exxos's Atari, Amiga & retro forum

More progress:

Thanks to everyone for the advice so far. The CPU has been replaced and bodge wires connected with no shorts between pins:


I have attempted to power the board but I don't get any video out. The fan spins up and the 3-in-1 video adapter shows the Falcon powered on, and my power supply shows a 1.35-ish amp draw on 5V and a 0.15-ish amp draw on 12V.

I did notice a few other odd things on the board that I would like to ask about. In general for all of these, is there a mod that calls for these to be removed and/or is the item needed for the board to boot?:

1. U27 (TL497ACN) is missing. I checked the schematics and this appears to be connected to VCC, ground, and VEE only. I assume this is a voltage regulator for an audio amplifier and was removed when the audio mods were done to this board. Is this correct?
2. C67, right below U27, was disconnected on the negative side. I have reconnected it.
3. R234 was disconnected. I have reconnected it.
4. L102 is missing.
5. C9 (on bottom) is missing.
6. R39 (on bottom) is missing.
7. Several resistors (R216, R221, R222) have been removed as part of a timer mod, so I think these are fine, but I thought I'd mention them.
8. A large portion of a circuit is unpopulated (see image). I assume this is normal and part of NTCS/PAL differences, but I thought I'd ask.


Thanks again!

Just checking you have jumper W1 on the expansion port fitted? It's missing on an earlier photo.

Acsi wrote: 08 Nov 2023 21:18 Just checking you have jumper W1 on the expansion port fitted? It's missing on an earlier photo.

Thanks. It was not. I just added it and, sadly, still no video output.

Did you check every CPU pin if it they are connected solid?
(search for Northbridgefix on YT if it does not ring a bel)

I could be wrong but I've got a feeling that if you have U65 fitted as well as U37 then R234 should be removed otherwise you have clashing clock signals? Sorry it's been awhile since I had a Falcon.

@hunsra It seems that machine used to have a Phantom clock booster installed, because R234 / L102 are removed for its installation. Here I'll attach the Phantom installation manual, you should be able to read that and then know what you need to reverse. L102 passes the 32mhz signal I think, so yeah your Falcon certainly won't boot without it. If you don't have that particular inductor part I think it can be safely bridged with wire.

All that missing circuitry by the fan is just the general differences between pal/ntsc. I think they're only populated on pal.

Maximilian wrote: 08 Nov 2023 23:16 Did you check every CPU pin if it they are connected solid?
(search for Northbridgefix on YT if it does not ring a bel)

That's a good question. Thanks. I believe they are all connected solid, but I have not done a thorough pin-by-pin check. I will have a look at the schematics and start verifying continuity of the signals.

Acsi wrote: 09 Nov 2023 02:59 I could be wrong but I've got a feeling that if you have U65 fitted as well as U37 then R234 should be removed otherwise you have clashing clock signals? Sorry it's been awhile since I had a Falcon.

Thanks. Those are both fitted, so that may be why R234 was disconnected. I'll review that in the schematics to see if I need to disconnect it again.

Steve wrote: 09 Nov 2023 07:35 @hunsra It seems that machine used to have a Phantom clock booster installed, because R234 / L102 are removed for its installation. Here I'll attach the Phantom installation manual, you should be able to read that and then know what you need to reverse. L102 passes the 32mhz signal I think, so yeah your Falcon certainly won't boot without it. If you don't have that particular inductor part I think it can be safely bridged with wire.

All that missing circuitry by the fan is just the general differences between pal/ntsc. I think they're only populated on pal.


Phantom_manual.pdf

Thanks for the manual! Yes, it does indeed look like that was previously installed. There are solder blobs and other signs of it having been there previously. Hopefully I can reverse the process.

Thanks for confirming the PAL/NTSC differences. I suspected that.

hunsra wrote: 09 Nov 2023 14:03 That's a good question. Thanks. I believe they are all connected solid, but I have not done a thorough pin-by-pin check. I will have a look at the schematics and start verifying continuity of the signals.

You cab use a no so sharp needle and just try to ever so lightly try to move a pin, if the pin moves with the needle, it is loose.
No need to continuity check if there is no apparent damage, and it can give you a false hope of security because if the pin isn't soldered correctly if will give problems when the machine heats up or cools down..