Author Topic: What more i can do?  (Read 37013 times)

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Offline Harry_22

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Re: What more i can do?
« Reply #125 on: November 11, 2024, 10:29:04 am »
Ok, there is a signal on the screen that has at least 20V value.
Did you use a probe with voltage divider?
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #126 on: November 11, 2024, 12:33:02 pm »
Ok, there is a signal on the screen that has at least 20V value.
Did you use a probe with voltage divider?
i used a regular probe.
 

Offline Harry_22

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Re: What more i can do?
« Reply #127 on: November 11, 2024, 01:04:13 pm »
Ok, there is a signal on the screen that has at least 20V value.
Did you use a probe with voltage divider?
i used a regular probe.

Check Vcc voltage on pin 5 IC1 (MB3771).
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #128 on: November 11, 2024, 01:57:08 pm »
Ok, there is a signal on the screen that has at least 20V value.
Did you use a probe with voltage divider?
i used a regular probe.

Check Vcc voltage on pin 5 IC1 (MB3771).

High 4.7v
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #129 on: November 11, 2024, 02:38:51 pm »
Harry

Can you explain or tell me what you been thinking or trying to do?
Maybe i can do some helps on it.

Did you have any ideas where we going or you are also testing everything and watching ICs like me.
If you have any potential causes or doubts on any of Motherboard ICs then let me know.
 

Offline Harry_22

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Re: What more i can do?
« Reply #130 on: November 11, 2024, 05:17:07 pm »
Harry

Can you explain or tell me what you been thinking or trying to do?
Maybe i can do some helps on it.

Did you have any ideas where we going or you are also testing everything and watching ICs like me.
If you have any potential causes or doubts on any of Motherboard ICs then let me know.
I just try to understand your measurements.
We cannot move forward without a clear picture of submitted measurements.

Please see the picture below.
The first yellow line is absolutely clear. This is Output Enable# on working board. Blue line has no base level. Is it High level or Low?
Reset# signal scares me. Where did 20 volts come from? Maybe I missed something?

Honestly, I have no idea where to go next. Let's worry gradually.

PS
Look at the neat pictures I'm returning to you. Nothing is upside down.
« Last Edit: November 12, 2024, 06:58:39 am by Harry_22 »
 

Offline Harry_22

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Re: What more i can do?
« Reply #131 on: November 11, 2024, 10:32:33 pm »
I trust you that the Reset# signal is good.
But I want the oscilloscope to see it too.
Please get a similar picture on his screen.
« Last Edit: November 11, 2024, 10:46:12 pm by Harry_22 »
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #132 on: November 11, 2024, 11:47:08 pm »
I trust you that the Reset# signal is good.
But I want the oscilloscope to see it too.
Please get a similar picture on his screen.

The First Image is non working board and second is working board.

Its same no different at all.
« Last Edit: November 12, 2024, 05:05:28 am by 222Lab_Test222 »
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #133 on: November 12, 2024, 12:27:46 am »

The first yellow line is absolutely clear. This is Output Enable# on working board. Blue line has no base level. Is it High level or Low?


BIOS OUTPUT ENABLE PIN updated image
Non Working board, The blue line no base lvl one, There were some issues in probe i guess in blue one, so i tried changing the probe.
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #134 on: November 12, 2024, 12:33:31 am »
We need more helping hands, i spent so much time and you Harry too on it, BUT still the progress is same.

We are getting nowhere, I am going on round and round, Its like a dead trap and looping all around.  :phew:

So, If any more people interested and who are well working in this fields with high experience especially working since 90s will be big helpful as it is 90s board, they are welcome.

Lets get it done guys. :-+
 

Offline Harry_22

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Re: What more i can do?
« Reply #135 on: November 12, 2024, 05:14:13 am »
Well done!
You will succeed.
The darkest hour is just before the dawn.

Now stay the first channel on Reset# pin as it is.
Connect the second channel to Bios Output Enable#.
Play with Time/Div.
Please remember you will get a signal at every power on.

PS
You have already changed the channels. Perfect!
« Last Edit: November 12, 2024, 05:16:59 am by Harry_22 »
 

Offline Harry_22

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Re: What more i can do?
« Reply #136 on: November 12, 2024, 05:22:34 am »
Our problem now is the time difference. My head doesn't work very well in the morning. Therefore, look at the signals now at your discretion. Be sure to use the reset signal start. After all, we are only interested in the moment the computer starts
 

Offline Harry_22

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Re: What more i can do?
« Reply #137 on: November 12, 2024, 05:32:29 am »
Look at the noise that appears when you turn on a running machine. It is very significant and says a lot.
We have to check CLK signals as well.
Look at the Data and Address buses.
Shit The problem lies somewhere in this circle.
« Last Edit: November 13, 2024, 05:43:26 pm by Harry_22 »
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #138 on: November 12, 2024, 05:49:22 am »
Look at the noise that appears when you turn on a running machine. This is very significant.
We have to check CLK signals as well.
Look at the Data and Address buses.
Shit The problem lies somewhere in this circle.

What type of noise it could be?
Does the voltage regulator may causes such type of issues? We have LT1085 voltage regulator.
 

