Author Topic: Odd display problem - anyone seen this before? (cpc 464)  (Read 1424 times)

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Offline backtogeek

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I had a quick search on the forum, could not find anything specifically like this, i wondered if anyone has seen this before or has any suggestions on what it may be caused by?



https://i.imgur.com/fR6xcsI.jpg

https://i.imgur.com/30Hwdi4.jpg

https://i.imgur.com/MIkumg8.jpg

https://i.imgur.com/lRyMqiT.jpg


It does not seem to impact the function at all, I left it running like that for an hour or so, no change.

edit: sorry the images did not resize so just posted links to the images instead.
« Last Edit: 17:30, 11 December 20 by backtogeek »

Offline backtogeek

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Re: Odd display problem - anyone seen this before?
« Reply #1 on: 13:07, 11 December 20 »
Sorry about the images I expected them to auto resize

Offline Bryce

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Re: Odd display problem - anyone seen this before?
« Reply #2 on: 14:25, 11 December 20 »
Yes, I had a CPC in for repair that did that. From what I can remember (it's a long time ago) it was a dodgy RAM that was on the verge of failing. However, the CPC in question had other issues, so I can't say for sure that that was the real cause. Leave it running for as long as you can, that might cause the RAM to fail completely.

You could also, try re-seating the CPU or try a different CPU to see if it goes away.


Bryce.
 

Offline backtogeek

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Re: Odd display problem - anyone seen this before?
« Reply #3 on: 15:02, 11 December 20 »
I have a z80 from that short board you gave me some advice on that I could not fix yet, so I will try swapping the z80's over, thanks Bryce.


Will they boot without a full ram compliment? I could always try taking out a bank at a time.

Offline Bryce

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Re: Odd display problem - anyone seen this before?
« Reply #4 on: 15:18, 11 December 20 »
If it's a 6128 it will boot with just the lower 64K in place, but it won't boot if any RAM is missing from the lower 64K.

If you don't have any luck with either of the boards, you can send them over to me for repair.

Bryce.

Offline backtogeek

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Re: Odd display problem - anyone seen this before? (CPC 464)
« Reply #5 on: 16:26, 11 December 20 »
If it's a 6128 it will boot with just the lower 64K in place, but it won't boot if any RAM is missing from the lower 64K.

If you don't have any luck with either of the boards, you can send them over to me for repair.

Bryce.


Thanks, its a 464 (added to the forum subject for clarity), I am going in now, wish me luck!

Offline backtogeek

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Re: Odd display problem - anyone seen this before?
« Reply #6 on: 16:39, 11 December 20 »
You could also, try re-seating the CPU or try a different CPU to see if it goes away.

CPU swapped same issue, I will try switching some of the ram, I assume the short board ram is compatible... desolder time, always fun.

Offline Bryce

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Re: Odd display problem - anyone seen this before?
« Reply #7 on: 16:44, 11 December 20 »
They should all be 4164 RAMs.

Bryce.

Offline backtogeek

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Re: Odd display problem - anyone seen this before?
« Reply #8 on: 17:20, 11 December 20 »
sadly my solder pump is no match for the volume of solder that is half way up the legs on the other side of the board too and I dont want to wick it and risk damaging the ram.

the one with this fault has socketed ram anyway so I will just buy a few 4164's and be patient.

Offline Bryce

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Re: Odd display problem - anyone seen this before?
« Reply #9 on: 17:30, 11 December 20 »
If the RAM is socketed, I'd definitely try re-seating all the RAM ICs first.

Bryce.

Offline backtogeek

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Re: Odd display problem - anyone seen this before? (cpc 464)
« Reply #10 on: 17:38, 11 December 20 »
yep I did that, no difference, then I swapped them all over so each one was in a different slot to see if that changed anything, it did not, ordered a 4146 should be here in <7 days so will start testing with the replacement in each position.


Can you piggy back them for testing like you can with the amiga? I imagine its fine.

Offline Bryce

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Re: Odd display problem - anyone seen this before? (cpc 464)
« Reply #11 on: 17:40, 11 December 20 »
Piggybacking only works in some limited circumstances, whether it's a CPC or Amiga doesn't matter. RAMs can fail in many ways and piggybacking won't work for many failures.

Bryce.

Offline GUNHED

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Re: Odd display problem - anyone seen this before? (cpc 464)
« Reply #12 on: 23:07, 12 December 20 »
That's grid bugs! Try to use a different PSU, if you have one at hand.
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Offline backtogeek

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Re: Odd display problem - anyone seen this before? (cpc 464)
« Reply #13 on: 22:33, 14 December 20 »
That's grid bugs! Try to use a different PSU, if you have one at hand.


Would it cause that on any CPC464, asking as I have gone through 4 in the past few months all on the same PSU and none of them have that, maybe this one is just particularly sensitive?

Offline GUNHED

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Re: Odd display problem - anyone seen this before? (cpc 464)
« Reply #14 on: 23:06, 14 December 20 »
Then no PSU... Open the CPC. let it run for 1 hour. Tap at the RAM chips (and others if you like). Fell of one IC gets particular hot. This may be the broken one.
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Offline backtogeek

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Re: Odd display problem - anyone seen this before? (cpc 464)
« Reply #15 on: 10:24, 16 December 20 »
Then no PSU... Open the CPC. let it run for 1 hour. Tap at the RAM chips (and others if you like). Fell of one IC gets particular hot. This may be the broken one.


I have 3 commodore 1530 datasettes to recap and service today and once I have made space again (I am a messy worker) I will power it back up for an hour or 2 and see what gets hot. thanks.

Offline lazapap

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Re: Odd display problem - anyone seen this before? (cpc 464)
« Reply #16 on: 00:32, 31 December 20 »
I had some similar problem with a cheap 5V power supply. Try to take power from a pc's or laptop's usb port, it's safer.