Newbie AV Mod help please

[bpharoah]

Hi All, I'm new to this forum, but not to the Atari scene, so please forgive me if I've put this in the wrong place!

 

I've recently been trying to carry out the AV mod on my Atari 7800 console, but I've run in to a bit of an issue. In my haste to remove the RF connector, I think I destroyed the +5v connection. So my first question is there somewhere else on the board I can pick up the +5v from? I've looked at the circuit diagrams, but I'm none the wiser!

 

I do have sound, just no video output, so I think if I get the voltage sorted then I'm good to go. However, is there anywhere else on the board to pick the video in feed from? (Just asking, just in case...!)

 

This is a PAL system by the way.

 

Thanks,

 

Lee.

[Osgeld]

is there a 74xx32 near by, if so pin 14 is +5

 

[+-^CrossBow^-]

I haven't really looked at the PAL board layout, but on the NTSC version there are too very large traces that run down the middle of the board from the cart slot down. On the NTSC version the traces on the left is a +5 volt rail and the large trace to the right is a large ground plane.

 

So..might get a meter and see if that is the case with the PAL boards as well?

[bpharoah]

Thank you for the quick responses, much appreciated.

 

I can't really identify the traces from the cartridge port, but I can see the 74xx32 chip, so I'll give that a whirl and report back.

 

Lee.

[+DrVenkman]

Thank you for the quick responses, much appreciated.

 

I can't really identify the traces from the cartridge port, but I can see the 74xx32 chip, so I'll give that a whirl and report back.

 

Lee.

 

Here's a photo of one of my (NTSC) 7800 boards. The thick traces running up either side of the board are what Crossbow is referring to. The vias on each trace should be good to use for +5V and Ground. Use a multimeter to verify which is which of course.

 

[bpharoah]

Wow! Nothing like that at all on my board. Shame. And I do need to remember where I put my multimeter...!

 

Incidentally, I picked up the 7800 'cos I have no idea what I've done with my old Woody console - it's here somewhere!

 

Thank you!

[+-^CrossBow^-]

I don't have a PAL board to verify, but what if anything might those unused VIAs on the larger traces that run under the cart connector horizontally be? I'm thinking they are similar to the vertically running +5 and ground rails on the NTSC, but without one on hand to verify...

 

And not to be a bastard..but how does one do any mod work hobby, professional, or otherwise without a meter to at least measure voltage and continuity/diode functions? Even with a hand hold and clear pics, you will still see me using my meter to verify my connections and verify where I'm pulling my voltage and grounds from.

[bpharoah]

You're right, I should be using a multimeter, but it looked like such a simple job!

 

Anyway, no luck so far, still no picture. I'll have to resume the fight tomorrow now...

[bpharoah]

Hi all, I've finally had a chance to work on this again tonight. I had indeed destroyed the connections from the old RF module! Luckily, I've managed to use alternative connections on the board (+5v - thanks Osgeld!) and everything is working wonderfully now!

 

So, thank you everyone for all your help and support.

 

Lee.