Hello everyone!
Here I am again with a CPC 464.
The symptoms are simple:
Black screen with LED on and no beep with LED.
I changed the GA 40010, the Z80, the ROM 40009 (also put a DIAGROM), the RAMS, IC105, IC114, IC115, as well as the CRTC.
Still the same problem.
I checked the tracks as best I could (to see if there were any cuts), I redid the soldering just in case.
I still have black screen
My dandanator doesn't show me anything at all (unlike the other failure I had: see other post).
If you can tell me the step-by-step procedure to check the components I would be delighted.
I am equipped: voltmeter, oscilloscope (I'm a beginner) and soldering station.
I also have the CPC 464 diagram which I can half understand :).
I also followed the Noellabs videos at the excellent LLOPIS, but I got a little lost.
A question to start with: at the CRTC level: Can you replace a UM6845R with an HD6845SP?
here are the photos of the motherboard
thank you for reading me,
and thank you in advance
willow
other photos
The CRTCs are interchangeable. They have differences but only noticeable to some demos and maybe some games.
For start use your oscilloscope to check the 16Mhz clock input at the GA as well as the 4Mhz input at the Z80 and 1Mhz input at the CRTC.
d_kef
Quote from: d_kef on 11:35, 14 August 24The CRTCs are interchangeable. They have differences but only noticeable to some demos and maybe some games.
For start use your oscilloscope to check the 16Mhz clock input at the GA as well as the 4Mhz input at the Z80 and 1Mhz input at the CRTC.
d_kef
Hi, Thanks for the response on the CRTC
Can you tell me which ports are used for testing with the oscilloscope?
thanks in advance
willow
Ports?
If you are not familiar with working with an oscilloscope I'd suggest to follow one of the many tutorials on YouTube.
Also I forgeot to tell you to ckeck the supply voltages on the motherboard. In fact you should start with it. The supply voltages on the ICs should be near 5V.
d_kef
@willow3411A question for you. What is the frequency of the INT signal and what circuit generates it?
What should be the CPU signal frequency?
Normally, I would start by checking power across the board to ensure I have 5V or as near to. But I also would use a bench power supply to check the current draw and limit it in the case of a short.
Hello Rabs
SO ,
I took the 5v line, I have 4.6v everywhere.
Here is the photo of my lab power supply.
I can't configure my DOS1102 oscilloscope to read the frequencies :(
thanks in advance
willow
That's too low. Try cleaning the power switch contacts or bypass the switch to check if that's the problem.
Bryce.
I think GA doesn't get voltage on the power pin through the socket.
Quote from: Bryce on 14:17, 15 August 24
That's too low. Try cleaning the power switch contacts or bypass the switch to check if that's the problem.
Bryce.
Hi Bryce,
Thank you for your help,
I bypassed the switch (see photo).
I also cleaned the power socket and redid the soldering on it.
thanks
willowQuote from: McArti0 on 14:45, 15 August 24
I think GA doesn't get voltage on the power pin through the socket.
hi McArti0,
I will check this again with the diagrams
thanks
willow
The current draw is too low and indicates to me that nothing is really running.
I have put an equivalent working board on my test rig.
20240815_154236.jpg
Quote from: Rabs on 15:56, 15 August 24The current draw is too low and indicates to me that nothing is really running.
I have put an equivalent working board on my test rig.
20240815_154236.jpg
hi,
I understood that.
but I don't know where it could come from...
I follow the tutorials and review my notes taken on other breakdowns encountered... I can't find anything there. thanks
willow
If you have extracted a lot of ICs from their sockets. The probability that all pins have the correct contact after reinsertion is small.
So.... https://www.cpcwiki.eu/forum/index.php?msg=241960
Schematic your 464 is near page 7-8 i this PDF https://www.cpcwiki.eu/manuals/Amendment%20Service%20Manual.zip
Normally once I am absolutely sure that power is correct and being provided to all ICs. I would check clock sources.
Z80 pin 6 should be about 4 Mhz maybe a little less
GA PIN 39 as above
GA PIN 8 16Mhz from the crystal logic circuit
Quote from: Rabs on 16:43, 15 August 24GA PIN 39 as above
GA PIN 8 16Mhz from the crystal logic circuit
Wrong, Wrong GA 40010, not 40007
Quote from: McArti0 on 17:47, 15 August 24Quote from: Rabs on 16:43, 15 August 24GA PIN 39 as above
GA PIN 8 16Mhz from the crystal logic circuit
Wrong, Wrong GA 40010, not 40007
Are sorry well spotted, did not notice that. What are the pins on the 40010?
24 - 16MHz yellow on Screen
19 - 4MHz yellow on Screen
14 - 1MHz (nCPU)
Your Power supply is showing 5V but the board is showing lower without an increased current. So no short, rather a series resistance. I'd check whether the power socket is clean and also look at the solder joints and traces around the power socket. Those volts must be going somewhere.
Bryce.
Quote from: Bryce on 18:51, 15 August 24Your Power supply is showing 5V but the board is showing lower without an increased current. So no short, rather a series resistance. I'd check whether the power socket is clean and also look at the solder joints and traces around the power socket. Those volts must be going somewhere.
