AKAI s900 power supply

[oxide54]

hi

i am trying to repair an AKAI s900 sampler.


basically there are two main boards, the voice board and the CPU board
but the cpu board aint exactly an intel xeon if you know what I mean.

the power comes in through a IEC socket. there is 220/240 switch. then to the coil, with 3 secondary windings one of which is center tapped.

(btw the description about winding might be technically inaccurate, i am quite new at this)


the coil outputs various AC voltages 7.1 /16.5/16.2/16.2 the two 16.2 are from the center tapped winding.

these test very close to the spec, a couple are slightly out. ( i can retest and give you exact readings) (not sure what the tolerance is here)

these AC voltages are fed to the "power supply board" which looking at the schematic has the 4 diode bridges which is not suprising given it outputs DC!


there are two DC output connectors whicd feed the voice and CPU board

the CPU board connector tests correctly. but the voice one doesn't there are +6V and -6V rails and they test around the 25V mark. so i would assume that isn't healthy. and although there may be damage to CPU or Voice board I should probably fix the power supply board before moving on.

i am starting to appreciate the level of detail in the schematic, and may start to test some of the voltages that are marked on the board for the output of various components,

has anyone anything help they could add?




if you want to see the service manual / schematic google "akai s900 service manual" the first result is a gearslutz post with a link to manual.