Amstrad Mega PC / Amstrad Mega PC Plus

[RetroJunkie]

Just thought I'd let everyone know that I finally got my Amstrad Mega PC!
The NiCad battery had leaked onto the motherboard damaging not just one side but two sides of the board.
Luckily I know someone who is pretty handy with a soldering iron and he fixed up the main damaged tracks.
The hard drive controller on the motherboard might be fried though since I can't get it to recognise drives properly.

I've found that the motherboard of the Mega PC (PC7386SX) looks as though it can be replaced with a PC7486SLC motherboard.
And from what I've read, that would effectively make the hardware a Mega PC Plus.
Running a crippled 486 (or enhanced 386 - take your pick of wording...) it is just crazy enough to work.

Currently I am waiting for the replacement board to arrive from the United Kingdom.
The chances of that board being available just after I'd bought a Mega PC.... it seems unlikely right?

Anyway, you can see all the details at my website in the signature below. There's some pictures too if you'd like to see them.
I've got some video coming along, sure is slow to upload when the original video is 1.7GB. Geez no wonder it is taking THAT long!

Edit: A few videos are up now at http://retrojunkie.net/2012/03/21/am...ega-pc-videos/
Images here and here. More videos over at my YouTube channel here.

[limboy777]

Just thought I'd let everyone know that I finally got my Amstrad Mega PC!
The NiCad battery had leaked onto the motherboard damaging not just one side but two sides of the board.
Luckily I know someone who is pretty handy with a soldering iron and he fixed up the main damaged tracks.
The hard drive controller on the motherboard might be fried though since I can't get it to recognise drives properly.

I've found that the motherboard of the Mega PC (PC7386SX) looks as though it can be replaced with a PC7486SLC motherboard.
And from what I've read, that would effectively make the hardware a Mega PC Plus.
Running a crippled 486 (or enhanced 386 - take your pick of wording...) it is just crazy enough to work.

Currently I am waiting for the replacement board to arrive from the United Kingdom.
The chances of that board being available just after I'd bought a Mega PC.... it seems unlikely right?

Anyway, you can see all the details at my website in the signature below. There's some pictures too if you'd like to see them.
I've got some video coming along, sure is slow to upload when the original video is 1.7GB. Geez no wonder it is taking THAT long!

Edit: A few videos are up now at http://retrojunkie.net/2012/03/21/am...ega-pc-videos/

Just been looking at tyour website. Brilliant what you have done with your mega pc. Woud love one myself.

[RetroJunkie]

I tell you, I need to get Windows 3.11 on it. Windows 95 is definitely a little bit too overpowered for it... The poor little 33MHz CPU just cannot keep up! I need to pickup a 15KHz converter so I can use a 4:3 flat panel LCD I picked up on the weekend too. So many things to do!

[limboy777]

What about putting small version of linux in it? Does it have an ethernet port as you could then connect to the internet with it?

[RetroJunkie]

Well yes! It does actually! Just recently got an ethernet card and put it in. Was browsing around in Netscape 4.8 - what great fun!
What distro might you recommend? Size isn't really a matter, since I can use a drive overlay tool. Performance on a really really slow 486 is where I'd need to be careful of. Can't want to try Windows 3.11 now

[limboy777]

Hi there I have used Puppy linux and slitaz just as a test. Both work well on 486 pc's with built in web browsers like firefox. I think these smaller linux distros will make the 486 more useable.

[RetroJunkie]

More usable? This thing isn't a toy! It has 16 MEGA BYTES of RAM! Will give them a shot and let you know how they go. Sadly it will not be for a few weeks as I am workin' for the weekend. Such is a life for me. Thanks for the suggestions though

[limboy777]

Not a problem, I think your mega pc project is the best I have seen. The fact that you are upgrading everything that can be upgraded and documenting it with photos is great. I think Linux allows you to use the computer as a internet browser and more will run faster whereas windows/dos will allow you to use the pc side as a DOS gaming machine.

Anyway your website has inspired to try and get hold of a mega pc so will put up a wanted poster here and on other forums. Hopefully if I get one, you can help me with suggestions. (How easy was it to find the slc 486 motherboard that you upgraded to?).

Also one more suggestion, you can replace the standard battery (that caused the leak in the original motherboard with the a modification to a circular batteries (usually numbered cr2032 etc). This will prevent any further leakages. I dont want to see your mega pc die from a leaky battery especially as it will be near impossible to find more amstrad slc/ mega pc motherboards!

[RetroJunkie]

How easy was it to find the slc 486 motherboard that you upgraded to?

Absolute and pure chance! I've been searching eBay for more Mega PC gear but none has appeared that ships to Australia. So either the sellers who have the Mega PC gear don't ship overseas OR they are really tough to find! I am amazed the 486SLC board I found worked as predicted!

Also one more suggestion, you can replace the standard battery (that caused the leak in the original motherboard with the a modification to a circular batteries (usually numbered cr2032 etc). This will prevent any further leakages. I dont want to see your mega pc die from a leaky battery especially as it will be near impossible to find more amstrad slc/ mega pc motherboards!

