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AuthorTopic: A4000 re-repair  (Read 1355 times)

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Offline anightin

A4000 re-repair
« on: July 23, 2021, 10:41:12 AM »
Dear All,

I hope you are well, I am new to this forum and it's my first post :)

I acquired an A4000 last year and the machine has been working well. However recently it has been losing it's time and date (U177?/U178?) and just this week it stopped registering fast RAM -- a quick hack with DiagROM revealed that the bottom 8 bytes is stuck at FF (U891?)

I knew the machine had previously been patched up -- apparently by someone in the Netherlands?

I am in the process of re-reparing the repair and have just started to take a look. First job was to take off some prime suspect components and give the board a bath in distilled vinegar and a rinse in IPA.

It's showing some patch wires touching the pads. What is the recommended best way of placing my replacement IC's?

Re-solder the patch wires to the pads, pop the IC on top and re-flow hoping the patch wire stays put?

Many thanks

« Last Edit: July 23, 2021, 10:41:51 AM by anightin »

Offline mechy

Re: A4000 re-repair
« Reply #1 on: July 23, 2021, 04:54:47 PM »
I would tin any exposed bare copper traces and/or coat them. Solder the chips on then run jumper wires where needed.
The board doesn't look too bad so i think you will be fine. good luck! Continuity check everything you repair with the multimeter
« Last Edit: July 23, 2021, 04:55:55 PM by mechy »

Offline Edwin Pouwel

Re: A4000 re-repair
« Reply #2 on: July 23, 2021, 09:46:40 PM »
Hi, I had simulator problems with my 2 A4000’s. What I did was get the rtc kits from amiably, I guy is selling those on that forum. If you want I can try to get his name. After replacing the rtc circuit the real-time clock was working again. But while replacing all the components I also checked the traces using a multimeter. This part of the board is very close the the famous battery and there is a big change that some of the traces are broken. You can fix the with some wires. This was what i did. Good luck.


Offline anightin

Re: A4000 re-repair
« Reply #3 on: August 17, 2021, 07:32:17 PM »
Thanks for the comments  :D

I have replaced U891 and U177 with new parts (Mouser) and have added a new RTC IC (AmigaKit).

The machine powers up from cold, remembers the time and date, and detects FASTRAM, however when warm (5-10mins) it starts misreading the bottom byte as above  >:(.

I am now down to having only 1 bit stuck in the lowest byte which I think is bit 5 of 8.

Investigation continues... I am hoping it is a bad joint/patch wire as the ICs are new...


Offline anightin

Re: A4000 re-repair
« Reply #4 on: August 24, 2021, 10:51:38 AM »
Wow that was an epic battle  ;D


Offline ahandyman59

Re: A4000 re-repair
« Reply #5 on: September 14, 2021, 06:59:50 AM »
Did you replace the 2032 battery? Those batteries are not receiving any kind of charge (and cannot be recharged), and only last about a year.