Help with XT Turbo Clone

[croissantking]

I need some help in trying to restore an Elonex PC-88C which has a Faraday FE2010A CPU, basically an 8088 XT Turbo clone. Here's a pic of the motherboard.

Upon recently powering on, it started booting up, with a good picture on-screen, and passed the RAM test. It couldn't find a hard drive to boot off, so I opened up the machine to inspect it. I found a Miniscribe drive attached to a controller board that turned out to have stiction and would not spin up. I removed it from the case and put it into an external hard drive enclosure and managed to free off the stuck drive motor by rapidly twisting the drive in the air whilst powering on. It now spins without issue and makes healthy sounds.

While the PC was open, I decided to clip off the leaking clock battery and superficially brush off the loose acid crystals/corrosion on top of a few nearby components including most prominently a set of 33 ohm resistors. I also had the graphics card and Miniscribe controller card out so I could take a closer look at them.

After putting the cards back and closing the case, I found that it would no longer boot, instead giving me one long and one short beep.

I really did not do much to the PC while it was open, so was rather surprised, and assumed I'd done something silly whilst clipping out the clock battery.

Anyway, I cleaned up the corroded area carefully, desoldering the 74LS04 chip and resistors. I checked all traces for continuity and installed a bodge wire where one trace was damaged. I installed a set of brand new resistors and cleaned up the legs of the IC, putting it back into a new socket. I had all the RAM chips out, cleaned up the ones with corroded legs and ran them all through an Arduino tester with no issues. Then I reinserted them. I also installed a brand new battery on long leads and out of the way of trouble.

The PC no longer does the long and short beep, but it does not start booting up either and nothing is displayed on-screen.

What else could be the matter here? Now that I've cleaned up the worst of the corrosion, it feels like the problem could literally be anything I don't know where to start.

Thanks so much, would love to get this machine running again.

 

[RetroTheory]

No doubt you have checked your work, but it may be worth checking those resistor solder points with a multimeter to make sure their is continuity from there to where the tracks go. Also those DIP sockets don't look the best, the fact that it does not beep at all would make me want to check the BIOS socket first , as it should still beep with memory error.

 

[croissantking]

No doubt you have checked your work, but it may be worth checking those resistor solder points with a multimeter to make sure their is continuity from there to where the tracks go. Also those DIP sockets don't look the best, the fact that it does not beep at all would make me want to check the BIOS socket first , as it should still beep with memory error.

I have checked my work, but of course I could have missed something. Agree about the RAM sockets - i have some new ones on order so will try replacing the ones that are visually corroded & also take the opportunity to inspect the traces that run underneath.

if the BIOS chip is the one to the left of where the battery sat, then I have reseated it. Actually, to be more specific about the beeping, it does still do it but only if the expansion cards are moved around or removed. It’s kind of random. Before my work on the resistors it would beep 100% of the time.

Edit: ah, sorry you were talking about the bios socket - i will order a replacement.

 

[croissantking]

I assume the PC doesn’t actually need the backup battery to be present to boot?

 

[RetroTheory]

Correct, battery is not needed to post.
Not sure how you select video mode (MDA,CGA, VGA) , if its soft set with the FE2010A.

 

[croissantking]

Does it need the video card in to POST?

 

[jdmcs]

I need some help in trying to restore an Elonex PC-88C which has a Faraday FE2010A CPU, basically an 8088 XT Turbo clone.

The Faraday FE2010A is actually the chipset.

Your CPU is actually that Sony-branded chip to the left of the Faraday chip in the photo. Good news: it’s actually a second-sourced NEC V20!

Thought you would like to know so that when you get this fixed, if you wanted to use the XT-IDE Universal BIOS with an XT-IDE card, you could actually use the V20 version for a slight performance boost.

And I just learned something: I didn’t realize that NEC had second-source manufacturers for their CPUs!

 

[croissantking]

Interesting info.
I see I could fit an 8087 next to it as well.
What does second-sourced mean?

 

[jdmcs]

A second-sourced chip is one authorized by the original manufacturer to be manufactured on their behalf.

I’m not sure if this started with IBM when they were in the release process for the IBM PC, or if there was earlier precedent, but some computer manufacturers were concerned with selecting a processor that could only be obtained from a single source. That is, we can only purchase the 68000 from Motorola and only purchase the 8088 from Intel.
This leads to original processor manufacturers licensing their chips to third parties such that OEMs could design a computer architecture around a platform and have some confidence that if the first source went bankrupt, they’d still be score l able to procure chips from another company.
IBM, while designing the original IBM PC, was considering the 68000 and the 8088. Rumor had it that IBM did not select the 68000 because Motorola didn’t have anyone else (a “second source”) licensed to manufacture 68000 chips by the time IBM needed to go to market.

So I’m the case of your motherboard, it appears as if NEC licensed their V20 design to at least Sony as a second source.

 

[croissantking]

To follow up, I got the PC fully working. But it wasn’t anything to do with the corrosion, it was the graphics card. It has a switch on it internally that sets either color or mono output. After fiddling with this switch, i.e. moving it back and forth several times, the machine started to POST normally.

The Miniscribe hard drive works fine since I freed it up from its stiction. The machine boots into DOS 3.3 and then automatically loads up WordPerfect 4.2. I believe the owner, who is my landlady, only ever used it as a word processor.