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AuthorTopic: A4000 issues  (Read 272 times)

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Offline amigakid

A4000 issues
« on: January 03, 2016, 05:07:48 AM »
I have an Amiga 4000 that when I turn it on only get a grey screen.  It powers on (lights and all come on), using CTRL A+A restarts it (HDD spins down then on again and Caps locks flashes).  I just put in a new A3640 CPU card and the motherboard I got was from Ebay (about year or so ago) with a coin battery replacement for the barrel.  The board is pretty clean and traces seem fine.  I have stripped it all the way to just chip RAM and 3640 board only and still only get gray screen.  Capacitors look good, but I was wondering if anyone had a electronic manual or Doc on testing motherboards (ICUs, Caps, resistors and such) and what the readouts should be on a multimeter.  Does anyone have any ideas on what I can check for?I really want to get her up and running (been a few years).  Also is there a way to test the PSU and what should the readings be on the pins in the plugin to the MB?
 

Offline Acill

Re: A4000 issues
« Reply #1 on: January 03, 2016, 05:11:56 AM »
When you first power on tap the caps lock key immediately and see if it locks on or off before you get past ten times. That will tell you if the CPU board is working for the most part.
Proud Retired Navy Chief!

A4000T - CSPPC - Mediator
Powerbook G4 15", 17"
Powermac G5 2GHZ
AmigaOne X5000
Need Amiga recap or other services in the US? Visit my website at http://www.acill.com and take a look or on facebook at http://facebook.com/acillclassics
 

Offline amigakid

Re: A4000 issues
« Reply #2 on: January 03, 2016, 09:49:19 AM »
It will for about 6-7 times.  From what I read it doesn't mean CPU is bad, just the the KB memory gets full and it can't light up anymore.  I was wondering if anyone has a doc or something that can walk you through troubleshooting a motherboard.  Something that tells you what maybe the multimeter readings should be for different chips.  Also how to test the power supply.  I am kind of thinking that might be a problem possibly since this is the second MB and second 3640 card in it.  Any ideas?
 

Offline rockape

Re: A4000 issues
« Reply #3 on: January 03, 2016, 01:03:35 PM »
Hi,

See  http://www.wonkity.com/~wblock/a4000hard/comprob.html

And

See  http://www.wonkity.com/~wblock/a4000hard/main.html

Quote

"Dead Machine Problems

A4000 does nothing on power-up; keyboard light, power light, and hard drive spin-up show that power supply is working, but screen is gray or black, and disk drive doesn't click.


Possible cause: the processor board is not firmly connected to the mother board, or has worked its way loose (the power LED may flash quickly in this situation).

Reseat the connector strip that is parallel to the floppy drive. Since this connector is quite long, it is possible for the ends to be firmly attached while the center is not making adequate contact.

Be careful not to flex either board too much while reconnecting them; using a large rubber eraser or other flat object will protect your fingers while pressing the boards together gently.

In extreme cases, it may be necessary to use a contact cleaner to clean accumulated gunk (like silicon heatsink compound) from the connectors.


Possible cause: expansion cards not inserted fully or properly. Remove and reinstall.


Possible cause: the motherboard is not supported very well near the internal IDE connector.

Solution: gently lift the motherboard near this connector. Installing an insulating support underneath the motherboard near here will be a more permanent solution.


Possible cause: badly-trimmed pins of the soldered power supply connector have poked through the insulating plastic under the motherboard and shorted to the case.

Solution: trim the pins and install more insulating plastic."


I hope this helps.

Regards, Michael

aka rockape
"A veteran is someone who, at one point in their life wrote a blank check made payable to \'Their Country\' for an amount of \'up to and including their life\'.
 

Offline amigakid

Re: A4000 issues
« Reply #4 on: January 03, 2016, 07:09:22 PM »
Thank you for the links I will try them out and let you guys know
 

Offline Acill

Re: A4000 issues
« Reply #5 on: January 03, 2016, 07:27:45 PM »
Quote from: amigakid;801279
Thank you for the links I will try them out and let you guys know

If your caps lock is locking up after 6 or 7 times your CPU isnt initializing. I would pull out the CPU card and clean the pins on the board using isopropyl and try again. MY A4000T had the same issue and its working great now.

Also if you had to install a second CPU and MB in this machine I would get that PSU out ASAP! That sounds like a killer to me.
Proud Retired Navy Chief!

