RGB NES / Famicom and jailbar removal

mvsfan wrote:

drakon - what do you think of the possibility that the lm1881 got damaged and isnt working right?

Unless you wired vcc and ground wrong it should be okay. Buy another, drop it in, see if that changes anything. It's always good to socket dip chips. Even when I build a cxa2075 circuit I solder the chip into a sop to dip adapter so I can swap the encoder chip easily.

no, the power was wired correctly.

out of the whole project, the sync lines were the only 2 wires that got swapped.

mvsfan wrote:

no, the power was wired correctly.

out of the whole project, the sync lines were the only 2 wires that got swapped.

btw, in case anyone else is having this problem, THIS is what happens when you swap the sync wires.

[quote="Drakon"]

mvsfan wrote:

drakon - what do you think of the possibility that the lm1881 got damaged and isnt working right?

Unless you wired vcc and ground wrong it should be okay. Buy another, drop it in, see if that changes anything. It's always good to socket dip chips. Even when I build a cxa2075 circuit I solder the chip into a sop to dip adapter so I can swap the encoder chip easily.[/quote

when i buy a part i usually buy more than one. Ive got 2 more right here.

I just bought some of that foil sheild tape im going to try sheilding the cpu/ppu like you and skips suggested.

Btw, did you sheild the bottom of them also, or just the top?

mvsfan wrote:

I just bought some of that foil sheild tape im going to try sheilding the cpu/ppu like you and skips suggested.

Btw, did you sheild the bottom of them also, or just the top?

Yes of course the bottom, the whole point of shielding is that it's shielded from the noise on the pcb itself.

mvsfan wrote:

I just bought some of that foil sheild tape im going to try sheilding the cpu/ppu like you and skips suggested.

Btw, did you sheild the bottom of them also, or just the top?

Also make sure you cover the top trace with electrical tape.

Skips wrote:

mvsfan wrote:

I just bought some of that foil sheild tape im going to try sheilding the cpu/ppu like you and skips suggested.

Btw, did you sheild the bottom of them also, or just the top?

Also make sure you cover the top trace with electrical tape.

i never realized that was a trace until i read your post skips. ill definately do that.

btw, skips - any input on why im having the sync issue? i really dont think the 1881 is blown because i had some issues with the old 1881 also.

am i missing a part? any parts that could clear up that wavy sync?

how about an amplifying transistor of some sort?

The LM1881 has always been sufficient for me. Make sure you have it wired correctly. Also make sure you have sync wired on the SCART connector properly. You should also check and see if your TV requires composite sync or raw sync. If it can only accept composite sync you may have to wire in a full CXA2075 circuit and mix in composite video with the raw sync coming out of the LM1881.

Skips wrote:

The LM1881 has always been sufficient for me. Make sure you have it wired correctly. Also make sure you have sync wired on the SCART connector properly. You should also check and see if your TV requires composite sync or raw sync. If it can only accept composite sync you may have to wire in a full CXA2075 circuit and mix in composite video with the raw sync coming out of the LM1881.

no, my tv is a 60hz 4:3 sony wega, standard res.

I shouldnt be having this problem. it accepts raw sync great from my snes.

But my clue about weak sync is this. My Pexhdcap 240p capture card doesnt recognize the nes it just gives a black screen. It works great for my snes and genesis.

mvsfan wrote:

Skips wrote:

The LM1881 has always been sufficient for me. Make sure you have it wired correctly. Also make sure you have sync wired on the SCART connector properly. You should also check and see if your TV requires composite sync or raw sync. If it can only accept composite sync you may have to wire in a full CXA2075 circuit and mix in composite video with the raw sync coming out of the LM1881.

no, my tv is a 60hz 4:3 sony wega, standard res.

I shouldnt be having this problem. it accepts raw sync great from my snes.

But my clue about weak sync is this. My Pexhdcap 240p capture card doesnt recognize the nes it just gives a black screen. It works great for my snes and genesis.

i think theres only one way to wire the sync on the scart connector - pin 20 right?

its on pin 20 or i shouldnt get a picture at all.

the 1881 is a very easy circuit to wire. i did use non-polarized caps, and a 680k ohm resistor.

Ive checked the continuity on everything related to the amp pcb and the 1881 and all the connections have nice solid beeps, and the meter reads 0 ohms resistance.

