Re: Intermittent fault on Korg SDD 3300

On 1/25/2025 3:13 PM, ehsjr wrote:

On 1/25/2025 12:29 PM, bitrex wrote:

I have a Korg SDD 3300 triple digital delay rack unit that was a bit of a basket case when I got it. Someone had tried to "fix" it at some point and it had a number of issues including the wrong voltage regulator slapped in the negative rail, miswired output jacks, dead EL backlight, bad SRAM 2032...
>
Fixed that up and I was able to get a copy of the service manual and use the three-finger-salute button combo to get its mind back after SRAM battery replacement as is common on units of this vintage, followed the adjustment procedure in the service manual and everything seems to work as it should now except one really irritating intermittent fault remains: the LCD will occasionally garble up at power-on or in use as so:
>
<https://imgur.com/a/BjxoQDP>
>
It's annoyingly unpredictable and seems somewhat related to how it's mounted? I can power it up 25 times on the bench and it works fine making me think I solved the problem, then slide it back in the rack and it starts acting up again.

 When the failure is position sensitive, look for a bad switch or cable that causes a line to float between a logic 0 and 1.
 War story: I had a bad ice maker in the freezer that failed only when it was installed. Worked 100% on the bench and not possible to troubleshoot when installed. Turned out to be a bad micro switch that failed (high resistance instead of ~0 ohms when closed) only when I held the thing at an angle.
 Your problem looks like a tough one if it's a switch or cable. :-(
 Ed

Thanks for your suggestions, I feel like there was some substance use going on when this unit was designed and servicing it makes me feel the same way so at least there is symmetry.. <https://youtu.be/BtMP2EiRH0Y?si=0klgHRWFFO8ybBiA&t=12>
--
This email has been checked for viruses by AVG antivirus software.
www.avg.com