SIEL DK 600 Synthesiser - Powers up but puts out nothing but white noise

[New Soul Rebel]

Ok guys, the title says it all.

i've gotten my hands on a very good condition Siel DK 600 but the fucker is putting out nothing but white noise. i've opened it up and I can't see ANY visibly damaged components on any of the board.

The digital board (i.e. patches/controls etc) seems to be functioning perfectly and there are LED's on each of the boards under the hood that seem to be alighting when I press the keys - so it seems that leccy is getting through all the circuit.

Checked all fuses and as I say - zero visible signs of any blown components. the superconductors/heatsinks all seem above board/clean and so on.

Has anyone here got any experience with fixing synthesisers - who could give me some advice on things I can start checking?

A logical path of diagnosis so to speak?

http://home.tiscali.nl/~smeyer/siel/

this is a website which hosts some pics on the machine opened up, so you can see the boards etc.

Any help grateful. Cheers

Matt
(New Soul Rebel/VP312 Nut)

 

[geoff004]

My DK600 is very finicky.  Sometimes it works fine, other times it just sits and makes glitching sounds.
I think the key to reliable operation is good connections with all the ribbon cables.  Pull them off and clean the contacts.

Also, check voltages to make sure they're as they should be.  And also I'd say pull the battery.  Mine's got no memory and it doesn't bother me.  If the battery corrodes things on the pcb can deteriorate.  It might be tricky to find it if my memory serves me well - maybe under the keyboard and off to one side?

 

[New Soul Rebel]

Hi Geoff

Okay, it is indeed the battery. Its leaked. So, i'd say that firstly I have a removal and cleaning job here.

I"ve just had a look at the battery (it is indeed under the keyboard, easy to get to.

It has leaked and spewed quite a a bit of battery shit all over that localised part of the pcb. my main fear is two MM74 chips very near to the battery. they appear to have oxidised quite badly.

Trying to remove the battery. It appears to be SOLDERED. Is this right? Is this the case? Bit nervous about getting my soldering iron to a LEAKED battery!!!

Seems a bit crazy to have a soldered backup battery.

How do you recommend I get the offending item out?

Regards Matt

PS thanks for replying

 

[geoff004]

How do you recommend I get the offending item out?

I think I cut mine out with a small pair of side cutters.  You might be able to unscrew the pcb and desolder it.  That might be a good plan anyway to clean the corrosion off.
Check all the traces to see if anything has been damaged.

My guess is that if the oscillators aren't putting out sound you've got another problem elsewhere.
Do all the buttons and lights work?

 

[New Soul Rebel]

Well, for starters... that lithium batt is proverbially fucked. so i've desoldered it and cleaned as much of the contaminated part of the pcb as possible, with some vinegar. dried out, powered the baby back up...

Jesus! CONSTANT hiss.

I seriously need to desolder all the contaminated resistors, semiconductor (or two) and diodes. theres a fair few (say around 15) that appear to have become corroded as a result.

 

[gyraf]

check (with an ohmmeter) the integrity of ALL near-by pcb traces...

 

[geoff004]

do a simple google search on both the DK600 and Opera 6 - I think they're pretty much the same synth.
There's a lot of technical information available.

Don't forget to check the power supply.