Roland RD300SX keyboard

[N_Cook]

Took a heavy bash , cracked pcb in area of effects control pot, which
must have been bashed. Obvious crack at an opamp, open circuiting
analogue ins and outs. I find it difficult to believe , that only, would
give the symptoms observed, whether powered up or not at the time.
No sound output , no midi control from external feed, no switch panel
response and just showing semi-random flashing of "r" of 2 segments in
one display

 

[N_Cook]

On 04/09/2015 16:36, N_Cook wrote:

Took a heavy bash , cracked pcb in area of effects control pot, which
must have been bashed. Obvious crack at an opamp, open circuiting
analogue ins and outs. I find it difficult to believe , that only, would
give the symptoms observed, whether powered up or not at the time.
No sound output , no midi control from external feed, no switch panel
response and just showing semi-random flashing of "r" of 2 segments in
one display

Looks as though owner gave me the wrong Roland ps, 9V dc 2.4W, specs of
proper one 9V 11W, I thought it seemed small although no speakers in
this keyboard. Perhaps flashing r just means insufficient power, will
check the NEC 24A05 and TA7807S of the ps section

 

[N_Cook]

Flashing r is lack of current, needs 9V , 700mA minimum.
Repaired that pcb and another problem under keyboard. One bank of keys
inoperative. Originally found the break on the common line to keys 25 to
32, then it disappeared. Could not find the break so will run a bypass
wire. Neatest way , for a good soldering point on wide trace of the
commons, is punch a hole through the pink silicone mambrane and pass a
wire through that and down to the ribbon connector. I asume the hairline
crack is somewhere along the 400mm or so run of fine track.

 

[N_Cook]

Come to the end of the road on this. For spares purchase on ebay I
suppose is the only chance. Main board problem , cracked die of a 100
pin Roland chip it seems.
Common rail to this IC11 for the missing bank of keys is pin92. pin 90
is the common for the next bank of keys 33 to 40, which do sound.
DVM-D and R checks on those 2 pins to 0 and 3.3V rail match as does
powering up and both commons drop from 3.3V to 2.9v on a relevant key push.
Any other ideas to persue?