A1200 expansion port RAM issue?

[voyager_1701e]

Hello All,
Hoping someone can give me some direction with the following problem.

I have a 1d.4 A1200 board. All functions normally without any expansion fitted (meaning boots to WB, shows boot menu with both buttons, shows purple insert disk screen with no HDD etc)...so CHIP RAM operation seems normal.

However, if I fit an ACA 1232, it doesn't boot....just remains on a dark grey screen. If I close the disable jumper, of course the ACA is disabled, but with it plugged in it boots normally.

If I plug in a DKB 1202 with no RAM, and correctly jumpered for no RAM, normal system operation. On a second DKB I added a 68882 with no RAM and system boots and the 68882 is identified. If I select incorrect RAM config jumper, system reports board as defective. Add RAM with correct jumper setting, the system wont boot, it just flicks between differing shade of grey screen (power LED remains on and doesn't change intensity).

I have tried both 3.0 and 3.1 ROM. I have re-flowed the ROM socket. When I got the board, someone had been at it with a screw driver or similar as it had scoring on the expansion connector and lower board (I found a broken track, which I have repaired). I have check continuity between all the connectors pads and the vias/endpoints all OK. As best I can I've visually inspected the board under good light and magnifier....no visual issues. The caps looked mostly good, But I've changed them anyway for good measure. The board has had the timing fix applied post production (I am sure even if it hadn't, that wouldn't cause this anyway)

I'm starting to think whatever controls RAM expansion in the system is at fault (Is that Budgie?)...although CHIP RAm operation is normal and the PCMCIA port works. Does anyone have any thoughts on where this issue could lay?

 

[roy_bates]

have you tried cleaning the edge connector?

 

[sputnik]

If he's recapped, reflowed, timing fixed, I should hope he'd already cleaned the connector

 

[r0jaws]

Sometimes it is the obvious you miss. Have you tried an alternate power supply?
It also can't hurt to check and apply the timing fixes anyway.

Sent from my GT-I9300 using Tapatalk

 

[voyager_1701e]

have you tried cleaning the edge connector?

Hi Roy, Indeed that was the first thing I did, but it was then I noted the screwdriver attack and had to correct the broken track.

If he's recapped, reflowed, timing fixed, I should hope he'd already cleaned the connector

Hi Sputnik, I agree with your comment....but indeed it is very easy to get carried away and tackle the difficult stuff first....either way I did clean the connector.

Sometimes it is the obvious you miss. Have you tried an alternate power supply?
It also can't hurt to check and apply the timing fixes anyway.

Sent from my GT-I9300 using Tapatalk

Hi r0jaws, yes I have tied 2 power supplies. I have also checked the "powered on state" voltages and both are very close to 5v and 12v respectively. Timing fixes had already been applied, but remember this occurs with both the ACA and just the RAM board (DKB1202)...I dont think the timing fixes affect RAM only board like the 1202. So regretfully it is more difficult than that!



Any other thoughts? I think maybe its not a simple cause (ie cleaning the connector or timing fix), unless its a passive that's stuffed.....but I'm not sure checking out the schematics (I can read them a little) that there are any passives in any of the paths from the connector.

 

[voyager_1701e]

For those interested....I have made some progress! I'm sometimes overly persistent and short of patience.....

After scouring the circuit diagram, measuring all the in-circuit components that seemed relevant, even measuring vs another board...nothing! So further scouring many many traces with a meter....nothing! Leaving either the CPU or Budgie. So I ordered another 2 CPU's but impatience got the better of me. I de-soldered the CPU from a 2B board I have so far been unable to resurrect, and swapped it onto the faulty 1d.4 board. Amazingly the 1d.4 booted (no expansion card)....so at least I did a proper job de-soldering and re-soldering the CPU (rather pleased with myself seeing its the first of this type of package IC I have done!).

Excitedly I plugged in my ACA......nothing (grey screen) Bugger! For hits and giggles I plugged in the DKB board.....and it booted!!! Woohooooooo Tried it with 0Mb, 4Mb, 8Mb and all worked. Its run the AIBB test make module and it has completed successfully. Keeps locking up in WhichAmiga...but I'm sure that's a software issue as I've had that happen before. Bit perplexed about the ACA, thinking maybe its not liking being plugged and un-plugged, but its still working in another board so it is fine!

Its 1am on a work morning, so further investigation will have to wait.......

"Donor" CPU

"Donor" 2B board

Recipient 1d.4 board