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General Category => Technical support - Hardware related => Topic started by: rntr on 12:50, 18 November 23

Title: Bad signal on cpc 6128
Post by: rntr on 12:50, 18 November 23
Hi,

My cpc6128 was working fine but after inserting the m4 now i get a moving signal on screen (see pic below) and nothing else. The m4 responds and seems to work remotely fine. Any ideas? 

Thanks.
JB

https://imgur.com/a/TKaIpib
Title: Re: Bad signal on cpc 6128
Post by: Rabs on 13:28, 18 November 23
Quote from: rntr on 12:50, 18 November 23Hi,

My cpc6128 was working fine but after inserting the m4 now i get a moving signal on screen (see pic below) and nothing else. The m4 responds and seems to work remotely fine. Any ideas?

Thanks.
JB

https://imgur.com/a/TKaIpib
Try cleaning the expansion edge connector with an old ink eraser. I am assuming the cpc is OK without anything connected?
Title: Re: Bad signal on cpc 6128
Post by: rntr on 13:50, 18 November 23
The cpc is not working without anything connected now. Just a moving signal on screen.

Title: Re: Bad signal on cpc 6128
Post by: Rabs on 15:21, 18 November 23
Quote from: rntr on 13:50, 18 November 23The cpc is not working without anything connected now. Just a moving signal on screen.


Oh dear, could it be the monitor rather than the CPC?
Title: Re: Bad signal on cpc 6128
Post by: rntr on 15:42, 18 November 23
I've another cpc with a faulty keyboard that boots fine on that monitor. And the m4 works fine also on that cpc. So, it's not the monitor. 

The cpc was working fine. I ran a game from the disk drive. Everything fine. Then I plug in the m4. Then I remove the m4 to update the microsd. The cpc is not working since then.

Title: Re: Bad signal on cpc 6128
Post by: Rabs on 16:11, 18 November 23
Quote from: rntr on 15:42, 18 November 23I've another cpc with a faulty keyboard that boots fine on that monitor. And the m4 works fine also on that cpc. So, it's not the monitor.

The cpc was working fine. I ran a game from the disk drive. Everything fine. Then I plug in the m4. Then I remove the m4 to update the microsd. The cpc is not working since then.


Does this help CPC video failure (https://youtu.be/BLzHPf1IY8c?si=LDUYtsE6YE54x7qC).
Title: Re: Bad signal on cpc 6128
Post by: eto on 17:43, 18 November 23
when you press the DEL key, do you get a beep?
Title: Re: Bad signal on cpc 6128
Post by: rntr on 17:57, 18 November 23
No beep.
Title: Re: Bad signal on cpc 6128
Post by: Bryce on 19:29, 18 November 23
You may have fried your CPU by accident (static discharge). Try the CPU from the other CPC.

Bryce.
Title: Re: Bad signal on cpc 6128
Post by: rntr on 20:08, 18 November 23
Hi Bryce,

Now that you mention it... that seems plausible. Maybe I didn't unplug the usb cable from the m4 board and when I touched it to remove it zap?

How can I avoid this in the future? Turn everything off before touching the m4 board? Use gloves? What the hell. :)

Is it easy to swap the cpu from another cpc?

Thanks!
Title: Re: Bad signal on cpc 6128
Post by: Bryce on 21:18, 18 November 23
The CPU is socketed, so it's a simple task to swap them. With retro computers there's no such thing as "Plug and Play". You need to connect everything before you power up the CPC.

Bryce.
Title: Re: Bad signal on cpc 6128
Post by: SerErris on 13:30, 19 November 23
And if you want to disconnect something (whatever it is) you need to fully power of everything.

Another Problem in your setup is propably that you power both the M4 and the CPC but have not disconnection in between the M4 +5V rail and the CPC +5V power rail.

If you connect the M4 with power from an external source there should be no connection to the +5V rail on the expansion port.

Because if you have that connection, and you power down the CPC with the power switch, it is actually still powered on via the M4 power supply. If you then pull of the M4, all kind of bad stuff can happen, esp. if you then short things.
Title: Re: Bad signal on cpc 6128
Post by: rntr on 16:42, 19 November 23
I guess is was being careless removing the m4 and had a bit of bad luck. I thought once you turn off the cpc it´s safe to remove the m4 board. 

Thank you all for the recommendations, I'll see if I can use my semi-broken cpc for parts and swap the cpu, and then pray it works.
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