Electronics > Repair

What more i can do?

<< < (35/112) > >>

Harry_22:

--- Quote from: Poroit on November 14, 2024, 06:33:55 am ---G'day Harry_22,

Is the OP focusing on the correct points for the signals you need to see?

It seems to me that you want him to focus on the D4990A.

I see there is a Test Pont near that IC.

BTW
My contact a Komatsu Australia can not find any details on these machines ever been brought into Australia.

--- End quote ---

Hi Poroit!

We focused on Calendar/Clock D4990A becase it it easy accesseble and have clear pinout. But we don't see the activity becase we observe only 600ms after Reset# release. I guess this TP is for RTC quartz frequency adjustment via C10.

The malfunction occurse immediately after Reset.

222Lab_Test222:

--- Quote from: Harry_22 on November 14, 2024, 06:58:03 am ---
--- Quote from: 222Lab_Test222 on November 14, 2024, 04:18:38 am ---This is Picture of CPU CLOCK and RESET PIN.
The working board and non working board is same.

1st is CLOCK  and 2nd is RESET.

--- End quote ---
Well done and going in the right direction!
But the CLK and Reset# signals must be present on the working board. Check the pinout.

 You will find here the Databook on 486DX2 processor
https://bitsavers.trailing-edge.com/components/intel/80486/Intel486_DX2_Microprocessor_Data_Book_Jul92.pdf

--- End quote ---

Its same i ,mean Both working board as well as non working board have same result thats what i am saying.

Did you check that PIN E 15 HOLD, thats only different in working and non working one.

Harry_22:

--- Quote from: 222Lab_Test222 on November 14, 2024, 07:12:47 am ---
--- Quote from: Harry_22 on November 14, 2024, 06:58:03 am ---
--- Quote from: 222Lab_Test222 on November 14, 2024, 04:18:38 am ---This is Picture of CPU CLOCK and RESET PIN.
The working board and non working board is same.

1st is CLOCK  and 2nd is RESET.

--- End quote ---
Well done and going in the right direction!
But the CLK and Reset# signals must be present on the working board. Check the pinout.

 You will find here the Databook on 486DX2 processor
https://bitsavers.trailing-edge.com/components/intel/80486/Intel486_DX2_Microprocessor_Data_Book_Jul92.pdf

--- End quote ---

Its same i ,mean Both working board as well as non working board have same result thats what i am saying.

Did you check that PIN E 15 HOLD, thats only different in working and non working one.

--- End quote ---

Regarding HOLD I found interesting information:
"The Intel486 DX2 microprocessor recognizes and
can respond to HOLD, AHOLD, and BOFF # requests
regardless of the state of RESET. Thus, even
though the processor is in reset, it can still float its
bus in response to any of these requests."

But please focuse on CLK and Reset. The signals must be on working board.

222Lab_Test222:

--- Quote from: Harry_22 on November 14, 2024, 07:16:45 am ---
But please focuse on CLK and Reset. The signals must be on working board.

--- End quote ---

Let me check again,

By the way i am using this PDF for CPU.
https://datasheets.chipdb.org/Intel/x86/486/datashts/27277002.PDF

Harry_22:
Ring the Reset signal from CPU to D1 Power supply monitor. It passes via some 74... logic

Also ring the path of CLK CPU signal.
Draw the scheme or mark them on the top PCB layer picture.

PS
Sorry I have to go run.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod