A500 Boot woes

[clefty]

Hi Guys

So after getting my partners A500 out of the loft over xmas to have a play (having not powered if on for a very many years) we have a black screen problem.

After some scouring of this forum and several other resources I've started troubleshooting the issue but have got to a blocker, I've got a diag rom on order which should come next week - but I thought I would put my findings here in the meantime to see if any of you bright sparks have any ideas what might be wrong.

Board revision 6A, Kickstart v1.3
Power on, black screen - no caps lock light, power light on keyboard.

Removed keyboard, memory upgrade and floppy drive: dark grey, light grey, white screen on boot and no workbench insert disk prompt
Swapped CIA chips - same
Removed both CIA chips - green screen (which I think is expected as I understand that CIA A needs to be plugged in)

Floppy drive appears to work as I can here is trying to read on boot.

Have removed the kickstart checked the contacts and plugged back in - still getting dark grey. light grey. white and no insert disk prompt
Board is clean and in good condition, no signs of corrosion anywhere.

suspecting the kickstart rom - but wont have a better idea until the diag rom arrives next week.

Any ideas guys?

Thanks in advance

Claire

[Boing-ball]

1st off, welcome to Amiga.org. Word of warning, this place is full of Sheldon’s who might want to start a 2-bits compliment argument with you 😆🤣👍🏻

Could be the Denise chip for the Video fault. Problem will be, even if you get a DiagROM chip, if you are not seeing a display then you will need a Serial connection to another computer such as PC to see any output.

I doubt it’s the Kickstart ROM as you have identified activity with the floppy drive. But you never know when it comes to Amigas.

Check out Stu’s videos (SHG Retro) on Amiga A500 and A500+ repair here:

https://youtu.be/CxARHzGi6Vk?si=qWtMGYgy5z_tsdz7

Also Chris Edwards channel:

https://youtu.be/J3HXOGkVCXE?si=DbFVziptmSs71t2M

[clefty]

Thanks for the welcome! I fix the internet for a living so know my way around serial ports and console connections 

Interesting what you said about the Denise chip, I’d assumed that since I was getting some sort of colour screen output Denise was working, but if that’s a separate thing, it could well be an issue.

Thanks for the links! I’ll report back when I can do some more diags

[Munchkin]

Just to ask, have you tried both RGB and Composite output to see if there is a difference?

[clefty]

Yep, that’s one of the first things I did when we were getting the black screen.

[AndyFC]

Welcome to the forum.

Where are you based? There are loads of active groups around.

[clefty]

Hi Andy, West London

[AndyFC]

Kickstart Amiga User Group us your nearest I know of. The groups are great way to share skills and ideas.
https://www.kickstartamigagroup.org.uk/
Take a look at http://Https://retro.directory for others too.

[F0LLETT]

Might sound silly. Have you tried reseating all chips?

[clefty]

So quick update from my side:

The keyboard is definitely dead - it's actually stopping the Amiga booting at all, and we only get colour screen codes when its unplugged - otherwise straight black screen. I've got a replacement coming from ebay.

Serial output from the ROM Diag as follows, this seems to suggest the memory and CPU is ok, I get a bunch of colours on the main screen ending in dark grey. It's not spawning the onscreen menu at all - which does make me suspect that it might be Denise as Boing-Ball suggested. I've pulled and reseated it to no avail. Annoyingly the mouse input doesn't respond in either port either.

Thoughts?


---start output

Amiga DiagROM V1.3 - 21-Apr-23  - By John (Chucky/The Gang) Hertell

- Parallel Code $ff - Start of ROM, CPU Seems somewhat alive
- Testing ROM Address-access
   OK
Testing if serial loopbackadapter is installed: <> NOT DETECTED
    Checking status of mousebuttons at power-on:
           
    Set all Interrupt enablebits (INTENA $dff09a) to Disabled: Done
    Set all Interrupt requestbits (INTREQ $dff09c) to Disabled: Done
    Set all DMA enablebits (DMACON $dff096) to Disabled: Done

