01/WFD Hissy outputs replacement motherboard.

teesquared · Post by **teesquared** » Fri Jan 02, 2015 5:45 am

Hello all. Greetings and a happy New Year.

I have a Korg 01W/FD. I havent used it much since i've owned it.
A friend of mine borrowed it for a session and it came back with hissy outputs. Sure enough C99 and C100 had burst sending electrolyte all over. Foolishly I left it in this state over last summer in a warm part of the house. I finally got round to fixing it. I've cleaned the splatter at least 7 or 8 times with IPA (No not India Pale Ale), I replaced those caps for higher rated electrolytics, I've replaced R142 and R143. Although the hiss is a little reduced and sometimes after a boot I may have up to 5 minutes of hiss-less use, it will return. All outputs are affected Phones, 1,2,3 &4 although 3 and 4 sometimes are not affected depending on the patch. Connector 100 whic is probably an audtio test point also has hiss.

I have remade and dodgy tracks and the board is once again clean.

Using a very simple signal tracer (Audio amp plus a .1uf capacitor as a probe), I traced it back to the DAC stage. IC34, IC35, IC37 all have hiss on their audio outputs so I'm thinking that its probably in the digital domain.

I do not have and test equipment other than my probe and a multimeter. Has anyone had this problem and solved it? DOes anyone know where if push comes to shove I can obtain a replacement motherboard part No. Korg KLM 1528B?

Many thanks in advance and best regards

Tee.

jhulk · Post by **jhulk** » Tue Jan 27, 2015 12:55 pm

you need to service the psu as its sounds like ripple in the psu filter caps they are failing and why it gets worse over time as they stop charging and discharging the voltage sand let the ac ripple through from the rectifiers

a sign that you already had burst caps is a good sign that others may also be faulty

teesquared · Post by **teesquared** » Wed Jan 28, 2015 6:08 am

Hi Hulk

Thanks for taking the time to comment.
Yes I've been through the PSU board and replaced all the electroletic caps with higher rated ones.

If anything it seems to be getting worse. Going toward the "No sound at all" fault. I am going to have one last go at replacing the main board remaining caps, and the rest of the op-amps, then my budget of time and money will be gone

Cheers.

jhulk · Post by **jhulk** » Thu Feb 12, 2015 10:45 pm

check for cold solder joints on the audio outs as they can crack and can be intermittent this happens to all korgs as they rely on the solder joints as the mechanical strength

i recommend the 90 degree phono 1/4 inch jacks as they dont put so much strain on the sockets where as the straight versions act as a lever which cause gravitational stress on the sockets which can eventually cause the sockets to crack which cases crackles