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Hi all.
I recenty got a PolySix that has issues..
Initially it would not power up / crash.
A few corroded traces on the Control Surface (directly above the battery) and a dead opamp caused most of this.
Surprisingly, even though the battery had corroded, the CPU board (367) was rather intact.
It now plays mostly fine except for one or two issues.
The preset buttons 1-4 do not work, as does the Attenuation rotary switch.
Pressing button 5 switches preset, but curiously switches on the LED's on buttons 4&5.
There are a few weird issues with incorrect LED's being lit up (Tape etc) when certain presets are selected.
The good news is I have a working 367 board, and swapping that over results in a perfect PolySix with none of the above issues.. So I can assume the fault is on the 367 board
I've replaced IC 31 & IC 30 (74LS08)
I've replaced IC's 26 & 24 (4042) - IC 24 is mislabled on my schematic as IC34
I've replaced IC's 29 & 35 (4042)
I've swapped over the CPU IC (uPD8048C)
I've thoroughly buzzed out for corroded traces in the digital lines, but can't seem to find any that are open circuit.
As the push buttons 1-4 are not responsive with the bad CPU board, I can only assume that the issue relates to DO4 - would this be correct?
The Attenuation also uses DO3 as well as P11,P12,P13
Does anyone have any pointers on what to check?
Could Faulty RAM be responsible for this kind of fault? I am suspecting not as I'm unable to change to some patches and faulty ram (probably) would not stop that from happening.
Any pointers / assistance will be greatly appreciated..
Regards.
Mike
Australia.