English Amiga Board

Go Back   English Amiga Board > Support > support.Hardware

Thread Tools
Old 17 June 2011, 18:59   #1
Posts: n/a
A500 Rev 3 help needed

I have an early revision 3 A500 that I'm trying to resurrect. Looking for any advice people can offer.

Initially all I got from it was a green screen and a 10/1 code blinking on the power light. There were no hot RAM chips and all the custom chips/CPU/Agnus have been tested in other boards.
I found that attaching a 501 in the trap door changed this to yellow but the 10/1 cycle continued.

I eventually got the board to boot by piggybacking another Ram chip over one which seemed to be bad. This however would only keep the machine stable for around 5 minutes before it crashes.
The capacitor for that chip seems to be dead but changing it for one of what I believe is the same value achieved nothing.

Any thoughts?
Old 17 June 2011, 20:59   #2
Jope's Avatar
Join Date: Jul 2003
Location: Helsinki / Finland
Age: 38
Posts: 6,920
Replace the defective RAM chip that you found by piggybacking.
Jope is offline  
Old 13 October 2013, 01:29   #3
Posts: n/a
A fix to green screen / 10 + 1 blinks error

Ok, I will tell what I made to repair the A500 rev. 5 ROM ver 1.2.

I opened the cover. I powered the computer using my own power supply that I knew to be in condition and waited for 5 minutes. I measured the temperature of the 16 RAM chips on U16 - U31 using my fingertips. The chip on U24 was warmer than the other. I turned off the power. I desoldered a Texas Instruments 2x8 pin 100ns DRAM chip from a circuit board that was thrown away. I desoldered the original 150 ns Samsung chip on U24 from the Amiga motherboard. Note that the TI DRAM chip was faster or as fast as the original. I took the original chip away from the board using a screwdriver. On the same time I accidentally damaged the bus because the chip legs weren't completely apart from the bus and they pulled some bus wires from the motherboard. I repaired the bus using thin copper wires that I soldered in the place of the damaged bus. Other ends were soldered to the bus and other ends put to the holes. I checked the fix using a multimeter that beeped to indicate that the bus was in condition. This was done by putting the other electrode of the multimeter to a hole and the other electrode to the respective pin of a neighbouring chip. This rule had a couple of exceptions as the bus wasn't originally planned to conduct that way. Then I put the TI chip to U24 and twisted the copper wires around the chip legs from the back side of the motherboard. I soldered those pins that didn't conduct otherwise. In addition I had to solder the pin 16 (enumeration from upper left corner to lower right corner one row at a time with respect to the text on the chip). That was even though the multimeter beeped. However I noticed that the circuit conducted also through other chips and I that's why couldn't become convinced that the power pin 16 was connected to the bus. I pushed the hole 16 from a 45 degrees angle so that it touched both the bus and the leg. I powered the computer. The led started to light continuously after a second and the floppy drive started to check the presence of a disk. I turned off the power and soldered the pin 16. Then I checked the video output using a TV and it showed the hand holding a floppy -picture. I put the cover back.

Last edited by jmvihtanen; 24 October 2013 at 17:22. Reason: CORRECTION OF CHIP POSITION NUMBER

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
A500 Rev 4 platatomi Hardware pics 11 12 October 2017 12:31
Need expert advice on installing KS 3.1 on A500 rev. 5 Benighted support.Hardware 8 05 October 2009 23:22
Board Revision ADVICE Rev 1D.1 vs Rev 2B D4Ni3L3 support.Other 1 03 December 2008 00:44
has anyone dislodged CIAs from a rev 6a?? possible defect on rev 6a?? NfernalNfluence support.Hardware 3 27 August 2007 11:27
Minimig (A500) Motherboard PCB rev 1.0 Paul News 15 02 July 2006 03:03

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT +2. The time now is 09:48.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Page generated in 0.07567 seconds with 13 queries