Bryce.
Hello everyone!
Thanks for trying to help me because I'm going crazy with this card.
SO :
@bryce: I cleaned the power socket, redid the soldering above and below.I have 4.8v everywhere on the ICs.Quote from: McArti0 on 18:07, 15 August 24
24 - 16MHz yellow on Screen
19 - 4MHz yellow on Screen
14 - 1MHz (nCPU)
@McArti0
I have no signals on ports 24, 19 and 14 of the 40010...
I have another identical motherboard that works well just in case?
other ideas?
thanks in advance
willow
IC125 Pin3,Pin4 should been voltage ~2.5V on multimeter and freq 16MHz on oscilloscope.
Quote from: McArti0 on 09:06, 16 August 24IC125 Pin3,Pin4 should been voltage ~2.5V on multimeter and freq 16MHz on oscilloscope.
houla !!
it's no good for me !!
look the photos
Please note, I am not an oscilloscope pro (I am learning) thanks
willow
remove GA40010 and check again.
write clearly which photo is from pin4
did you press AutoSet?
Quote from: McArti0 on 09:47, 16 August 24did you press AutoSet?
yes !
Quote from: McArti0 on 09:37, 16 August 24remove GA40010 and check again.
write clearly which photo is from pin4
exactly the same thing
on the name of the photo I put pin 3 and pin4
ok, I guess I didn't get enough sleep ??? :laugh:
Quote from: McArti0 on 09:56, 16 August 24ok, I guess I didn't get enough sleep ??? :laugh:
hihi
What setting are you using for the x1, x10, x100 probe?
Did you calibrate the probe on a square waveform?
Did you see the full shape of the clock waveform (pin4) on the screen?
Did you adjust the image scale with the knobs?
Quote from: McArti0 on 10:11, 16 August 24What setting are you using for the x1, x10, x100 probe?
Did you calibrate the probe on a square waveform?
Did you see the full shape of the clock waveform (pin4) on the screen?
Did you adjust the image scale with the knobs?
What setting are you using for the x1, x10, x100 probe?
X10
Did you calibrate the probe on a square waveform?
yes
Did you see the full shape of the clock waveform (pin4) on the screen?
no
error message: DC voltage detected
Did you adjust the image scale with the knobs?
scale on oscillo button?
Yes.
have you manual?
Quote from: McArti0 on 10:31, 16 August 24Yes.
have you manual?
yes but is little manual for oscillo
find How set AC input
https://www.youtube.com/watch?v=01oXonkubqA&t=900s
Quote from: McArti0 on 10:38, 16 August 24find How set AC input
I switched to AC
here are the measurements
photos pin 3 and pin 4 without the 40010
thank you for your help
willow
Quote from: willow3411 on 09:32, 16 August 24@Bryce
Did you do the reflow to the solder on the top side of R126 and R128? Whoever did it either used the wrong type of solder or the iron wasn't hot enough.
Also, you seem to have incorrect settings on the scope. All the values being stated in amps (A) should be stating them in Volts (V).
Bryce.
Quote from: willow3411 on 08:48, 16 August 24I have another identical motherboard that works well just in case?
Check what your oscilloscope shows on that mainboard. But give a photo to check if it is really the same.
Quote from: Bryce on 11:19, 16 August 24Quote from: willow3411 on 09:32, 16 August 24@Bryce
Did you do the reflow to the solder on the top side of R126 and R128? Whoever did it either used the wrong type of solder or the iron wasn't hot enough.
Also, you seem to have incorrect settings on the scope. All the values being stated in amps (A) should be stating them in Volts (V).
Bryce.
hi Bryce,
I switched to Volts on the oscilloscope (at least I think) and re-soldered the resistors
always black screen
Quote from: McArti0 on 11:43, 16 August 24Quote from: willow3411 on 08:48, 16 August 24I have another identical motherboard that works well just in case?
Check what your oscilloscope shows on that mainboard. But give a photo to check if it is really the same.
@McArti0 and
@Bryce Well I compared the signals on the two motherboards.
Here are the photos.
Pin 3 and Pin 4 of IC125 with the results.
I think I found the right oscilloscope configuration (thanks for the video).
FYI no signal comes out (unknown signal) on pin 39 and 38 of the CRTC. (while I have a signal on the motherboard OK)
pin 4 on the two motherboard
Pk-Pk 4.8v is good. 0.8v is wrong. Pin 4 is used by GA.
Quote from: McArti0 on 17:41, 16 August 24Pk-Pk 4.8v is good. 0.8v is wrong. Pin 4 is used by GA.
I don't understand
sorry....
Quote from: willow3411 on 10:06, 17 August 24Quote from: McArti0 on 17:41, 16 August 24Pk-Pk 4.8v is good. 0.8v is wrong. Pin 4 is used by GA.
I don't understand
sorry....
What he's saying is, that on the working CPC your measurements show a Peak to Peak Voltage of 4.8V, but on the non-working CPC the same signal is only showing a peak to peak voltage of 800mV. This would suggest that the possible failures are: A bad solder joint in that area. A broken or "drifted" resistor (value no longer correct). Or a broken IC125.
