Falcon Restoration Project

[HigashiJun]

BTW, Best Electronics sells the VIDEL, COMBEL or SDMA for $45 each.

Always forget Brad and his good deals...

[HigashiJun]

That's for a bulk lot

I only realised now that's the price for a bulk lot...

Always thought the guy was selling at a LOL price.

[hunsra]

Thanks @@Rustynutt, @sporniket, @mikro, @HigashiJun. Yes, I now see the $2400 is for a lot of 96 units. That makes me feel a little better. As soon as I get the parts I've already ordered from Exxos, I'll be able to try to power up the board and I can determine better what is working and what isn't. Thanks again for all the great advice!

[alexh]

Might be worth performing a test for power <-> gnd shorts just before you switch on? Just in case anything has become a short. It just takes a fleck of solder dropped while someone was removing something.

I think the Exxos PSU has short detection but better to test than accidentally burn a track or two first power on.

You seem experienced so I'm sure you are planning to do it.

[exxos]

I think the Exxos PSU has short detection but better to test than accidentally burn a track or two first power on.

It has a "soft start". Think it's current limited to 1amp during power up. If the voltage doesn't rise it trips short-circuit protection. Basically doesn't shove full amps at power on like most PSUs tend to do. The slower ramp up means it shouldn't vaporise tracks and can help limit abuse to silicon also.

[hunsra]

Might be worth performing a test for power <-> gnd shorts just before you switch on? Just in case anything has become a short. It just takes a fleck of solder dropped while someone was removing something.

I think the Exxos PSU has short detection but better to test than accidentally burn a track or two first power on.

You seem experienced so I'm sure you are planning to do it.

Thanks. Yes, I was planning on doing a continuity test on power traces and ground before powering on, but I appreciate the advice. I'm definitely not very experienced so anything you or anyone else can suggest is very welcome and appreciated!

[hunsra]

I think the Exxos PSU has short detection but better to test than accidentally burn a track or two first power on.

It has a "soft start". Think it's current limited to 1amp during power up. If the voltage doesn't rise it trips short-circuit protection. Basically doesn't shove full amps at power on like most PSUs tend to do. The slower ramp up means it shouldn't vaporise tracks and can help limit abuse to silicon also.

Thanks. This is good to know, since I did order that PSU.

[hunsra]

I have received all the parts I ordered and have started to do some work on the restoration.

• First, I checked the power rails and traces for continuity with a multimeter and there seem to be no shorts (thanks to @alexh for the suggestion).
• Programmed and installed the missing GAL (see photos).
• The original CMOS chip had been cut out instead of desoldered (see photos), so I removed all of the pins left in the board. This was more difficult than I expected. A few pins required significant heat and time to remove. I assume this is due to those pins being connected to a large ground plane area. I was able to finally get them all out without any apparent damage.
• Installed a low-profile DIP socket for the CMOS chip (see photos).
• Removed the CPU mod remains. Doing this snapped the bent pins from the CPU (see photos). I have doubts that this is repairable, but I'll ask the forum for advice: should I replace the CPU or try to attach leads to the broken pins and traces? If I replace, is there any way to socket a CPU with this board?

GAL.jpg (519.2 KiB) Viewed 1078 times

PINS.jpg (466.46 KiB) Viewed 1078 times

CMOS Socket

CMOS.JPG (471.39 KiB) Viewed 1078 times

CPU Mod

mods-1.jpg (545.3 KiB) Viewed 1078 times

After Removing CPU Mod

CPU.JPG (481.86 KiB) Viewed 1078 times

CPU-PINS-TRACES

CPU-PINS-TRACES.jpg (202.02 KiB) Viewed 1078 times

[HigashiJun]

Repairing your CPU pins is doable, but it wouldn't be a neat job if done with wires.

In this case, it would be better to de-solder the CPU with a hot-air station and then fit a SMD socket and a new CPU.

But of course, it's up to you and your abilities.

[hunsra]

Repairing your CPU pins is doable, but it wouldn't be a neat job if done with wires.

In this case, it would be better to de-solder the CPU with a hot-air station and then fit a SMD socket and a new CPU.

But of course, it's up to you and your abilities.

Thanks @HigashiJun. I think I'd rather replace it with a new CPU. Regarding the SMD socket - I can't locate one with the correct pin count. The CPU seems to have 132 pins, and the largest PLCC socket I can find from the usual suppliers has 84 pins. Any suggestions on where to locate one?