yell0w_lantern, on Sun Nov 6, 2011 12:37 PM, said:
Over a year ago I installed a Longhorn AV mod on my Atari Jr. It worked fine for a while (several months?) but then I had to start tapping it when I started it up so that I would get picture. I hooked it up after several more months and now I get absolutely nothing. The screen stays black when I turn it on although the power LED turns on; no sound. I get the same black screen with or without a cartridge. I even tried cleaning a couple of carts. I tried the Harmony cart too. I even considered it might just be a video problem so I pressed reset half expecting to hear a game start but no such luck.
I opened up the console and checked the ground which turned out to be a little loose so I resoldered it but that did nothing. I tug tested the wires and examined the traces on LE's board but everything looked okay. No loose components either.
I'm wondering if a chip died or something. Anyone seen this before?
From the sound of things with the console needing to be smacked around there is a loose connection
somewhere. You said the display was black. Does the screen flicker as you power up the unit?
If no I would check continuity from the display chip to the cables.
If yes I would check continuity of the cart slot pins, since the console is not detecting the cartridge.
Check the traces from the addresses and data lines back to the chips and check the ground/OE lines. Good traces will read near zero ohms.(some meters will have a beep function also)
With the console on and a cart in find test points for pin6 and pin11. Set the meter to DCvolts.
Pin 11 should read close to +5V and pin6 shoud read +2.2V to +5V.
If you want to test the indivudual chips you will need a logic probe. They are fairly cheap ($20) and
come in handy for us classics collectors.