CPC 464 black screen - LED on - no beep

[McArti0]

Check CRTC pin 39 but first pin4 GA cclk 2MHz

[willow3411]

can You use triger? in oscylo.

arff ; i not understand .... triger ??

yes !! is good i'm looking triger on the oscillo : 3.6v

signal detected

Check CRTC pin 39 but first pin4 GA cclk 2MHz

pin4 GA cclk 1Mhz !!

CRTC pin 39 random frequency

[McArti0]

ok cclk 1MHz. 
pin39 crtc. What's you see on oscylo and stable by trigger

[Bryce]

Hi Willow,
    assuming you've used the Auto button or set the trigger level correctly. Could you upload a screenshot of the output from pins 39 and 40 of the CRTC. What you may consider "random" might actually be a good VSync or HSync signal.
For information: The Trigger is the voltage level where the scope starts recording and displaying what it's currently measuring. It always needs to be lower than the highest (peak) voltage of the signal being measured. It can also be set to start recording when the signal is rising above (leading edge) or falling below (trailing edge) the voltage level chosen.
Also, if you swap IC125, it has to be the HCU version of the chip. An LS, HC or any other version of the chip is not suitable for this application.

Bryce.

[McArti0]

On Pin 39 freq should be ~4 kHz
On Pin 40 freq should be ~2-3 Hz

When Rom not set CRTC.

[Bryce]

On Pin 39 freq should be ~4 kHz
On Pin 40 freq should be ~2-3 Hz

When Rom not set CRTC.

Yes, but you should also mention that these are single "spikes" and not a nice sine wave. Willow doesn't know what to expect and might think these are just random spikes.

Bryce.

[McArti0]

That's why beter way is use oscylophone.

Pin1 expansion port connect to Pin39 crtc and hear CPC speaker. After this Pin40, pin38, pin 37 etc.

[Bryce]

That's why beter way is use oscylophone.

Pin1 expansion port connect to Pin39 crtc and hear CPC speaker. After this Pin40, pin38, pin 37 etc.

Not sure about that. That doesn't tell you exact frequencies or voltages. I'd prefer that people learn how to use the equipment they have, than use "alternative" methods to measure things. Especially when these other methods can potentially cause problems. It's also more difficult to share these readings on a forum.

Bryce.

[willow3411]

That's why beter way is use oscylophone.

Pin1 expansion port connect to Pin39 crtc and hear CPC speaker. After this Pin40, pin38, pin 37 etc.

Not sure about that. That doesn't tell you exact frequencies or voltages. I'd prefer that people learn how to use the equipment they have, than use "alternative" methods to measure things. Especially when these other methods can potentially cause problems. It's also more difficult to share these readings on a forum.

Bryce.

hi Bryce,

I'm watching tutorials to get my oscilloscope to work correctly.
I use the auto button, so I see how the Trigger works.
just one question: the mass of the oscillator probe can I take it anywhere on the motherboard? 
not on the mass of the lab power supply?
because I don't have a wire grip, I only have a hook clip at the mass of the probe (and it's a bit big).
As soon as I can take the measurements with photos I will post them.
thank you again for your patience

FYI: I set CH1 to 2v and the trigger to 1v 
It's good ?

willow

[McArti0]

At the moment we need confirmation that the CRTC is working, so 1sec pin1 exp port to pin39 CRTC and we go further. 
Then you can look for this signal on the oscilloscope, because you will know that this signal exists at all, because you heard it.

[willow3411]

hi,
@McArti0 and @Bryce

Good,
I didn't understand everything from your explanations (the translator is a little light ).
but here are my measurements using the oscilloscope's autodetect and taking the ground on a leg of a capacitor on the motherboard.
for GA 40010:
Pin 22 --> ok signal (see photos)
Pin 32 --> ok Signal (see photos)
For the CRTC:
pin 40 --> ok signal (see photos)
Pin 39 --> no signal detected
Pin 13 ---> no signal detected
this is where I am....

thanks
willow

[McArti0]

At the moment we need confirmation that the CRTC is working, so 1sec pin1 exp port to pin39 CRTC and we go further.

