Author Topic: Dead CPC464  (Read 428 times)

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Offline JonB

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Dead CPC464
« on: 10:25, 18 February 19 »
Hi

I just got my hands on a 464 with some interesting add ons. Serial interface, 64k Ram expansion, Amstrad disk drive with CP/M and a stack of technical manuals. Oh, a CTM 640 monitor too (the one without the 12v supply that can't be used on a 6128).

The machine itself looks like it's been sat in water. There's a lot of what appears to be mineral deposits on the left lower corner of the keyboard, and the steel chassis that the keys mount through is badly rusted. Looks like the keyboard PCB escaped harm. I need to take the keys out of the chassis so I can de-rust it, can anyone advise how they are fixed in? I couldn't see any clips.

I did attempt to run the board on its own, then with the keyboard PCB connected. Got nothing on screen, but the power LED came on so I think the monitor is supplying 5v. The board is clean but I am a bit surprised at how little there is on it. I did try to reseat the only socketed IC (I think it's the Amstrad gate array or ROM, not sure) but this had no effect.

Trying to work out if I should try to fix it or junk it for parts.

Also, can someone advise on the expansion port? Is it the same as the 6128's (meaning that Amstrad accessories should work on both machines)?

Lots of questions..

Offline llopis

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Re: Dead CPC464
« Reply #1 on: 10:36, 18 February 19 »
Hi

I just got my hands on a 464 with some interesting add ons. Serial interface, 64k Ram expansion, Amstrad disk drive with CP/M and a stack of technical manuals. Oh, a CTM 640 monitor too (the one without the 12v supply that can't be used on a 6128).

The machine itself looks like it's been sat in water. There's a lot of what appears to be mineral deposits on the left lower corner of the keyboard, and the steel chassis that the keys mount through is badly rusted. Looks like the keyboard PCB escaped harm. I need to take the keys out of the chassis so I can de-rust it, can anyone advise how they are fixed in? I couldn't see any clips.

I did attempt to run the board on its own, then with the keyboard PCB connected. Got nothing on screen, but the power LED came on so I think the monitor is supplying 5v. The board is clean but I am a bit surprised at how little there is on it. I did try to reseat the only socketed IC (I think it's the Amstrad gate array or ROM, not sure) but this had no effect.

Trying to work out if I should try to fix it or junk it for parts.

Also, can someone advise on the expansion port? Is it the same as the 6128's (meaning that Amstrad accessories should work on both machines)?

Lots of questions..


Put up a picture! I'm curious to see how badly damaged the board is. And yes, the original 464 board is super roomy. So nice to work on! :-)


I would start measuring that you're getting 5V everywhere on the board. If you do, then we can start looking at whether there's any activity, etc. But if it's so water damaged, you may not even be getting the minimum voltage for operation.


And yes, the expansion port is the same as the 6128.
« Last Edit: 12:24, 18 February 19 by llopis »

Offline Bryce

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Re: Dead CPC464
« Reply #2 on: 12:13, 18 February 19 »
The deposits on the PCB may just be leftovers from the PCB cleaning. It usually looks like white water marks around one end. The metal will rust even if it's in a slightly humid environment. If the case is in good condition I'd fix it up rather than use it for parts.

Bryce.

Offline JonB

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Re: Dead CPC464
« Reply #3 on: 15:56, 18 February 19 »
OK, good. So at the very least I can roll those expansions over to the 6128 (the serial port is the most important to me).

@Bryce : The PCB deposits are like limescale, sort of hard and mineral-like, and they are on the exterior of the case as well. Have not responded that well to cleaning (I used a limescale cleaner, so acidic). But the keyboard itself is the main problem. Has the scaly deposit on the bottom left keys and when I tried to pull the shift key off it broke (not enough to prevent me reassembling, but I was surprised at the brittleness of the thing).