However... As the frequencies are all present and close to what they should be, I'm not 100% sure about your measurements. It would be very difficult to get a crystal to start oscillating in those conditions. What measurement do you get on pin 8 of both computers?
Bryce.
Quote from: Bryce on 11:26, 17 August 24What he's saying is, that on the working CPC your measurements show a Peak to Peak Voltage of 4.8V, but on the non-working CPC the same signal is only showing a peak to peak voltage of 800mV. This would suggest that the possible failures are: A bad solder joint in that area. A broken or "drifted" resistor (value no longer correct). Or a broken IC125.
However... As the frequencies are all present and close to what they should be, I'm not 100% sure about your measurements. It would be very difficult to get a crystal to start oscillating in those conditions. What measurement do you get on pin 8 of both computers?
Hi Bryce,
thanks a lot.
pin 8 on IC125 ?
set your probe to x100.
where do you attach the probe ground?
Quote from: willow3411 on 15:19, 17 August 24Quote from: Bryce on 11:26, 17 August 24What he's saying is, that on the working CPC your measurements show a Peak to Peak Voltage of 4.8V, but on the non-working CPC the same signal is only showing a peak to peak voltage of 800mV. This would suggest that the possible failures are: A bad solder joint in that area. A broken or "drifted" resistor (value no longer correct). Or a broken IC125.
However... As the frequencies are all present and close to what they should be, I'm not 100% sure about your measurements. It would be very difficult to get a crystal to start oscillating in those conditions. What measurement do you get on pin 8 of both computers?
Hi Bryce,
thanks a lot.
pin 8 on IC125 ?
The CLK input pin of the GA.
@McArti0: I doubt he has a x100 probe, I hope he is using 10x though and not 1x. But I also meant to ask the other question earlier: Where are you connecting to the CPC GND for these measurements?
Bryce.
Quote from: McArti0 on 15:36, 17 August 24set your probe to x100.
where do you attach the probe ground?
Quote from: Bryce on 16:10, 17 August 24Quote from: willow3411 on 15:19, 17 August 24Quote from: Bryce on 11:26, 17 August 24What he's saying is, that on the working CPC your measurements show a Peak to Peak Voltage of 4.8V, but on the non-working CPC the same signal is only showing a peak to peak voltage of 800mV. This would suggest that the possible failures are: A bad solder joint in that area. A broken or "drifted" resistor (value no longer correct). Or a broken IC125.
However... As the frequencies are all present and close to what they should be, I'm not 100% sure about your measurements. It would be very difficult to get a crystal to start oscillating in those conditions. What measurement do you get on pin 8 of both computers?
Hi Bryce,
thanks a lot.
pin 8 on IC125 ?
The CLK input pin of the GA.
@McArti0: I doubt he has a x100 probe, I hope he is using 10x though and not 1x. But I also meant to ask the other question earlier: Where are you connecting to the CPC GND for these measurements?
Bryce.
Thank you both for trying to help me.
I really appreciate it.
So I have an X10 probe with my HANMATEK DOS1102. The problem is that I still have big gaps in making it work and above all understanding how it works and its logic.
for the mass I take it from the CPC power socket or directly from my lab power supply.
Is this the right procedure?
I suspect that my oscilloscope is incorrectly adjusted...
I'm going to take the signal on pin 8 of the GA.
thanks again
willow
Quote from: Bryce on 16:10, 17 August 24Quote from: willow3411 on 15:19, 17 August 24Quote from: Bryce on 11:26, 17 August 24What he's saying is, that on the working CPC your measurements show a Peak to Peak Voltage of 4.8V, but on the non-working CPC the same signal is only showing a peak to peak voltage of 800mV. This would suggest that the possible failures are: A bad solder joint in that area. A broken or "drifted" resistor (value no longer correct). Or a broken IC125.
However... As the frequencies are all present and close to what they should be, I'm not 100% sure about your measurements. It would be very difficult to get a crystal to start oscillating in those conditions. What measurement do you get on pin 8 of both computers?
Hi Bryce,
thanks a lot.
pin 8 on IC125 ?
The CLK input pin of the GA.
@McArti0: I doubt he has a x100 probe, I hope he is using 10x though and not 1x. But I also meant to ask the other question earlier: Where are you connecting to the CPC GND for these measurements?
Bryce.
hi Bryce,
here is my connection and measurements pin 8 on GA 40010.
the first on an ok motherboard and the second on an HS motherboard.
At each measurement I press the "self-test" key on the oscilloscope.
thanks
willow
Sorry, I didn't realise your 464 had a 40010. On a 40010 you should be measuring the signal on pin 24. It should have a clean 16MHz signal on it. If it does, all components (including IC125) in the clock generation circuit are good. Do both computers have a 40010 GA?
Your latest measurements were also partially useful too though. Pin 8 on a 40010 GA is the Blue output signal to the monitor. The good CPC shows exactly what would be expected. The broken computer is just showing noise.
My guess at the moment is that the CRTC has bad solder joints.
Bryce.
First I want to see 16MHz Pk-Pk on pin4 IC125.
ps. what's meaning HS?
