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From Planet Sinclair

Leningrad-1: A simple and cheap machine, this Spectrum clone acquired widespread popularity. Not very Spectrum-compatible, due to the way the machine was designed.
Leningrad-2: A much improved version of the above with built-in Kempston joystick compatibility.

Various other sources say that Leningrad-2 was slightly improved, or much improved, depending on who you ask. The above quote I believe is false because Leningrad from 1988 also had a Kempston-compatible joystick.

Either way, I haven't been able to find much information about what the differences actually are. Does anyone here know?

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  • I presume the details can be found on Russian resources and, obviously, in Russian. I made a note in my notepad - might try to do some search tomorrow.
    – tum_
    Feb 9 at 0:22
  • Can you read the schematics? Both can be found on this resource: Leningrad-I, Leningrad-II. You'll need a DiVu Viewer.
    – tum_
    Feb 9 at 0:39
  • @tum_ I can kind of read schematics. but not easily. I will take a look and see what I understand
    – OmarL
    Feb 9 at 14:21
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The second paragraph of this article lists the differences of Leningrad-2 from the original Leningrad:

Из конструктивных отличий от Ленинград следует отметить, что изменилась схема сброса кадровых счетчиков, теперь сброс происходил по 312 строке, что является стандартом для ZX Spectrum машин. Продолжительность сигнала прерывания теперь задается не RC цепочкой, а фиксированно по сигналу счетчика строчной развертки. Кроме того введен дешифратор для разделения обращения процессора к ПЗУ и ОЗУ. В видеоформирователе была заменена связка К555ИР9 и К555ИР16 на три микросхемы К555ИР16, в выходном каскаде цвета вместо транзисторов используются логические элементы с открытым коллекотором К555ЛН2. Также был изменен и магнитофонный интерфейс, вместо компаратора К512СА3, узел был собран на микросхеме К561ЛН2. Кроме того на плате появились разъемы ОНЦ-КГ-4-5/16Р, которые позволяли обходится без кучи проводов, при подключения внешних устройств делая саму плату более аккуратной и ремонтопригодной. Но главным нововведением, на мой взгляд, является добавление системного разъема, который давал возможность подключать внешние устройства, как например контроллер дисковода.

I'm providing this auto-translation by translate.ru online service, which, with a bit of imagination, does make some sense:

From the design differences from Leningrad, it should be noted that the scheme for resetting the frame counters has changed; now the reset takes place on line 312, which is the standard for ZX Spectrum machines. The duration of the interrupt signal is now set not by the RC filter, but by the horizontal scan counter signal. In addition, a decoder is introduced to separate the processor's access to ROM and RAM. In the video generator, the bundle K555IR9 and K555IR16 was replaced with three microcircuits K555IR16, in the color output stage, instead of transistors, logic elements with an open collector K555LN2 are used. The tape interface was also changed, instead of the comparator K512SA3, the node was assembled on the chip K561LN2. In addition, ONTs-KG-4-5/16R connectors appeared on the board, which made it possible to do without a heap of wires, when connecting external devices, making the board itself neater and more repairable. But the main innovation, in my opinion, is the addition of a system connector that made it possible to connect external devices, such as a disk drive controller.

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  • 1
    I touched the machine translation up a bit
    – OmarL
    Feb 9 at 16:12
  • I could not figure this out myself, so I asked the author of the quoted article through the Contact link on his site. Let's see if I get a reply.
    – tum_
    Feb 10 at 11:34

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