REPAIR GUIDE - TurboDuo/PC Engine Duo: Total capacitor replacement chart

[gtsamour]

Ahhh thanks, that answers my question... so I need two 22uF 16v polarized tantalum for each console.

Actually I tried the "to solve jail-bar issue on rgb modded system replace capacitor C961 10uf with 100uf tant or 220uf aluminum" mod, which was also steve's but did nothing for me. I hope that one works

[thesteve]

this one works on the same concept, except it eliminates the variances in the boards by going direct to the chip and adds a cap to the 5v rail

[gtsamour]

Well I know some people said they saw a difference by doing the C961 cap mod, but I didn't (on my black PCEngine DUO R).
Already ordered some 22uF 16V polarized tantalums and I'll try the other mod, hope this one will make a difference for me

[thesteve]

its possible your getting jailbars from cabling as well

[gtsamour]

From cabling you mean the RGB cabling? Well I thought that too but I could see jailbars on composite even without the RGB amplifier installed.
I see jailbars even on simple unmodified TG-16 on composite taken from the expansion slot so I doubt its my cabling.... if it was I would be able to see changes at the jailbars just by moving cables around which I don't.

And anyway, nobody reported a significant improvement by just doing the C961 mod so why should it be my cabling....

[thesteve]

when i did an lm1881 on the far end of a cable, it caused them as well.
it was solved by adding a cap to the lm1881 power pin

[gtsamour]

What capacitor value did you use?
Using the lm1881 on the far end of the cable.... doesn't that make the cable an "antenna" for introducng interference in the power line?

I use the amplifier with the 4 transistors (R G B and Sync amplification ) that was published for the PCEngine ages ago, but always inside the console. Cables are as short as possible (considering the lengths needed to pick the signals), and are taken from an IDE stripe cable.

[thesteve]

i put a 470uf across the lm1881
the cap was overkill
the reason i did it like i did was, to make a scart to RGBS adapter for my display

[gtsamour]

The PCEngine DUO (black) must have the worst jailbar problem of them all.

I did mine with two 22uF 16V tantalum caps, here's a picture...



There is an improvement (LCD tv), I would call it an average and not vast one though... jailbars are kind of dispersed but still there.
Or maybe I'm just being anal about them (like looking for jailbars at the lcd screen from different angles)

I wish there was a solution that completely eradicates the deam jail bars, like there is one for the famicom system. It involves shielding the chip with copper foil among other things... don't know if that would help the PCE though

[thesteve]

where is your amp ground?
your RGB amp needs to ground by that chip

[gtsamour]

The amp is on the other side of the board, here's a picture. I'm getting ground from the video out socket.



Where exactly do you mean I have to get ground for the amp? Like from one of the tantalum capacitor's negative pole to prevent ground loop?

I take +5V from the socket too... do you think I should be taking it from another spot?

What happens with other PCEs like the Core II for example.... I use the same amp but I took all signals and ground and 5V from the expansion port... Is that ok or should I get ground right next to the chip again?

Thanx for your help.

[NightWolve]

http://img442.imageshack.us/img442/4126/imag0053rx.jpg

A little big those two, but you managed to pull it off. The seller typically provides the dimensions of a cap so you can better pick ones that'll fit BTW.

Where exactly do you mean I have to get ground for the amp? Like from one of the tantalum capacitor's negative pole to prevent ground loop?

Yeah, that sounds like what he's saying. There should be a 5th wire close to that chip and where you soldered the negative end of the caps is ground, so that'd be one place. I would guess identifying an actual pin that IS grounded would be even better according to what he's saying. As for a +5V source, tapping it right from the regulator is the best if you can manage it. Tapping it elsewhere means more resistance having traveled around via traces, so it's less clean. This seems to matter with region mods or something and those older flashcarts not working right unless you tap the +5V needed power from the regulator. Anyway, I don't think it matters much here powering a little amplifier, so I'd just try his ground suggestion.

[gtsamour]

Yeah I think thats the case too

Well since these caps are tantalum 22uF 16V, Ι dont think they come in smaller sizes for this capacitance at least. Ceramic may be smaller though. Compare with the tantalums (non SMD) steve has in his picture http://imageshack.us/a/img221/3182/20130314222631.jpg ... they are just about the same size. The weird thing is that I don't see a ground cable close to the chip, unless he's not using an amp.

ps
The video socket's 5V is pretty close to the regulator so I think its OK, unless steve suggests otherwise.

[NightWolve]

http://gamesx.com/wiki/doku.php?id=hu6260_netlist

OK, going by that, pin 39 is GND (next to pin 40/Luma), pin 48 is GND (in between Red and Green), etc. There are several.

Use a DMM and do a continuity test to make sure with a known ground point and I guess I would solder directly on one of those pins.

The video socket's 5V is pretty close to the regulator so I think its OK, unless steve suggests otherwise.

Well, that's where a +5V source is normally taken on the top of the PCB and you've had reports of the problems with this region mod/flashcart issue which are solved by tapping the output pin of one of the regulators, etc. But yeah, I guess it's a matter of "juice" and this is a little amplifier, so probably not necessary to go that far.

EDIT: OK, here's some context, a thread about the +5V regulator/switchless region mod issue. Just so you know what I was referring to. People report they fixed some crashes/issues with flashcarts and that region mod or whatever. Drakon says he always taps +5V from the regulator, etc. Your voltage will likely read higher, ~5.32 V or so whereas the at the AV out, I was getting like 5.02 V, etc.

[gtsamour]

Yes I understand the issue about 5V, but its an analog amp with low power consumption. Region mods are complicated and probably more power consuming. Anyway, its hooked on the video socket's 5V and if you exclude the jailbar issue, the picture is perfect otherwise. If unclean power supply can cause jailbars then I'll go for the regulator but I doubt it can...

OK I'll try it tomorrow and see if the jailbars go away even more.

But what about PCEngines that the signals aren't taken straight from the chip but from the expansion board... is the chip still the best point to get ground from or the GRND dron the expansion port is OK?