Quote from: Bryce on 19:22, 17 August 24Sorry, I didn't realise your 464 had a 40010. On a 40010 you should be measuring the signal on pin 24. It should have a clean 16MHz signal on it. If it does, all components (including IC125) in the clock generation circuit are good. Do both computers have a 40010 GA?
Your latest measurements were also partially useful too though. Pin 8 on a 40010 GA is the Blue output signal to the monitor. The good CPC shows exactly what would be expected. The broken computer is just showing noise.
My guess at the moment is that the CRTC has bad solder joints.
Bryce.
hi Bryce !
yes it's 40010 on both motherboards.
so here are the measurements.
first my power supply connected to the motherboard with black screen (Out of Service).
The first photos are the measurements on the GA 40010 pin 24.
the last two, the measurements on Pin4 of IC125
(for information my oscilloscope was configured in DC and not in AC!!).
thanks.
Willow
Quote from: McArti0 on 22:20, 17 August 24First I want to see 16MHz Pk-Pk on pin4 IC125.
ps. what's meaning HS?
HS = black screen
Ok (meaning not ok).
Now connect Pin1 IC125 to ground and multimeter to pin 3. Voltage should be ~5V.
connect Pin1 IC125 to ground and multimeter to pin 4. Voltage should be ~0V.
connect Pin1 IC125 to 5V and multimeter to pin 3. Voltage should be ~0V.
connect Pin1 IC125 to 5V and multimeter to pin 4. Voltage should be ~5V.
beter without GA40010
Quote from: McArti0 on 09:08, 18 August 24Ok (meaning not ok).
Now connect Pin1 IC125 to ground and multimeter to pin 3. Voltage should be ~5V.
connect Pin1 IC125 to ground and multimeter to pin 4. Voltage should be ~0V.
connect Pin1 IC125 to 5V and multimeter to pin 3. Voltage should be ~0V.
connect Pin1 IC125 to 5V and multimeter to pin 4. Voltage should be ~5V.
hello,
I disconnect the motherboard from the 5v?
No.
I told you ADD small connection. 5V You have on Pin 14. Ground You have on Pin7. for .ex.
ps, its test of 74HCU04
Quote from: McArti0 on 09:16, 18 August 24No.
I told you ADD small connection. 5V You have on Pin 14. Ground You have on Pin7. for .ex.
ps, its test of 74HCU04
OK, I understand.
Sorry for my ignorance, but my English is a bit poor hihi.
I don't have the pliers required to take the right measurements without risk.
I'm going to order them (grip pliers).
thank you for your patience
willow
Here isnt risk. currents are very small.
Check only Pin1 to ground. Pin4 should be 0V
Quote from: McArti0 on 09:40, 18 August 24Here isnt risk. currents are very small.
Check only Pin1 to ground. Pin4 should be 0V
ok
So to summarize and if I understood correctly:
I supply the motherboard with 5v without the GA.
I supply IC125 with 5v on pin 14 and ground on pin 7.
then I take the measurement with the multimeter on pin 1 and 4?
is that right?
willow
Yes but Pin14 always have 5v and pin7 ground.
You don't have to do anything with pin14 and pin7.
Hi,
please don't do any jumper tests. Just measure the frequency on CLK input of the GA. The pin numbers that McArti0 is referring to are from the 6128 and later 464's. Original 464's used this chip differently and pin 4 is NOT the output of the clock circuit. So I don't think you should be comparing the pins 1 to 1 on these two computers and bridging 5V to an unknown point could damage your computer.
If there is a good 16MHz signal on the CLK input of the GA, then the clock circuitry is fine. One test, no jumpers.
Bryce.
@Bryce You confused IC125 for 464 with IC117 for 6128
I checked schem 464 with two GA socket and photo.
Quote from: Bryce on 11:27, 18 August 24Hi,
please don't do any jumper tests. Just measure the frequency on CLK input of the GA. The pin numbers that McArti0 is referring to are from the 6128 and later 464's. Original 464's used this chip differently and pin 4 is NOT the output of the clock circuit. So I don't think you should be comparing the pins 1 to 1 on these two computers and bridging 5V to an unknown point could damage your computer.
If there is a good 16MHz signal on the CLK input of the GA, then the clock circuitry is fine. One test, no jumpers.
Bryce.
hi Bryce,
ok I understand !
so my measurements are good?
Quote from: McArti0 on 12:00, 18 August 24@Bryce You confused IC125 for 464 with IC117 for 6128
I checked schem 464 with two GA socket and photo.
hi,
So here is my measurement with the multimeter.
this oscillates between 0.02V and 0.06v
and I'm 4.7V to pin 14 and pin 7
it's good ?
Jump pin1 ic125 to ground and check pin4 by multimeter.
Quote from: willow3411 on 12:02, 18 August 24Quote from: Bryce on 11:27, 18 August 24Hi,
please don't do any jumper tests. Just measure the frequency on CLK input of the GA. The pin numbers that McArti0 is referring to are from the 6128 and later 464's. Original 464's used this chip differently and pin 4 is NOT the output of the clock circuit. So I don't think you should be comparing the pins 1 to 1 on these two computers and bridging 5V to an unknown point could damage your computer.
