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Author Topic: A600 glitches after recap  (Read 258 times)

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Offline JacksoftTopic starter

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A600 glitches after recap
« on: December 19, 2025, 12:47:34 AM »
Hi all,
I encountered a strange issue during/after a recap on A600 rev. 1.5.
I've not repaired so many Amigas but fixed some 500's with minor problems.
This machine had floppy drive issue and no video on composite.
No video was caused by Z222 and I bypassed it just to make sure it works, floppy drive was recapped and now looks working' (not fully tested yet), so there's the main A600 plague, bad caps and some corroded traces.
Initially the machine worked ok, after I replaced all the capacitors (found about 4-5 ceramic caps on the 5V line in nearly short too and replaced them!) and removed Paula to check traces under the chip (some of them were "blacky") I putted all back and powered on the A600 with some ugly glitches on the half-down screen like in attached pictures.
For older machines like A500/500+ I used the Test Disk floppy but in this case, after loading the Test Disk, I could only see garbages on the screen, so I bought a DiagROM and did some tests. Most of all seems working ok, except option 1, 2, 3 in Graphics tests: it causes glitches, empty screen or no video at all. RAM, CIA, IRQ are ok, sound tests are ok.
I also tried disabling and removing Paula again (thinking about some wrong soldering or other) but nothing changed.

I've seen around that this kind of problems is caused by a bad Agnus, but I don't understand how it could be correlated the work I did.
Before starting messing anymore around and buying replacements there is some others checks and tests I can do?

Thanks in advance.
« Last Edit: December 19, 2025, 12:57:38 AM by Jacksoft »
 

Offline JacksoftTopic starter

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Re: A600 glitches after recap
« Reply #1 on: December 19, 2025, 02:34:08 PM »
Hi! Thanks for the fast reply.
About the ceramic caps I noticed that one under the board was very hot. I removed and tested it in Ohm and returned me about 33Ohm. But one ceramic cap in short or nearly can happens. The strange fact is that other two caps on that line where also like this (60ohm, 100ohm, etc). Also the one on the Paula alimentation (after the big 1R resistor) had trouble so he messed with the tension partitor for the 2.4V.
I removed them all and tested and about 4-5 of them where faulty (this is REALLY strange).

I'll check where you suggested and report you asap. Thanks!