English Amiga Board


Go Back   English Amiga Board > Support > support.Hardware

 
 
Thread Tools
Old 10 November 2018, 06:27   #1
lesta_smsc
Registered User

lesta_smsc's Avatar
 
Join Date: Feb 2012
Location: United Kingdom
Posts: 1,362
A500+ black

Hello all yet again!

I'm really trying to add an A500 plus to my collection but this is the 2nd one which is not working! It shows a black screen.

The corrosion seems much less but to my untrained eye it looks ok apart from the odd corrosion at the legs of chips.

Can anyone identify why it might not be working or what pins to check and retrack?

I've replaced Gary, CIA, Paula so far with no change.

On the odd occasion it has been a dark blue or white screen but this seldom occurs to identify a pattern.

Please see pics and advise accordingly.

Thank you!
Regards,
Lesta
lesta_smsc is offline  
Old 10 November 2018, 07:55   #2
kirk_m
Registered User

 
Join Date: May 2016
Location: Mandeville USA
Posts: 170
My friend, I hate to be the bearer of bad news, but, there is corrosion everywhere on that board. More than half of the pins on the Agnus socket are green. I hope you've removed the battery as well. There is even what appears to be a burned resistor at the bottom of the series of resistors under the "AUDIO FILTER" label. Many of the smaller logic ICs are also corroded on their pins.

Carefully cut out the battery, then start cleaning everything. Clean all of the green out of each of those sockets after removing the ICs from them. With the Agnus, it is BEST removed by an amateur by removing the board from the case, removing the bottom shield, and then approaching the chip from the underside of the board and PUSHING it out through the two holes under the chip with pencil eraser or other DULL implement. If you don't know what you're doing, you definitely should NOT use a PLCC puller, as you will invariably break some pins off it.

When removing DIP chips, don't use a screwdriver to pry it, as if you slip, you'll cut traces under the sockets. Use a plastic implement, or a proper DIP IC remover.

Hopefully, it's just a bad contact issue with the Agnus and its badly corroded socket. Ultimately, you'll be replacing quite a few ICs and their sockets on this one, I fear. Enlist help from someone who does this kind of work (like Steve Clifford in the UK [I think his website is AmigaPassion.com]), because if you don't know what you're doing, you'll likely damage things much further.
kirk_m is offline  
Old 10 November 2018, 11:07   #3
ajk
Registered User
ajk's Avatar
 
Join Date: May 2010
Location: Helsinki, Finland
Posts: 1,176
I don't think that resistor (or diode) is burned, it's probably just hand soldered in as a factory mod and that brown stuff is rosin flux.

But yes, definitely battery leakage all over. The board is almost certainly salvageable but it's going to take some work. First step would be to clean out all of the visible green corrosion, then check all suspicious connections against the schematics with a multimeter.

The Agnus socket may need replacing if it doesn't clean out well. I suggest applying lubricant (silicone oil is safe) before trying to get the Agnus chip out; with all that corrosion it's not going to come out with the same amount of force it went in originally.
ajk is online now  
Old 10 November 2018, 21:39   #4
lesta_smsc
Registered User

lesta_smsc's Avatar
 
Join Date: Feb 2012
Location: United Kingdom
Posts: 1,362
Oh boy... looks can be deceiving. My last one showed more oxidation so I assumed this would have been a lemon juice job and it'll work.

How much will it cost to repair roughly?
lesta_smsc is offline  
Old 11 November 2018, 00:41   #5
ubermick
Registered User

ubermick's Avatar
 
Join Date: Jun 2012
Location: San Francisco-ish, via Ireland
Age: 45
Posts: 66
Quote:
Originally Posted by lesta_smsc View Post
How much will it cost to repair roughly?
How long is a piece of string? Hard to say until someone who knows their onions gets their hands on it. Like you say, looks can be deceiving.

Paging @amigapassion?

http://eab.abime.net/member.php?u=66922
ubermick is offline  
Old 11 November 2018, 00:55   #6
Daedalus
Registered User

Daedalus's Avatar
 
Join Date: Jun 2009
Location: Dublin, then Glasgow
Posts: 3,493
Quote:
Originally Posted by kirk_m View Post
When removing DIP chips, don't use a screwdriver to pry it, as if you slip, you'll cut traces under the sockets. Use a plastic implement, or a proper DIP IC remover.
Just to add to this: One of these U-shaped hook implements is *not* a proper DIP remover, or at least, not for large chips like anything in a socket in an Amiga. They're only meant for small chips, maybe up to 20 pins. It's very easy for them to slip off one end of larger chips, resulting in a sudden jerk that rips pins off the chip and damages the socket.



If you're looking for a proper DIP puller, they look something like this, and are many time more expensive than the ones above:
Daedalus is offline  
Old 11 November 2018, 01:08   #7
lesta_smsc
Registered User

lesta_smsc's Avatar
 
Join Date: Feb 2012
Location: United Kingdom
Posts: 1,362
Quote:
Originally Posted by Daedalus View Post
Just to add to this: One of these U-shaped hook implements is *not* a proper DIP remover, or at least, not for large chips like anything in a socket in an Amiga. They're only meant for small chips, maybe up to 20 pins. It's very easy for them to slip off one end of larger chips, resulting in a sudden jerk that rips pins off the chip and damages the socket.