If there is a good 16MHz signal on the CLK input of the GA, then the clock circuitry is fine. One test, no jumpers.
Bryce.
hi Bryce,
ok I understand !
so my measurements are good?
The frequency is good, but the voltages are wrong. Can you check the resistance of R143, 144 and 145?
Bryce.
Quote from: Bryce on 12:26, 18 August 24Quote from: willow3411 on 12:02, 18 August 24Quote from: Bryce on 11:27, 18 August 24Hi,
please don't do any jumper tests. Just measure the frequency on CLK input of the GA. The pin numbers that McArti0 is referring to are from the 6128 and later 464's. Original 464's used this chip differently and pin 4 is NOT the output of the clock circuit. So I don't think you should be comparing the pins 1 to 1 on these two computers and bridging 5V to an unknown point could damage your computer.
If there is a good 16MHz signal on the CLK input of the GA, then the clock circuitry is fine. One test, no jumpers.
Bryce.
hi Bryce,
ok I understand !
so my measurements are good?
The frequency is good, but the voltages are wrong. Can you check the resistance of R143, 144 and 145?
Bryce.
Hi Bryce,
so I soldered a leg to each resistor to take the measurements.
On
R143: 9.47 Mohms
R144: 4.671 Kohms
R145: 9.97 Mohms
I think it's good if I understand the electronic diagram correctly
No ?
Thanks
willow
Quote from: McArti0 on 12:20, 18 August 24Jump pin1 ic125 to ground and check pin4 by multimeter.
Quote from: McArti0 on 16:19, 18 August 24Quote from: McArti0 on 12:20, 18 August 24Jump pin1 ic125 to ground and check pin4 by multimeter.
hi, McArti0
I put pin1 to ground and measured pin4, I have 1.8V
on pin3 4.7v
Pin 4 should have about 0.1V. The inverter between pin 3 and pin 4 is damaged. IC125 (74HCU04) is damaged.
Quote from: McArti0 on 16:30, 18 August 24Pin 4 should have about 0.1V. The inverter between pin 3 and pin 4 is damaged. IC125 (74HCU04) is damaged.
hi,
ok,
I'm going to see if I have stock on this component to do a test...
This is not due to the fact that I only have 4.7v entering the CPC just after the power socket?
THANKS
I will test and get back to you.
willow
Quote from: willow3411 on 16:36, 18 August 24This is not due to the fact that I only have 4.7v entering the CPC just after the power socket?
No.
Look at manual this IC...
https://www.ti.com/lit/gpn/sn74hcu04
For power supply vcc=4.5v, ViH= 3,6v - is interpreted as Hi.
Quote from: McArti0 on 16:30, 18 August 24Pin 4 should have about 0.1V. The inverter between pin 3 and pin 4 is damaged. IC125 (74HCU04) is damaged.
hi,
so I changed IC125 (put on support and taken from a CPC 6128 donor motherboard).
I took the measurements on pin4, I have 0.2V and on pin3 4.5v and pin 1 on the ground
frequency level:
pin6 Z80: 4Mhz
Pin 24 GA 40010: 16Mhz
Pin 19 GA 40010: 4Mhz
Pin 14 GA 40010: 1Mhz
Results : Black Screen
@Bryce
@McArti0
Greate! GA work.
Now CRTC.
Pin 39 Hsync
Pin 40 Vsync
Pin 13 MA9
any Freq?
GA
Pin32 INT
Pin22 Ready/Wait
any freq?
Quote from: McArti0 on 18:15, 18 August 24Greate! GA work.
Now CRTC.
Pin 39 Hsync
Pin 40 Vsync
Pin 13 MA9
any Freq?
GA
Pin32 INT
Pin22 Ready/Wait
any freq?
hi
@McArti0 Now CRTC.
Pin 39 Hsync: Random frequency
Pin 40 Vsync: Random frequency
Pin 13 MA9: random frequency
GA
Pin32 INT: OK
Pin22 Ready/Wait: OK
So to summarize:
when I take the measurements three times in a row, the oscilloscope shows me no signal detected but finds a frequency (I think it's noise, right?)
This does it to me on the CRTC.
Or maybe I didn't get the mass right.
FYI the CRTC is new and changed twice
Thanks
can You use triger? in oscylo.
Quote from: McArti0 on 19:21, 18 August 24can You use triger? in oscylo.
arff ; i not understand .... triger ??
Check CRTC pin 39 but first pin4 GA cclk 2MHz
Quote from: willow3411 on 19:22, 18 August 24Quote from: McArti0 on 19:21, 18 August 24can You use triger? in oscylo.
arff ; i not understand .... triger ??
yes !! is good i'm looking triger on the oscillo : 3.6v
signal detected
Quote from: McArti0 on 19:34, 18 August 24Check CRTC pin 39 but first pin4 GA cclk 2MHz
pin4 GA cclk 1Mhz !!
CRTC pin 39 random frequency
ok cclk 1MHz.
pin39 crtc. What's you see on oscylo and stable by trigger
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.
On Pin 39 freq should be ~4 kHz
On Pin 40 freq should be ~2-3 Hz
When Rom not set CRTC.
Quote from: McArti0 on 20:01, 18 August 24On 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.
