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TheCorfiot
25th March 2009, 15:28
Hi Guys & Girls

As some of you maybe aware I picked up An A4000D / 040 in superb condition from our friend Kin Hell recently.
The Motherboard had been subject to some nasty Battery damage and the end result was that the Clock was not being found by the system.
Kin had kindly sent some very hi-res piccys prior to the A4000D arriving and in fairness to us both the extent of battery damage looked very minimal.
However neither of us took into account that this A4000 had been stored on it's side for an extended period of time & gravity being what it was, the acid had travelled :shock:

Firstly I need to post this link

http://amiga.serveftp.net/RTCrepair.html

Mr Hoffman is indeed a true gentleman & this link is a real Bible for diagnosing & checking the circuit. Numerous emails later and Anthony sent me the parts I required as follows
1 x RP5C01 RTC chip - U178
1 x 74HCT174 Data Latch - U177
1 x 10KOhm SIL pack - RP176
I cannot recomend this guy enough, he offered so much advice & help, sent the parts very quickly and charged a very low price for them - All brand new components BTW.

Diagnosis began,
All continuity checks passed the circuit appeared complete, corrosion maybe not that bad ( :lol: )
The only anomoly found was that element 3 of the Resistor pack was reading 6K to gnd instead of 10K which suggested a problem with the RTC's A2 line being incorrectly read on the memory map, hence clock not found.
Culprit either Resistor pack or U177 or U178..... That helped....NOT

Resistor pack carefully replaced & the reading remaned the same. :(
U177 Surface mount IC next on the list, now really the likely culprit.
Not having a hot air rework station, I gently scored along the chip legs right along the ceramic package with a very sharp scalpel.
Now this is when the corrosion really reared it's head, The Acid had gone under the chip & built up a nice pyramid of light blue crap between pins 2 to 7, worse it had actually eaten the pads between the Solder & the PCB, the pads no longer existed.
I carefully removed the old pins with a soldering Iron, some chem-wick & then stared broken hearted at the fact that pads & tracking for pins 2,3,4,7 had gone.
Was this board now beyond repair................ I don't think so :wink:

Pad's 3 & 4 were repairable by using a single strand of copper wire, pushed through the pinholes under the IC, soldered on the reverse of the board at the pin hole & then left extended where the solder pads should have been.

The New IC was fitted and carefully soldered, the left hand side had no issues, but on the right, pins 2,3,4 & 7 were left unsoldered.
The extended copper strands were raised and carefully wrapped around pins 3 & 4 respectively & soldered.
Pin 7's leg was raised and another new copper strand was wrapped around the pin, soldered, placed gently across the chip's body & soldered direct to the Resistor packs relevent solder joint.
Pin 2 was repaired by adding a very short copper strand between the IC leg & the small remainder of the pad.
Used magnifying glass to inspect all joints & solder points.

Time for continuity tests again, some slight rework to the reverse of the board pinholes & the circuit all proved true... :D
Gently cleaned & removed all flux from the board using IPA

A4000D reassembled.........System Booted.................CLOCK FOUND and fully functional.
It works.......

Anyway finishing touches... added some clear nail varnish to affected area, installed small signal diode to Battery + & soldered in replacement CR2032, temporary as I need to speak to someone soon to get a PCB mounted rechargeable lithium battery.

System now keeps & shows perfect time and I am over the moon.

Needless to say I was totally fuxxord, tired, my back & eyes were hurting but the repair was a success and I was overjoyed.
Would have been nice to have just replaced the IC, an invisible repair but it was not to be.
Oh and I have a spare RP5C01 chip as well now :lol:

Now it's Piccy time
It's not as tidy as I would have liked but given the choice & dilemma I faced I think it came off looking a whole lot better than it could have ..... and it's fully functional too.

Big Thanks and Hugs to Kin Hell & Zetr0 for their inspiration & motivation too.

TC :mrgreen:

davideo
25th March 2009, 16:29
temporary as I need to speak to someone soon to get a PCB mounted rechargeable lithium battery.

She's awaiting eagerly to help you fill the void - her legs are a kimbo :lol: :lol:

Another rescued from the grave - well done TC.

Dave G 8)

arnljot
25th March 2009, 16:39
That temp solution, will it not also have a problem with the recharge current from the motherboard. Isn't it why one usually put a diode there to stop it when using normal coin batteries?

davideo
25th March 2009, 16:46
That temp solution, will it not also have a problem with the recharge current from the motherboard. Isn't it why one usually put a diode there to stop it when using normal coin batteries?


installed small signal diode to Battery + & soldered in replacement CR2032

TC has fitted a diode in the temporary setup.

Dave G 8)

SkydivinGirl
25th March 2009, 16:50
@TC

Excellent job! I really hope you enjoy all that A4000 goodness!

Ciao!

Heather

Kin Hell
25th March 2009, 18:47
What else can I say! - Enjoy M8y! :D

Kin

Zetr0
25th March 2009, 20:18
@TC


NIIIICE!!!!!

some damn fine work and great links :)

Merlin
25th March 2009, 21:56
Oh yes, we likes us hardware pr0n, precious......

Nice work TC, well done.
:mrgreen:

r0jaws
25th March 2009, 22:22
Very nice clean up job there TC :mrgreen:

Hessu
25th March 2009, 23:48
Nice job indeed, i know the feeling, after the repair done and all working :)

rkauer
26th March 2009, 01:57
Excellent job, mate.

Too bad I can't repeat it on the 4k I have here: the damage is too vast: from all SIMM sockets to the mouse/joy ports and beyond! :(