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

[NightWolve]

He said the RGB amp needs to ground as close as possible to the 6260 chip (going by what he's saying), so a grounded pin on the chip would be the best. Grounding via the expansion port would be worse, further away from the chip.

[gtsamour]

So taking the signals and power from the expansion port is OK as long as you're getting ground from 6260's pin or close right? Or geting the other signals straight from the chip too is mandatory to avoid jailbars? I would love steve's confirmation on that one too 

[NightWolve]

Well, people have been doing it that way, so yeah, I guess. But if you gotta ground at the chip to really solve this jailbar issue as he is saying anyway, you might as well tap the RGB+S directly with new/good wires as just by basic physics you'll get the strongest signal sources there pre-amplification. At the expansion port, the signals have traveled from the chip to the traces to those pins, etc. hence resistance. Your new wires directly from the chip to the amp will likely subtract a little resistance.

[thesteve]

the signals should be fine
the ground traces are sig and power
when power flows thru a ground it causes noise
the longer the wire/trace the more noise it causes
the caps clamp the noise from point to point

[NightWolve]

How do you determine the capacitance value for these caps to "clamp" the noise ?? Would an official method be to connect an oscilloscope and see the noise, then add values from 10 uF and up and observe what value best helps "clamp" off the noise ?? Something like that ??

[thesteve]

consider its not so much correct value, as sufficient value
the best way to test it is be visual effect, as the noise is to small to see on a scope (normally)

[gtsamour]

Thanks Steve.

So taking the signals and +5V from the expansion port's pins isn't a problem I guess so I'll only change the ground to all six of my modded PCEngines (and install the tantalums ofcourse)

Do you think that connecting the ground wire to the 6260 chip's ground pin (pin 55 or 56 according to this guy ) is better than connecting it just next to it (onboard)? Well ofcourse it sounds better but will it make any difference?

Actually my DUO R (white) must be personally modded by the guy in the video because it is exactly the same (same amp, same connections and all). It gives very good picture with very faint jailbars but he's using composite instead of sync.
He's getting 5V from the 7805 regulator.... I will do the same like NightWolve suggested.

[NightWolve]

Yeah, pin 55 and 56 are also ground according to the list I linked you earlier and what he used in the video. Whether he knew it or not as far as the benefits, he did a steve-approved modding job. I would probably use pin 48 since it's right in between Red and Green, but yeah, any of the pins listed as GND will work. He probably used 55 cause it'd be easier to solder, less chance of bridging since you'd have Red, Gnd, and Green soldered next to each other. I think I could do it with my equipment, but maybe not.

Anyhow, very cool modding video by this guy! That's close to what I would like to have been making already...

P.S.

Why do you have 6 PC Engines ??

[gtsamour]

Why do I have 6? (hehehehe..... good question)... 2xTG16 (plus 1x SuperCD Rom), 1xCore II, 1xPCE DUO, 1xPCE DUO R, 1x Super Grafx, all boxed. I'm still missing some Huuuuge PCE fan  

I think pins 55 and 56 is the ideal place for ground exactly for the reason you mentioned (easier to solder) plus its good for the ground wire to be thicker (same for the 5V wire too). So you could just solder it on both pins...

edit...
I did the connections of both ground (to pins 55-56) and +5V to the right leg of the 7805 regulator.
Didn't notice any change compared to the previous state which had the two caps installed that indeed made a whole lot of difference.
If there was indeed a ground loop, it wasn't causing something noticable (at my DUO system at least).

To put it all in a nutshell, the caps do make a big difference. My DUO had the worse jailbars (very obvious and irritating) and now its the best of all my PCE systems. The jailbars don't go away completely, you'll spot them if you're anal about it but you must be looking for them to see them.

I even compared the DUO R which the guy on the video must have modded and the jailbars are more intense compared to the DUO with the tantalum caps.

I will install the caps on all the rest of my systems.... I won't switch the 5V source to the regulator and I'm not so sure changing the ground will add anything to the equation....

[NightWolve]

That first photo looks great, gt! Bravo, ya modding-maga! I think I like that you can bridge pins 55+56 and use a thicker gauge wire, so I changed my mind, that's how I'll do my Turbo Duo when it comes to the YPbPr Component mod for -/GND. No, scratch that, it's a great idea!

You know what else would be good ?? Some hot glue over the wires as they come around right next to the the cap in your first photo instead of black tape. All that grounded area would be perfect to position all the wires over and hot glue 'em down to make things permanent. My wires, since they're not solid copper and *thin*, right where they've been soldered and are metalized by the lead/tin, if they're bended back'n'forth for like 4-8 times (it's unpredictable, but it's easy to happen) and what not, they'll break off... So some hot glue to permanently fix the wires down a little bit after they've been soldered somewhere I find is useful. Since the 6260 chip is on the bottom of a US Turbo Duo, I think it's a very good idea so that you'll never have to flip the PCB over again if there's a problem in the future. All the needed wires will be accessible on the top and very secure on the bottom. Just need to make sure you cut them at a good enough length.

