MegaST 4 will not boot, but looks fine with diagnostics

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exxos
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Re: MegaST 4 will not boot, but looks fine with diagnostics

Post by exxos » Wed Jan 03, 2018 9:45 pm

guus.assmann wrote:
Wed Jan 03, 2018 9:23 pm
Have replaced the sockets, now two quality sockets with round contacts are in.
Still with these it doesn't work either. :( :shock:

However it was a very good idea. :)
:( Doesn't make much sense.

I would check the CE and OE pins on the ROM and make sure they are switching.. maybe broken trace/bad glue socket, from GLUE to ROM for chip enables, you changed the LS11 already.. but I think you should check the ROM select lines from GLUE to ROM sockets.

If TOS206 worked on another board, then onboard TOS104 isn't working, GLUE does decoding for that...
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guus.assmann
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Re: MegaST 4 will not boot, but looks fine with diagnostics

Post by guus.assmann » Sun Mar 18, 2018 9:42 pm

Finally, I found some courage and inpiration.
And solved the problem.
Jumper W2 had a bad contact.
But it was hidden below the body of the part.
So there was no or a bad connection from the decoding chip to the Eprom.
The board works fine again.

BR/
Guus

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