IC based region mod woes

I've tried installing a region mod based upon the IC design into an American TurboGrafx 16 and I'm getting nowhere. I've checked my wiring a half dozen times and the soldering and I'm continually coming up empty. Everything looks fine but I can't get the system to recognize any hucards.

The only thing I can think of is that the +5v is +4.5v at the 7805 and the IC design requires +5v. I didn't measure what the voltage drop was with the mod installed but with a CXA1645 alone it dropped to +3.4v which was well below what the CXA1646 was designed to be used with.

On top of that I've wired up a composite video connected using the pin on the expansion connector. It looks great but seems to have a bit of trouble with my display in terms of placing the picture from boot up square in the middle of the tube. There also seems to be an alternating set of bars of contrast moving up the screen.

Brighter/Darker/Brighter/Darker rolling up gently. Doesn't seem to be an interference problem but I'm thinking it might need some sort of filter?

 

That thought did cross my mind. I'm also tempted to swap out the 7805 built into the system for a new one with the hope that it being 20+ years old means it doesn't perform as well as it should. The power brick provides 9v supposedly but I'd swear I measured 5.5v somewhere in the system before the voltage regulator.

Still trying to track down the rolling contrast bars.

 

4.5V/3.4V isn't right, I think you have a short unless the supply is shot.

The console worked before the mod?

A 7805 needs 7V in to properly regulate. Maybe the TG16 has an internal rectifier like the NES? If so, you'll need at least a 8.4V supply, otherwise a little over 7V should do.

Also the analog multiplexer circuit people use looks pretty dubious to begin with for the application. I'd go with digital buffers for speed, bus loading and to help with noise.

 

It worked before the mod and it works fine after the mod has been removed and the card slot reconnected. The power supply itself is rated at 9v 850ma and it tests at 9v when not under load and while connected to the system but not turned on. As soon as it turns on I get a reading of somewhere between 5.5-8.5v with some fluctuations that I can't pin down as being the power supply's fault or my DMM being picky for whatever reason.

I did trace the circuit from the 7805, basically runs through the switch on one end with both getting routed back through a few ceramic capacitors (whose values I didn't work out yet) into a small board with another ceramic disc capacitor and aluminum electrolytic which easily could be a doornail. Neither had a very high value either (10uF at 16v IIRC).

Quite honestly I thought the same thing (about the multiplexer circuit) if only because I've found extremely few mentions of the circuit working and most people resorting to a 8P8T switch to get the job done.

Though I can't for the life of me figure out why the CXA1645 won't put out any video. I rewired the circuit up to the expansion connector and got something out of it. Nothing usable in the least but at least I got something out of it when the TG16 was turned on/off, just noise realistically but it was a definitive cause->effect. I did run an external power supply into it to eliminate that as a possible problem and it didn't change how the circuit worked, even while unpowered. I'm assuming I screwed up on the circuit somewhere (wholly possible given that I'm a novice at complicated circuits on veroboard. Plus component place was a bit haphazard out of space constraints) or the sync being output isn't as clean as the CXA1645 is expecting.

I still haven't solved the contrast bar rolling across the screen. Doesn't seem to be interference from the console itself but since it never was intended to be used with composite video I'm assuming there wasn't a basic filter installed to remove high frequency interference. Probably be a good idea to test it on a second display as well.

Edit:
Just found this as well:

http://web.archive.org/web/20051216185246/http://www.massystems.com/TD-Mod.html

Twice as many chips, two resistors. Looks a lot different though I'm going to bite the bullet and install two switches for this thing. Mechanical can't go wrong until the switch dies.

 

ASSEMbler means your system is suffering of DRY ELECTROLYTIC CAPACITOR SYNDROME or DECS for short... :lol:

 

I was suspecting such a thing on the side but was hoping it wasn't. Thankfully I seem to have enough spare caps to redo them all.

EDIT:

I've replaced every electrolytic on the board aside from the 22uF 16v cap on the daughterboard with the power connector. Haven't checked voltages yet but the thing works just as well as it did before replacing them down to the stupid rolling bar of contrast. Thankfully its visible on RF and composite so I know it isn't anything I've introduced into the system, unless running it without the RF shielding is the problem. Will run voltage tests in the morning.

 

APE, not sure if this helps but I used

http://www.mmmonkey.co.uk/console/pce/region.htm on white PC-engine and then I used the D-Lite PCB for my grey PC-engine, both worked well. I did try to region my Turbografx but for some reason it never worked. No idea why. I figured I messed something up, but one would think the smaller-pc-engine would have better harder due to space.

 

That is the exact guide I was trying to duplicate with continued failure as my only result.

Interesting that it didn't work on your TurboGrafx console as well. I've already ordered 2 4PDT switches to just get something working. I'll have to look into what Calpis said and see about building a region mod around that.

 

I think my US power brick is 10v and JPN ones say 9v. 7805 input should be somewhere around there. Output of chip should be 5v as you know. I might have spare transformer if you need one.

 

I followed the mmmonkey guide* too to mod my DUO-R - with the result it boots JAP games sometimes and US game not at all. After a few tries it doesn't even boot the JAP games (of course I switched between the regions only when the console was turned off and after a power brick reset).

I even tried it a couple of times, first with IDE cable, then with Kynar wire - nothing. When soldering the wires together to connect the pins like before it works again (JAP only of course).
Then I double checked the PCB I made with the two ICs and soldered everything again on a new PCB with IC sockets - nothing.

It just sits there for a year or so now, I'm really tired of it...


*(I mean, I followed the guide mmmonkey based his guide upon, http://playoffline.wordpress.com/mod/pceswitch/, of course with lifting pin 29 of HuC6280)

 

Interesting, this is a US made power brick to my knowledge and its rated at 9v; wonder if they did multiple runs? I appreciate the offer but I'm just installing an A/V and region mod for someone else. Not that a different brick would be a big deal but I'd have to assume something new that fit the spec with a higher amperage rating would be a good idea.

Glad I'm not the only one to have problems. I've seen a few posts here and there around the internet about this and most have been "anyone seen any 8PDT switches?" or "I'll install the IC mod for anyone interested and look at my cool install job". Rarely do I see anyone praising it for working 100% consistently.

Addendum:
Just finished wiring in two 4PDT switches for the region mod and it works perfectly. To hell with this crappy circuit.

 

Fascinating, got a replacement TG16 in the mail today with a much larger NEC branded power brick rated at 10.5v 730ma. The one I was originally provided was 9v 850ma.

Probably had something to do with the problems I saw. Though this TG16 also has the rolling contrast bar in the background which probably means there is some universal design flaw in these models.

 

I did the guide on a JAP PCE and get similar results. All JAP games work perfectly but TG ones not at all.
I have checked everything like 50 times including rebuilding the circuit but still the same issues.

 

Well, that's more than my DUO-R does...

Did you lift pin 29 of HuC6280 and connected it to GND?

 

If you got a completely different system in the mail, booted it up with a game, and it gives you the exact same 'rolling contrast bar' (whatever that is), then logic dictates that it's mostly likely not the consoles

 

Or its a problem with every TG16. I tried two different TVs with the same problem. RF and composite (don't have any RGB capable TVs). I suppose there could be bad power but it'd have to be coming in from the pole that way as I had tried different rooms on different circuits.

That thought did not cross my mind but that seems perfectly plausible. The first power brick didn't have any markings to indicate anything NEC related though. Doesn't mean much on its own I'll admit.

 

Sure did. As I said I double and tRiple checked the damn thing. I think I will just reverse the mod and leave it as jap only. Really only did it for shits and giggles.