CPC 6128 CRTC4 issue

[francouai]

Hi Guys.
I have here one of the last CPC 6128 made by Amstrad.He got an CRTC 4 inside.  I have to say, this mother board is very interesting to see compare to the previous version.The CRTC 4 from AMSTRAD looks very modern style 
I bought this CPC with a problem on the 5volts rail.When I connect the 5volts on it, the Z80 and the 40051 starts to be very hot.I don't have any video out, no BIP, nothing... only the red LED on.I have no idea what the previous owner did with it but but looks like he removed the 12 and 5 volts connectors from the mobo.

Any idea where to start the trouble shooting ?I cannot find any CRTC4 service manual .  I'm not sure if I'll find the time to fix it or to sell it.

[llopis]

Hi Guys.
I have here one of the last CPC 6128 made by Amstrad.He got an CRTC 4 inside.  I have to say, this mother board is very interesting to see compare to the previous version.The CRTC 4 from AMSTRAD looks very modern style 
I bought this CPC with a problem on the 5volts rail.When I connect the 5volts on it, the Z80 and the 40051 starts to be very hot.I don't have any video out, no BIP, nothing... only the red LED on.I have no idea what the previous owner did with it but but looks like he removed the 12 and 5 volts connectors from the mobo.

Any idea where to start the trouble shooting ?I cannot find any CRTC4 service manual .  I'm not sure if I'll find the time to fix it or to sell it.

If the Z80 and the ROM start out hot, it's pretty safe to replace them. Chances are there's a lot more than that though. Just saying :-b


Could you post a picture of your motherboard? It's not one of the versions listed here? http://www.cpcwiki.eu/index.php/Mainboard_Versions

[Bryce]

Replace anything getting hot as they most likely have a partial short inside. Then see how it reacts after they've been replaced.

Bryce.

[francouai]

this is exactly the same has this one.
http://www.cpcwiki.eu/imgs/e/ed/CPC6128_Z80330_Yarek.jpg

[francouai]

Replace anything getting hot as they most likely have a partial short inside. Then see how it reacts after they've been replaced.

Bryce.

I don't have spare Z80 and other parts. 

[Bryce]

And you intend fixing it without needing any spare parts?

Bryce.

[llopis]

this is exactly the same has this one.
http://www.cpcwiki.eu/imgs/e/ed/CPC6128_Z80330_Yarek.jpg

Oh wow, I had never seen that version before. Neat!


And yeah, it looks like maybe it's sending 5V to the drive, and over there it's converting it to 12V maybe?


It actually reminds me of the Spectrum +3 quite a bit.

[francouai]

And you intend fixing it without needing any spare parts?

Bryce.

well.. I can have some resistors and diodes but no IC.Sorry, we all are not up to speed to fix CPC.

[Bryce]

Do you have the knowledge and equipment to fix it? If not, then send it to someone for repair.

Bryce.

[gerald]

I cannot find any CRTC4 service manual

On the wiki : http://www.cpcwiki.eu/manuals/Amendment%20Service%20Manual.zip
CRTC4 6128 starts from page 16

[robcfg]

Let's hope it's these two chips and not the ASIC chip.


If the ASIC is damaged, it would be almost impossible to find a spare as it's a custom part.

[llopis]

Let's hope it's these two chips and not the ASIC chip.

If the ASIC is damaged, it would be almost impossible to find a spare as it's a custom part.

Agreed. Although don't give up if it seems it's the ASIC. Spectrums +2 have an ASIC, and I've twice fixed a problem that seemed to be a faulty ASIC chip, but really was a bad connection on one of the pins. Apparently those connections can be quite brittle, and just getting a tiny bit of fresh solder (very carefully!) can fix them.