Do it.  do it now.

[willow3411]

At the moment we need confirmation that the CRTC is working, so 1sec pin1 exp port to pin39 CRTC

I don't understand manipulation

Pin1 exp Port ?

sorry,
thanks

[Bryce]

That's why beter way is use oscylophone.

Pin1 expansion port connect to Pin39 crtc and hear CPC speaker. After this Pin40, pin38, pin 37 etc.

Not sure about that. That doesn't tell you exact frequencies or voltages. I'd prefer that people learn how to use the equipment they have, than use "alternative" methods to measure things. Especially when these other methods can potentially cause problems. It's also more difficult to share these readings on a forum.

Bryce.

hi Bryce,

I'm watching tutorials to get my oscilloscope to work correctly.
I use the auto button, so I see how the Trigger works.
just one question: the mass of the oscillator probe can I take it anywhere on the motherboard? 
not on the mass of the lab power supply?
because I don't have a wire grip, I only have a hook clip at the mass of the probe (and it's a bit big).
As soon as I can take the measurements with photos I will post them.
thank you again for your patience

FYI: I set CH1 to 2v and the trigger to 1v 
It's good ?

willow

I usually solder a 10cm insulated wire to some point in the middle of the PCB ground plane and clip the Scope ground clip to the end of the wire. That will give the most accurate readings and allow you to probe anywhere on the board.

Those values on the CRTC aren't good. It's not doing what it should be doing.

Bryce.

[McArti0]

At the moment we need confirmation that the CRTC is working, so 1sec pin1 exp port to pin39 CRTC

I don't understand manipulation

Pin1 exp Port ?

And you must join speaker cpc and hi voice level.
Sound input pin1 ext port is only on up side pcb. Dont use crocodile! On down side is ground.

[willow3411]

At the moment we need confirmation that the CRTC is working, so 1sec pin1 exp port to pin39 CRTC

I don't understand manipulation

Pin1 exp Port ?

And you must join speaker cpc and hi voice level.
Sound input pin1 ext port is only on up side pcb. Dont use crocodile! On down side is ground.

@McArti0 

I connected pin 39 of the CRTC to pin 1 on the top of the motherboard for 1 second
the speaker crackled

[McArti0]

there is no squeak? CRTC isnt work.

Try Pin38,37,36,35,34,8,9 CRTC

Try if on Pin21 CRTC he has Clock. 1MHz

[willow3411]

there is no squeak? CRTC isnt work.

no just a little crackle of sound

[McArti0]

Try voltage on pin20 Vcc CRTC and try voltage bitween power cpc and power charger.

[willow3411]

@Bryce
@McArti0

OK, I changed my lab power supply.
I have 5v that goes into the CPC and no longer 4.6v
I have crackles on the CRTC ports 38,37,36,35,34,8,9 

I have 1mhz on pin 21 CRTC
i have 5v on pin 20 CRTC

I have a spurious signal on pin40 and pin39 with random frequency
unlike my motherboard which works where I have very clean signals on pin 40 and pin39
I learned to reflash a 40009 ROM
always black screen

[Bryce]

Is the CRTC hot when it's running?

Unfortunately everything is pointing towards a broken CRTC right now. There are a few other obscure possibilities, but they all seem extremely unlikely at this point.

Bryce.

[willow3411]

Is the CRTC hot when it's running?

Unfortunately everything is pointing towards a broken CRTC right now. There are a few other obscure possibilities, but they all seem extremely unlikely at this point.

Bryce.

@Bryce 

not too hot, I would have to compare with my second motherboard (I didn't think about it)

Well I must have been fooled 
because I bought 2 new ones (aliexpress ).
Do you have a nice address to buy this CRTC?
thanks in advance
willow

[McArti0]

maybe it's a fake chip?

[willow3411]

maybe it's a fake chip?

It's sure !!!!

[McArti0]

remove crtc and check voltage power ~5v