Lone in the night

Symptom I had an issue with this pedal, suspecting something wrong with the voltage regulator (actually, the issue was caused by external PSU itself). Since I was not able to find the schematics, I opened it and decided to do a quick review of the chips. Description of chips Once removed all the screws and nuts, be aware the PCB is super-stiff to remove from the casing. It took me 15 minutes at least to do so. Here are the chips I was able to identify: Id Man Chip ref Description Used for U1 CL CZ4272-CZZ 114 dB, 24-Bit, 192 kHz Stereo Codec DAC U2 TI TLC2272C Dual operational amplifier U3 No chip found with this reference U4 AD ADSP-BF532 SBSTZ400 400 MHz High Performance Blackfin Digital Signal Processor Signal processing U5 SJ6E U6 No chip found with this reference U7 TI MC33078 Dual high-speed low noise operational amplifier U8 TI MC33078 Dual high-speed low noise operational amplifier U9 TI MC33078 Dual high-sp...

Symptom The pedal works well when powered with internal 9V battery, but nothing when powered with external PSU. Component side Back side Possible cause Check the fuse labelled FB3 (red box above) is passing; replace if not. Check the diode labelled D3 (yellow box, a MMBD4148SE from OnSemi) with a diode tester or adequate DMM Setting the + probe on pin 3 and - on pin 2 should be passing with ~0.5V voltage drop. Must be blocking when reversing the probes. Setting the - probe on pin 3 and + on pin 1 should be passing with ~0.5V voltage drop. Must be blocking when reversing the probes. On my unit, this junction is always blocking hence possibly defective. Edit: the diode has been replaced and the pedal now works perfectly.

Part 1 - FIXING The issue Three issues actually: Oxydation: some switches are bouncy and pots are scratchy One voice is out of tune by a semitone when the synth is left unused for some time, but goes in tune when used more regularly The synth goes crazy after 10-15 min PWM is not working Fixes Fixing the oxydation issue I decided to replace all the 31 tactile switches. The new ones are B3F-4000 from Omron Electronics, costing 0.26 cents each. On the 4 PCB bearing switches (KLM-01, KLM-381, KLM-403, KLM-404), each tactile switch itself is enclosed in a plastic casing wich helds the button and the LED. Remove the button first, the small felt underneath, then desolder the 6 leads (2 for LED, 4 the switch). Its sometime easier to remove the casing first, then the tactile switch. I took the opportunity to clean the felts: put then all in a little hermetic box, pour some hot water and soap, close and shake vigorously. Repeat 2-3 times wit...