🇧🇾 Квант (Quantum): Part 1 [TCE

Let's have a look at this Belarusian Sinclair ZX Spectrum clone called the КВАНТ (KVANT) or Quant(um) in English.
It's labelled "КВАНТ МИКРО ЗВМ" where ЗВМ is an abbreviation for "Электронная Вычислительная Машина" ... Electronic Calculating Machine ... so it's a "Quantum Micro Computer".
I'm not sure if КВАНТ should be "quant" or "quantum" in English - going with "quantum".
It came with half of the polys, power supply (220VAC to 5VDC), joystick and cassette. The machine itself has one joystick port (using a non-standard 2x4 pin connector), a 5V input socket (using the same 2x4 pin connector), a DIN5 cassette (magnetophone) socket and a DIN5 RGBS output socket for video.
Cleverly, if you insert the power plug into the joystick socket there should be no harm as they do not use the same two pins as the power socket uses - they are left unconnected.
It also includes a reset button.
It has no other expansion, including on its motherboard. It appears to have an East German U880D clone of the Zilog Z80, but uses a pair of Western 8KByte EPROMs. All other parts are Soviet-era.
It doesn't utilise a ULA (yay!), just discrete logic which greatly helps with troubleshooting.
In includes a full size speaker.
The keyboard is, well, pretty rubbish. It's functional and won't have an issue with degrading rubber contacts, etc. but just doesn't feel that nice to use.
The included joystick is one of the better ones I've encountered from the former Soviet territories. The stick itself is of metal construction and the way its constructed should ensure it still works. It is, however, let down by the buttons - a bit too mushy for my liking. It include three fire buttons in total - two ambidextrous button on the base and one on the top of the stick.
{Updated 24-May-2024, thanks to ‪@LastofAvari‬}
Lots of excellent information (in Russian), including documentation & circuit fixes:
zxbyte.ru/inter.htm

[@LastofAvari]

DID NOT freakin expect to see a computer from the town where I live. Our family got one around 1993. It was heavily modified through the years to include 128K RAM, Beta Disk interface, Centronix-compatible printer interface and keyboard out of EC1840, which was super smooth and quiet. The keyboard is a nightmare. One of those rare cases when a Speccy clone keyboard is far worse than the original one which was already not great, so that's quite an achievement.

[@Brfff]

Nice, thanks for the comment! I will give the keyboard one positive though ... there's no rubber contacts to degrade or thin-film contacts to break! Any chance you'd remember about the video output? I was looking at the DIN5 cable ... and it only had three wires connected ... so wondering whether it was a rare post-Soviet clone that output composite instead of RGBS ... ? Although all five pins in the machine are connected ... {puzzled look on my face}

[@LastofAvari]

@@Brfff YT blocks the links, so I've replied via email in the channel description.

[@Brfff]

@@LastofAvari Yep, got it. It's strange - sometime it allows links, sometimes not. But I'll put the link you sent me here - it's excellent information, including circuit improvements. Thanks. I'm refurbishing the joystick at the moment - re-spaying the top plastic a nice blue and cleaning the inside parts. zxbyte.ru/inter.htm

[@WacKEDmaN]

quite a neat little board layout

[@LaserFur]

For the joystick... I find AL antioxidant stuff for power wires helps with these kinds of bare copper contacts. The stuff has a grease that keeps oxygen out and the other stuff eats the copper oxide.

[@charlesdorval394]

If only the keyboard was as nice as it's hard to put back together... hehehe

[@Brfff]

😂 Actually, maybe slightly stiffer springs could improve the feel a little bit ... a bit too weak at the moment. But still, I don't think I'd want to be typing out long lists of dissidents' names on that thing.

[@yurasergienko6890]

Green Soviet "KM" capacitors contain palladium and platinum. Because of this, many old Soviet computers were vandalized.

[@Brfff]

I know, I have a few machines that I’ve had to repair 😠 … I quite like them, they’re much better looking than ceramic disc capacitors.

[@MrWaalkman]

@46:56 looks like #11 & #12 might be bridged, and #8 is lacking a bit of solder.

[@Brfff]

Yeah, well spotted, they are looking a bit dodgy ... I'll probably have another look today or tomorrow. When I had a look at the DIN5 cable for video, only three pins were actually connected and not the five required for RGBS ... so it might just be composite and sound output perhaps ... ? And Eugene (pinned comment) sent me the link to the ZXBYTE website with lots of useful info (in Russian, but got the web browser to translate the page).

[@MrWaalkman]

@@Brfff Nice! That should help. :)

[@jerrs1989]

If you can record sound from tape cassette which was included to this spectrum in wav or mp3 i may try to recognize and transfer to digital tape image in tap or tzx format

[@Brfff]

I will try that. I’m assuming … if I can get a good read of the tape … that it’ll contain the usual test programs

[@jerrs1989]

@@Brfff Yeah, that's is possible about system programs but who knows maybe there is something different. Also maybe beside this tape you have another tapes which was included to another zx spectrum clones (with 60-90 minutes duration)?