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Author Topic: Amstrad CPC 6128 (not plus) - Kbd/jstick doesn't respond after games load  (Read 626 times)

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Offline swainey83

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Hi all,

This is my first post on this forum so please be kind.

In the past few months I've obtained a few CPCs via eBay to re-live some nostalgia from my childhood. One of these is 6128 (non-plus) which when I first unboxed it, had some weird quirks with the keyboard - some keys not working and characters appear when booting up. Lifting the lid on the machine and re-seating the keyboard ribbon seemed to solve most of these leaving only a minor niggle of the number 4 being displayed when I boot up now. Otherwise all looked good. The other is a 464 (again non plus) which I'll post seperately about later.

With the 6128, I've since been loading CDT files in via tapdancer and a tape lead from a mobile phone. This in general seems to work quite well (once I got the volume level right) though I've noticed that with quite a few games, they load fine but once loaded, no keys on the keyboard will trigger a response nor will any input from a connected joystick (so things look frozen). What's strange though is that all seems fine with some other games and at the basic screen, all seem to respond fine to input. I also tried a view games using an external Sony tape player I obtained and again, some games work others not so much with the same symptom.

It's a lovely machine in general, I'd just love to know what's going on with it and whether it's repairable. Grateful for any input or responses I received!

Cheers

Swainey

Offline Chinnery

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Hi, and welcome!


As an uneducated guess regarding your 6128, do the games that are unresponsive playing music? I only ask as the sound chip in the cpc also plays a role in decoding the keyboard.


Probably nothing other than a suggestion.

Offline swainey83

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Hi Chinnery,


Thanks for the reply and he welcome!


My recollection is that after loading games exhibiting this fault, there has been no music. However not sure if this is indicative of the fault or just coincidence.


FWIW for games that do work the sound seems fine.


Cheers


Swainey

Offline Chinnery

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If you completely unplug the keyboard and power up, do you still get the number 4 pop up?
Also, in this state, does the joystick work in these games?
« Last Edit: 20:50, 18 April 18 by Chinnery »

Offline blackdalek

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If you completely unplug the keyboard and power up, do you still get the number 4 pop up?
Also, in this state, does the joystick work in these games?
I am curious to know how one would load a game with no keyboard plugged in?
CPC6128 modded with ABBA switch. External 5.25" floppy drive with side switch and Multiface 2. Now also sporting a joystick splitter and M4 WiFi board.

Offline CraigsBar

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I am curious to know how one would load a game with no keyboard plugged in?
First does the 4 popup with no keyboard? This will isolate the fault to the keyboard or ay/pcb.

Second load a game *carefully* unplug the keyboard and check the joystick.

Sent from my ONEPLUS 3t using Tapatalk


Offline Bryce

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Highly likely that the AY is starting to fail.

Bryce.

Offline swainey83

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Thank you all for your responses and suggestions. Hoping to get some time to play over the weekend so I'll try out the suggestions and post back with results.


Cheers


Swainey

Offline swainey83

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Hi guys,


Having just had the 6128 apart for testing (I've been attempting to load in Turbo Outrun from tapdancer), I can confirm:


- The number 4 key on boot does not appear if the keyboard is disconnected
- The game fails to load both with the keyboard connected and with it being disconnected once loading commences
- When it freezes on a black screen after loading I hear a low pitched constant tone for about 4 seconds and then the system resets itself.


Whilst I had it apart I located the AY chip and gently pushed directly down to make sure it's properly seated which it seems to be.


Given the above do you think it might be salvagable? If so could anyone point me in the direction of someone who might repair it for a reasonable fee that they'd recommend please?


I hope you all are having a great weekend!


Swainey

Offline Bryce

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First off, if the 4 only appears when the keyboard is connected, the the membrane probably just needs to be cleaned, this may also solve the other issues.

Secondly, if the AY is socketed as you seem to be suggesting, then someone has already done repairs on the machine, the AY was never socketed on original CPCs.

Bryce.

Offline Chinnery

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Hi again,


As Bryce mentioned, the AY chip is not normally in a socket on the 6128. Can you just double check that you have the right chip? It should be slightly above the keyboard connector, and have printed on it "Sound AY-3-8912", and in a larger font, "GI". If this is socketed then there has been a previous repair to the board. And whilst we are checking chips, to the right of the keyboard connector is one wit 74LS145 printed on it. Is that looking ok? I would assume so but its worth a double check.


Your choice of game to try load, and the method used (tapdancer), is perhaps not optimal. If I remember correctly, later tape games on the Amstrad used fancy loaders, with counter-piracy measures thrown in for good measure. Maybe starting with a simple loader, such as (for example) Harrier Attack or Oh Mummy which use the standard Amstrad firmware loader may get things running. Have you tried loading games from the disc drive?


Either way, don't worry. It will be salvageable. If the CPC boots up you are 90% of the way there. Again, as Bryce said, the fact when there is no keyboard connected there is no "4" displayed hints heavily towards the keyboard membrane. It is an easy job to clean the keyboard. There are a few large screws to remove and about 16 black clips that need gentle prying to release the metal base. Top tip - make a note of where these large screws were removed from!!!


Once apart, you should then be able to see the membrane and perhaps 30 years of grime build up. Just check both the number 4 position on the top of the keyboard and on the numeric keypad for excess grime or damaged springs. What ever you do though, don't try separate the two sheets of the membrane - bad things will happen :)




Offline swainey83

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Hi Chinnery,

When I get some time (hopefully the weekend again), I'll have the 6128 apart and post photos. At the same time, I'll look at disassembling the keyboard as you suggest and attempting to clean this up. Thanks for the tips and warning!

With regards to the game and method of loading, I take your points on board. However I have noticed hanging behaviour (as in my original message) when loading other games in via an external cassette player. I don't have any software on disc to test yet unfortunately but I keep an eye out for this and I'm considering investing in a DD-3 to load in games from.

As you know, I do have another CPC (the 464) which I need to make some repairs on. I hope to be able to do these soon and have a working machine there for comparison if all else fails.

Cheers

Swainey