Electronics > Repair
What more i can do?
Harry_22:
--- Quote from: 222Lab_Test222 on November 08, 2024, 11:52:22 pm ---
--- Quote from: Harry_22 on November 08, 2024, 11:38:09 pm ---Chеck the signals Chip Enable and Output Enable (please see the picture).
It would be good to compare them with the working board.
--- End quote ---
They are all good, Except there is no volatges in A pins which are input pins in Non working board, Thats the case i am mentioning from the start of this forum.
Other is everything good.
Ps
When I check where some of those pins connecetd they are connected to near tornado IC and few of them to other ICs
--- End quote ---
You have to look the signal at power on by oscilloscope.
Play with trigger function to see the beginning process.
Note: All IC15, IC16 EPROM pins are in parallel except Chip Enable#.
Track the Reset# sinal at pin 8 IC1. It should be low at the beginning and getting high if all voltages are good.
It is possible to use Reset# rising front as a trigger to see other signals at start up.
Could you attach some pictures with start up signals on Chip Enable# and Reset#
Harry_22:
I'll bet a few bucks that due to increased leakage current (DCL) in capacitor C1 (after 30 years it is allowed), MB3771 chip does not release Reset# signal.
222Lab_Test222:
--- Quote from: Harry_22 on November 09, 2024, 06:56:34 pm ---I'll bet a few bucks that due to increased leakage current (DCL) in capacitor C1 (after 30 years it is allowed), MB3771 chip does not release Reset# signal.
--- End quote ---
IC1 8# RESET PIN
I guess it is working fine.
-Connected to IC2 1st Pin
-Connected to IC5 1st Pin
222Lab_Test222:
--- Quote from: Harry_22 on November 09, 2024, 05:15:02 am ---
You have to look the signal at power on by oscilloscope.
Play with trigger function to see the beginning process.
Note: All IC15, IC16 EPROM pins are in parallel except Chip Enable#.
Could you attach some pictures with start up signals on Chip Enable# and Reset#
--- End quote ---
It seems all ok, both ic15 and 16 have similiar results.
Note : Not sure why images are being rotated automatically.
222Lab_Test222:
Output enable
Yellow is working board.
Blue is non working board.
The chip enable is same on working and not working board.
Note : Does the op enable pins matters as there is no input voltages to proceed.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version