Hello guys!

I got this dead Arabic Enterprise 64 computer along with a power adapter and a IS-Basic cartridge.

I tested it by plugging one yellow RCA cable into its video output and the other end to my TV's video input. I then plugged in my ZX Spectrum's power adapter because I know it works and is compatible with E64 (9V negative center).

The computer didn't power up. There was no sign of life at all; no sound nor video signal.

I don't have previous experience with Enterprise computers and really don't know where to look at in order to bring this machine to life again. Are there components known to be prone to error I should check first? Any help would be appreciated.

Thank you.

Nope, the led didn't light. I tried to press some random keys, but nothing. I also booted the machine while the cartridge is inserted, but the same result, nothing.

From the look of the adapter I received with the computer, I have a doubt that someone had tried to power up the computer with a wrong polarity adapter and fried the power module inside the machine!

Thank you

Power LED also not light?
If not then very possible someone tried it earlier with wrong polarity PSU.
If this happened then need to replace 2x7805, one BC337 transistor (TR2), and LM386 (U38).

There is a schematics at my page.

No, the LED didn't light. I think it was previously connected to a reversed polarity PSU as you mentioned. I'll open it up and see what I can do.

Thank you Zozo

One more hint: if you see Philips electrolytic capacitors on the board then replace it. (Early boards built with these)
The most critical the C9, if it is dried out (which is very possible at machine from the hot Egypt) then will kill the TR2 again.

Ok, will check that too.

By the way, I measured the voltage output from the PSU that came with the machine and found it 12V (- center). Can the E64 tolerate this extra 3V in its input, or has it caused other damages as well?

Thank you.

You're right. One screw is under paper with serial (in the corner).

Ah, thank you. Now it’s exposed:)

Now I see the Philips capacitors!

Anyway it is a rare board: ISSUE 6, with a second (bugfixed) version of Nick chip (08-47). This is very rare at EP64, usually the EP128 built with ISSUE 6, but not all got the better Nick chip.

What is the S/N of your machine?

I have a same motherboard.

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This one also has the Nick chip (08-47)
I swapped the Phillips capacitors to a different type.

I can see "EXDOS 2.0  TEST FC" message at the top of screen now.

EXOS, not a EXDOS
Your monitor slow detect video signal. It is a TESTING FE, FD, FC... this is the memory test. (on a 128K machine contined with a FB,FA,F9,F8)

After that, the word "E N T E R P R I S E" starts glowing on screen in black and white. Nothing happened after that. There was no memory test and the computer never booted. I wonder if this is a normal behaviour?

Yes, ENTERPRISE screen normal, system started. Then need to press any key. Then Basic started if cartridge inserted. If no cartride then the built in Word Processor started (you can also load machine code games from WP).

But interesting why BW the screen? SCART switch signal right for set RGB mode?