Bad signal on cpc 6128

rntr · 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

Rabs · 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?

rntr · 13:50, 18 November 23

The cpc is not working without anything connected now. Just a moving signal on screen.

Rabs · 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?

rntr · 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.

Rabs · 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.

eto · 17:43, 18 November 23

when you press the DEL key, do you get a beep?

rntr · 17:57, 18 November 23

No beep.

Bryce · 19:29, 18 November 23

You may have fried your CPU by accident (static discharge). Try the CPU from the other CPC.

Bryce.

rntr · 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!

Bryce · 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.

SerErris · 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.

rntr · 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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Bad signal on cpc 6128