I Have a CPC 464 that I have Killed with 12 Volts ** FIXED **

[Audronic]

I Have a CPC 464 that I have Killed  with 12 Volts   Grrrrr

The Model info is :- Z70200, MC 0002C

No Raster displayed  (Rectangle) Just a Blank screen.

The 16 Mhz clock works.

I have taken chips from the faulty  machine and tested them in the working machine.

I have swapped the 40010.   It is Ok
I have swapped the Z80        It is OK

I looks like I will have to cut out the 6845 , socket and see what happens
Any comments Please.

Thanks.  Ray

[llopis]

Before you cut out anything, do some basic checks:
- 5V everywhere
- No shorts between 5V and grnd
- Clock signal on Z80 (pin .
- Vsync signals from GA
- Basic activity on address and data buses

I recently had a COC without video, but it has complete lack of activity, starting with a clock signal (even though the 16MHz crystal was working). It turns out it was part of the circuit that feeds back that clock signal and generates the signal to the GA.



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[Audronic]

Before you cut out anything, do some basic checks:

- 5V everywhere
@ Checked all OK

- No shorts between 5V and grnd
@ Checked all OK

- Clock signal on Z80 (pin 6 ).
@ Checked OK

- Vsync signals from GA
@ Not looked at yet

- Basic activity on address and data buses
@ On the Z80 3 lines  Odd



See the tables ?
Thanks.   Ray

[00WReX]

Did you try Geralds 'Quick and Dirty RAM test'.


Cheers,
Shane

[Audronic]

@00WReX


Hi Shane


No I have not used the Ram test yet.
If I don't have a raster, I have no video out and I thought that I will have to wait until I have a raster.


I have discovered that I have 1 (one) warmer than usual Ram chip, this morning I will replace that.
Had a quick look at the schematic and the 3 (Three) questionable data lines go " Everywhere ".


Thanks for the thought


Ray

[gerald]

No I have not used the Ram test yet.
If I don't have a raster, I have no video out and I thought that I will have to wait until I have a raster.

Running the RamTest also have the side effect of bypassing the internal lower ROM, which is initialising the CRTC.
If this one is nuked, you for sure will not have any video 

If the ram test start you will know that the internal ROM is bad and hopefully get a idea of the RAM state.
If you still have no video, then the CRTC can be bad, but also the ROM too, or anything else .

[Audronic]

@gerald


Ok Thanks for the info.


I will do the RamTest.


Thanks.   Ray

[Audronic]

@gerald


Hi Gerald


I have plugged in the RamTest and still a Blank screen.


I tested the Ram test on an other 464 that I have here.


Thanks.  Ray

[Audronic]

@gerald


Ok I have cut out the 40009 fitted a socket.
I have NOT put a replacement 40009 in the socket.
Ran the " RAM Test "

and Voila. the screen shows this.:-

Just waiting for a 40009 file to burn.
Thanks
Ray

[00WReX]

Oh, I just came back to this to see how you got on...and realised I had read your last post wrong.
I thought you going off to burn a 40009 EPROM, but realise you are waiting for the file to then burn 

So I have just done a quick search for the files.
Looks like you went down this path 3 years ago 

http://www.cpcwiki.eu/forum/hardware-related/wanted-a-dump-of-a-rom-40009/

That Grim link is dead now, so I grabbed the 2x 16k ROMs (OS+BASIC) from an emulator and concatenated them for you.
The checksum matches what you found last time (link above)...checksum F700

[attach=1]

Cheers,
Shane

[Audronic]

@00WReX


Hi Shane


Thanks. for all the effort to remake the rom.


I have been looking in all my hard drives BUT could not find the File.
Thanks I will burn it NOW and see what happens.


Ray

[Audronic]

@gerald


@00WReX

@llopis


Thanks for all the support it Works


Replaced 1 Ram chip and a 40009.


I will try NOT to put +12 Volts instead of +5 Volts in the future


Thanks again


Ray

[00WReX]

Cool 
So only 2 'fuses', that was lucky 

Cheers,
Shane

[LambdaMikel]

Now I feel better that I am not the only one who did kill his 464 with 12 V  Glad you fixed it, congrats!