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Old 19 November 2010, 09:30   #1
craggus2000
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A600 Intermittent Black Screen

Hi Guys,
I've bought a pretty manky looking A600 (all yellowed - prime candidate for Retr0brite! But i digress...)
It has a seemingly intermittent problem...
When I bought it, it was described as caps death - black screen.
But when I first received and turned it on it worked!
On and off a few times, and then suddenly just a black screen on power-on No clicking no nothing.

I've open it up and visually the capacitors all look fine. What's the best way to test them?

Is there anything else that could cause this black screen? (I've swapped the Kickstart and same thing happens )

Please help!!

Thanks
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Old 19 November 2010, 09:56   #2
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verify cap 10 micro 16 volt for reset near ic 555 under floppy, i have change 2 recently
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Old 19 November 2010, 11:43   #3
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Originally Posted by cpiac64 View Post
verify cap 10 micro 16 volt for reset near ic 555 under floppy, i have change 2 recently
cap 10 micro? is that one of the tiny ones?

What's the best way to test a cap?
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Old 19 November 2010, 19:47   #4
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with tester on pin 1 of harddisk, verify if 5 volt the reset is ok, if zero are ko

the cap is c613

the led on keyboard are ok?
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Old 20 November 2010, 07:23   #5
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Swap ALL electrolytic capacitors. Period.

If the fault is the same after replacing the caps, then you can search for something else (start for the SMD 555 on the mobo).
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Old 20 November 2010, 13:52   #6
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@Craggus

After you have replaced the caps, if the system is still having issues -

Resolder the 68000 CPU:
These SMD components can have (or should I say develope) pad-leg cracks over time - as such you will have intermittent power-up issues. to solve this problem is quite simple - lay down some no-clean flux and tap some solder to each of the legs and pads =)


Still not Booting propperly?
Then we need to replace the 3mhz resonator for the keyboard MPU (Y621) (brown/blue pending mobo revision) - if this resonator isn't pumping the Keyboard MPU it holds up the boot sequence on a black screen.


Still having issues?
Without blaming the custom chips, the next likely culprite could be the ROM socket itself - if this has had a Kickrom yammed in hard then its possible it has dry solder fault under the socket - easy to fix - whip the board out - turn it upside down - slap on some no-clean flux and resolder the 42 points.
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Old 20 November 2010, 14:29   #7
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@Craggus

After you have replaced the caps, if the system is still having issues -

Resolder the 68000 CPU:
These SMD components can have (or should I say develope) pad-leg cracks over time - as such you will have intermittent power-up issues. to solve this problem is quite simple - lay down some no-clean flux and tap some solder to each of the legs and pads =)


Still not Booting propperly?
Then we need to replace the 3mhz resonator for the keyboard MPU (Y621) (brown/blue pending mobo revision) - if this resonator isn't pumping the Keyboard MPU it holds up the boot sequence on a black screen.


Still having issues?
Without blaming the custom chips, the next likely culprite could be the ROM socket itself - if this has had a Kickrom yammed in hard then its possible it has dry solder fault under the socket - easy to fix - whip the board out - turn it upside down - slap on some no-clean flux and resolder the 42 points.
I used to work for a company that shall remain nameless and one of their products had a small board that caused about 90% of all the board issues because it was manufactured badly, resoldering the main IC would fix the problems about 90% of the time.

Quality control, they've heard of it.
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Old 22 November 2010, 15:14   #8
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I've ordered a set of caps for my A600 so when they arrive i'll be having some fun.................
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Old 30 November 2010, 13:02   #9
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Still waiting for the caps to arrive....
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Old 03 December 2010, 17:45   #10
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They've arrived now! Going to see if I can have a go at replacing them myself at the weekend (after we've bought our xmas tree................ )
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Old 07 December 2010, 10:55   #11
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OK,
So it turns out I need to repair some parts of the mobo, as a couple of tracks/pads have come off with the caps I was removing...

How many layers is the A600 mobo, I'm hoping just 2 (top and bottom)???

I'm going to connect from the vias where possible, but any tips for repairing the tracks and pads? I was planning on using something like CAT5 stranded to replace the tracks and then coil it up a little to make a pad?

Thanks
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Old 07 December 2010, 12:48   #12
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>So it turns out I need to repair some parts of the mobo, as a couple of tracks/pads have come off with the caps I was removing...

PRACTICE AND TRAINING ON NOT WORKING PCB BEFORE ON YOUR AMIGA

Why it's so hard to understand ??
(You are not the first guy, craggus2000)

Last edited by TCD; 07 December 2010 at 12:48. Reason: Back-to-back posts merged. Use the edit function.
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Old 07 December 2010, 12:52   #13
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How about a Cosmos?
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Old 07 December 2010, 13:10   #14
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Quote:
Originally Posted by Cosmos View Post
>So it turns out I need to repair some parts of the mobo, as a couple of tracks/pads have come off with the caps I was removing...
PRACTICE AND TRAINING ON NOT WORKING PCB BEFORE ON YOUR AMIGA

Why it's so hard to understand ??
(You are not the first guy, craggus2000)
Wow. I did actually. I was just unlucky

Any one have any tips?
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Old 07 December 2010, 13:48   #15
Cosmos
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@TheCyberDruid

Hey man, after that, it's my time, during hours for fixing...
Watch my last article on my Blog about a 1260 : near 2 hours to repair...


@craggus2000

When you practice, you improve your skill... No luck on soldering : only experience...
It's like read and write : you have learned/practice/training before... Incredible...
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Old 07 December 2010, 13:51   #16
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Did craggus2000 ask you to do it? If you feel like POSTING BIG RED CAPS next time, think about it twice.
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Old 07 December 2010, 14:47   #17
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Everyone makes mistakes at some point or another.
While I know my soldering skills are hardly that of a pro, I don't think they are too bad either.

I do the best I can with the kit I can afford, the skills I learn and improve upon over time, and the determination/enjoyment of taking stuff apart and repairing it!

If I make a mistake, I just do my best to correct/fix it and carry on with the hope that I won't make that same mistake again, but hey, no one's perfect....
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Old 07 December 2010, 16:45   #18
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OK,
So it turns out I need to repair some parts of the mobo, as a couple of tracks/pads have come off with the caps I was removing...

How many layers is the A600 mobo, I'm hoping just 2 (top and bottom)???

I'm going to connect from the vias where possible, but any tips for repairing the tracks and pads? I was planning on using something like CAT5 stranded to replace the tracks and then coil it up a little to make a pad?

Thanks

The A600 is a 2 layered board, you may be able to fix the traces with some solid core awg 26 - 30 kynar wire, a good magnifying glass, some flux and a fine pointed solder tip. To remove the surface caps you really need the proper tools to do it. The best is a solder hot air rework station with a small nozzle, regular solderingh irons are awkward to use and needs a bit of practice. Patience is definately a virtue and you should alays put a bit of flux down on the pads.

To remove the through hole caps i use 2 different methods, mabbe the first method will make people groan a bit, but its never let me down yet after about 50 boards, i grab the through hole capacitor with pliers, brace the board so it doesnt flex, and pull the capacitor upwards and it will pop off, its just a case then of removing the legs which is then a lot easier

the other method is to use desoldering braid to remove most of the solder, then use a product called "chipquik" its like solder but it lowers the melting point of the solder at the joint so you apply that to the pads and then you can easily rock the capacitor back up through the hole. Make sure you clean up afterwards. This works well even if one of the legs are on a large ground plane which makes heating the legs up hard.

for the SMD caps removal, then i really recommend using a hot air rework station (google it)
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