Repairing A4000 leaky NiCd damage?

[Alexandre Souza]

the chip isn't hard to come by, Steve. You can find it on ebay.

On Fri, Jan 2, 2015 at 10:39 AM, Steven Hirsch <snhirsch at gmail.com> wrote:

> On Fri, 2 Jan 2015, Ethan Dicks wrote:
>
>  Has anyone here gone through the process of reparing leaky NiCd damage
>> to an A4000 motherboard?  I _thought_ I had removed the battery some
>> time ago but puttering around today, I cracked open the case to find
>> the battery still there and some damage around U891 (a 74F245) and
>> U850 (Bank 3 DIMM socket).  I have washed off the residue but I may
>> have to pull a DIMM socket to get access to the vias under it.
>>
>> I know the general process, but I'm curious if anyone has done this
>> specifically to an A4000 board and has any tips.  As I said, I'm
>> probably going to have to pull the DIMM socket to get to all the
>> damage.
>>
>
> Went through this entire process on my A4000 a couple of years back. In my
> case there was damage to traces underneath several of the adjacent chips
> and the clock chip was dead to boot.  I would suggest soaking the board
> overnight in dilute vinegar in addition to washing, since the alkaline crud
> gets into via holes where washing won't dislodge it.  If traces are not
> already eaten, this may eliminate the need to remove the DIMM sockets.
>
> I ended up removing all the chips in the immdiate vicinity of the battery
> and piecing things back together with 30g wire.  This did include threading
> through a few of the vias.  One random bit of advice:  The leaked crud
> tends to dissolve the solder mask on the circuit board and makes hot-air
> reflow a bit touch and go.  The solder will migrate underneath the chip
> rather than flowing around the legs.  After two unsuccesful rounds with the
> reflow tool (shorted traces underneath) I ended up hand-soldering the
> smaller parts.
>
> At the time I did this work, the Ricoh clock chip was still available from
> Amigakit in the UK.  Unfortunately its function goes beyond simple
> timekeeping.  It has some involvement in the power-up sequence and the
> system won't function with it.  There may be a way to mod around this, but
> I simply replaced the chip.
>
> Steve
>
>
>
> --
>