So it was dead while the dude sold it as working.
Anyway, I got 4.78V at pin 8 on RAM chips, swapped them with new in sockets just in case.
Z80, 40010 work, tested them on my 6128.
The screen is black but sometimes I have this:
https://www.youtube.com/watch?v=8fRuy6nQ_74 (https://www.youtube.com/watch?v=8fRuy6nQ_74)
The flickering is NOT from my camera, this is what you get in real life.
Thanks in advance.
Video not working
It's working on YouTube but not via the Forum.
Cheers,
Peter
Stick a scope on pins 39 and 40 of the CRTC and see if it's producing sync signals. If one of the is missing then the CRTC is bad.
Bryce.
I don't have a scope Bryce, I've only tested the voltage on CRTC too.
Then measure the voltages on the two pins.
Bryce.
Yes I only did that, 4.9V.
4.9V on the sync pins? Or is that the supply voltage? Pins 39 and 40 should be giving V and H sync signals. Both are active high, so you should be reading a lot less than 4.9V. Try measuring them with the multimeter. If they are very close to 5V or 0V, that could indicate an issue.
Bryce.
Pins 1 and 20 have 4.9V.
39 and 40 0.12V...
That sounds reasonable. Possibly a 74LS153 has failed?
Bryce.
8 -16 gives voltage? 5V?
Quote from: VincentGR on 15:22, 01 April 19
8 -16 gives voltage? 5V?
On what chip? If it's the CRTC then you have an issue. Pins 14 and 15 aren't even connected to anything!
Bryce.
I was talking about 74LS.
Measured all chips on board, voltage is ok.
Dunno, I might swap crtc and rom :-X
Measuring supply voltage only tells you that they're getting power and that they don't have a major short circuit. But don't just swap things for the sake of it. It could be a simple trace break or bad solder joint.
Bryce.
So re soldered all connections and checked every line, nothing.
Swapped CRTC to another machine and worked.
The last chip is the ROM.
I hope this is it because then I'll have to replace LS chips :picard:
Good news everyone!!!
AMSTRAD 40009 => Dead
1x RAM IC => Dead
CPC is working ;D
Thank you all.
Quote from: VincentGR on 15:13, 03 April 19
Good news everyone!!!
Uh-oh, I don't like the sound of that.
;D
Lol.
With a dead ram ic, I had the same screen like with a dead Z80.
BTW is there a post with faulty screens here?
If not we must make one with photos and possible problems.
I'm not sure that a faulty screen page would help that much. The CPC isn't like a C64 which has about 10 different screen "clues" to the failure, it has only three or four and all of them can point to multiple things:
- Completely blank screen - Possible problems: Power, CPU, GA, CRTC, clock circuitry, reset circuitry, broken trace, short circuit. In fact almost anything on the PCB or PSU.
- Blank screen with square in the middle - Possible problems: CPU, CRTC, RAM, Multiplexer IC's, ROM IC, buffer IC's, broken trace.
- Non-synced screen (what you had) - Same as above.
- Screen that stops just before the ready prompt appears - AmDOS ROM or any part of the disk system.
Bryce.