Key to N64 RGB Amplification Problem?

[RARusk]

I recently purchased two RGB modifiable (NTSC) N64 units from Goodwill Computerworks on the cheap for RGB experiments.

I had heard about the pin-lifting method (on the RGB pins) for picture brightness and I gave that a try on one of the two units. It brightened the picture a little but also brought about interference issues. Certainly not the solution I was looking for.

On the other unit I tried something different.

On my main N64 I use a CXA-1145 RGB chip cut from a dead Genesis for RGB amplification. In order to get it to work as an amplifier you have to put in a sync source on one of the pins.

Inspired by that I decided to try this with the N64's VDC chip (labeled U4 on the right side of the motherboard). I identified pin 14 as sync (it is stable but not usable on a monitor). So I soldered a 30-gauge wire to pin 14 and applied the other end to the various pins.

I found that the picture brightened when applied to pin 23. However, it went to the same brightness level as the pin-lifting method. But, there was no discernable interference (BTW, I am using "Star Wars Episode I: Racer" as my test cartridge).

Then I poked around some more. I removed the wire from pin 14 and soldered it to pin 23 and tried other points on the motherboard.

When pin 23 is attached to ground, the picture brightens dramatically and to where I felt it should be. Unfortunately, there were two issues that cropped up:

First, there was interference (especially at the title screen).

Second, and more serious, was the fact that the chip got hot. Not hot enough to burn your finger but hot enough to possibly shorten the lifespan and maybe burn out the chip at some point. When pin 23 was removed from ground the chip immediately cooled down.

So I removed the wire, lifted pin 23 from the board, and re-soldered the wire to the pin.

When attached to ground, there is less interference however the chip still heats up (but takes longer to do so).

Despite these obstacles I believe I may have found something promising that can be used to hopefully solve the N64's RGB amplification problem. Maybe somebody here that has better equipment and skills can take a crack at it or provide better information on this chip.

[viletim]

Do you have access to a CRO?

[Link83]

I had alot of trouble getting a decent clear picture from an N64 aswell, in the end I settled on lifting the legs on a NUS-CPU-03 board (which has some components off the C-Sync line that are missing on later board revisions) This works very well on my Scart enabled CRT TV. Unfortunately I guess it hasnt worked well for you - perhaps this method is affected too much by the Monitor/TV used?

I had also read about the 'linking two points boost' in a few places. you can see the two points at the bottom of this page:-
http://www.mmmonkey.co.uk/console/nintendo/ntsc_nintendo_64_rgb.htm

I also read in this thread:-
http://nfggames.com/forum2/index.php?topic=510
that pins 22 & 23 of the VDC-NUS chip can be linked to produce the same effect - I think they are in fact all the same points, just on opposite sides of the board.

When I tried linking the two points I got lots of interference on screen, no matter what I tried. Also, as you say the chip gets very hot.

The VDC-NUS chip was never really designed to directly drive a TV/Monitor. I think the only 'proper' way we are ever going to find would involve building/using an amp. Any other method we try is probably going to be pushing the VDC-NUS chips beyond its limits/capabilities. I can understand why everyone keeps trying though - adding a few extra wires is heck of a alot easier than building an amp.

What I think we really need is someone to produce an easy to make amp that works perfectly for any RGB N64. Most of the amps I have seen are designed for other games consoles (eg. PCEngine) and have just been passed over for use on an N64. I have seen Waltazars Amp, but the transistors used (BF494) dont seem to be easy to find anymore.

Preferably this 'perfect amp' would not require the VDC-NUS legs to be lifted - just either connected directly from the chips legs, or from the R8, R9 and R10 points on the underside of the board (Which are actually both the same, just the 'R' points make it easier to route the wiring as you dont need to go round the edge of the board to connect them to the AV Multi out)

Viletim, perhaps you could possibly take a look at this and come up with the 'perfect amp' for the N64 using easy to find parts? 

[RARusk]

I have the CXA-1145 inside my main unit and that works well for amplification.

But, as with everybody else, I am always looking for better alternatives to this problem.

Considering that one of my units has three pins lifted I may sacrifice that unit and remove the VDC chip from it to see the traces that run under it.

[viletim]

Viletim, perhaps you could possibly take a look at this and come up with the 'perfect amp' for the N64 using easy to find parts? 

I could but I'd need somebody to loan me an unmolestered RGB-able N64.

[Link83]

I have the CXA-1145 inside my main unit and that works well for amplification.

But, as with everybody else, I am always looking for better alternatives to this problem.

Considering that one of my units has three pins lifted I may sacrifice that unit and remove the VDC chip from it to see the traces that run under it.

I have a busted N64 motherboard that I would be happy to remove the VDC-NUS chip from and take picture if youd like? (I fried it by putting 5v though one of the legs of the VDC-NUS chip whilst testing a 'theory' lol - I have used the PIF-NUS chip though so it wasnt a total waste)

I could but I'd need somebody to loan me an unmolestered RGB-able N64.

Viletim I would be happy to send you an 'unmolested' RGB-able NTSC N64 to take a look at if you are interested? - I live in the UK though so dont know if that would be a problem (Could just send the motherboard if youd like - would save me abit on postage)

[Link83]

Well, since I was bored I though i'd go ahead and desolder the VDC-NUS chip on my busted N64 anyway, so heres a pic:-


Doesnt look to be much there really, just looks like a a 'pass through' for traces from another chip.

Please excuse the tiny piece of fluff in the middle, and also note that the R8, R9 and R10 points have been filled with solder due to a previous mod - they would usually be empty.

Does it help at all?

[john]

Viletim I would be happy to send you an 'unmolested' RGB-able NTSC N64 to take a look at if you are interested? - I live in the UK though so dont know if that would be a problem (Could just send the motherboard if youd like - would save me abit on postage)

You wouldn't happen to have a RGB modded NTSC N64 you want to sell (cheaply =] ) do you?  Mine had an accident involving a child.  :/  I'd only need the n64 itself - no psu or anything if that'd make it cheaper.  :>

Sorry to be so cheeky, but I miss my n64.  :/

[Link83]

You wouldn't happen to have a RGB modded NTSC N64 you want to sell (cheaply =] ) do you?  Mine had an accident involving a child.  :/  I'd only need the n64 itself - no psu or anything if that'd make it cheaper.  :>

Sorry to be so cheeky, but I miss my n64.  :/

I havent - sorry. I just bought a few early model US N64's off eBay.com in order to experiment with, one I accidentally busted, one im currently using, and the last one is untouched and im sending it to Viletim so that he can take a look at the amplification problem and hopefully come up with a solution which will benefit everybody 

You can find the early model N64s (unmodded) relatively easily if you willing to email a few sellers on eBay.com - I bought mine for around $35 each including shipping to the UK. Sorry I couldnt be of more help  If youd like anymore info feel free to PM me

[john]

Sorry I couldnt be of more help  If youd like anymore info feel free to PM me

No worries.  I don't use ebay and have no way of paying international sellers unfortunately.  I'll keep looking at the car bootsale, one is bound to turn up soon enough.

Thanks for the offer of info too.


As an aside, I don't know if you have a wii but GAME are currently clearing out official Wii RGB scart cables for 98pence each.  Worth buying just for the future even if you don't have a wii.  =]