English Amiga Board


Go Back   English Amiga Board > Support > support.Hardware

 
 
Thread Tools
Old 15 November 2018, 16:36   #1
Agrajag
Registered User

 
Join Date: Nov 2018
Location: Sheffield, UK.
Posts: 4
Faulty A500 Rev 6a board, help needed.

I have an A500 rev 6a (1MB chip RAM upgraded) board that is driving me crazy.

The board boots to WB 1.3 OK, all the RAM appears present and it passes multiple, long Memory Doctor tests. Everything appears fine until I run specific demos or games.

For example, the State of the Art demo will run for a couple of seconds, but freeze just before the music starts. Armalyte will appear to load, but again freeze just before the music starts. The problem is the same every time - a complete freeze with the power LED flasing 5 times, no guru or error messages.

Wizball, Rainbow Islands, Parasol Stars and many others all run perfectly.

The thing is, if I press down on the board in the area highlighted in the picture, both SOTA demo and Armalyte will run OK, until I stop pressing, then the system freezes.

I have replaced the Agnus, CPU and ROM sockets and swapped out all the main chips with a known working set, but it made no difference at all.

Since flexing the board seems to fix the issue, I thought maybe a dry solder joint or even a crack in the board itself. I re-flowed everything that looked even remotely suspect and I have been over every mm of the board many times, but can't see anything obvious.

Any help appreciated.
Attached Thumbnails
Click image for larger version

Name:	amiga.jpg
Views:	47
Size:	538.6 KB
ID:	60825  

Last edited by Agrajag; 15 November 2018 at 20:58.
Agrajag is offline  
Old 15 November 2018, 20:22   #2
gdunlapsd
Registered User

 
Join Date: Jul 2018
Location: San Diego / USA
Posts: 19
I had similar issues with occasional lockups and graphics glitches in some games and demos, and I also replaced my Agnus socket (which did have a crack) but to no avail.

I did notice however that one of the pins on the Agnus chip itself felt a little loose! So, I ordered a new Agnus on ebay and that completely solved my problems. Been running perfectly fine ever since. Maybe you're having the same problem?
gdunlapsd is offline  
Old 15 November 2018, 20:54   #3
Agrajag
Registered User

 
Join Date: Nov 2018
Location: Sheffield, UK.
Posts: 4
I tried a replacement Agnus from a working system, but the problem remained.

I'm beginning to suspect that it may be audio related. When I get to the point at the beginning of the SOTA demo where there's a pause and no music, I stop pressing the board and the demo runs until the music starts again. Then it locks up. The Lockups aren't occasional. They occur at exactly the same point each time.

I'm not sure how the audio could lock up the system, except for a bad Paula maybe, but I have tried 3 different Paula chips and it's exactly same, so it can't be that.

I'll experiment some more.

Last edited by Agrajag; 15 November 2018 at 21:08.
Agrajag is offline  
Old 16 November 2018, 03:36   #4
Shadowfire
Registered User
Shadowfire's Avatar
 
Join Date: Aug 2001
Location: Connecticut USA
Posts: 561
All custom chip DMA (including audio) is routed through Agnus, so you can't just write it off like that.

Visually inspect the Agnus socket under magnification, including the pins on the bottom where they are soldered to the motherboard. Measure resistance from each pin to another location on the board.
Shadowfire is offline  
Old 16 November 2018, 17:34   #5
kaffer
Registered User
 
Join Date: May 2011
Location: Cambridge
Posts: 585
I would simply replace the Agnus socket at this point. It is the most likely cause.

EDIT: Oh you already did that... Is this issue exactly reproducible every time at the exact same place in the two titles? You might have to buzz every track.

Last edited by kaffer; 16 November 2018 at 17:39.
kaffer is offline  
Old 16 November 2018, 20:38   #6
Agrajag
Registered User

 
Join Date: Nov 2018
Location: Sheffield, UK.
Posts: 4
I spent a few hours probing the Agnus socket to various points around the board and I couldn't find anything wrong.

This board is far more trouble than its worth, so I think it will end up as a parts board.
Agrajag is offline  
 


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

Similar Threads
Thread Thread Starter Forum Replies Last Post
KCS Power PC Board Plus + A500 Plus - drivers & help needed Jacques support.Hardware 3 28 April 2016 13:00
A500 rev 8a board green screen causes. Vot support.Hardware 0 10 May 2014 15:54
A500 Rev 3 help needed StLovell support.Hardware 2 13 October 2013 01:29
Board Revision ADVICE Rev 1D.1 vs Rev 2B D4Ni3L3 support.Other 1 03 December 2008 00:44
Faulty A600, diagnostic help needed. Freakyweakywoo support.Hardware 6 29 October 2005 14:39

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 10:24.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Page generated in 0.06343 seconds with 14 queries