Amiga 4000t boot gray screen please help !

[nandogames]

Hello , sorry for my bad English, I have a Amiga 4000D with toaster video, flyer, Tbc, CyberStorm PPC, Cyber ​​Vision 64 etc.The Amiga stood for a long time, for security removed the battery.. I'm electronic technician, before you turn it decided to replace all capacitors on the main board, after repair,power on the main board /cyberStorm with monitor 1084s , appeared the picture insert disc, after something strange ocorred , now when connected, I see flashing image and turn light gray all time, put a disc floopy drive and Cf card with OS 3.9 , the computer accesses the Cf card and floppy disc normally, I can hear the disk in demo music play .. I decided to put the expansion Zorro with cyber vision board 64 and VGA monitor plugged into scandoubler ,, to my surprise now see the image of 0S3.9, but only with 4-color pallete, I can not change anything in the color palette, I received an error message - Program failed - error # 800000004 - wait for disk activity to finish ....... boot through the the floppy drive the colors are perfect , with demo disc ... removing the cyber vision board zorro , no appears image of the port DB23 of the main board, another situation, pressing on both mouse buttons Early boot menu" after startup video, the menu no appears , the video disappears in scandoubler .. black screen , I'll be grateful for any help ..

 

[nandogames]

new tests, checked all the traces around the RTC everything perfect, i put only the floppy drive on the main board, put the TEF Gigamix 1991 disc, the sound is perfect .. no image RGB port DB23 connected a monitor 1084s .. .. I have. image only putting the expansion zorro III + scandoubler + VGA monitor, I belive that you know this demo Gigamix,, when press the mouse button should advance to another song, this does not happen !
leaving the intro music playing this demo should go to the next song, at the moment the sound starts to fail and back again to loopy music intro

 

[Hanzu]

Not sure if you have solved this already but here are some thoughts.

Very hard to understand what you try to describe. Not so much to do about the English language but they way you use , (comma) when you should use . (period) for most people to understand when one thing ends and when the next one starts.

Anyway if left mouse button line may not work (that demo is not advancing to the next part and Early Startup-screen is not showing up when both LMB and RMB are held down after reset). Please notice there is no Early Startup in very old Kickstarts. I would suspect U975, U976 and/or U177 may be damaged and replace them all.

I have experience that when one of these 3 is faulty. A4000 may have no picture if mouse is not connected, but when mouse is connected there is picture but mouse will only move on one axis. So this is a proof they really cause weird things even grey screen.

You have removed the battery, but sometimes it is too late. Even a little bit of leak before the removing may go active after years of waiting. Corrode some VIA, track or damage IC. I also suspect there 3 ICs may get damaged on mouse hotplugging, which is generally considered safe, but with already weakened IC this could be harmful I believe.

Not only battery will leak and corrode, but also the electrolytic capacitors. I once found faulty VIA under Bridgette. Possibly corroded by C190 leak or factory PCB factory chemicals trapped under lacquer and going active decades later.

If computer is stored working and then later taken into use as faulty, I would always name 2 main suspects 1) corrosion and 2) electrolytic capacitors leaking/going bad.