I also checked the pcb socket for continuity i figured mabeye i had a loose joint somewhere. nope, it all checks out.

I also swapped the scart cable for another one that works good - no difference.

No, on CRT televisions you will still get picture even without sync present with the RGB NES. It just comes through all fucked up like your screenshot shows.

I didnt realize that. Thanks for the help skips. I will try another 1881 circuit i already have built then and get back to you.

Btw, for a test could i have 2 1881s powered up at the same time, with the sync connected to the new one - will the voltage regulator be able to handle that or do i have to de-solder the old one first?

The power draw of the LM1881 is minimal, two should be fine. You really should get sockets for this type of stuff. They are fairly cheap and allow you to switch parts out easily.

i didnt know what to look for for smt parts. both of these chips are smt. what would the socket be called?

You need SOP to dip then. The LM1881 comes in dip form as well. next time get those they are much easier to work with.

Skips wrote:

You need SOP to dip then. The LM1881 comes in dip form as well. next time get those they are much easier to work with.

yeah. i wont build it like this again i wanted everything socketed.

are manufacturers just abandoning dip altogether? ive noticed a lot of parts i cant get in dip.

thats stupid but i guess its how they are doing it.

mvsfan wrote:

Skips wrote:

You need SOP to dip then. The LM1881 comes in dip form as well. next time get those they are much easier to work with.

yeah. i wont build it like this again i wanted everything socketed.

are manufacturers just abandoning dip altogether? ive noticed a lot of parts i cant get in dip.

thats stupid but i guess its how they are doing it.

it doesnt matter though cause im going to build another nes using an rc2c05-03. when i do that, ill have the pcb for the 74hc151 to work with and everything will be socketed.

btw, i realized something when i test-fit the parts for the rc2c05. You must be using single - row headers for the ppu instead of a socket, otherwise you cant make the connections with them staggered like that.

Ill have to order some.

mvsfan wrote:

Im wondering if the fpga interpreter or the universal ppu will work in a playchoice so i can put some of these boards back together.

Universal PPU is supposed to work as a replacement for all Playchoice PPUs in Playchoice 10s.

mvsfan wrote:

I shouldnt be having this problem. it accepts raw sync great from my snes.

But my clue about weak sync is this. My Pexhdcap 240p capture card doesnt recognize the nes it just gives a black screen. It works great for my snes and genesis.

The SNES or Genesis output raw sync out their multi AV ports, but it's quite common for SCART adapters to just use the CVBS as composite sync. Saves a wire.

mvsfan wrote:

I noticed your SCART pin 17 isn't hooked up. Leads me to wonder if your composite sync is even grounded.
I have zero experience with SCART, so I can't say this is your issue for sure. Everything in my analog setup hooks up with BNC/RCA.

Grambo wrote:

mvsfan wrote:

Im wondering if the fpga interpreter or the universal ppu will work in a playchoice so i can put some of these boards back together.

Universal PPU is supposed to work as a replacement for all Playchoice PPUs in Playchoice 10s.

thats great.

The SNES or Genesis output raw sync out their multi AV ports, but it's quite common for SCART adapters to just use the CVBS as composite sync. Saves a wire.

pin 20 also works as raw sync.


I noticed your SCART pin 17 isn't hooked up.

I didnt think it has to be unless i was using composite video. I could be wrong though.


Leads me to wonder if your composite sync is even grounded.
I have zero experience with SCART, so I can't say this is your issue for sure. Everything in my analog setup hooks up with BNC/RCA.[/quote]

the only thing thats grounded on the scart connector are the rgb lines. I havent even played with audio yet.

I could be wrong with the way im grounding the scart. the component converter could be expecting a ground somewhere that its not getting.

I tried to get schematics for it from the guy who sold it to me but the manufacturer wouldnt give them to him.

Ive got a solid picture now it no longer rolls when it feels like it.

The problem was my power switch. I discovered that if i just barely moved it it would cause the screen to roll.

It hasnt rolled for an hour now since i put a new one in.

But ive still got that other issue.

who woulda thought something so stupid would cause the picture to roll.

another issue - since i fixed the power switch, for about 10 seconds of the hour its been on, the interference on my picture magically disappeared and i got to see how good this rgb nes really looks.

but its back again.