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.
Quote from: McArti0 on 20:30, 18 August 24That'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.
Quote from: Bryce on 07:53, 19 August 24Quote from: McArti0 on 20:30, 18 August 24That'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
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.
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
Quote from: McArti0 on 08:42, 19 August 24At the moment we need confirmation that the CRTC is working, so 1sec pin1 exp port to pin39 CRTC and we go further.
Do it. ;D do it now. 8)
Quote from: McArti0 on 08:42, 19 August 24At 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
Quote from: willow3411 on 08:00, 19 August 24Quote from: Bryce on 07:53, 19 August 24Quote from: McArti0 on 20:30, 18 August 24That'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.
Quote from: willow3411 on 09:31, 19 August 24Quote from: McArti0 on 08:42, 19 August 24At 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.
Quote from: McArti0 on 09:47, 19 August 24Quote from: willow3411 on 09:31, 19 August 24Quote from: McArti0 on 08:42, 19 August 24At 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
there is no squeak? CRTC isnt work. :-X
Try Pin38,37,36,35,34,8,9 CRTC
Try if on Pin21 CRTC he has Clock. 1MHz
Quote from: McArti0 on 17:24, 19 August 24there is no squeak? CRTC isnt work. :-X
no just a little crackle of sound
Try voltage on pin20 Vcc CRTC and try voltage bitween power cpc and power charger.
@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
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.
Quote from: Bryce on 19:39, 19 August 24Is 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
maybe it's a fake chip?
https://www.youtube.com/watch?v=12u_hBkHB88
Quote from: McArti0 on 20:08, 19 August 24maybe it's a fake chip?
https://www.youtube.com/watch?v=12u_hBkHB88
It's sure !!!!
remove crtc and check voltage power ~5v
Never buy retro chips from Aliexpress. China wasn't involved in either chip production or product assembly back then. With modern chips there's a chance that Aliexpress has genuine left over stock, but with retro chips... Why would those chips ever have been there?
There are several EU sellers on ebay where you can get CRTC's that are either old stock or have been removed from old equipment.
Bryce.
https://www.youtube.com/watch?v=XfvnLdiuokM
@Bryce @McArti0 Hi,
me again: the pain :)
Come on, let me move forward a little...
I replaced the CRTC (taken from a donor CPC 6128 motherboard).
I did the oscillophone test.
Test OK
I have a signal on pin 39
on the other hand no signal on Pin40 :(
1Mhz on pin21
thanks
willow
If you listen carefully, there should be ticks on pin40 approximately every 0,5 seconds.
Quote from: McArti0 on 10:30, 20 August 24If you listen carefully, there should be ticks on pin40 approximately every 0,5 seconds.
I don't have ticks on pin 40 nor on pin 39 (like in your video)
Now check pin32 GA. Should be freq of pin39 crtc divide by 52. ~150 Hz. Somethink like brum.
Quote from: McArti0 on 10:47, 20 August 24Now check pin32 GA. Should be freq of pin39 crtc divide by 52. ~150 Hz. Somethink like brum.
random frequency on pin 32 of the GA.
one shot 7Mhz
one shot 17Mhz
suddenly 10Mhz...
With an oscilloscope you have to work the horizontal knob.
Check if you can see the signal from pin 39 of the crtc, because you heard it is there.
And pin 32 GA first check with an oscillophone.
Quote from: McArti0 on 11:48, 20 August 24With an oscilloscope you have to work the horizontal knob.
Check if you can see the signal from pin 39 of the crtc, because you heard it is there.
And pin 32 GA first check with an oscillophone.
So on pin 32 of the GA --> no sound
and no signal
I adjusted the horizontal each time.
I configured the oscillator at 2v and the trigger at 3.6v
I have no signal on pin 39 of the CRTC (which does not beep on the oscillophone)
on pin 40 of crtc random signal
I'm going crazy!!!
I'm going to reread the entire post and start from scratch because I'm getting lost with all these measurements..
thank you once again
willow
Forget about pin32 GA. No IC is configured by software.
The fact that you can't catch a signal on an oscilloscope from pin39 of the crtc shows that it's too early for you to use an oscilloscope on a broken CPC. You can test difficult signals on a working CPC. An oscillophone is better, simpler and cheaper. Besides, an oscillophone is retro :D
Now check if the Z80 works. On the oscilloscope, check the M1 pin27, MREQ pin19 and RD pin21 signal and A0 pin30. These won't be constant frequencies, but there will be life on them at about 1MHz.
Quote from: willow3411 on 09:51, 20 August 24I have a signal on pin 39
Quote from: willow3411 on 10:39, 20 August 24nor on pin 39 (like in your video)
What have You and what haven't you?
Quote from: McArti0 on 17:48, 20 August 24Forget about pin32 GA. No IC is configured by software.
The fact that you can't catch a signal on an oscilloscope from pin39 of the crtc shows that it's too early for you to use an oscilloscope on a broken CPC. You can test difficult signals on a working CPC. An oscillophone is better, simpler and cheaper. Besides, an oscillophone is retro :D
Now check if the Z80 works. On the oscilloscope, check the M1 pin27, MREQ pin19 and RD pin21 signal and A0 pin30. These won't be constant frequencies, but there will be life on them at about 1MHz.
