A4000 will not boot with fast RAM

I had my A4000 upgraded with Buster 11 to be ZorRAM compatible. It was working normally before but now it refuses to boot if there is fast RAM installed. The screen and power led just flashes. If there is only chip RAM, the it will boot. With ZorRAM it is the same flashing. I've tried with basic setup and full setup but that does not make any difference. I've tried with two CPU cards (3640 and 3630) but that doesn't make any difference either. If I've tried booting with fast RAM, I have to re-seat CPU card to get it booting without. One peculiar thing is that there is a jump wire from one leg of the Buster to another. I remember it being there with the old Buster 9. All reference pics I've seen of A4000 Busters don't have any jumper wires soldered into them. Should I just try to remove the wire or could it be there for a reason? My mobo is Rev 2, yes 2.

Any help is greatly appreciated.

@protek

Its quite likely you have a micro-fracture of the solder on the Buster Socket (or of the solder from the chip to the board if not socketed)

its a common fault with age lately.

also has the battery been removed and any damage repaired recently?


You should have the socket solder re-flowed or the solder of the Buster chip if its installed directly on the motherboard, this should cure your problem

---------- Post added at 18:16 ---------- Previous post was at 18:07 ----------

In regards to the Jump wire, I have worked on three Rev B A4000's ... 1 soldered Buster 11, 2 Buster 9's (one socketed one soldered)... none of these had any Jump-wire on the Buster.

@Zetr0:
Thanks! The Buster is directly soldered onto the motherboard. I don't have re-flow tools myself. That's why I had it done. I know someone, who might be able to do it for me. I do have a soldering station but would it be too crude a method of prodding the legs with a hot tip?

The battery was removed, when I originally got the A4000. I did put a coin battery clip with a diode, when I got the mobo back. I had also had the caps replaced while the Buster was upgraded.

Might as well try snipping the wire and try if it makes any difference.

Give a quick check that R79 (last resistor underneath the CPU connector) is showing 1.2kOhm or thereabouts... Mine had burnt out for no explainable reason, and this appears to have happened to others. Give the others a quick resistance check, too, whilst there...

That probably won't be it, but it eliminates another thing :thumbsup:

@chiark:
Thanks! Will check that too.

@thread:
Snipped the jump wire. No effect to one direction or other. Wonder why that has been there in the first place.
Probably should invest to re-flow tools...

I did some research and found out that there is a buffer IC that, when malfunctioning, prevents the A4000 from booting, when there's fast RAM onboard. Does anyone know, whether it causes the kind of loop what I'm experiencing or is it absolutely dead? Is there a way to test the buffer?

U891, 892, 893 or 894. If you've had a battery leak, you might see that traces to 891 are damaged...

I left bank 0 unpopulated and fired her up. Lo and behold! She booted up. Fast RAM reported 0 even though rest of the banks were populated. With ZorRAM installed I still get the flashing loop.

So bank 0 would indicate that U891 or its traces are damaged, right? Have to take a closer look tomorrow, when there's better light.

I'd definitely start checking traces, and I *think* u891 connections are the most likely culprit. Good luck!

Here's a closeup of the U891. At least my untrained eye can't pick anything out of the ordinary with the traces. Of course there are not that many visible traces for the U891.

The mobo is pretty much in the condition that I got it in 2009. The caps and the Buster has been changed and I recently installed the coin clip battery with the diode. Original battery had already been removed, when I got it.

http://koti.mbnet.fi/tsaarela/TF/P1010348.JPG