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Forums - Synths & synthesis
Subject: my broke 303 and 909
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Original Message 1/3 20-Oct-00 @ 09:48 PM - RE: my broke 303 and 909
Lately I have been having a problems with my gear. 1 day my 909 just decided it doesnt want to turn on. I just bought and replaced the fuse, but the problem still persists. My 303 sometimes all the lights just come on, and just sits there glowing, although I think that that pertains to a bad sotter joint to the battery compartment. I dont know any one in this area who has a 303 or a 909, so I have no one to ask. Can anyone shed some light on this problem. Thanx
Message 2/3 20-Oct-00 @ 10:48 PM - RE: my broke 303 and 909
I dunno where you are matey, but I know both of these machines inside out and I could get them running for you. But, erm, I'm in the UK and I guess your'e probably not ;-)
As for the TR909, if it is totally dead then I'd start looking at the psu, obviously. If my tired brain serves me right, without looking in my 909 service manual, I think the power supply is a rather simple job that uses 78xx series regulators. Pretty easy to fault find, this one. I am aware that there were problems in some models whereby glitches on the AC line could cause the machine to crash / reset - this was cured by replacing a zener diode in the psu for one of a different voltage drop... but this problem did not cause the 909 to stop working altogether. I'm assuming simple things like fuses, faulty switches/ sockets etc have been eliminated...
As for the 303. The cpu is doing something funny. It sounds like the cpu's I/O ports which scan the LED matrix are latching in a cerain state and this could therefore cause all LEDs to light. The CPU is latching up. Possible reasions: bad interrupt clock generator to CPU. Bad oscillator circuit. Bad reset circuit. Bad solder joint somewhere. Maybe the 5.333V rail is over/undervoltage (does the tuning of your TB303 ever drift?). I am not sure about a faulty battery terminal. The 303's reset circuit would just reset the CPU. Or the thing would not power up at all. The RAM does go quite frequently, but RAM failure would not cause the CPU to crash.
Good luck... the offer is there to look at these for you if you can't find anyone to do it.
~ Trev
As for the TR909, if it is totally dead then I'd start looking at the psu, obviously. If my tired brain serves me right, without looking in my 909 service manual, I think the power supply is a rather simple job that uses 78xx series regulators. Pretty easy to fault find, this one. I am aware that there were problems in some models whereby glitches on the AC line could cause the machine to crash / reset - this was cured by replacing a zener diode in the psu for one of a different voltage drop... but this problem did not cause the 909 to stop working altogether. I'm assuming simple things like fuses, faulty switches/ sockets etc have been eliminated...
As for the 303. The cpu is doing something funny. It sounds like the cpu's I/O ports which scan the LED matrix are latching in a cerain state and this could therefore cause all LEDs to light. The CPU is latching up. Possible reasions: bad interrupt clock generator to CPU. Bad oscillator circuit. Bad reset circuit. Bad solder joint somewhere. Maybe the 5.333V rail is over/undervoltage (does the tuning of your TB303 ever drift?). I am not sure about a faulty battery terminal. The 303's reset circuit would just reset the CPU. Or the thing would not power up at all. The RAM does go quite frequently, but RAM failure would not cause the CPU to crash.
Good luck... the offer is there to look at these for you if you can't find anyone to do it.
~ Trev
Message 3/3 18-Nov-00 @ 09:49 PM - RE: my broke 303 and 909
http://www.firstpr.com.au/
check out this place for repairs and mods
check out this place for repairs and mods
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