I have recently acquired some IV-3 VFDs (Vacuum Fluorescent Displays) and they came on an old PCB with drivers. The driver is a к2лн641 and have found a datasheet on it with some information, but it is all in Russian (I believe) and have no idea what anything says.

Can anyone please advise if they know any of the pin outs for this? Or could help work this out.

here is the datasheet I managed to find

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    \$\begingroup\$ Looks like inputs on the left, outputs on the right, and rails -24V and -48V. The KT120A/B transistors are really wimpy extremely slow 60V types with rather low min hFE but unusually high Veb rating. I think pin 1 is common but my phone is not translating. The schematic and pin outs are self-evident, the other Cyrillic is not very useful- but the application circuit needs to be figured out. \$\endgroup\$ Sep 8, 2021 at 11:56

2 Answers 2


I'm Russian, so I'll help you out with this one.

First of all, the first link google gives when I search for that is the museum of soviet electronics. Interesting choice of parts haha.

Secondly, this part was later renamed into К264УМ1 K264UM1. Just for reference.

Source: link (russian)

As for schematic

enter image description here

Going from top-left down and counter clockwise, name - pin number:
In1 - 3
In2 - 9
In3 - 11
Minus24V - 4
Common - 1
Out3 - 10
Out2 - 6
Out1 - 5
Minus48V - 7

Text on the right:

R1-R6 30k +-10%
T1-T3 silicon transistor of KT120A type
T4-T6 silicon transistor of KT120B type
Replacement with KT120A acceptable

  • \$\begingroup\$ Thank you very much. This is very useful! The reason I am using such an old driver is because I bought the VFDs on a pcb with the drivers on. I wasn’t going to use them but thought I may as well try… \$\endgroup\$
    – Tom
    Sep 8, 2021 at 19:20

enter image description here

These are all low-power, low-capacitance, high-side switches using PNP transistors and a common pull-down bus to ground but shown here above the emitter supply +V voltage shown right side up.

2N2907 PNP 600 mA 8 pF is better, but likely a suitable replacement than this 20 mA 5pF switch

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    \$\begingroup\$ I'm sorry...are you australian? (your picture is upside down and strangely it seems to bother no one) \$\endgroup\$
    – Ilya
    Sep 9, 2021 at 8:06
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    \$\begingroup\$ I think the picture is flipped intentionally to be positive up. Easier to read if you are not used to ancient USSR electronics, \$\endgroup\$
    – fraxinus
    Sep 9, 2021 at 9:16

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