Author Topic: CPC464 Blank Screen  (Read 1315 times)

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Offline bobuk

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CPC464 Blank Screen
« on: 12:13, 23 February 19 »
Hi,


This is my first post here and was hoping that someone might be able to point me in the right direction.


I've just found my old CPC464 while clearing out cupboards at my parents house and thought I'd get it going again after some 25 years but alas it does not just power on.  Symptoms and troubleshooting so far;


  • When I power it on I get a blank screen, occasionally with some marks in random locations (different every time I power it on), I have attached some pictures. 
  • I do not get a beep when I hold down the Del key
  • I have checked the voltages and I get 4.95V on the expected IC vcc inputs. 
  • I have removed and re-seated the z80.
  • If I leave it powered on for a few minutes , none of the IC's get very hot, they all just get luke warm.
  • The cassette drive will fast forward but will not play after pressing crtl + enter followed by a key.


Any ideas on what to try next?


Thanks in advance.


Offline llopis

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Re: CPC464 Blank Screen
« Reply #1 on: 12:28, 23 February 19 »
It's almost sure a faulty RAM IC. I'm afraid you need to desolder them and put new ones (or test them one at a time and replace the bad one(s)).

Offline twox

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Re: CPC464 Blank Screen
« Reply #2 on: 14:51, 23 February 19 »
If you have zero soldering experience, learn from my mistake - and dont try to repair it yourself.

Offline angelcaio

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Re: CPC464 Blank Screen
« Reply #3 on: 16:45, 23 February 19 »
hi, maybe this utility can help you identify if it's a memory chip
http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/quick-and-dirty-ram-test-for-cpc/?PHPSESSID=1ec5np0nptbeahvop7glbtas53


Enviado desde mi iPad utilizando Tapatalk

Offline bobuk

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Re: CPC464 Blank Screen
« Reply #4 on: 11:35, 26 February 19 »
Thanks, I'll have a go at replacing the faulty RAM IC.


Is piggybacking a known working chip a viable method for identifying the faulty IC (assuming that only one is faulty).


Thanks.

Offline Bryce

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Re: CPC464 Blank Screen
« Reply #5 on: 12:39, 26 February 19 »
Thanks, I'll have a go at replacing the faulty RAM IC.


Is piggybacking a known working chip a viable method for identifying the faulty IC (assuming that only one is faulty).


Thanks.

No, there are several ways a RAM IC can fail and many of them (internal short-circuit / Stuck bit / etc) would still cause a problem when a good chip is piggybacked on top.

Bryce.

Offline bobuk

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Re: CPC464 Blank Screen
« Reply #6 on: 15:35, 04 March 19 »
Hi,


Over the weekend I removed all of the old RAM, soldered in sockets and replaced the RAM IC's with ones purchased (listed as working).  But still get the same blank screen with some random markings.


I'll spend some time checking my solder joints this week but can anyone advise what the next steps in troubleshooting are?


Thanks,




Offline Bryce

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Re: CPC464 Blank Screen
« Reply #7 on: 16:56, 04 March 19 »
Have you tried a different Z80?

Bryce.

Offline bobuk

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Re: CPC464 Blank Screen
« Reply #8 on: 18:58, 04 March 19 »
Not yet, I've just ordered one so will swap it later in the week.


Thanks.