My 664 does not boot anymore:
- Power LED of the CPC is ON
- CTM is fully OK (tested with a 6128) but show a complete black screen when power ON the keyboard
- Gate array OK
- Z80 OK
- ROM 40015 OK
Any idea ?
are the Z80/GA/(ROM?) socket clean ?
Is the power switch OK ? If its resistance is high enough the voltage will drop enough for the CPC to fail, but the LED still on
Does the Z80 get a clock ?
I have cleaned the 3 sockets and replaced each chips with good ones from a 6128: results is the same.
Power switch is OK (tested on a 6128 as well).
Not tested the clock on the Z80, I will have my oscillo with me tomorrow, it will be easier....
Thank you for your help.
Edit: here is the clock signal onto the Z80:
(http://nsa38.casimages.com/img/2016/05/19/mini_160519114836286303.jpg) (http://www.casimages.com/i/160519114836286303.jpg.html)
Have a look at the Power Supply with the CRO, a lot of noise on the Photo between pulses ?
Ray
These is no clock. You expect a 5V square wave (50% duty cycle). Here only noise can be seen.
Did you check it at Z80 input pin or GA output pin ? There is a buffer and a resistor between the two.
And while you have the scope out, check that the 16MHz is there at GA iinput.
Quote from: gerald on 19:22, 19 May 16
Is the power switch OK ? If its resistance is high enough the voltage will drop enough for the CPC to fail, but the LED still on
IMHO Unusual tip - BUT Cool, i tried them, and now is an other CPC6128 back to life. :D
Thanks Gerald!
Quote from: SOS on 08:35, 20 January 17
IMHO Unusual tip - BUT Cool, i tried them, and now is an other CPC6128 back to life. :D
Thanks Gerald!
It's not that unusual, it actually happens quite often.
Bryce.
Indeed!
I got a 6128 from a friend this Christmas ans wasn't powering on.
So, I opened it, cleaned the power switch with contact cleaner and it's working like a charm!