Hi!
I have been browsing around this mailinglist but haven't found a solution to my problem (but some help to get this far!). However, I think it is the right place to post my questions.
I got an EX-800 that my friend found in the garbage. He has kept it for some time and tested it the last time one year ago when he says it worked fine. He is not very much into making music and thought I would have more use for it. The user interface (buttons and LED displays seem to work fine), but I don't get much sound out of it. With some settings I get some low level filtered noise.
After checking the MIDI in with bank change messages I opened the device. Looks very clean inside. I have backtracked the circuit to the MSM5232. I just have a mutimeter right now, but this is what I got so far:
- The outputs (2'-1 ... 16'-2) of MSM5232 (pin 28-31 and 33-36) are constantly 4.6V no matter if keys are pressed or not.
- The control inputs (E0 ... E7) of MSM5232 (pin 24-27 and pin 37-40) give -4.3V before key on and -0.3V when key on.
- The clock signals (clk1 and clk2) seem to be OK. DC 2.5V and about 1MHz.
- VDD1 (pin 3) = 5.0V
- VDD2 (pin 41) = 5.0V
- VSS1 (pin 21) = 0.0V
- VSS2 (pin 23) = -5.0V
- VSS3 (pin 32) = -5.0V
- WR (pin 12) of MSM5232 is 5.0V no matter how I send notes. I cannot see any pulses since I don't have a scope. If this signal is active low, I guess the pulses are to short to affect the DC reading. I should meassure this with a scope, but this seems like my small hope for non broken MSM5232. In the datasheet for the MSM5232 it looks like this signal should be 2.4 - 0.8 V, am I right?
- 8 bit data bus (D0 ... D7) of MSM5232 (pin 4-11) is hard to measure without scope, but there is some action going on when keys are pressed. They wobble around 2.5V. Should messure these with a scope to see if they look like digital control signals, but I have no reason to expect other than that they are healthy.
- ALE of MSM5232 (pin 13) has a steady signal of high frequency with a average voltage of 1.5V. Seems right.
- RST of MSM5232 has a voltage of about 4.4V that lowers some mV when keys are pressed. Guess those are correct reset signals and the signal is active high.
- Address inputs (A0 ... A3) of MSM5232 (pin 14-17) are about 2.5V and change some mV when keyes are pressed.
Anybody have some clues? Did I miss something? Is my MSM5232 broken or is it possible that the input to WR is messed up?
Thankful for any ideas!
Regards Johan Nilsson