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  1. F

    Replacing an IBM XT power supply unit with an ATX one

    "Key" means the plastic tabs on the P8 and P9 connectors to make sure you don't plug them in 180 degrees out.
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    Using digital memo recorders as storage.

    The volume level needs to be quite high for the signal to be detected. I have a cassette deck for my Spectrum and have to turn the volume up to 8 (of 10) before the Spectrum will even start recognising it.
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    PCB design simm module

    The need for parity was kind of overblown though, and if you could turn the check off in the BIOS (or by jumper) then it was no real loss. How many people have ever even seen the parity error screen? PC's of that era had no way to recover from a parity error so they just dropped into a 40-col...
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    Just got an Amstrad CPC 464 and I got a couple of questions...

    The later 664 and 6128 models needed 12V for the built-in floppy drive.
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    Just got a BBC Micro, Model B, And I have questions

    I forgot to mention the floppies... Floppy drives on the BBC are generally the common Shugart type and it shouldn't be hard to find something that will work, the TRS-80 drive may work but it might need a few jumpers changing. The official BBC floppy option used an Intel 8721 controller that...
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    Just got a BBC Micro, Model B, And I have questions

    I'm not familiar with the Sidewise board, but it's most likely some additional ROM sockets - the BBC architecture supports up to 16 option ROMs, but the PCB only had sockets for four, and add-on PCBs providing extra sockets were common. The board might also have extra RAM, mapped to appear as...
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    VGA to MDA Adapter for IBM Monochrome Monitor?

    I think it's not even talking about MDA monitors. 15khz mono TTL monitors were common-ish in the mid 80s, meant to be used with non-PC platforms. This circuit is just separating composite video into video and separate syncs to work with one of those monitors.
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    Can I trust these listings for NEC V20’s?

    Most ICs sourced from China are not "fake" in the sense of being counterfeit. Rather, they are genuine used parts that have been cleaned up and re-marked. 95% of the time they will be the part they claim to be, but will be used rather than new. However one annoying thing they do when re-marking...
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    Need help with TS2068 repair

    The regular repeating pattern on the display makes it look like either a memory problem, or a problem with the ULA (the square chip). The soldering around the ULA looks particularly bad, I'd check all the pins and make sure none of them are shorted to the pin next to them.
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    Datasheet for National Semiconductor MM5262N RAM

    This one? https://datasheetspdf.com/pdf/1147913/NationalSemiconductor/MM5262/1
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    Sinclair PC200 display

    The output is CGA I think, so you won't be able to connect it to VGA with a simple adaptor. Can you try the RF output with a different TV?
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    Was Server 2008 bad in ways like Vista?

    OEMs pressured Microsoft into lowering the official minimum RAM and processor specs for Vista because they wanted to sell their current stock of bargain basement hardware as "Vista Compatible". So the kind of people who buy whatever PC is the cheapest in the supermarket would go home with a...
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    Connecting power switch on AT PSU to the case

    I've come across this before. The mounting posts on the case are too far apart to line up with the screw holes on the switch. I ended up having to make an adaptor bracket out of a strip of metal.
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    WTB: 4x Commodore PET key caps

    Hi. I acquired a PET 2001-N recently, but it's missing a few keys so I'm looking for four key caps: - Left shift - Right shift - Shift lock - Right angle-bracket ...for the normal graphical keyboard with the PETSCII symbols on the front, not the chiclet or business keyboards.
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    PET 2001-N screen distorion

    I picked up a 32K 2001-N recently, and while everything is in working order there's some noticeable horizontal distortion on the screen. The display is correctly centred and vertical edges are all straight, but characters get gradually narrower towards the right. Characters in column 1 are...
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    Manuals for HP Laserjet 4+

    Does anyone have either the User's Manual or Technical Reference Manual for the HP Laserjet 4+? Google turns up nothing but mis-labelled Service Manuals (which I already have) or those annoying sites which claim to have it but all the links eventually lead to random other HP manuals.
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    Drive cases for external 3.5" drives

    Do these exist? I've got two 3.5" DD drives which I've modified to work on a couple of 8-bit machines (BBC Micro and a ZX Spectrum +3), but they're bare drives meant to mount internally, so I need some kind of enclosures for them. Searching just turns up USB floppy drives and cases meant for...
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    1526 / MPS-802 printer repair

    Is anyone familiar with fixing these? I picked one up as part of an ebay lot recently, although it was listing as non-working and that indeed turned out to be the case. It turns on and powers up, but just starts flashing the red paper out light and doesn't respond to button presses or commands...
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    386 will only POST on 2nd attempt

    I have a 386 motherboard (a Shuttle HOT-307 according to TH99). If it's been powered off for more than a few minutes then the POST will hang after the memory count. Resetting will then make it POST normally and work perfectly the whole time it's powered up, but switch it off for more than 15...
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    Best way to organize ICs?

    For storage I use old cigar tins. I bought about 200 of them for £20 on ebay some years ago. They're quite thin so you can pack a lot of them into a small space. A shoe box will hold 40-60. If I've got more than a couple of tins worth of something then the extras are kept in tubes and I refill...
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