15 votes
Accepted

ZX81 screen corrupted

Thank you @Raffzahn for the comment that inspired me to think of something blocking the video signal. The initial problem described in the previous question was that the ZX81 was showing a white ...
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  • 1,025
15 votes
Accepted

On the video signal generated by the ULA of the ZX81

That portion of the video signal is generated directly by the ULA; early ZX81s just don't generate a back porch, which was seemingly good enough for the majority of televisions but problematic enough ...
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  • 32.2k
14 votes

Why would a laptop freeze randomly after running fine for a while?

Unfortunately, the reason for random freezes can be hard to identify as a lot of different failure modes can lead to this outcome. Try to get hold of a bootable burn-in test program that works with a ...
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  • 4,090
9 votes
Accepted

Booting from SD card on a Compaq LTE 4/75 – DOS 6 works, Windows 95 doesn't

The problem is in the geometry. Not in the physical disk geometry, but rather in the translation how the BIOS must translate the geometry for DOS when using disks larger than 1024 cylinders. The ...
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  • 16.1k
9 votes

Why is my Macintosh LC 475 playing chimes of death when I install more ram?

I fixed it. I used a known working logic board from a different mac and a multimeter set to continuity to find the bad trace. first I tested the first 16 pins of the simm slot to the ground on the ...
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  • 1,143
9 votes
Accepted

CBM PET 2001 garbled screen

The garbled screen is normal on startup, but should be replaced by the BASIC screen after a moment. There's a rather detailed troubleshooting guide, including links, at http://www.dasarodesigns.com/...
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  • 7,799
7 votes

What are the normal signals on a 65C02 in an Apple IIe?

65C02 is a CMOS version of 6502 (which was NMOS) chip. Judging from Wikipedia articles on these chips and few of the datasheets I found, it seems like it should work exactly the same way it did on ...
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  • 1,324
6 votes

Booting from SD card on a Compaq LTE 4/75 – DOS 6 works, Windows 95 doesn't

Whew, I've got it solved! I took one of the disk images with Windows 95 installed on it, and examined it with a hex editor. I noticed that when the Windows installer program initially sets up the ...
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5 votes
Accepted

What are the normal signals on a 65C02 in an Apple IIe?

I've been meaning to get around to this for ages, sorry. Tonight I stumbled across SAMS COMPUTERFACTS for the Apple IIe which I had downloaded from the Internet Archive. Here is the logic chart data ...
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5 votes
Accepted

Parity error under DOS

In such cases, the problem is almost always in one of three places: One of the memory modules. The motherboard itself. A plug-in device. To help with the testing, you should start be removing all ...
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5 votes

N64 displays dark picture with barely recognisable contours

Possible reasons IMHO could be: Older computers and consoles sometimes do not work with modern TVs. Modern TV needs a more precise TV signal, especially the timing and voltage level, than older TVs. ...
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  • 5,152
5 votes

PS/2 Keyboard not working on Windows 95 and MS-DOS

One thing I can say for certain: installing an earlier version of MS-DOS could not have made anything worse (or better, anyway). Both MS-DOS 6.22 and 7.x (the version built into Windows 95) rely on ...
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  • 16.4k
4 votes

Amiga 500 WorkBench 1.2 Freezes

Workbench 1.2 is known to have some bugs, and it would be better if you could boot into Workbench 1.3 instead. Based on your description, I suspect your mouse could be malfunctioning. It sounds like ...
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  • 56.5k
2 votes

Parity error under DOS

You mention there are 4 2Mb modules. If I remember correctly, many 486 era boards would let you populate in banks of 2. If your board supports it, you can try removing 2 of the memory modules and ...
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  • 8,416
2 votes

CBM PET 2001 garbled screen

This is anecdotal, so take with a big grain of salt... I have a C-64 power supply that was home-brewed for me by my Dad when I was a kid from the remnants of the original. My Dad, never being one to ...
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  • 8,416
1 vote

Booting from SD card on a Compaq LTE 4/75 – DOS 6 works, Windows 95 doesn't

This is a logical–physical geometry mismatch. Like @Justme’s answer explains, the ‘logical’ geometry used by the BIOS disk interrupt services, and the ‘physical’ geometry reported by the disk ...
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  • 16.4k
1 vote

PS/2 Keyboard not working on Windows 95 and MS-DOS

Many vintage PCs have a PS/2 port that can be configured (via jumpers, BIOS, or both) to work as either PS/2 keyboard, PS/2 mouse, or combined keyboard+mouse with a Y-cable adapter. Having the port ...
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  • 56.5k
1 vote

PlayStation 2 Slim with analog A/V output having noise interference issues

I would recommend getting decent PS2 cable with RF shielding. I had the same issue when connected to TV, even though console's audio was muted.
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1 vote

What are the normal signals on a 65C02 in an Apple IIe?

Who made your 65C02? Was it WDC? If it's WDC, then there are a few pins that should be held high with a 3.3k pull-up resistor. Such as the BE pin which is only on WDC versions. BE (Bus Enable) ...
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