Amiga 3000 restoration

[danbeaver]

The diode Mech mentions is D800 and if working it should be installed with the black line heading IN toward the motherboard.

[ozkano]

can battery acid breakdown 74HC74,

[danbeaver]

Yes and yes; the 38% sulfuric acid in a car battery can damage the copper traces on a motherboard, if one placed it there, and the Potassium Hydroxide of a barrel-type Amiga battery can also dissolve the fine copper traces connecting an integrated circuit.

[mechy]

can battery acid breakdown 74HC74,

Yes, any chip. although its not "acid" its more like lye. It can creep up pins(notice green/corroded pins) on chips and inside. I have seen bad 68000 chips in 2000's that this has happened to. I also repaired a 3000 where the leakage had eaten a socket pin between the board and socket-tough intermittent problem to find!

[ozkano]

I test another psu
I test all removeable chips on my working a3000, all of them works,    


nothing changed black screen

[tonyvdb]

What does it do if you disconnect the hard drive and the CD drive if it has one?

[mikolas]

This really sounds like SCSI termination/power problem. If any of the chips (or the daughterboard, check it) is badly socketed, you either get a black screen or red one w/ daughterboard/memory/kickstart problems. So, check that you have terminator diodes in place on the motherboard. Also, add active terminator to the external connector, that should make the SCSI bus pretty much fail safe.

There are some SCSI bus signals near the battery, so you also might have cut traces. Check with multimeter, visual inspection is not enough. For me, the SCSI led is dead although I can not see any problems by eyesight only...

[ozkano]

only hdd connected all chips heat is normal

[danbeaver]

Although I doubt it is a SCSI controller or drive issue (taking bets that is is a damaged trace/track or chip lead), it would not hurt to unplug everything except the daughterboard to do your testing.

[matt3k]

Although I doubt it is a SCSI controller or drive issue (taking bets that is is a damaged trace/track or chip lead), it would not hurt to unplug everything except the daughterboard to do your testing.

Dan is right on this one.

Have had many 3000's fail with black screens.  It will be a chore but it is going to be trace or chip related for sure.

You can try pressing the caps lock multiple times and if the light freezes after 5 times the cpu isn't responding.

[ozkano]

Dan is right on this one.

Have had many 3000's fail with black screens.  It will be a chore but it is going to be trace or chip related for sure.

You can try pressing the caps lock multiple times and if the light freezes after 5 times the cpu isn't responding.

as matt3k said I press 5 times, keyboard led stop working, when ı reset from keyboard scsi drive also reset and keyboard led blink once as usual

[ozkano]

can i by pass onboard cpu by installing 3640

[matt3k]

Won't fix the problem.

Yellow screens like when the daughter board is out indicates bad CPU and that can be bypassed with a CPU card.  

You could always try it but isn't getting far enough to even see the CPU.

[ozkano]

is there any way to find a3000 pcbs gerber files