Offline Harry_22

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Re: What more i can do?
« Reply #139 on: November 12, 2024, 05:59:18 am »
No, this is noise of life.
This is a good noise.
« Last Edit: November 12, 2024, 06:08:39 am by Harry_22 »
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #140 on: November 12, 2024, 06:09:47 am »

Now stay the first channel on Reset# pin as it is.
Connect the second channel to Bios Output Enable#.
Play with Time/Div.
Please remember you will get a signal at every power on.
Non Working Board 1st image, Working Board 2nd image
Yellow is reset pin, blue is OP ENABLE
 

Offline Harry_22

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Re: What more i can do?
« Reply #141 on: November 12, 2024, 06:26:40 am »
Just like a picture from a radio engineer's handbook. Nice to see!
Check for 66 MHz quartz. One pin should work. Use the probe 1:10 if possible.
« Last Edit: November 12, 2024, 06:57:17 am by Harry_22 »
 

Offline Harry_22

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Re: What more i can do?
« Reply #142 on: November 12, 2024, 07:16:29 am »
Do the following for me.
On the working board press your finger against the 66 MHz crystal pins. Then turn it on and listen for beep.
If it doesn't help, lightly wet your finger and try again.
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #143 on: November 12, 2024, 07:31:34 am »
Do the following for me.
On the working board press your finger against the 66 MHz crystal pins. Then turn it on and listen for beep.
If it doesn't help, lightly wet your finger and try again.

I Tried, Even when i didn't press, its a one tone beep always on starting of motherboard.

After I pressed, I did not see any changes, I used alcohol as well BUT its same beep, not a different one.
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #144 on: November 12, 2024, 07:39:13 am »
Just like a picture from a radio engineer's handbook. Nice to see!
Check for 66 MHz quartz. One pin should work. Use the probe 1:10 if possible.

In working as well as non working board its same, I see a wave and a 66MHz frequency.
 

Offline Harry_22

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Re: What more i can do?
« Reply #145 on: November 12, 2024, 08:31:48 am »

In working as well as non working board its same, I see a wave and a 66MHz frequency.

Try to stop it as I described above (you can unsolder it) and watch the beep. On working board.

I have a question.
What do these two LEDs do? (Please see the picture below.)

Also don't forget to stop CPU clock (66MHz) and check the beep sound.

PS
At the bottom picture you will find some curves explanation.
« Last Edit: November 12, 2024, 03:03:57 pm by Harry_22 »
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #146 on: November 12, 2024, 03:12:15 pm »

In working as well as non working board its same, I see a wave and a 66MHz frequency.

Try to stop it as I described above (you can unsolder it) and watch the beep. On working board.

I have a question.
What do these two LEDs do? (Please see the picture below.)

Also don't forget to stop CPU clock (66MHz) and check the beep sound.

PS
At the bottom picture you will find some curves explanation.

Red Led is blink at startup power on, it also keep on glowing if the voltage is less than 4v, regarding other uses not sure.
Green Led refers to the ok board, If it glows continuosly, not bright nor dim, then the motherboard is ok.

Still, i need more details on stopping to those CLOCK signals, desolder is not possible i guess, Maybe any other options.

As for the Pics, Yeah the BIOS is not getting input signals to process so BIOS not loading in non working board i guess.
 

Offline Harry_22

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Re: What more i can do?
« Reply #147 on: November 12, 2024, 07:47:29 pm »

Red Led is blink at startup power on, it also keep on glowing if the voltage is less than 4v, regarding other uses not sure.
Green Led refers to the ok board, If it glows continuosly, not bright nor dim, then the motherboard is ok.

Still, i need more details on stopping to those CLOCK signals, desolder is not possible i guess, Maybe any other options.

As for the Pics, Yeah the BIOS is not getting input signals to process so BIOS not loading in non working board i guess.

It is very likely that the red LED represents a Reset state. Here the reset signal acts also as Power Good.
If the green LED is neither bright nor dim, it means it is monitoring some CLK pulses.
How does it glow on a non-working board?

I want to stop the clock generator on the working board in order to emulate this fault. I still don't understand the reason.
There is no clock frequency or the processor is faulty, for example. But in our case, several boards are equally faulty.
It would be instructive if at the end it turns out that some capacitor has dried out.
There is another one low loss cap right next to the processor.

I found the start up sequence procedure here. It is for IBM5170 (80286 processor).
https://www.minuszerodegrees.net/5170/motherboard/IBM%205170%20-%20Startup%20sequence.htm

« Last Edit: November 12, 2024, 09:38:12 pm by Harry_22 »
 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #148 on: November 12, 2024, 11:02:12 pm »

If the green LED is neither bright nor dim, it means it is monitoring some CLK pulses.
How does it glow on a non-working board?

It Sometimes glow so bright or sometimes the lED is not turn on.

 

Offline 222Lab_Test222Topic starter

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Re: What more i can do?
« Reply #149 on: November 12, 2024, 11:05:48 pm »

It would be instructive if at the end it turns out that some capacitor has dried out.
There is another one low loss cap right next to the processor.

I found the start up sequence procedure here. It is for IBM5170 (80286 processor).
Could be The capacitor has dried out or maybe processor is not working as it should be.
Either way the reason i hesitate to desolder is, this is only working board i have, if in case it also start showing issues then, i would not have any working boards to compare.
 


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