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56

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 one. When feeding Z80 clock pin from a TTL output, you should use pullup resistor of 200..500 Ohm. NMOS Z80 uses dynamic logic, that means it has some minimal ...


19

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, and maybe a mouse. If the Amiga works in this state, then the fault is most likely to be one of the peripherals. But if it still doesn't work, then read on. ...


14

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 powered up the CPU. It's worked for me, but if you're having problems it's best to build a proper reset circuit. Many CPUs have a minimum length for the reset ...


13

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 case. It's curious that this component is designed to survive overvoltage and short circuit conditions, but it is very vulnerable to a polarity inversion. The ...


12

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 replacing the chip as there is more of a chance of damaging the 6502 if you solder it directly. You can get low profile sockets if head space is an issue...


11

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 Apple II or II+ where if there's a card in slot 0 it's likely a "Language Card" with RAM and/or ROM, so that should initially be left in, then perhaps be removed ...


11

Whatever would have taken place occurred inside the RF modulator: I haven't been able to find a C128 schematic that includes the modulator, however if it's anything like the C64 modulator, there's a current limiting resistor in the path between +9V UNREG, a couple of transistors (only the last of which is shown here) and ground. For this particular C64 ...


9

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 Atari and spray plastic safe contact cleaner into the controller socket and system pins and then insert and remove several times to clean up those connections. ...


9

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 selling drives for Amigas probably already made any necessary electrical modifications. Then, those drives are 1" tall, so if the Amiga 3000 takes 1-1/4" tall drives,...


9

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's the one that mattered. Here's a complete list of ways in which I nubbed this up, for future readers benefit: I forgot the 120 V AC plug (see above) I tested ...


9

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/projects/troubleshooting-common-problems-with-the-commodore-pet-2001/ I'd suggest that you ignore the spare parts sales pitch at the beginning and work your way ...


9

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 and a 150pF capacitor. Normally the composite output is disconnected when using the RF modulator, but when using the composite output to a TV, it will be ...


8

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 hand genesis and used toothpicks to clean up the immense dust buildup in my console. Early Mega Drives did not have BIOS - they boot directly from the ...


8

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 the PS1 read any other discs like audio CDs? It might need an entire spindle hub or optical drive replacement. Maybe some of the tips in this iFixit ...


8

(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 each pair is wired separate (AFAIR simply in parallel). Such dual package LED were already back then special types. Nowadays they are no longer needed, as LED ...


7

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 written to a ROM, PROM, EPROM or EEPROM. It does not a working battery to maintain the information stored in this fixed memory. It does store volatile ...


7

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 marked on board, you can use the pinout of this extension cord to match them. If there isn't, you'll have to match them "by hand". Cut the mouse cable a very ...


7

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 to cut each sideways (cutting flat), as large pliers and frontal cutting may twist the pin, which could damage traces or even the board. Clip all pins before ...


7

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 through a ferrite (L11) and 5 Ohms (two 10 Ohm resistors in parallel, R14 and R15). That means that you tried to take up to 2.4 Amps from the 12V. I doubt it was ...


7

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 option. Periodic cleaning with isopropanol will help. In fact after handling the parts try to clean them with alcohol to remove skin oils and other contaminants that ...


7

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 game, a chip can get corrosion after a year. The one thing I do, is I collect and throw any desiccant bags I come across into each machine cabinet to help ...


7

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 have an oscilloscope it'd be useful to check whether the voltage on that line droops when the floppy is accessed or the horizontal screen size is changed. Based ...


6

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 latches. Your screwdriver trick could be freeing it enough to work for a while. I would clean the part as much as possible. Use a residue-free solvent - I ...


6

When I patched up my Xi keyboard, I used double-sided adhesive pads cut to the right size, with aluminium foil tape to replace any missing discs. These days it's also possible to buy replacement foam pads -- disintegrating foam is a problem common in KeyTronic keyboards, and searching for 'KeyTronic foam' on eBay finds a seller of replacements.


6

AFAIK, BIOS has always allowed booting from floppy. I can't imagine why any manufacturer would override that possibility. IIRC, the default boot order in the 386 era was A, B, and then C. Some BIOSs had settings that let you override that, and boot from C immediately without annoying floppy drive noise as it (they) tried to access a floppy. The reason for ...


6

I don't know if this is the "best" solution, but I have found applying Singer light sewing machine oil to a dried-out fabric printer ribbon appears to be effective. This oil is odorless. Amazon: https://www.amazon.com/dp/B000YZ1Y06 Apply sparingly a drop at a time, and then set the ribbon aside and allow it time to soak or it will make a mess on the paper ...


5

In the old days(tm) it was common to reink fabric ribbons for typewriters, in fact, the early ones where made that way. I kept using that practice during the 70s and 80s for daisy wheel and dot matrix printers. In theory ribbons could be reinked an unlimited time, but in reality wear on the fabric (too much movement due the hammer) limited this to like a ...


5

I was just working on restoring an original c64 breadbin model and ran into the same issue you have: how do you safely desolder a multi-pin dip chip. I also happened to have a black screen of death failure. For a 40-pin chip it's gonna be nearly impossible to remove the chip with just a soldering iron and solder wick or a solder sucker. After I struggled to ...


5

The most common failure of the NES is the 72-pin connector. In short, the pins get bent "open" from the cartridges in the slot after much use and stop making good contact. The blinking power light is the symptom you'd see. Many people felt that blowing in the cartridge would help, but it rarely did anything to help as it was more the re-insertion that would ...


5

I managed to fix the floppy disk drive mechanism. I completly disassemblied the floppy disk drive mechanical system and cleaned each part with lighter fluid. Then I applied a very light lubrication to the areas where the parts where in contact with one another. Only a really small amount of lubricant is needed (I used an unfolded paperclip to apply it). I ...


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