Testing if OVL is working: OK
- Parallel Code $fe - Test UDS/LDS line
  - Test of writing word $AAAA to $400 OK
  - Test of writing word $00AA to $400 OK
  - Test of writing word $AA00 to $400 OK
  - Test of writing word $0000 to $400 OK
  - Test of writing byte (even) $AA to $400 OK
  - Test of writing byte (odd) $AA to $401 OK
- Parallel Code $fd - Start of chipmemdetection

Addr $00080400   OK  Number of 64K blocks found: $08
Chipmem Shadowram detected, guess there is no more chipmem, stopping here

Startaddr: $00000400  Endaddr: $0007FFFF
- Testing detected Chipmem for addresserrors
   - Filling memoryarea with addressdata
.......
   - Checking block of ram that it contains the correct addressdata
.......   CHIPMEM OK
    - Checking status of mousebuttons for different startups, if still pressed
      we assume not working and ignore those in the future.
      Green newly pressed, Yellow pressed at startup - Startupaction taken.
      Red = Pressed at both poweron and now so it is stuck and being ignored

           
  The following special action will be taken:
NONE
  - Fastmemcheck skipped as we found chipmem
- Parallel Code $fb - Memorydetection done

  Using $0006C47A as start of workmem (Base)

- Testing Workarea Address-access
   WORKAREA OK
- Parallel Code $fa - Starting to use detected memory

Testing if serial loopbackadapter is installed: <> NOT DETECTED
Detecting if we have a working raster: DETECTED
Detected Chipmem: 512kB
Detected Motherboard Fastmem (not reliable result): 0kB
Basememory address (Start of workarea): $0006C47A
As a very fast test of variablearea working this SHOULD read OK: OK!
- Parallel Code $f9 - Detected memory in use, we now have a stack etc
 - Doing Initstuff
 - Setting up Chipmemdata
   - Copy Menu Copperlist from ROM to Chipmem
   - Copy ECS TestCopperlist from ROM to Chipmem
   - Copy ECS testCopperlist2 from ROM to Chipmem
   - Fixing Bitplane Pointers etc in Menu Copperlist
   - Copy Audio Data from ROM to Chipmem
   - Do final Bitplanedata in Menu Copperlist
 - Initstuff done!

    Set Start of copper (COP1LCH $dff080): Done
    Starting Copper (COPJMP1 $dff088): Done
    Set all DMA enablebits (DMACON $dff096) to Enabled: Done
    Set Beam Conter control register to 32 (PAL) (BEAMCON0 $dff1dc): Done
    Set POTGO to all OUTPUT ($FF00) (POTGO $dff034): Done
- Parallel Code $f8 - Starting up screen, text echoed to serialport
Amiga DiagROM V1.3 - 21-Apr-23  - By John (Chucky/The Gang) Hertell



Doing ROM Checksumtest: (64K blocks, Green OK, Red Failed)
$CED3BA58 $98C6080B $3980DA0F $003EC000 $003F0000 $003F4000 $003F8000 $00DFBCEA

CPU: 68000  FPU: NONE  MMU: NOT CHECKED

Checking for fastmem
Pressing left mousebutton will cancel detection (if hanged)

Checking if a 24 Bit address cpu is used: YES
 - Checking for Memory in 24 Bit area (NON AUTOCONFIG)
 - Checking for Memory in Ranger or Fakefast area

Extra workareas Chipmem: $00000400 - $0007FFFF  Fastmem: $00000000 - $00000000

To use serial communication please hold down ANY key now
OR click the RIGHT mousebutton.

----end output

[Boing-ball]

Without some sort of working input device, then ideally you need to get into the DiagROM menu to proceed further.
As for the mouse. Only 1 port can be used for the mouse. The other is dedicated to Joystick/Joypad. The mouse port can also be used for a second joystick.
You can try swapping the CIA chips over to see if that helps with the mouse input. Fingers crossed not both CIAs are at fault.
But from the looks of things you have a few issues going on. CPU and Chip RAM are not an issue from the looks of things.
There are also micro fuses/resistors on the board that might have popped for the mouse to also not work.

CIA chips can be bought second hand plus other A500 bits and bobs:

https://www.ebay.co.uk/itm/387439406742?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=7irsl2-xrhg&sssrc=4429486&ssuid=udhysnkvtsy&var=&widget_ver=artemis&media=COPY