Electronics > Repair
What more i can do?
Harry_22:
--- Quote from: 222Lab_Test222 on November 29, 2024, 08:02:39 am ---
--- Quote from: Harry_22 on November 29, 2024, 04:27:27 am ---Another idea came to me.
You can try the effect of temperature on the board. I foresee that a manual reset button has already been installed.
Gradually heating different parts of the board by hot air gun, periodically press reset and watch the reaction.
Only without fanaticism. Don't overheat. Old components are more delicate.
--- End quote ---
I did heat with around 300 degree, and tried pressing reset button, I did not see any changed from naked eye, After a while i stop as board started to get more heat.
--- End quote ---
Let's see. 300 degrees is the temperature of the gun. Heating also depends on the air speed. I used QUICK 861Pro for this test with the speed setting at 20. You do not need to heat the entire board at once. Start with one 5x5 cm area. It will take some time to heat, about 30 seconds at distance of 5 cm. Do not force it to avoid a large temperature difference through material. This is a typical mistake of most. Heat up to 100 degrees. Check the temperature with your finger. If you can not hold it for half a second, that's enough.
The only change we are looking for is stopping of continuous beep.
PS
Check both PCB sides.
PPS
Don't forget to check Address and Data buses as was described in #346.
drhex:
If you have two address lines not working the CPU may well read bogus code from the ROMs and then die in execution once it hits something illegal. So as per @harry_22 suggestion check all address and data lines. If two are non wroking as you have written mutliple times we need to identify what goes wrong there. Have you compared beahvior working/non-working on thes lines? Address and Data will be shared all across the board, they are a bus. Any connected chip can kill them - see my repair of a even older pinball CPU in another thread.
222Lab_Test222:
--- Quote from: drhex on November 29, 2024, 04:52:48 pm ---If you have two address lines not working the CPU may well read bogus code from the ROMs and then die in execution once it hits something illegal. So as per @harry_22 suggestion check all address and data lines. If two are non wroking as you have written mutliple times we need to identify what goes wrong there. Have you compared beahvior working/non-working on thes lines? Address and Data will be shared all across the board, they are a bus. Any connected chip can kill them - see my repair of a even older pinball CPU in another thread.
--- End quote ---
I somehow feel something is triggering the IC TORNADO, If we can solve IC tornado, i am 100% sure we will fix this beep problem.
Because everything is related to this IC tornado.
Harry_22:
Ok, heat it and try to reset.
Please measure the Data and Address bus as agreed.
smaultre:
Hello, you can try to check (&click) all of the dip switches, it looks like BIOS is not well configured or so. Click them ~20 times for each position and check that they are in right position compared with the working board.
Check (replace) condensers, power lines, clean connections (memory), check voltage amplitudes on IC's main legs,
Does it trying to read BIOS? than MS-DOS from ROM? How long ? Compare with working board. Check adress&datalines.
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