| Electronics > Repair |
| What more i can do? |
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| 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. |
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