LENINGRAD-2010. Сборка, наладка, расширение.

[zx-kit]

Длина или период ?

По телевизионному стандарту период строчной развертки 64 мкс (частота 1/64мкс=15,625 кГц), а период кадровой 20 мс (частота 1/20 мс = 50 Гц).
У вашего Ленинграда частота вроде правильная (http://www.zx.pk.ru/showpost.php?p=416791&postcount=118).

На сколько я знаю должно быть 8 мкс не зависимо не от чего.

Должно быть 32 такта Z80 = 32/3.5 МГц = 9.14 мкс.
Это заложено в вашей доработке на триггере ТМ2 и в теме про Harlequin об этом написано (http://www.zxdesign.info/interrupts.shtml ):

A Z80 interrupt must not be held active for longer than is necessary as this may lead to the Z80 responding to it multiple times. It is documented somewhere that the ZX Spectrum holds the interrupt active for 32 T-states, which is long enough for all instructions to have time to respond to it, but is still long enough for it to be detected more than once.

The Z80 provides a mechanism for indicating acknowledgement of an interrupt, and I propose to use that to clear the interrupt so that we don't hold it active for longer than required, removing the chance of multiple detection. Sinclair probably chose to implement a 32 T-state interrupt period to avoid having to dedicate a ULA pin to the interrupt acknowledge.