1) Are you sure about the Nick is the faulty? A lot of other component failure can result broken or empty black screen.

Biztos vagy benne, hogy a Nick hibásodott meg? Sok más alkatrész hibája okozhat hibás vagy üres, fekete képernyőt.

2) If the Nick is really dead then the only hope is to find a faulty machine where the Dave is dead and the Nick is good...
Few weeks ago there was one in this topic.

Ha tényleg a Nick hibásodott meg, akkor az egyetlen remény találni olyan hibás gépet, amiben a Dave halott és a Nick jó.
Pár hete volt egy ilyenről szó itt.

What is your language? You can write in English or in your language without Hungarian Google translate. We will understand.

Orosz nyelv.

Thank you, at least someone answered.
The situation is as follows. They tried to put quartz at 40 MHz in the car, it is clear that it did not go further than the start. And he left him for the night. Black screen in the morning. Nick's radiator fell off almost completely. When turned on, noise is visible on the screen, but rarely, more often only a black screen. Do you offer to change memory, buffers?

Yes, they replaced it with 8 MHz, which was. No, there is no oscilloscope, alas ((

Most of the keyboard buttons did not work. The cable was found to be cracked, cut off, and the keyboard connectors replaced.

It is not a surprise, the 35+ years membranes are very often crack.

Nick's radiator fell off almost completely.

It is also common problem, the old glue is aged.
But the Nick chip can run without it! The heat shink are only as "first aid" for the first generation Nick chips (08-04) display problems.
08-47 can work without it.

The most dangerous about it: if completely fell off, and moving in machine inside, possible to make short circuit on some pins.

When turned on, noise is visible on the screen, but rarely, more often only a black screen. Do you offer to change memory, buffers?

First important thing: the Nick are completly software controlled. On other machines, for example on ZX Spectrum you can get stable screen with border and screen area even if system don't start.
The un-initialised Nick chip only display some little screen garbage, depending how the video memory chips are random filled on powerup. These gargabe are generaly random, but usually always same on each machines. Probably depend of memory chip type.
Most usual types:
- wide black-white columns
- black screen with a little running lines (which are border color, it is random initialised at power on)
- black screen with running dark red garbage

Second important thing: EXOS ROM have a bug: place the stack pointer to unverified memory when call testing routine for a System Segment. If the onboard memory faulty then when returning from CALL, get a broken return address from the stack, then system crash without report the memory problem. (Because jump to random address then possible make some sound at crash)
And at the beginning the EXOS set the border color to black, then very often you got a empty black screen when this happen.

First try: remove the ROM chip, then the Nick remain fully uninitialised (border not set black). Need often see the mentoined screen garbage.

There is a programmer

Nice!
Then try my beeping diag ROMs:
It is don't use any memory, don't use stack.
Start testing the onboard memory, writing 00h, FFh, 55h, AAh to each byte. After write read back and make a sound of each bits, low and high tone beeps bor a 0 and 1. Then you can detect if some RAM chips are dead.
When beeping the border color are also flashing.
TESZTOLD: don't touch the Nick chip, remain with the power on state
TESZT: define a character screen (but if the onboard memory very faulty this can't displayed)

If this test can started, you can get some life sign from the machine. If not started then more serious problem

One note: connect speakers to the tape output, for avoid if there is a problem with the internal speaker.