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Author Topic: Enterprise 64 dead (Read 3338 times)

Offline neurox

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  • Posts: 7
  • Country: dk
Enterprise 64 dead
« on: 2024.May.01. 12:44:37 »
Hi!

A couple of years ago, I bought my second Enterprise 64, ISSUE 4, S/N 030391. It worked for a brief moment, and then died on me. In an attempt to fix it, I replaced the capacitors, voltage regulators and socketed the RAM and CPU to allow for testing other components. Nothing seemed to work - screen was blank, as far as I recall. Today I took a leap and powered it up with the same setup as I recently tested another Enterprise on - stabile original power supply and a SCART->HDMI converter. The result was white/black vertical stripes. No sound.

I reached out to Zozo a couple of years ago, and while he suggested a number of checks I could do, I never managed to get the system working. As far as I recall, power levels were good and the CPU was receiving a clock signal.

I'm not sure where to go from here - obviously I'd love to get the system working again, but while I do have both a soldering iron and a digital scope, I don't have a lot of experience fixing computers. If you have any suggestions on where to probe and what to look for, I'd be happy to provide screenshots if anyone wants to help me out :-)

Regards,
HC
Hans Christian Saustrup
Mastodon: https://mstdn.dk/@saustrup

Collection:
EP S/N 000828 - 64K+256K (wirewrapped!) - Works
EP S/N 030391 - 64K - Dead
EP S/N 030490 - 64K+1024K - Works
SD-Card Premium Cartridge (works)
Original EXDOS Controller (works)


Offline neurox

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  • Posts: 7
  • Country: dk
Re: Enterprise 64 dead
« Reply #2 on: 2024.May.01. 13:16:04 »
Wow, plenty to read and test - thanks! :-)

Slava Ukraini!
Hans Christian Saustrup
Mastodon: https://mstdn.dk/@saustrup

Collection:
EP S/N 000828 - 64K+256K (wirewrapped!) - Works
EP S/N 030391 - 64K - Dead
EP S/N 030490 - 64K+1024K - Works
SD-Card Premium Cartridge (works)
Original EXDOS Controller (works)

Offline SlashNet

  • EP addict
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  • Posts: 1239
  • Country: ua
  • Enterprise 128K | Cubietruck
    • My old site about Enterprise
Re: Enterprise 64 dead
« Reply #3 on: 2024.May.01. 13:46:22 »
Wow, plenty to read and test - thanks! :-)

Slava Ukraini!

You're welcome. ;-)

Offline neurox

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  • Posts: 7
  • Country: dk
Re: Enterprise 64 dead
« Reply #4 on: 2024.May.01. 14:24:05 »
Small, fruitless update:

Just tested with a couple of other brand new CPUs from a trusted supplier, as well as with the myriad of EPROMs I made while testing with Zozo a while back.
Same result - black and white bars. If I remove one memory chip, I get black and red bars. Another, and I get black and green bars. No sound.

CPUs tested:
- Zilog Z84C0006PEG (original)
- Zilog Z84C0006PEG (brand new)
- Zilog Z84C0010PEC (brand new)

ROMs tested:
- EXOS 2.1
- "TEST1"
- "TEST2"
- "REGTEST"
- "VRAM"
- "VRAM TEST"
(I seem to recall one of them being the beep-test)

Memory chips are KM4164B-12-227C.
Hans Christian Saustrup
Mastodon: https://mstdn.dk/@saustrup

Collection:
EP S/N 000828 - 64K+256K (wirewrapped!) - Works
EP S/N 030391 - 64K - Dead
EP S/N 030490 - 64K+1024K - Works
SD-Card Premium Cartridge (works)
Original EXDOS Controller (works)

Offline Zozosoft

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  • EP addict
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  • Posts: 14754
  • Country: hu
    • http://enterprise.iko.hu/
Re: Enterprise 64 dead
« Reply #5 on: 2024.May.01. 15:42:23 »
Z80 RD,MREQ,M1 are active? And ROM chip CE,OE?

It is looks the ROM not running.
Worst case if Dave dead :cry: Better if only ROM signal missing from Dave, can be substitued with few 74 chips.

Better case if some mechanical signal problems: contact problem at ROM socket. Broken via somewhere on board. SMD contact problem at Dave pins.