[sdiy] Broken Siel Opera 6, any ideas?

[klosmon]

The Opera 6 (a.k.a. DK600) is a notoriously problematic machine -- I've 
attempted repair of 5 battery-damaged CPU boards, with only two 
successes (as opposed to 40 out of 42 successes for PolySix 
battery-damaged boards).
Part of the problem is the circuit board design -- it's close to 
impossible to unsolder & replace any components without affecting the 
ridiculously weak traces that pass between the component pads (and I'm 
saying this as someone with 25 years experience in 
soldering/desoldering).  Also, this synth has a large number of ribbon 
cables, whose contacts can oxidize over the years & cause faulty 
connection, resulting in poor (or no) performance.

Successful repair of these units involves a detailed familiarity with 
the schematics, a scope, excellent soldering technique,
much time, and a quantity of luck.  Not for the faint of heart.

The CPU, 2031s (and the power supply) usually run very hot -- these 
synths can also double as room heaters, during the winter months.

~GMM

Mattias Rickardsson wrote:
> 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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