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Thread: Amstrad CPC464 - Repair

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    Vnman's Avatar
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    Default Amstrad CPC464 - Repair

    So I just got myself an Amstrad 464 for pennies, it advertised as "dead".

    this is what I did -
    • connected power supply and nothing, no light nothing.
    • opened the 464 up and found that the power switch is covered with "fluff" clean the switch and got the red light.
    • removed the 40007(?) just above the RAM chips and founf that one row of the socket was covered with thermal paste. Cleaned the socket and put new heatsink, powered on and still black screen.
    • found on the power socket that the three solder points are "dried" will re-solder.


    Questions -

    The board is the long board with no "jumpers", is this the version one board?
    Is the 40007 fried? where can I get a replacement?
    The RAM chips are socketed, are these original or the previous owner has tinkered with the board?

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    Amibayer! Bryce's Avatar
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    Hi,
    the very first versions of the 464 had real wires (not flat membrane) coming from the keyboard to a long white connector and the PCB will have a part No. Z70100 MC0001A. Version 2 had an unpopulated space for an alternative GA (40010) and the PCB part No. will start with Z70200 MC.... . There was only these two long PCB versions, version 3 was the short PCB. RAM was never socketed on any of them, so I would assume someone has tried to fix this in the past.
    The 40007 may be fried, but it could be many other things too, so I wouldn't go looking for a 40007 until you are sure.
    If you don't have the equipment or knowledge to find the fault, you could send the board over to me for repair.

    Bryce.

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    Vnman's Avatar
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    Thanks for the offer.

    Since I got it for cheap I will try to repair it myself. Just need a few pointers.

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    Amibayer! Bryce's Avatar
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    Ok. Choose one of the TTL chips somewhere on the PCB and check that they are really getting the 5V they need. After that try reseating the Z80 which should also be socketed.

    If possible, could you post a picture of the screen you are getting?

    Bryce.

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    Vnman's Avatar
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    my board is Z70100 no jumper wires and no MC marking on the board. Just reflow the power socket and still black screen, no sound when pressing the keyboard. The cassette deck seems to be ok, rewind and forward work.

    will check the voltage next....

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    Click image for larger version. 

Name:	IMG_20170320_095219_edited.jpg 
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ID:	119650

    Click image for larger version. 

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    Last edited by Vnman; 20th March 2017 at 09:05.

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    Amibayer! Bryce's Avatar
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    That's a pretty early model. Looks like someone did some modding to it, the heatsink is definitely not what Amstrad originally used and there are several ICs that aren't normally socketed.

    Bryce.

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    That's me with the heatsink, before it was the aluminium heatsink and found that there was too much thermal paste applied that it covered the whole bottom row.

    4.8v on the power supply, 4.7v on the sound chip, 4.8v on the z80 & 4.4v on the 40007.

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    Amibayer! Bryce's Avatar
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    They're borderline voltages. What's the voltage on the plug supplying the voltage? I'd recommend cleaning the contacts inside the power socket and cleaning the contacts inside the switch. You could also try shorting the pins that go to the power switch to override the switch completely and see if the computer then starts.

    Bryce.

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    8 Bit Dreams DjCook's Avatar
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    Hi,
    also CRT controller can often cause black screen, ir runs pretty hot and may be faulty..
    be aware, do NOT buy HD46505SP as it works partially. (looks like it works good in Basic on first look, but on some games like Turrican - there is a thick black horisontal line in the middle of the screen. What You need - is HD46505RP.. give it a try, these chips are not expensive usually..
    regards

    -Viktor
    Last edited by DjCook; 20th March 2017 at 21:04.

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