A4000 wont boot after replacing caps

[mechy]

Agreed, AmigaKit will have certainly tested the board.  Sounds as though something has been upset with the Cyberstorm board when it's been removed and refitted.  Could be anything from dirty connectors to cracked/intermittent solder joints.  It's not a Cyberstorm mk3 by any chance?  I'd agree that a known good CPU board is the best way to test.

I'm intrigued as to why the clock source jumpers should be set to internal when the CPU board is operating at 25MHz, please fill me in here.

By my understanding, a board such as the Cyberstorm is clocked using its own on-board oscillator, so obviously the A4000 main board needs to be exactly synchronised for all bus communications with the CPU board, which is the entire point of shifting the jumpers to 'EXT' so that the timing of the main board is identical to that of the CPU board.  If the CPU board and main board are using different clock sources (jumpers set to INT) then both clock sources must be identical in phase and frequency.  From memory the stability of those oscillator modules are around 20ppm or worse, so to have two oscillators running at exactly the same phase and frequency for any length of time is practically impossible.  Which would mean the computer will either fail to boot, or not run for very long at all.

If memory serves me the cyberstorm MKII uses the motherboard jumpers set to internal while the other cyberstorms all use external. i guess it uses some type of PLL to keep it all in sync..

[mechy]

Hi to all amigans !
It's the first time i'm posting here.
Here's the story :
I  live in Paris and I couldn't resist when I saw an A4000 complete with  its 1942 monitor, pickable near me on ebay. Was a child dream, as I was  an A500 then A2000 user as a teenager.
It worked good, i upgraded the ram and roms. I also put a cf card, dvd rom, and network card.
But  after a while, it began to show its age, having crackling audio and  unstable video. So i disconnected everything from the motherboard and  sent it for caps replacement to amigakit in england. I have very little  soldering skills, but wouldnt dare to put my hands on this vintage item  
It took quite a long time, but it went back to me with amigakit "QC passed".
Now  i resettle everything, and sadly it doesnt boot. I got red screens so i  suspected the roms and bought new ones. Now i can only get gray, or at  times purple, screen. The disk drive is not reacting. I did the  caps-lock test, it blinks 6 times then sticks off.
Could this be the  CPU card ? I kept it and didnt send it with the MB. It's a phase 5  cyberstorm carrier with a 040 CPU. Or maybe the RAM ? With the chip only  or even all slots empty, i get the same results.
Do you have any  clue ? Do you think something went wrong when they fixed the board ? Or  maybe there's a jumper setting that i missed ?
Thanks in advance !
JM

I have fixed many a board where a trace under a cap has been damaged by cap leaks. maybe this is the case for you. Its very well possible it worked fine at amigakit but in shipping the marginal trace quit making contact-Its tough to find things like this sometimes especially when they are working and you have no reason to suspect it.. I wouldn't of believed this but it happened to me! In any case, i would try a A3640 or other accelerator before assuming its the amiga. Also pull the roms and make sure a pin didn't get bent under when they were installed.

you might try and contact Cosmos,not sure where in France he is but he may be of help.