The address/data bus to the MegaII VLSI is dead on, otherwise you wouldnt be able to generate any legible characters.  The chip very well could be bad. But it would be odd, but no…

Pitou said: I already checked all pins with an oscilloscope. Continuity is good. Signals seem to be on all pins except for 1,2,4 and 6 if I remember correctly. Again, I'm not…

Fix it please!

I already checked all pins with an oscilloscope. Continuity is good. Signals seem to be on all pins except for 1,2,4 and 6 if I remember correctly. Again, I'm not sure what to expe…

I had to review again a few times the video as the first few seconds as comes up scrambled on the old OSX 10.4 QuickTime. Now I see the start up screen come up scrambled but not re…

This is something totally different. ProDOS-IIgs works with the windows and other things and all. So there is nothing wrong with the system at all. This is a software issue, looks…

I'm not able to get into Applesoft BASIC using ctrl-reset. I also tried running BASIC from a system disk. See this video. test.zip Any idea? Pitou!

NJRoadfan said: According to the Apple IIgs Technical Reference, the character ROM is stored in the Mega II chip, not the main ROM. The Mega II is also responsible for genera…

Pitou said: @Gorgonops, ok thanks, will try that. I have another question about the ROM chip. it's a 128kx8, so it needs 17 lines of addresses in order to access the entire …

According to the Apple IIgs Technical Reference, the character ROM is stored in the Mega II chip, not the main ROM. The Mega II is also responsible for generating text screens on t…

@Gorgonops, ok thanks, will try that. I have another question about the ROM chip. it's a 128kx8, so it needs 17 lines of addresses in order to access the entire memory of the rom.…

ctrl-reset.

@Elfen, very good suggestion, I would try that for sure. However, with no drive connected , it stays on "Check status device" and a kind of bar run from left to right and right to…

I wonder if this is for all the characters in the ROM or just a segment of them? Boot it up without the disk drives attached so it goes into AppleSoft Basic. Then type the follow…

techknight said: Your not gonna see via corrosion AFTER you already washed it. You needed to take note of those beforehand. Click to expand... That's why I'm having troub…

Well it's hard to tell if it's the ROM chip or the Mega II. I also played around with the scope and followed the schematics, but I'm not able to pinpoint the root cause. Here they…

This happens if the ROM cant see the SWIM. grab the classic schematics and go throught it. Your not gonna see via corrosion AFTER you already washed it. You needed to take note of…

Thanks for the suggestion, I don't get a flashing ?, yet.  I removed the RAM card and it did not help, in a separate attempt, I removed the HD cable and the startup remains unchang…

As long as you got the flashing '?' inside a floppy disk icon, the Classic is or should be working. You got a Bong an you got video - that's 2 out of 3, which the third is booting.…

Could be the HD, try disconnecting it and booting from floppy

Its weird that only text is having a problem. That and the ROM checksum is passing. The only other chip I can suspect having a problem is the MEGA II which contains the character g…

I picked up a Mac Classic (2MB, 40MB HD) and it was immediately subjected to a recap.  As part of that process, I cleaned around the old cap areas with alcohol and re-tinnned the p…

It actually looks like what my vision does to me, from time to time. lol. But I digress.... double data = missing upper address bit/select signal on character ROM. 

Elfen said: If it were a Mac SE/30, I'd say part of your video circuit has lost a couple traces. Click to expand... Something like this would be my guess as well. I don't…

I can make out "System Good" on that image, but you say it freezes at that point? Interesting. What cards are you running on the IIgs? Have you run it without cards? If it were a…