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Author Topic: Help Recovering an Enterprise 64 (Read 986 times)

Offline Tech

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Help Recovering an Enterprise 64
« on: 2019.December.25. 18:48:50 »
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.

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Re: Help Recovering an Enterprise 64
« Reply #1 on: 2019.December.25. 18:59:12 »
Welcome to the forum!
Did you see the led lighting on the top of the computer?
After some memory test the Enterprise text should appear on the screen. Here you can press a button and hear the click from the speaker. Did you try to press a button, did you hear click sound?
As I know you have to be very careful with the polarity of the power cable. But the other members will tell you if you should use it in another way.
100 SOUND SOURCE 3,STYLE 16,LEFT 16,RIGHT 64,SYNC 2
110 SOUND SOURCE 2,STYLE 128,PITCH 25.2,SYNC 2
120 SOUND PITCH 25,SYNC 2
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Offline Tech

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Re: Help Recovering an Enterprise 64
« Reply #2 on: 2019.December.25. 19:33:58 »
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 :)

Offline Zozosoft

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Re: Help Recovering an Enterprise 64
« Reply #3 on: 2019.December.25. 19:38:42 »
The computer didn't power up. There was no sign of life at all; no sound nor video signal.
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.

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).
Where you connected the RCA cable? The RCA socket on the EP not a video output! It is az RF output for a antenna cable, like on ZX Spectrum.
You can found a video signal on a monitor connector. You can found a pinout at my page. Best way is using RGB scart cable. You can make it, or order complete cable.

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Re: Help Recovering an Enterprise 64
« Reply #4 on: 2019.December.25. 19:59:50 »
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 :)

Offline Zozosoft

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Re: Help Recovering an Enterprise 64
« Reply #5 on: 2019.December.25. 20:10:16 »
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.

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Re: Help Recovering an Enterprise 64
« Reply #6 on: 2019.December.25. 20:45:29 »
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.

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Re: Help Recovering an Enterprise 64
« Reply #7 on: 2019.December.25. 21:16:14 »
I’m trying to disassemble the machine and I’m not able to separate the two plastic shells from the back! Is there a screw beneath the paper label (where the serial is printed)? Or is it just some plastic clips jammed together?

Offline SlashNet

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Re: Help Recovering an Enterprise 64
« Reply #8 on: 2019.December.25. 21:46:36 »
You're right. One screw is under paper with serial (in the corner).


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Re: Help Recovering an Enterprise 64
« Reply #9 on: 2019.December.25. 22:03:10 »
Ah, thank you. Now it’s exposed:)

Offline Zozosoft

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Re: Help Recovering an Enterprise 64
« Reply #10 on: 2019.December.25. 22:32:32 »
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?

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Re: Help Recovering an Enterprise 64
« Reply #11 on: 2019.December.26. 09:52:29 »
What is the S/N of your machine?
Interesting! Here is the serial label

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Re: Help Recovering an Enterprise 64
« Reply #12 on: 2020.January.01. 16:25:03 »
I have a same motherboard.

24209-0

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

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Re: Help Recovering an Enterprise 64
« Reply #13 on: 2020.January.11. 15:40:31 »
Thank you @Judge for the picture.

I changed C9 and the other chips. I also made an RGB to SCART cable. I can see "EXDOS 2.0  TEST FC" message at the top of screen now. 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?

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Re: Help Recovering an Enterprise 64
« Reply #14 on: 2020.January.11. 15:52:10 »
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)

Quote
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?