No need to worry! The 386SX has the evil NiCad removed and is safe, and the 486SLC uses a battery that is embedded inside a RTC. It was a TH6887A chip which turned out to be a Dallas DS1287 / DS1287A / DS12887. They all seem to be compatible with each other and thankfully are sealed airtight. You just need to pick one up that has a date code that is recent. I bought one on eBay that was 2 years older than the 1993 dated one I bought and surprisingly the battery was shot. 21 years without use will do that to a battery though. Got a full refund and picked up another that had a date stamp of 2011 which worked a charm.

The Dallas chips can be hacked apart to add external battery if it does go flat, however removing the chip off the motherboard completely prevents it from booting and will just give some beep beep beep beep beeps. The beeping is far less annoying that battery acid all over the precious tracks on the motherboard though

[limboy777]

Just been watching your youtube videos so should have seen these first before asking the question on the batttery replacement!

In regards to the 7486 motherboard, Im assumming that this may be similiar to all 486 motherboards that were housed in slimline pc cases. Would it be worth sending you a picture of a similiar slimline 486 sx33 motherboard and see if you could do a compare and contrast with your 486 slc? (I have a chance to buy one before it goes in the dump so might be worht saving as it may save another mega pc).

[Bad_Ad84]

You should see the state of the Amiga 4000 motherboard I am currently working on.

Battery leakage sucks. But at least I got the machine for free because of it

here is a link to my work log:

http://www.amibay.com/showthread.php?t=28267

[RetroJunkie]

In regards to the 7486 motherboard, Im assumming that this may be similiar to all 486 motherboards that were housed in slimline pc cases. Would it be worth sending you a picture of a similiar slimline 486 sx33 motherboard and see if you could do a compare and contrast with your 486 slc? (I have a chance to buy one before it goes in the dump so might be worht saving as it may save another mega pc).

Have a look here - I uploaded some high res scans of the motherboards so you can have a look and compare.

You should see the state of the Amiga 4000 motherboard I am currently working on.

Battery leakage sucks. But at least I got the machine for free because of it

here is a link to my work log:

http://www.amibay.com/showthread.php?t=28267

Ouch, that sure has damaged a fair few components. I miss free shipping from Farnell. Gone are the days!

[Bad_Ad84]

Components arent such a huge deal (long as they arent custom chips you cant buy!)

Its a few of the traces have been completely eaten.

But I should get it running soon!

If you didnt already, you should look at page 2 of the thread.

[RetroJunkie]

I wish you the best of luck getting that beast fully operational! Looks like you have it under control too!

[Druid II]

If the Megadrive parts are all on just a ISA card, can't you put that in a newer machine? Like, a pentium 2 or something?

[RetroJunkie]

If the Megadrive parts are all on just a ISA card, can't you put that in a newer machine? Like, a pentium 2 or something?

I wish! The mega drive sends it's video signal and likely sound as well through the CON15 connector on the motherboard. I have been searching around, however it seems to be a unique connector sadly. The PC and Mega Drive are almost completely independent of each other - except for the sound which seems to be shared between the two.

I am looking forward to getting the Mega PC hooked up to a Mega CD unit though. I just can't decide whether it should be a Model 1 or Model 2. I am leaning toward Model 1 as they are far better shaped. Wish the parts would hurry up and arrive!

[Bad_Ad84]

Its probably just RGB though? as the monitors were multisync (so basically accepted a TV signal)

If you can get the pinout of the card, there will be a way

[pc_91]

looking at the isa card that port which connects to the mobo like is some kind of simple I/O has normal transistors around, maybe the joysticks port? maybe video? try disconnect to see whats lacking

[RetroJunkie]

looking at the isa card that port which connects to the mobo like is some kind of simple I/O has normal transistors around, maybe the joysticks port? maybe video? try disconnect to see whats lacking

When disconnected it shows no internal video at all. When jumpers have been activated the PC side works OK - five jumpers need to be installed. That is how the 486SLC board came and it appeared to have been pulled from a non-Mega PC model of Amstrad. Boxy looking thing it was. The 386SX board functions the same when it is jumpered to give video out.
Here's a look at the jumper settings.
You can track down the full album here with all the photos I have taken so far - there will be more to come in the next few weeks.

Its probably just RGB though? as the monitors were multisync (so basically accepted a TV signal) If you can get the pinout of the card, there will be a way

I'd say you are right, but have no idea how I could achieve that - any pointers are more than welcome.

[pc_91]

to see if it's rgb, by what you say now i'm totally sure that is RGB video, on the conector discard which of them are GND simply measure it to chassis with a multimeter, then remove one jumper at a time to see what is lacking, there are five jumpers almost sure is Red , Green, Blue , HSync and VSync the transistors on the MD PCB are for the switching between internal video or MD video, and the connections of the free pins im almost sure is Red and its GND, and like this, right next to the jumper that switchs between internal or MD, i assume that shorted is internal video and open vide passtrought, you should try with a multimeter if on the jumpered pins theres positive or negative signal, that might help you to see if is a enable/disable signal or is the internal video signaling.