I'd better post some pix: (link at the bottom of the big grey rectangle)


https://drive.google.com/open?id=1nQ8dTVjAPZug07KWTUzmph0kd3Oo_H5Q
« Last Edit: 16:17, 18 February 19 by JonB »

Offline JonB

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Re: Dead CPC464
« Reply #4 on: 16:22, 18 February 19 »
As you can see there is a lot of rust on the bottom of keyboard plate. I want to remove the keys and their bodies so I can clean the plate. How do you do this? There is no obvious latch or clip holding the keys in place on the plate.

Other alternative is to ask if anyone has a spare 464 keyboard?

Offline Bryce

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Re: Dead CPC464
« Reply #5 on: 16:47, 18 February 19 »
Oh dear, I'm not sure I'd bother. That looks like something extremely aggressive (Bleach perhaps?) has been splashed over it. Some of the keyboard traces are definitely damaged, so you'd need to bridge them. Maybe it is a "for spares" 464.

Bryce.

Offline llopis

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Re: Dead CPC464
« Reply #6 on: 16:53, 18 February 19 »
Yeah, the keyboard looks horrible, but the main board is probably salvageable. The only thing is that he's going to need to find that exact type of case to make it work (the one for long boards and with cable connectors instead of flimsy membranes).

Offline JonB

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Re: Dead CPC464
« Reply #7 on: 17:01, 18 February 19 »
Can the keys be removed from the metal plate?

(Incidentally, I surmise the value is with the accessories - getting a new 464 is pretty easy. They can be had for £20 if you look hard enough.)

Offline llopis

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Re: Dead CPC464
« Reply #8 on: 17:03, 18 February 19 »
Can the keys be removed from the metal plate?
Yes, just pull on them vertically. Use a key wrench ideally, but you can do it with your fingers even. I don't remember if that model keyboard has some long rods of metal under the longest keys or not. If you can you see them by peeking under the keys and carefully unsnap them with a small screwdriver.

Offline JonB

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Re: Dead CPC464
« Reply #9 on: 18:12, 18 February 19 »
Sorry, I don't mean the key caps. I'm referring to the black plungers and housings that are pressed into the steel plate. If I can get those out, the keyboard can be restored.

Offline llopis

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Re: Dead CPC464
« Reply #10 on: 22:34, 18 February 19 »
Sorry, I don't mean the key caps. I'm referring to the black plungers and housings that are pressed into the steel plate. If I can get those out, the keyboard can be restored.
Yeah, you can get those out. You need to unscrew the fifty gazillion tiny screws on the plate behind the keyboard. Keep that side facing up because there are some plastic membranes and all the plungers will be loose. You can remove/replace them as you wish and put everything back afterwards.

Offline JonB

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Re: Dead CPC464
« Reply #11 on: 00:22, 19 February 19 »
No membrane on this keyboard, just a couple of silicone sheets with the cups moulded into them. I do not see any tiny screws. The PCB was held in place with plastic clips. I'll have a closer look, but I think I am dealing with a different keyboard variant than what you are describing.

Update: I removed one of the arrow key tops and its plunger and had a good look at the switch body. No way to remove it. I think it is bonded in place though I cannot see any join. Best approach seems to be to remove all the plungers and key tops, get the Dremel out to remove as much rust as can be accessed, treat it with phosphoric acid then brush paint over the rusty bits. There is nothing stopping the keys from working - it looks bad but it's just cosmetic. Of course, i am not going to bother unless the machine wakes up!
« Last Edit: 00:28, 19 February 19 by JonB »

Offline Cholo

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Re: Dead CPC464
« Reply #12 on: 01:25, 19 February 19 »
...
And yes, the expansion port is the same as the 6128.


Indeed, but in the case of the 64k ram expansion its perhaps a bit pointless as all 3 machines 464, 664 & 6128 are actually basic 64k machines. The "128kb" of the 6128 is the basic 64k + a 64k build in ram expansion, so adding a 464 64k ram expansion does work but then again does nothing. Of cause adding a 464 256k ram expansion does expand a 6128 to 320kb.


