I bought this some time ago, but I did not keep the power supply with it. It does not have any product name on it, and I can't locate the correct information. What is the correct power supply and what is the product name?

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    Please note that even if the product itself is used to connect with a retro computer, this is about using a new, supported non-retro product.
    – Justme
    Nov 4, 2023 at 12:18
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    I'd like to say I fully endorse questions of this type. At some point, all original media and all recordable media will become unusable and only third party software loaders will be able to let people use certain retro computers at all. Of course RC isn't tech support for random online shops/hobbyists/clone resellers, but it should be support for users who want to use their retro computers. It is after all retrocomputing, not retro computers. :)
    – knol
    Nov 4, 2023 at 21:55
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    Once you know the details, it's very definitely worth attaching a label so that when it gets separated again, you don't have to redo the detective work. A cheap sticky-label printer is very useful to have around the retrocomputing lab. Nov 5, 2023 at 15:12

3 Answers 3


That looks to be a MaxDuino tape emulator. According to the website, it wants to see a 12V power supply. Polarity is always a bit of a gamble with Sinclair computers and accessories. I'd rather not gamble and open up the device to check whether the barrel plug wants center negative or positive (but maybe you can contact the manufacturer for information).


That appears to be a MAXDuino / TZXDuino: https://retroready.one/products/maxduino-tzxduino-zx-spectrum-16k-48k-128k-amstrad-cpc-digital-tape-deck

The listing says it requires a 12V charger. Since its a currently sold product I suggest you contact the store* for a manual and/or the specifications of the charger. (And having done so, post both here with a photograph of the charger's label :) )

However, the suggestions the previous answers give about dismantling the item if it's easy to do so have a lot of merit if you'd like to be certain. Just because it looks like that product isn't any guarantee that the one you hold in your hands is one of those, given that it's a low manufacturing run unlabelled item. Different revisions of the same product could even flip the polarity around: Sega flipped polarity when revising the Mega Drive as the Mega Drive 2.

*Have you also checked your e-mail history for any shop checkout/eBay bidding receipts too?

  1. open it up so you can see the electronics inside

  2. ground Gnd is usually used for shielding

    so look for thick or fully filled PCB areas. The biggest areas are usually Gnd

  3. look for polarized capacitors (usually several uF electrolytic)

    check if they connected to power connector polarity will hint where +,- goes and their voltage marking hint max voltage (so power will be less that smallest voltage marking you found) ...

    beware if device uses also negative voltage some (like one or two) capacitors might have connected + pin to Gnd but majority of capacitors would have - pin connected to Gnd ...

    The stuff looks like this:


    the - sign is visible on the right side (+ sign is usually not present).

  4. look for known IC (chip) markings

    download and check ist datasheet. Look for power pins Gnd,Vcc and trace them back to power connector. Also datasheet will tell you desired voltage.

    So try to find stabilzator, or any TTL or MCU IC. From there its easy to trace back to power connector.

  5. look for blocking capacitors

    each IC usually have one or more blocking capacitors (small usually ceramic 1..100 nF) soldered very near IC pins (usually those which provide power like Vcc) one side connects to IC pin and the other to blocking ground Gnd

    if SMD is not used then it looks usually like this:


    SMD version looks like this (showing soldering side, the top is without the metalic pads):

    SMD ceramic

  • 1
    I'm not sure what this answer is trying to say, and it feels a bit AI-generated. I'm not sure what all the detail looking at capacitors is there for, since that only puts an upper limit on voltage, and only on rails which aren't further regulated from the input supply (plus you'd normally keep a decent margin to rated voltage). Small ceramic caps usually don't have any indication of rated voltage, so I'm not sure why they're discussed here. Nov 5, 2023 at 14:57
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    @ThomasJager caps can very easily identify polarity and rule out too high input voltage ... as voltage is already known (12V) polarity has to be verified that's why I focused there. Most of the caps (if not all) will be connected directly to Gnd so the other pin in power supply connector left is + voltage... And no this is not generated by AI
    – Spektre
    Nov 5, 2023 at 17:11

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