A4000T - CSPPC - Mediator
Powerbook G4 15", 17"
Powermac G5 2GHZ
AmigaOne X5000
Need Amiga recap or other services in the US? Visit my website at http://www.acill.com and take a look or on facebook at http://facebook.com/acillclassics
 

Offline SACC-guy

Re: A4000 issues
« Reply #6 on: January 03, 2016, 08:49:05 PM »
Quote from: amigakid;801255
It will for about 6-7 times.  From what I read it doesn't mean CPU is bad, just the the KB memory gets full and it can't light up anymore.  I was wondering if anyone has a doc or something that can walk you through troubleshooting a motherboard.  Something that tells you what maybe the multimeter readings should be for different chips.  Also how to test the power supply.  I am kind of thinking that might be a problem possibly since this is the second MB and second 3640 card in it.  Any ideas?
Something else to check...

Under the cpu board is a set of jumpers for int/ext.

If they are set incorrectly for your cpu, it will hang the system.

BTW, If memory serves, for the 3640 should be set to ext.
 

Offline Castellen

Re: A4000 issues
« Reply #7 on: January 03, 2016, 10:56:09 PM »
Quote from: amigakid;801249
I was wondering if anyone had a electronic manual or Doc on testing motherboards (ICUs, Caps, resistors and such) and what the readouts should be on a multimeter.  Does anyone have any ideas on what I can check for?I really want to get her up and running (been a few years).  Also is there a way to test the PSU and what should the readings be on the pins in the plugin to the MB?




The board only needs +5V (+/- 10%) to boot, which is from the fat yellow wire on the main board power conector.  Probably not power supply related given your clues so far.

The schematics are easily available.

In terms of fault finding, you need to start with the basics such as are all reset lines inactive (high/5V), are all clocks valid, valid p-p levels on address and data bus lines.  Check the overlay line from U350 is being set after power on, indicating initial ROM data is being read and CIAs can be written to.

Common faults are battery corrosion around U177, U891, etc.  If these parts look corroded, remove them using a SMD rework station and see if the system boots.  It doesn't need these parts fitted to boot, though of course you'll have no RTC or fast memory.

If you can't get anywhere, I can send you an estimate to repair.

http://amiga.serveftp.net
 

Offline Acill

Re: A4000 issues
« Reply #8 on: January 03, 2016, 11:20:49 PM »
Quote from: Castellen;801300
The board only needs +5V (+/- 10%) to boot, which is from the fat yellow wire on the main board power conector.  Probably not power supply related given your clues so far.

The schematics are easily available.

In terms of fault finding, you need to start with the basics such as are all reset lines inactive (high/5V), are all clocks valid, valid p-p levels on address and data bus lines.  Check the overlay line from U350 is being set after power on, indicating initial ROM data is being read and CIAs can be written to.

Common faults are battery corrosion around U177, U891, etc.  If these parts look corroded, remove them using a SMD rework station and see if the system boots.  It doesn't need these parts fitted to boot, though of course you'll have no RTC or fast memory.

If you can't get anywhere, I can send you an estimate to repair.

http://amiga.serveftp.net

If you want to try and replace SMD I'd recommend getting this rework station. For the price I have found mine to be excellent! Its never let me down. You can practice on old broken cards. It doesnt take long to get a feel for it if you use a good pair of ESD tweezers and a good workstation with lots of light and a magnifier. https://www.adafruit.com/products/1869?gclid=Cj0KEQiAqqO0BRDyo8mkv9y259EBEiQApVQD_Yc1fPcmm8HJAnxk9gvWtZTzqkkB6t9a52lg2f40brEaAlIq8P8HAQ
Proud Retired Navy Chief!

A4000T - CSPPC - Mediator
Powerbook G4 15", 17"
Powermac G5 2GHZ
AmigaOne X5000
Need Amiga recap or other services in the US? Visit my website at http://www.acill.com and take a look or on facebook at http://facebook.com/acillclassics
 

Offline amigakid

Re: A4000 issues
« Reply #9 on: January 04, 2016, 04:14:21 AM »
Thank you everyone for your responses.  That rework station looks good, and pretty fair price.  I will be trying the basics and testing tomorrow, then if need to order the rework station.
@Castellen - I may end up taken you up on having you fix it.  If so do you need the whole unit (case and all) or just the MB and CPU card?
 

Offline Castellen

Re: A4000 issues
« Reply #10 on: January 04, 2016, 04:43:25 AM »
Quote from: amigakid;801319
do you need the whole unit (case and all) or just the MB and CPU card?



Just the main board.  If you want to update the A3640 to revision 3.2 (logic image change) and replace the capacitors and correct polarity, it's no problem to do that at the same time.

If you want to pursue the repair, Email me with what country you're in and I'll work out approx. costs including return freight.

I've just caught up on a large backlog of Amiga jobs, so turnaround times should be about a week or less.

Contact details on the front page:
http://amiga.serveftp.net
 

Offline dannyp1

Re: A4000 issues
« Reply #11 on: January 04, 2016, 08:31:05 AM »
His A3640 is a working revision 3.2 that has been recapped.  He just got it from me.  That is assuming it wasn't damaged during shipping.