Atari 520STFM bombs on boot

[bartekmalysz]

I just dug out Atari 520STFM with extra 4MB ram:

https://ibb.co/1n1BR3n

and I get scrambled bombs on the screen when booting, then it changes to vertical, distorted lines.

https://retrocomputing.stackexchange.co ... bs-on-boot

Where I can find information on how many bombs mean what and where to start looming for problems? Thanks, Bartek

[kodak80]

Hi Bartek

First easy thing to try is remove and re-insert any chips that are in sockets. Cleaning the chip pins may also help.

Have you replaced the capacitors on the PSU? This is one of the first things that can cause strange issues on the Atari.

As you say you have 4mb RAM, what add-in do you have for the RAM? There are various cards and solutions around and a picture of the board with the RAM shown would help.

I had a similar sounding issue recently with a 520STFM board and it was one of the TOS ROM chips was faulty. My board had the TOS chips soldered directly onto the motherboard and I removed them, soldered in some sockets and was then able to swap the ROM chips for known working ones. https://www.exxosforum.co.uk/forum/viewt ... mbs#p42761

Bombs and there reason, as noted here https://www.atariarchives.org/cfn/13/0222.php

Those bombs that appear on your screen are error messages from the 68000 micro-processor.


Description....................Number of bombs
===========================================
Reset: Initial PC2...............1
Bus Error........................2
Address Error....................3
Illegal Instruction..............4
Zero Divide......................5
CHK Instruction..................6
TRAPV Instruction................7
Privilege Violation..............8
Trace............................9
Line 1010 Emulator..............10
Line 1111 Emulator..............11
[unassigned, reserved]..........12
[unassigned, reserved]..........13
Format Error....................14
Uninitialized Interrupt Vector..15
[unassigned, reserved].......16-23
Spurious Interrupt..............24
Level 1 Interrupt Autovector....25
Level 2 Interrupt Autovector....26
Level 3 Interrupt Autovector....27
Level 4 Interrupt Autovector....28
Level 5 Interrupt Autovector....29
Level 6 Interrupt Autovector....30
Level 7 Interrupt Autovector....31
Trap Instruction Vectors.....32-47
[unassigned, reserved].......48-63
User Interrupt Vectors......64-255

[bartekmalysz]

thank you so much, I will try poking the chips tomorrow. I was hoping to get exactly what you provided in your answer.