Advice needed on A3640 repair - caps orientation

keropi

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Hiya!!!

I have here a good friend's A3640 accelerator: it was working fine, until it needed some reboots to have the amiga boot OK and finally it just stopped working.
Naturally I suspect the aging caps... but what about their orientation? I have checked the old ones and they seem OK to me but I may be wrong too :LOL:

Sooooo.... (Z :p) , take a look at the pics of the card, do they seem OK ??? (I have marked with red the ground pin of the caps)
thanks! (y)

5btpfn.jpg
 

salaxi54

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@keropi: Seeing as this is a Rev 3.0, is it plugged in an A3000 or an A4000? According to this http://www.amiga-hardware.com/showhardware.cgi?HARDID=223 it won't work in an A3000!
"V3.0
This revision will not work in A3000's at all (unknown if this also applies to the A3000T and A4000T) because of a conflict with the DMA handling of the onboard SCSI controller and some Zorro cards. Although it will work with A4000's. A bug in the design allows the board to grant DMA access to more than one device, causing the machine to hang. There is also a problem with the STERM* signal that can cause sporadic crashes with some cards such as the Cybervison 64. The PAL or GAL chip located at U209 should be -01. "
Go figure...:huh:
By the way, comparing this to the rev 3.2 pic from http://amiga.resource.cx/photos/photo2.pl?id=a3640&pg=2&res=hi&lang=en where the caps are named the same, there's some difference in polarity of those! To be precise, it shows C107, 105, and 106 soldered the other way around... Caps are on the same locations as your card, and named likewise.
 

arnljot

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To me it looks like all caps on that board are correctly mounted according to the silk screen.

which is wrong.

At least some A3640s suffer from a serious bug that can drastically reduce the life of the accelerator. Three capacitors on the board were soldered in the reverse position which can cause them to leak electrolyte over a period of time. These capacitors are labelled C105, C106 and C107

So, if you replace them or do anything with that card, it would perhaps be smart to have Z weight in on that :)

There is also lots of other 3640 info in the boing balls thread.
 

keropi

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ah, thanks, that serverftp page solved all my questions :)
there where 2 leaking caps btw, those near the 040 (and the card is used and was working perfect in an A4000D)
 

Kin Hell

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Hi keropi.....

Talk to TC about this. I sent him a Rev 3.2 in Kinelle a while back & that one needed a cap soldering on. I included a full set for him & he checked polarity on each one. Some go one way round, the others went another way around. Talk to him though, he has all the science on it. ;)

@ TC

How about a Photo shoot on what you did do m8?

Kin
 
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psodas

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Also a 4000 from a friend, and also at her last heart beats, dont boot at all.
After an inspection with Ohm meter, from silk screen (-) of capacitors, to ground (metal shield of crystal) , I find the C105-106-107 is fitted with wrong polarity!! :eek:
All the capacitors are leaking, because except dirty looking of some component around of them, they smell like HELL when you try to desold them from pcb.:LOL:
I prefer to change them with axial types, because I dont trust the smd aluminium capacitors at all.:dry:

Ok the steps was.... clean flux to desold them, FluxOff for cleaning the residues, clean aceton for any leakage, and sold the new one with right polarity!

And final the big LALALA. From my mistake I give the monitor cable back to my friend.:Doh:

So..... to morrow will see.

I pray to boot even once, so I can go further in changing all the capacitors on the mainboard, and the cleaning of the board near the clock which has undergone significant corrosion from battery leak.


picture.php


picture.php


picture.php
 
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rkauer

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Time to do the "overclock" hack on the board, my friend.
 

Zetr0

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@psodas

(y) Nice work indeed! (y)


I think thats the best through-hole made SMD I have seen in a very long time =D


For others wanting to know what to do then please read this PDF file you only need to replace 3 capacitors C105,C106 and C107

however depending on the age and or leaking capcitors you may need to change more, always replace with the same value capcitance and always make sure the component is the same voltage range or higher.

the PDF is from www.a68k.de, alas I don't know whom to thank as theres no names in the PDF, so who ever did make the PDF, a HUGE thanks and a job well done!
 

keropi

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funny thing - on the 3640 I replaced the caps - is that the caps that leaked where not the C105-C106-C107 ... the 2 remaining correct placed ones had leaked LOL
 

hikey

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Funnily enough, i got done replacing the caps and updating the GALS on mine the other day. Also socketed the crystal in case i want to overclock one day. Even made new stickers for the updated GALS. lol
If anyone needs the files to update their gal chips I archived them here:
http://amigaromarchives.limewebs.com/
 

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rkauer

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Excellent content!

Do you have the updated "innards" of the PAL chips of the A3000 motherboard?:mrgreen:
 
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