9V regulated PSU instead of a 14.5V unregulated PSU

Edit: 7 minutes in got a reset again.
 
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put a 470uf cap on the syncline. Negative facing the TV. If you havnt already.
 

Trimesh

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7805 under load gives between 4.99 and 5.02V.

That said, I stopped the frequent resets/glitches and haven't tested enough to see if the earlier +- half and hour to an hour long and then resets are gone as I can now easily play Galaga 90 for some 10 minutes without a reset happening. I seem to have fixed the issue of the 1 minute resets by removing a wire I use to give the 7805's screw a better anchor (not necessary). What's weird though is testing the voltage, specifically touching the ground with the ground probe resets the console.

Also runs a lot cooler now with a 9V regulated PSU instead of a 14.5V unregulated PSU

Edit: 7 minutes in got a reset again.

I think you might have a broken trace somewhere - one of the not so nice things about the PC Engine is that it uses a board that's made of rather fragile FR3 material rather than FR4 - try examining all the areas where you have carried out rework on the board and look for damaged traces.

It certainly shouldn't fall over just because you connected a probe to the ground line.
 

relo999

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put a 470uf cap on the syncline. Negative facing the TV. If you havnt already.
Don't have one atm, will try tomorrow.

I think you might have a broken trace somewhere - one of the not so nice things about the PC Engine is that it uses a board that's made of rather fragile FR3 material rather than FR4 - try examining all the areas where you have carried out rework on the board and look for damaged traces.

It certainly shouldn't fall over just because you connected a probe to the ground line.
Probe might have been coincidence, I now can't recreate it. And I checked all the places I've soldered and with a multimeter checked if it connected to the locations the traces go to all giving continuity both times I checked.
 

relo999

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put a 470uf cap on the syncline. Negative facing the TV. If you havnt already.
Just did this, this might have fixed the issue. At least I now have played galaga 90 for 40 minutes without any resets instead of it happening after 10~15 minutes. And can keep the black test screen from the 240p test suit on for at least ~105 minutes. Though still need to test beyond 15 minutes under load (as I doubt a simple black screen pushes much data through).

Also if this is the final solution to my troubles, can someone explain to me how this solved the issue. As I don't the link between 470uf on sync and random resets/glitches.

Edit: one hour game of star parodier went fine without any freezing glitches or resets. Only one tiny graphics glitch, which is probably the game.
 
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Oakleaf

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I actually dont think this is a crashing issue. The losses in sync cumulate until the picture goes black and it seems like the system crashes. I think its a problem where the sync is wierd and weak. A timing problem that gets worse over time.

I have had this problem a lot. Now i always add a 470uf on the sync on all pcengine/turbographx related consoles. Keeps the sync stable.

Great to hear that it works.
 

relo999

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I actually dont think this is a crashing issue. The losses in sync cumulate until the picture goes black and it seems like the system crashes. I think its a problem where the sync is wierd and weak. A timing problem that gets worse over time.

I have had this problem a lot. Now i always add a 470uf on the sync on all pcengine/turbographx related consoles. Keeps the sync stable.

Great to hear that it works.
But what I saw wasn't just a black screen, only at the beginning. After the recap I got random glitchy freezes after some minutes on CD games and random resets on hucard games.
 

relo999

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I celebrated to early, got it again without changing anything.
 

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check around the 2 hu chips and make sure that there are no small shorts and or other problems, like dull solderjoints. Reflow if needed.
 
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