Well, sucks that you didn't get a further improvement for the jailbar issue, but I bet it varies. At least the cap idea has a significant impact!

P.S. Quite a tangent, but I happen to have a Savings account in the Ethniki Trapeza of Greece, and it has a couple of thousand US dollars in it. I kinda think I should've emptied the whole thing out last time I was there in '08... Anyway, I notice you're in Athens, so what the hell is going on over there with these socialist 10% raids or whatever on bank accounts that they're talking about ? Is that limited to Cyprus or is that shit gonna spread elsewhere to Euro countries ?? The ole "running out of other people's money" is in full swing, eh ??

[gtsamour]

Thanks NightWolve, I try to make things as neat as possible when modding systems. As you can see the whole board is sqeaky clean, thats what you get after imersing the whole board under a significant amount of isopropyl alcohol. Being a chemist and working in a pharmaceutical company has its benefits

Actually I use hard disk ribbon cable stripes. The thin ones are from E-IDE ribbon cable and the gray thicker one from standard IDE cable. These cables must have very low resistance. The good thing with these cables is that they're really flexible. You can bend and twist them but they won't break inside. And you can get many many cable lines from just one ribbon.

As for the banks issue... there is none here. The "raid" on people's money (the ones that have more than 100000 euros in accounts) is limited to Cyprus.
Is it going to spread elsewhere? They're saying it won't but who knows these days... specially when the 4th Reich is running Europe.

[NightWolve]

As for the banks issue... there is none here. The "raid" on people's money (the ones that have more than 100000 euros in accounts) is limited to Cyprus. Is it going to spread elsewhere? They're saying it won't but who knows these days... specially when the 4th Reich is running Europe.

Oh, pfffft, OK, it's for accounts over 100,000 EUR. It's a soak the rich raid. Yeah, then no problem (for me). The way it was reported made people paranoid! I hadn't seen that figure. But I believe I read that Spain/Italy or something were talking about the same sort of thing. Anyway, it's only some chump change left in my account so next time I'm visiting/vacationing, I'll have access to local spending cash. I was trying to decide if I should just cash out last time I was there, but I left most of it for that reason. Chicago actually used to have a Greek Ethniki Trapeza branch, but it closed some time ago (we are considered Tsipiana/Nestani here, hehe!). There is another one in New York for the Greek community there, so in theory, I could drive there with my Savings book and close it out if I got freaked out about the economic situation in Greece. That conversion to Euro sure was a killer man... For you and for Americans visiting...

Anyway, thumbs up on the modding! Good luck!

[gtsamour]

I wouldn't worry about it, and from experience... if they're talking about such a thing, it aint gonna happen. What's the point of letting it be known to people so they can withdraw their money before it happens?
Take Cyprus for example... it happened before people had the chance to do anything, except the b@astards that had informations from within... (like Cyprus priminister's daughter for example).
Euro is nice.... specially when buying from the US but it can be a pain in lots of things.

ps
I may do the hot glue thing on it, I hate the sticky residue this insulating tape leaves after some time if you choose to remoe it. I don't particularly like the hot glue solution either but I don't see a better alternative.

edit...

Saturday morning eye candy

[thesteve]

ok the pic brings up another point
your amp is sitting on top of digital signals
your signal wires cross power and data traces
shielding the amp and shortening the wires should help
also because that amp uses transistor bias resistors from its 5V supply, the supply needs a large filter cap on the amp board.

[gtsamour]

There is no place onboard without digital signals that an amp can sit on. Actually there aren't many places that the amp can sit on and have the top shell being able to close completely. The location I picked is the most convenient, its flat (no caps there) and the top shell closes. There is also a 2mm thick double sided adhesive tape holding it in place so there is some spacing between the bottom of the amp and the top of the chips it sits on.
The wires cannot get shorter, take a look... no loose cables, straight from source to destination through the shorter possible path. How can they get shorter and reach the desirable points at the same time?

Yes I could shield the amp but I've never seen anyone do it on a PCE rgb mod and somehow, I don't think it will improve much (if any).

Anyway, the system went from "worse Jailbar system" to "best" within my PCE collection so it is a major improvement. Have you managed to make the jailbars completely disapear on your system? (with shieldings or whatever?)

The amp is constucted according to this design http://www.gamesx.com/grafx/pce_rgb.jpg , its supposed to be PCE specific.

The jb aren't coming from the amp, they're comming from the 6260 chip and they were there even without the amp and I'm sure they will still be there on composite even if I disconnect the amp completely (although much weaker because of the tantalum caps). Maybe the 6260 chip needs shielding. Thats how the guy that completely solved the jb issue on the Famicom did it (by shielding the picture generator chip)... complete absense of jb, not the slightest sign of them.