Pin27 ---> 35Mhz
Pin19 ---> 32 Mhz
Pin21 ---> 32 Mhz
Pin30 ----> No signal
Z80 it's hot but works on the other motherboard
Quote from: McArti0 on 17:53, 20 August 24Quote from: willow3411 on 09:51, 20 August 24I have a signal on pin 39
Quote from: willow3411 on 10:39, 20 August 24nor on pin 39 (like in your video)
What have You and what haven't you?
Not the ticks on pin39
Quote from: willow3411 on 09:51, 20 August 24I did the oscillophone test.
Test OK
Test not OK?
First you need to know how to control an oscilloscope without an automaton. Find out how to set V/div vertically and ms/div or us/div. horizontally.
Quote from: McArti0 on 18:20, 20 August 24Quote from: willow3411 on 09:51, 20 August 24I did the oscillophone test.
Test OK
Test not OK?
Yes pin 40 , 38,37,36,35.... without pin39 no Sound
Has pin39 sound?
Quote from: McArti0 on 19:00, 20 August 24Has pin39 sound?
Sorry,
No sound pin39
Sound Pin 38,37,36,35....
clic on pin40
Quote from: McArti0 on 18:26, 20 August 24First you need to know how to control an oscilloscope without an automaton. Find out how to set V/div vertically and ms/div or us/div. horizontally.
but I can't find a good tutorial.
So I watch the Noel's Retro Labs video.
I look at how he configured his oscilloscope
V/div vertically: 2v
ms/div: 800ns
us/div. horizontally: 2.88v
Is it good?
I have a lot of trouble understanding how this oscilloscope works.
Oscilloscop show fast history of voltage. Left -Right you have time, up down you have voltage. How many time you see on screen you set by scale horizontal knob. Thats all.
Quote from: willow3411 on 19:04, 20 August 24Quote from: McArti0 on 18:26, 20 August 24First you need to know how to control an oscilloscope without an automaton. Find out how to set V/div vertically and ms/div or us/div. horizontally.
but I can't find a good tutorial.
So I watch the Noel's Retro Labs video.
I look at how he configured his oscilloscope
V/div vertically: 2v
ms/div: 800ns
us/div. horizontally: 2.88v
Is it good?
I have a lot of trouble understanding how this oscilloscope works.
You mentioned earlier, that your trigger is set to 3.6V. This is too high to catch weak signals. You should set it to 1V to make sure that you catch everything.
Bryce.
Quote from: Bryce on 09:50, 21 August 24Quote from: willow3411 on 19:04, 20 August 24Quote from: McArti0 on 18:26, 20 August 24First you need to know how to control an oscilloscope without an automaton. Find out how to set V/div vertically and ms/div or us/div. horizontally.
but I can't find a good tutorial.
So I watch the Noel's Retro Labs video.
I look at how he configured his oscilloscope
V/div vertically: 2v
ms/div: 800ns
us/div. horizontally: 2.88v
Is it good?
I have a lot of trouble understanding how this oscilloscope works.
You mentioned earlier, that your trigger is set to 3.6V. This is too high to catch weak signals. You should set it to 1V to make sure that you catch everything.
Bryce.
hi,
ok it's good for me
Quote from: McArti0 on 19:27, 20 August 24Oscilloscop show fast history of voltage. Left -Right you have time, up down you have voltage. How many time you see on screen you set by scale horizontal knob. Thats all.
I'm starting to understand how the oscilloscope works.
I just watched 3 hours of video on oscilloscopes :).
so I will take all the measures requested in the post.
with my motherboard working and then with the motherboard broken.
If I understood correctly, when I do not have a frequency displayed in my oscilloscope table. Should I move the scale button?
thank you very much to both of you.
I swear I will get there!!
willow
There are signals that do not have one characteristic frequency. Think about it. Two short voltage pulses and one longer one and so on and so forth. This does not have one specific frequency.
Ps. Touch the probe with your finger. You will have a frequency of 50Hz and turn the horiz scale knob left and right.
@Bryce @McArti0 hello !
here are the different measurements taken on the motherboard which works very well.
Z80 Pin 6 : 1Mhz
GA 40010 Pin 24 : 4Khz
GA 40010 Pin 19 : 1Mhz
GA 40010 Pin 14 : 250Hz ( ????)
CRTC Pin 39 : 15Khz
CRTC Pin 40 : ????(( no frequency )
CRTC Pin 13 : ????(( no frequency )
CRTC Pin 21 : 1Mhz
GA 40010 Pin 22 : 1Mhz
GA 40010 Pin 4 ( cclk ) : 1Mhz
Voltage CRTC Pin 20 : 4.725v
Z80 Pin 27 : 355Khz
Z80 Pin 19 : 1.333 Mhz
Z80 Pin 21 : 696Khz
Z80 Pin 30 : 357Khz
I repeat that it is the motherboard which works very well.
At the oscilloscope level:
2Volts probe in X10
Trigger 1v
then I modulate Scale Horizontal over time.
I don't use automatic measurement
Am I all right?
now I can take the same measurements on the broken motherboard...