If you're looking for a proper DIP puller, they look something like this, and are many time more expensive than the ones above:
What is the 2nd known as? That looks good but will it not get stuck in smaller spaces between chips and components?
lesta_smsc is offline  
Old 11 November 2018, 01:24   #8
Daedalus
Registered User

Daedalus's Avatar
 
Join Date: Jun 2009
Location: Dublin, then Glasgow
Posts: 3,493
It's just a DIP extractor tool, might be called a "pro" version or similar. It does require a little bit more space around the chip, but not that much. A few mm at most.

In reality though, the advice on a plastic implement to do the lifting is probably better for something you're not going to use much. Using a screwdriver is doable if you know what you're doing (thinking you know what you're doing is not the same thing) and ensure that you never apply force in such a way that a slip could let it come into contact with the board. This isn't always possible either with other components in close proximity.
Daedalus is offline  
Old 11 November 2018, 15:02   #9
idrougge
Registered User
 
Join Date: Sep 2007
Location: Stockholm
Posts: 3,679
Use a short flat screwdriver. Insert it in the short end of a socket and turn it back and forth around its axis to dislodge the chip. Repeat on the other end.
idrougge is offline  
Old 11 November 2018, 15:04   #10
lesta_smsc
Registered User

lesta_smsc's Avatar
 
Join Date: Feb 2012
Location: United Kingdom
Posts: 1,362
I have managed to remove and re-seat the smaller chips without any problems but I'm of tackling Agnus! Also, the large CPU is unlikely to need doing based on the damage visible or do I have to check this too?
lesta_smsc is offline  
Old 22 November 2018, 19:10   #11
simon_m74
Registered User
 
Join Date: Mar 2013
Location: UK
Posts: 78
I also have an Amiga 500+ that I`m trying to revive from a black screen.
The photos of your board look identical to mine - hence no need for me to add pics..

So far.. I have cleaned to the best I can. Most green crust is off the PCB, but still around the `Data Path` logic, as well as Agnus socket.

I plan to replace Gary, Data Path, Agnus and their sockets - if I can that is.

I also checked some traces - some working - some not - so I know damaged tracks.

To help, I`m using these tow webpages:
http://www.amigapcb.org - VERY cool PCB layouts and `Net` tracking!

and

https://www.amigawiki.org/doku.php?i...ice:schematics

Very clear Amiga schematics.

But any help other than what I`m trying - would be very appreciated..
As - this is a `practice run`, for trying to repair one of 5 Amiga 3000 boards I have with battery leakage.
(just hoping that Amiga PCB will add the A3000 soon!)
simon_m74 is offline  
Old 22 November 2018, 21:26   #12
lesta_smsc
Registered User

lesta_smsc's Avatar
 
Join Date: Feb 2012
Location: United Kingdom
Posts: 1,362
Quote:
Originally Posted by simon_m74 View Post
I also have an Amiga 500+ that I`m trying to revive from a black screen.
The photos of your board look identical to mine - hence no need for me to add pics..

So far.. I have cleaned to the best I can. Most green crust is off the PCB, but still around the `Data Path` logic, as well as Agnus socket.

I plan to replace Gary, Data Path, Agnus and their sockets - if I can that is.

I also checked some traces - some working - some not - so I know damaged tracks.

To help, I`m using these tow webpages:
http://www.amigapcb.org - VERY cool PCB layouts and `Net` tracking!

and

https://www.amigawiki.org/doku.php?i...ice:schematics

Very clear Amiga schematics.

But any help other than what I`m trying - would be very appreciated..
As - this is a `practice run`, for trying to repair one of 5 Amiga 3000 boards I have with battery leakage.
(just hoping that Amiga PCB will add the A3000 soon!)
If the board damage is limited. It might be worth fixing tracks first and seeing if it resolves the issue. It may transpire that other chips then don't need replacing.
lesta_smsc is offline  
Old 23 November 2018, 14:33   #13
simon_m74
Registered User
 
Join Date: Mar 2013
Location: UK
Posts: 78
The board does look quite good - but as I say, sure some damaged tracks.
Replacing the data path IC`s will cost less than £10, so I`ll try that anyway.

As for Gary & Agnus - I have spare chips anyway from a donor board - and the socket for Gary is only about £2 too.

I`m going to continuity between :
Top to IC leg to bottom of the board (to check if chip pin is getting to the PCB via socket ok - to test the sockets)
then from Point to Point around the board for each pin on Gary, Agnus & Data path.
simon_m74 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
A500 with ks 3.1 sometimes kickstart most time black screen solidcore support.Hardware 3 30 March 2018 16:51
Black Screen on A500+ with Keyboard attached Amicol support.Hardware 5 29 March 2018 17:13
Black and white composite output from PAL A500 vext01 support.Hardware 2 26 November 2012 23:37
A500 black screen without trapdoor ram toastrackjack support.Hardware 3 26 August 2012 09:00
A500+ problems (Black Screen) Eny- support.Hardware 16 05 June 2004 21:09

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 14:16.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Page generated in 0.07513 seconds with 13 queries