Phoenix PCB Repair

[adrianomartins]

Hello everyone,

I bought a defective Phoenix board at auction, which displays graphic garbage (pic2) and emits a siren sound. It appears to be an Irecsa / G.G.I. Corporation board (pic1).

What I have done so far:
- Checked and replaced the CPU
- Checked the SRAMs and replaced 2 ICs
- Read out the EPROMs and burned 2 new sets
- Checked most of the logic ICs between the CPU, RAM and ROM
- Checked address and data signals with an oscilloscope
- Used Phil's test ROM

I used the original MB8516 and newer 2716 and checked the contents several times. Depending on which set I use, graphic garbage still appears and the CPU continues to run normally.
With the second set, I'm seeing some very strange behaviour. There's still graphics garbage, but the address lines stop toggling (starting with the CPU).
When I use Phil's test ROM, the test seems to run, the image stays at the RAM test, but no error is displayed (pic3).
When I adjust the test ROM (according to Phil's instructions, so that the error output is displayed a few lines further down), the test no longer runs at all (pic4).

Does anyone have experience repairing the Phoenix PCB and have any tips?

Thanks!

 

[sukhbir]

What is the reset pin doing on the cpu?
Locate the video rams and check all pins especially CS and RW.
Schematics are available on the Web.

 

[adrianomartins]

There is no watchdog. Signals look good at CPU, RAM and ROM.

 

[philmurr]

I have tested the modified code you sent me and it works as intended

If your original test ROM runs, but your modified test ROM doesn't, then it is a problem either with how you have burned the modified test ROM, or the EPROM itself

 

[Lurch666]

I had a pheonix that did this and it turned out to be a missing pin on the connections between the boards.

 

[adrianomartins]

I had a pheonix that did this and it turned out to be a missing pin on the connections between the boards.

I checked the connections between the CPU, RAM and ROM, and all the tracks are fine. Can you remember which connection was broken?

 

[Lurch666]

Check the connectors that the ribbon cables plug into that connect the two boards. They have lots of pins and if one is broken then that can cause issues.

 

[adrianomartins]

Check the connectors that the ribbon cables plug into that connect the two boards. They have lots of pins and if one is broken then that can cause issues.

Thank you, checked and all connections are good.

 

[Lurch666]

When you say you have checked the logic ICs how did you check them?

 

[adrianomartins]

When you say you have checked the logic ICs how did you check them?

First, I examined the signals with the oscilloscope, but then desoldered most of the ICs between the CPU and ROM (multiplexers, decoders, etc.) and tested them with the Retro Chip Tester.