Recommending "recaping" as a general fix, is something of meme now. It's no joke on the Korgs though. I advise replacing all the electrolytics in them, so I made a the following images and lists to help.
The logic board only has a few capacitors. The 470u are the large, axial type, and don't seem to be an issue. They're listed for completeness.
| Name | Value | Voltage |
| C21 | .33u | 50V |
| C1 | 10u | 16V |
| C22 | 470u | 25V |
| C23 | 470u | 25V |
Here are the relevant capacitors on the sound board. They're color coded by value.
Red = 1u / 50V
Org = 10u / 16V
Ylw = 100u / 16V
Grn = other
Here are the footprints on the bottom, to help with desoldering. These are not coded, because they should all be removed.
Here are the types and totals of capacitors:
| Value | Voltage | Total |
| .15u | 50V | 2 |
| .22u | 50V | 2 |
| 100u | 16V | 5 |
| 10u | 16V | 14 |
| 1u | 50V | 14 |
| 47u | 16V | 1 |
Here are the individual capacitors, and their function in the circuit. This can be helpful for debugging.
| Name | Value | Voltage | Role |
| C59 | .15u | 50V | Low Conga |
| C60 | .15u | 50V | Hi Conga |
| C49 | .22u | 50V | HiHat |
| C61 | .22u | 50V | Tom Noise Audio |
| C50 | 100u | 16V | Cymbal Power |
| C52 | 100u | 16V | Hat Power |
| C106 | 100u | 16V | Power |
| C107 | 100u | 16V | Power |
| C123 | 100u | 16V | Metal Power |
| C20 | 10u | 16V | Bd, Sn Power |
| C21 | 10u | 16V | Bd, Sn Power |
| C51 | 10u | 16V | Cymbal Power |
| C71 | 10u | 16V | Tom/Conga Audio |
| C72 | 10u | 16V | Tom/Conga Power |
| C73 | 10u | 16V | Tom/Conga Power |
| C98 | 10u | 16V | RS/Clav/CB Audio |
| C99 | 10u | 16V | RS/Clav/CB Power |
| C100 | 10u | 16V | RS/Clav/CB Power |
| C101 | 10u | 16V | RS/Clav/CB Power |
| C103 | 10u | 16V | Mix Audio |
| C105 (C05) | 10u | 16V | Power |
| C112 | 10u | 16V | Noise |
| C114 | 10u | 16V | Noise Power |
| C2 | 1u | 50v | Bd Trigger |
| C5 | 1u | 50v | Bd Audio |
| C10 | 1u | 50V | Sn |
| C13 | 1u | 50V | Sn Audio |
| C16 | 1u | 50V | Sn Body Audio |
| C18 | 1u | 50V | Sn Audio |
| C54 | 1u | 50V | Low Conga |
| C55 | 1u | 50V | Low Conga |
| C64 | 1u | 50V | Hi Conga |
| C65 | 1u | 50V | Hi Conga |
| C90 | 1u | 50V | Claves Audio |
| C95 | 1u | 50V | Cowbell |
| C108 | 1u | 50V | Noise |
| C111 | 1u | 50V | Noise |
| C19 | 47u | 16V | Bd, Sn Power |
Great post and thanks for the information.
ReplyDeleteI just acquired a kr55B that is non functional. No audio output and when I push start the tempo led just stays on. Maybe an issue with the internal clock oscillator? Any thoughts on such an issue?
ReplyDeleteKind regards,
Chris
Yeah, I would suspect the clock oscillator (Q1, Q2). It could also be one of the signals that is supposed to reset it. Check IC9 maybe.
DeleteHello Zack. Thank you for your reply. I suspected q1/q2 as well so I replaced them with new general purpose NpN pn2222 with no change. I can only see 1/2 of Ic9 used on the rimshot circuit. Is ic9 part of the reset ? Sorry I am having a hard time understanding the clock oscillator /reset functionality
ReplyDeleteOn the schematic, it's the NANDs below Q1/2. The labeling isn't super clear, but I think it's IC9.
DeleteThe NANDs connect to the oscillator's reset line via diodes D10/20.
Ahh yes. I figured that was the reset circuit. That IC is not labeled on the schematics. I will probe around that area and see if I can make sense of it. Thanks again for the input! Greatly appreciated
ReplyDeleteHey Chris, I have a KR-55B with the exact same problem. Did you manage to fix it? Thanks in advance!
Delete