But unlike American avionics the Russian avionics, at least up to the 1970s, are far more reliable. That said many of those avionics were developed from US ww2 units.
When the USAF were doing flight comparisons of the MiG-15/17 against the F-86/100 the Russian avionics were faultless but the US avionics caused multiple flight cancellations.
The MiG com unit looks exactly like the old SCR-522 and even fits the SCR-522 mounts/trays/racks but internally they are totally different. Likewise the ADF looks exactly like the Bendix MN-26 until you open the box - and, again, it fits in the
reliability is function of complexity - russian avionics is less sophisticated thus in some aspects more reliable - this is whole mystery. From my personal experience - 12 years working mainly as a avionics engineer with both russian/soviet and western systems it looks as follow:
1985 onward
russian analog avionics (military grade)- dials, switches, power electronics, navigation gear, sensors - bulky, unsophisticated, highly reliable, - radios, radars, dopplers, fire control systems (analog) - just hopeless - unstable in parameters, very limited functionality, moderate/poor quality/reliability
russian digital systems all of kind - moderate/poor reliability, human machine interfaces are ...... i'm trying to find proper description.... shitty
western avionics (nonmilitary grade) hybrid/digital - depends what - many things is offering better reliability and much bigger functional value than russian ones - especially communication, radars, navigation and fire control systems, some elements are not up to standard - for example artificial horizon indicators made by Bendix - just disaster....
western avionics (military grade) - some systems are presenting surprisingly (considering its complexity) high reliability level (especially i like Collins radios of all kinds - just engineering masterpiece), 5 class better human-machine interfaces,
Reparability - past mid of 80's both russian and western avionics reparability is module level - below of this is nonexistent, thus difference in this matter is none.
Maintainability - in russian equipment is nonexistent - i think if something has been designed with this concept in mind it happen just by accident. In western aircrafts in general repairs are much, much easier.