I await your reply.
Thanks again for the advice.
Quote from: willow3411 on 16:40, 21 August 24GA 40010 Pin 14 : 250Hz ( ????) 300Hz
CRTC Pin 40 : ????(( no frequency ) 50Hz check by oscyllophone!
CRTC Pin 13 : ????(( no frequency )
CRTC Pin 21 : 1Mhz
Pin40 crtc - you should set horis. scale 2-5ms /div.
Quote from: McArti0 on 17:01, 21 August 24Quote from: willow3411 on 16:40, 21 August 24GA 40010 Pin 14 : 250Hz ( ????) 300Hz
CRTC Pin 40 : ????(( no frequency ) 50Hz check by oscyllophone!
CRTC Pin 13 : ????(( no frequency )
CRTC Pin 21 : 1Mhz
Pin40 crtc - you should set horis. scale 2-5ms /div.
I'm confirm
GA 40010 Pin 14 : 255Hz
And yes
CRTC Pin 40 : 50Hz ( it's good with scale 5ms /div and CH1 2Volts with TRIGGER 1v )
i'm repeat :it's the motherboard that works
300Hz 8)
Now you need to know one thing.
The program that is in the ROM at the very beginning configures the CRTC and GA. If you want to see how the CPC works, functional but not configured. You can turn off the ROM by applying +5V to ROMDIS. (Pin22 ROM IC103 or top end R112). And turn On CPC
Quote from: McArti0 on 17:38, 21 August 24300Hz 8)
Now you need to know one thing.
The program that is in the ROM at the very beginning configures the CRTC and GA. If you want to see how the CPC works, functional but not configured. You can turn off the ROM by applying +5V to ROMDIS. (Pin22 ROM IC103 or top end R112). And turn On CPC
OK thanks
I will test this
For now I would like to understand and above all make my motherboard which has a black screen work.
ps: I confirm that I have 250Hz on pin14 of the GA
what can I do now?
I am disappointed...
For now you are gathering knowledge to understand what you are doing.
You fixed the clock. You started CRTC and GA. Now you know that Z80 does not execute configuration code from ROM.
Quote from: McArti0 on 17:52, 21 August 24For now you are gathering knowledge to understand what you are doing.
You fixed the clock. You started CRTC and GA. Now you know that Z80 does not execute configuration code from ROM.
yes
what I mean is that the measurements taken just before come from my functional motherboard
Quote from: willow3411 on 17:57, 21 August 24Quote from: McArti0 on 17:52, 21 August 24For now you are gathering knowledge to understand what you are doing.
You fixed the clock. You started CRTC and GA. Now you know that Z80 does not execute configuration code from ROM.
yes
what I mean is that the measurements taken just before come from my functional motherboard
Hi,
I,m burned eeprom rom 40009 . It's not ok ....
Sorry i'm with m'y phone....
Willow
@Bryce @McArti0 now we should test the ROM right?
Do you want the measurements of the faulty motherboard?
THANKS
Do you have a ROM programmer and can you check the correctness of the input in it?
Quote from: McArti0 on 11:38, 22 August 24Avez-vous un programmateur ROM et pouvez-vous vérifier l'exactitude de l'entrée qu'il contient ?
oui j'ai un programmateur t48. j'ai déjà flashé un 40009 mais ça ne marche toujours pas.
je dois le tester avec le programmeur ?
Some device must tell you that the ROM contents were burned successfully.
Quote from: McArti0 on 11:51, 22 August 24Some device must tell you that the ROM contents were burned successfully.
yes it is. no worries on that side
anyway I even have a diagROM.
and even with it I have black screen.
Also with my Dandanator black screen.
If that's the case, then something else is permanently holding an Address or Data bit high or low. Use the scope to see if there is any bit on those buses that never changes.
Bryce.
Quote from: Bryce on 11:15, 23 August 24If that's the case, then something else is permanently holding an Address or Data bit high or low. Use the scope to see if there is any bit on those buses that never changes.
Bryce.
hi
@Bryce hi,
Which Buses do you want to talk about?
the frequencies measured on the GA, the Z80 and the CRTC?
is that right?
THANKS
Lines D0,D1,D2...D7 at z80, 8255 or crtc.
And A0,A1.... A15 z80
Quote from: McArti0 on 11:45, 23 August 24Lines D0,D1,D2...D7 at z80, 8255 or crtc.
And A0,A1.... A15 z80
hi
@McArti0 ,
Ok so if I understood correctly the frequency must not be the same at each measurement (3 times in a row is it good?)
thanks
Not freq. Any Changes.
Quote from: McArti0 on 11:53, 23 August 24Not freq. Any Changes.
???
No understand.... sorry....
https://m.youtube.com/watch?v=QjEyjmNkN3k
Quote from: McArti0 on 12:02, 23 August 24https://m.youtube.com/watch?v=QjEyjmNkN3k
heu....
humor ?... :)
Yes but no..
if you see flat line , that signal is suspect to be dead.
Quote from: McArti0 on 16:19, 23 August 24Yes but no..
if you see flat line , that signal is suspect to be dead.
:) :) :)
I understood everything