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15 votes

On my NES, the color red displays as black. What could be the cause?

Because the NES cartridge port uses a separate bus for fetching graphics data versus CPU code, dirty cartridge connectors can often cause graphical anomalies without otherwise affecting cartridge ...
supercat's user avatar
  • 36.5k
15 votes

Why would installing a 486DX2 make the system freeze for minutes on boot?

There might be a timing loop calibration in the BIOS which is responsible for working with different speed CPUs to have similar delays. Or the BIOS tries to determine the CPU type with the CPUID ...
Justme's user avatar
  • 32.8k
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 ...
Paul Ghobril's user avatar
  • 1,035
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 ...
Tommy's user avatar
  • 37.3k
12 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 ...
Justme's user avatar
  • 32.8k
10 votes
Accepted

Commodore SX-64 White screen

Just in case you are unaware, there are CRT controls hidden behind the panel on the right side. There's also a floppy reset button and volume control. I don't suspect this will fix your display but ...
Brian H's user avatar
  • 60.8k
10 votes

1984 accounting software running in VirtualBox fails to print property to an LPT passthrough, but other software seems fine

Back in the 1970s, as a college project, I wrote an emulator for a minicomputer (in Fortran (!!)). When my professor ran a program written for the minicomputer, the teletype output was doubled, ...
DoxyLover's user avatar
  • 241
9 votes

How do I diagnose a "system board error" on IBM Thinkpad 600E?

I was able to download the Thinkpad 600E service manual from this site. If I am understanding the info in the section "How to Use Error Messages" correctly, the FRU = 3610 part says the ...
user224727's user avatar
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 ...
acolchagoff's user avatar
  • 1,231
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/...
Michael Graf's user avatar
  • 10.1k
9 votes

1984 accounting software running in VirtualBox fails to print property to an LPT passthrough, but other software seems fine

Back in the early 1980s, some applications would operate the printer port hardware directly, not going through DOS or BIOS. I'm suspicious that Virtual Box is emulating the hardware, but being fooled ...
John Dallman's user avatar
  • 13.3k
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 ...
Algimantas's user avatar
  • 1,344
7 votes

Toshiba laptop with Windows 98 shows corrupted characters while booting, then the system goes entirely blind

This is not a full diagnosis, but one hypothesis can be formulated just from the screenshot. It shows a setting from AUTOEXEC.BAT printed to the screen during booting. What the setting does is ...
user3840170's user avatar
  • 23.1k
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 ...
Dmitry Brant's user avatar
5 votes

IBM Model F XT is typing random characters / what cable is this?

Thanks for the answers and comments. The problem has been intermittent but really bothered me today so now that I have a soldering iron, I took a blade, cut out the damaged part of the cable, stripped ...
cardamom's user avatar
  • 321
5 votes

IBM Model F XT is typing random characters / what cable is this?

I think what you have there is an IBM Model F keyboard. The pictured cable is certainly suspect, though it does not have to be the main/only culprit. If you can easily find a replacement cable, it is ...
Brian H's user avatar
  • 60.8k
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 ...
Nick Westgate's user avatar
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 ...
Peter Camilleri's user avatar
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. ...
Martin Maly's user avatar
  • 5,575
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 ...
user3840170's user avatar
  • 23.1k
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 ...
Brian H's user avatar
  • 60.8k
4 votes

Reviving a Mac Mini (PowerPc) - Not booting correctly: video is out of sync, blinking, usb boot not enabled

I have to disagree with Jacob Krall. To paraphrase what the maintainer of one of the big Mac abandonware sites almost constantly finds himself saying in the chat while helping visitors to get their ...
ssokolow's user avatar
  • 7,065
3 votes

Old IBM ThinkPad laptop gets stuck booting Windows on a weird screen. How to proceed?

The most likely cause is a bad hard drive. Get the Lenovo Hardware Test app, put it on a bootable CD or USB key and run hardware diagnostics. Chances are high (because it turns on) that the hard drive ...
John's user avatar
  • 209
3 votes

Windows NT drive recovery without ERD or backups

Windows NT 4.0 does NOT have any "repair" option on the install disc (or disks). At least not as you're familiar with from newer versions of Windows. Instead the repair option will just ...
esc's user avatar
  • 149
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 ...
Geo...'s user avatar
  • 10.2k
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 ...
Geo...'s user avatar
  • 10.2k
2 votes

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 ...
user3840170's user avatar
  • 23.1k
2 votes

Toshiba laptop with Windows 98 shows corrupted characters while booting, then the system goes entirely blind

If booting into safe mode works, it means that your machine is basically working. The issue only occurs when you load additional software that gets skipped when you boot normally. This extra software ...
Michael Karcher's user avatar
2 votes

How do I diagnose a "system board error" on IBM Thinkpad 600E?

I read somewhere else that it might be the little CMOS battery on the motherboard which probably went dead about 20 years ago :) The problem is as I mentioned in the post. You get some cryptic ...
Cool Pontiac's user avatar

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