[sdiy] Broken Siel Opera 6, any ideas?

Mattias Rickardsson mr at analogue.org
Wed Aug 27 00:05:40 CEST 2008


Hi,

I have a faulty Siel Opera 6 opened here, and I've removed the leaked 
battery and replaced the CD40106 (IC16) that was more or less destroyed by it.

Before this, I could see that the voice LEDs indicated that 
keypresses were assigned to voices in a correct manner, but the panel 
controls/indicators behaved strangely or not at all.

Now, no voices get assigned when pressing keys. The panel 
controls/indicators are still strange.

When I look on different CPU pins on the oscilloscope, many of them 
seem to "blink" in the sense that they are 0 V for a while and then 
quickly changing between 0 and 5 V for a while, and so on. This 
"blinking" occurs with approx 2 Hz. I can see similarly timed things 
going on in the multiplexing address lines, they are turned on and 
off at 2 Hz. The panel indicators can show similar blinks when 
buttons are pressed. The DAC doesn't seem to change its output value.

I wouldn't really expect this to happen, unless the CPU has entered 
some quite useless state waiting for something else to happen... has 
anybody had a similar experience here?

What more... the CPU runs quite hot, the SSM2031 VCOs run EXTREMELY hot.
Power seems to be OK everywhere, I havent found any broken PCB lines 
or other components eaten by the battery acid. The synth has been 
lying under my bed for a couple of years, can it be the ghosts perhaps?

Any advice? :-)


/mr




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