Amiga 500 not booting after oops

Chris71 · 31 December 2020, 02:25

Hello

I had a working A500 with a rev5 motherboard, I fitted a 512k expansion card I got off flee-bay from Spain and that's when thing went south.

The card was fitted inadvertently upside down and the computer powder on, then the dreaded smell of smoke!

On checking inside I could see that U38 (MC4188) was shorted and fried.

So I replaced MC1488 at U38, but now no boot

. All I get is a light grey screen showing with no power light or drive light coming on at all.

I have changed all the chips Gary, Paula, Denise, CPU, ROM & both CIA's for Known working ones (in another A500) but still the same. There is no visible damage on the board at all, the board is free form any dirt or corrosion.

Should I have replaced MC1489 at U39 as well?

I haven't got a 8371 Agnus to try, could it be that?

Any ideas would be wonderful.... Please help

P.s I don't have a oscilloscope just a multimeter

DigitalKeeper · 02 January 2021, 00:47

1489 new? Yes!

And - have a look at NE555 -> Reset Circuit

31 December 2020, 02:25	#1
Chris71 Registered User Join Date: Dec 2020 Location: Auckland, New Zealand Posts: 19	Amiga 500 not booting after oops Hello I had a working A500 with a rev5 motherboard, I fitted a 512k expansion card I got off flee-bay from Spain and that's when thing went south. The card was fitted inadvertently upside down and the computer powder on, then the dreaded smell of smoke! On checking inside I could see that U38 (MC4188) was shorted and fried. So I replaced MC1488 at U38, but now no boot . All I get is a light grey screen showing with no power light or drive light coming on at all. I have changed all the chips Gary, Paula, Denise, CPU, ROM & both CIA's for Known working ones (in another A500) but still the same. There is no visible damage on the board at all, the board is free form any dirt or corrosion. Should I have replaced MC1489 at U39 as well? I haven't got a 8371 Agnus to try, could it be that? Any ideas would be wonderful.... Please help P.s I don't have a oscilloscope just a multimeter Last edited by Chris71; 31 December 2020 at 03:15.

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02 January 2021, 00:47	#2
DigitalKeeper _Repair_Nerd_ Join Date: Jun 2020 Location: Germany Posts: 71	1489 new? Yes! And - have a look at NE555 -> Reset Circuit

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