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56 votes
Accepted

Zilog Z80 freezes while binary counting up to 65 536 (2^16)

There are many issues here. As it is already said in comments, decoupling capacitor is a must! 555 (non-CMOS) timer output is very much like the output of TTL ICs, however Z80 requires a firm logic ...
lvd's user avatar
  • 10.5k
25 votes

I cleaned the grease off an old floppy drive’s motor; do I need to lubricate it?

It sounds like you've cleaned-off the lubricant grease that is there to facilitate the movement of the rotor. It was almost certainly the original factory-applied material, and therefore likely to be ...
Eight-Bit Guru's user avatar
19 votes

I've taken my Amiga computer out of storage after several years and it doesn't work. What's the likely cause?

First of all you should remove all unnecessary peripherals and cables from the Amiga, in case it is a faulty device that is preventing it from working. All you need is the power cable, display cable, ...
Richard Downer's user avatar
18 votes
Accepted

Zip drive eject "tool"

The problem is almost certainly the quality of the dollar store paperclip. If you buy a box of paperclips from a stationary store, you are more likely to get paperclips made from thicker and stronger ...
Wayne Conrad's user avatar
  • 2,736
14 votes

Zilog Z80 freezes while binary counting up to 65 536 (2^16)

I'd just like to expand on a couple of points in lvd's excellent answer. Reset Circuit You might get by with just using a jumper wire to short the reset pin to ground for a brief moment after you've ...
cjs's user avatar
  • 26.6k
14 votes
Accepted

Can I use a volume wheel with different specs for the GBA?

The VOL pin in the schematic is surely a voltage signal. Based on the schematic, the original volume wheel delivers (30K+4.7K)/(30K+4.7K+470) = 98.7% of Vcc at its maximum setting (not sure whether ...
Quitting Due To Antisemitism's user avatar
14 votes

Zip drive eject "tool"

A very thin Allen key. I've got a .05" one in my toolkit which was originally there for aligning Shugart floppy discs and by now is used almost entirely for misbehaving DVD drives etc. I'd ...
Mark Morgan Lloyd's user avatar
13 votes

Can polarity inversion damage a ZX Spectrum?

You have damaged your Spectrum for sure. The first casualty is the 7805 regulator. These normally explode and release a "black smoke of the death" clearly visible, but yours doesn't seem to be the ...
mcleod_ideafix's user avatar
12 votes
Accepted

What's a safe and easy way to desolder the CPU from C64?

The easiest way to desolder a dead chip is to cut the legs with your snips then remove each pin one at a time. Use a solder pump or solder braid to clean the holes. I would use an IC socket when ...
Tim Ring's user avatar
  • 406
11 votes

How do I troubleshoot an Apple //e with no power light?

Some of your general questions can be answered here. As I said above, for an Apple //e remove all cards for troubleshooting - none are necessary for boot-up in a typical system. (As opposed to an ...
Nick Westgate's user avatar
9 votes
Accepted

Is it possible to bend tension back into Atari 2600 joystick contact domes?

TLDR; Yes you can bend them, don't bend them too much and don't flatten the dimples. First be sure the contact disk is the issue. If the problem is intermittent, You can also remove power from the ...
Rowan Hawkins's user avatar
9 votes

Replacing the floppy drives in my Amiga 3000

Here and here are lists of drives that work on Amigas either natively or that can be electrically modified to work on Amigas. Some of the drives are still in production. Those vendors you found ...
snips-n-snails's user avatar
9 votes
Accepted

Why does my IBM 5154 have an undulating wave?

It was because I forgot to plug a jumper into a socket that switches it from a 240V AC input to 120V AC input (socket M5). I simply forgot to plug it in. That's not the ONLY thing I did wrong, but it'...
Sydius's user avatar
  • 2,594
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

C128D shorted Composite and Ground

The C128D modulator uses 5V for power supply, and the composite output (pin 4) is driven with luma signal via an emitter follower and a 120 ohm resistor, and with chroma signal via an emitter follower ...
Justme's user avatar
  • 32.6k
8 votes
Accepted

What cleaning/repair can be done to a Mega Drive cartridge slot?

Have you tried cleaning the pin connector inside the Mega Drive? It's fairly simple to remove the shell and access the pin connectors. (don't forget to remove the LED wires for model 1) I got a second ...
nabulator's user avatar
  • 929
8 votes

Used PS1 "slim" (PSone) freezes on boot

I bet you have a dirty lens or faulty optical drive. Try cleaning the diode with a Q-Tip and a electronic lens cleaning solution. It's also possible that the entire drive is broken or dirty. Does ...
JAL's user avatar
  • 9,520
8 votes
Accepted

Finding replacement LEDs for Commodore gear?

(This question is a bit close to 'what to buy', but examples given are just such, as there are other suppliers) These are not wide ones, but two within one package. Looking at the back will show that ...
Raffzahn's user avatar
  • 224k
8 votes

Modern heat sinks for Commodore C64/C128

Modern heat sinks I assume this is about heat spreaders, as that is what they do. What is a reliable modern replacement Any one available at the usual stores will do it Which chips in the C64 and ...
Raffzahn's user avatar
  • 224k
7 votes
Accepted

Installing hdd on PhoenixBIOS A486 on Gateway 2000 4DX-33

When the battery died and reset the system, could this have reverted the BIOS to an earlier version that did not support the hard drive? No. BIOS is a motherboard firmware program which is usually ...
Hennes's user avatar
  • 186
7 votes

Replacing Amiga 9 pin D-Sub mouse cable

Unfortunately there were a few "revisions" of the mouse, and the pads on the mouse side were not always signed; the color coding isn't guaranteed to be repeatable either. If your mouse has the pins ...
SF.'s user avatar
  • 7,105
7 votes

What's a safe and easy way to desolder the CPU from C64?

For destructive desoldering @Tim Rings method is usually the fastest: clip all pins, remove the chip and desolder each pin separately. Just be careful when clipping the pins. Use a small tool and try ...
Raffzahn's user avatar
  • 224k
7 votes

Is is possible to repair a SE/30 with reversed C2 and C11 capacitors?

The schematics for the SE/30 can easily be found on internet, for example here This is what I can see on the main circuit board. A quick glance tells that C2 is connected between ground and +12 V ...
UncleBod's user avatar
  • 1,775
7 votes

Preventing socketed chip corrosion?

Low humidity helps, but beyond that there are no good solutions. You can coat the exposed parts with a protective seal but then they become difficult to maintain. Preventative maintenance is an ...
user's user avatar
  • 15.2k
7 votes
Accepted

Preventing socketed chip corrosion?

As already stated, there is no solution. I am a collector/restorer of stand up video arcade machines and pinball machines, and these all suffer from corrosion. Even after I have cleaned and restore a ...
LewinskyS's user avatar
  • 549
7 votes

Modern heat sinks for Commodore C64/C128

An unmodified machine includes a large metal RF shield which usually performs the duty of being a heat sink for VIC-II, SID, and other chips. I've worked on dozens of C64s, and have only seen the ...
Jessica Petersen's user avatar
7 votes

Macintosh Plus always resets on power up

My guess is transient undervoltages on the +12V rail. I'm basing this on both the floppy drive (schematic top-right, G4) and the flyback circuitry (figure 2) drawing power from that rail. If you ...
Alex Hajnal's user avatar
  • 9,350
6 votes

Repairing/Lubing/Fixing Amiga 500 floppy drive

It is possible that the old lubrication on the sticking part has absorbed some fluff or grit and so is no longer working as a lubricant. The build-up of muck could be around the point where the arm ...
Chenmunka's user avatar
  • 8,141

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