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Roland Tr-909 Strange issue

Posted: Wed Oct 09, 2013 11:21 am
by cutoffres
i'm repairing a TR909. Evrything is now ok except :

Even if the pattern is erased, There is always a LowTomand and a HIHat at the first step of pattern 1; pattern 3; pattern 5; pattern 7; pattern 9; pattern 11; pattern 13; pattern 15 (so every odd number)

I've replaced eprom : no success

-Maybe a switch scanning problem ? as the technical manual indicate: "... in basic opération , the cpu scans panel switches, store switch outputs, and generates trigger (TRIG) and volume (ACCENT) data for the voice generators..."

-A cpu problem ? (i doubt)

-A Ram problem ?

service maunal is here: ... TR-909.pdf

Any help is welcome.

Thank you

Re: Roland Tr-909 Strange issue

Posted: Thu Oct 24, 2013 7:58 pm
by AK79
Hi there,
never seen that but I would suspect the RAM because neither the CPU or the switch Matrix could produce a failure that is limited to odd numbered patterns.