Also the 3" drive (DDI) can also be connected to a 6128, however not with the 464 drive interface & cable, but instead a normal old pc ide cable with at least one edge connector (5,25" connector). Those old cables shouldnt be to hard to find on ebay for a couple of bucks. So you can connect your DDI as a second drive B to a 6128. However im still not sure if you are supposed to do it. Im no eletronic expert so there could be something inside a 464 DDI that there isnt in a 6128 FD1 external drive. However ive exchanged around my DDI & FD1 drive multiple times & so far my 464, 6128, DDI & FD1 all still work fine. But that dosnt mean something couldnt happen.

Offline JonB

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Re: Dead CPC464
« Reply #13 on: 08:20, 19 February 19 »
There are two 64k expansions and they came joined together. These are dk'Tronics  branded, so they might behave differently to Amstrad RAM packs (in terms of address decoding). I've opened them up and they look like 256k RAM boards (PCBs labelled "464 256" and "DK 256"), but populated with 8 64Kx1 bit chips. There are also two missing ICs, so it is conceivable that they could be upgraded, if the PAL is universal.

Getting a bit ahead of ourselves here - still need to fix the main board!
« Last Edit: 08:45, 19 February 19 by JonB »

Offline Bryce

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Re: Dead CPC464
« Reply #14 on: 09:17, 19 February 19 »
There are two 64k expansions and they came joined together. These are dk'Tronics  branded, so they might behave differently to Amstrad RAM packs (in terms of address decoding). I've opened them up and they look like 256k RAM boards (PCBs labelled "464 256" and "DK 256"), but populated with 8 64Kx1 bit chips. There are also two missing ICs, so it is conceivable that they could be upgraded, if the PAL is universal.

Getting a bit ahead of ourselves here - still need to fix the main board!

I did an article here explaining how to upgrade these to 256K if you want. Easy project if you have basic soldering skills: http://www.cpcwiki.eu/index.php/Upgrading_a_Dk%27tronics_RAM_Expansion

Bryce.

Offline JonB

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Re: Dead CPC464
« Reply #15 on: 09:46, 19 February 19 »
That's pretty cool, Bryce..!

Your description says that as a 256K expansion it is mapped to banks 0-3, but what happens to the internal RAM (which I assume starts at Bank 0)? Is it lost?

I've just opened mine again to look at the bank select options. They're both wired the same so both are vanilla 64K expansions. No idea why there are two of them with one machine.
« Last Edit: 09:51, 19 February 19 by JonB »

Offline Bryce

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Re: Dead CPC464
« Reply #16 on: 10:30, 19 February 19 »
The upper 64K in a 6128 are no longer used when one of these are connected. At the bottom of the article you'll see a section about switching one to "silicon disc mode" which really just mapped the RAM to banks 4 to 7. With both connected and converted to 256K (with one changed to silicon disc mode) you then have the base 64K plus 512K externally, but the upper internal 64K is then disabled.

Bryce.

Offline JonB

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Re: Dead CPC464
« Reply #17 on: 13:55, 19 February 19 »
So on a 6128 I have the potential for a total of 576K? Not sure what I'd use it for!

What about the 464's memory map? I guess as-is, it just extends a 464 to 128k? And if I modify for 256K I get 320K? Possibly with the second expansion updated and configured as a Silicon Disk, does that mean I can get 320K + 256K silicon disk (on a 464)?

Where do we stand with CP/M disks? It came with a 2.2 disk but no CP/M Plus. Guessing the 6128 CP/M Plus would work, on the assumption that 464 + 64K expansion + Amstrad DD1 = CPC6128 with a nicer keyboard and a tape drive - is that correct?
« Last Edit: 14:03, 19 February 19 by JonB »

Offline Bryce

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Re: Dead CPC464
« Reply #18 on: 14:28, 19 February 19 »
A quick read here perhaps: http://www.cpcwiki.eu/index.php/DkTronics_CPM

A 464 doesn't quite become a 6128: Different BASIC, Different LowerROM and I think some of the memory modes can't achieved.


Bryce.