CT-605 Accompaniment Not Working—ISO service manual

Synth Repair
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[CASIO] [CT-605] – [No Accompaniment/Bass/Rhythm Audio]

Hey y’all,

Does anyone have a Casiotone CT-605 Service Manual?

I’ve got a CT-605 where the whole accompaniment section is not playing audio (chords/bass/rhythm). I have been working from a CT-405 schematic and I have confirmed that the LSI handling the accompaniment section is good—but I have also determined that the tempo fader is faulty. Would replacing that fader be enough to fix the problem? If the 605 is the same as the 405, then I have narrowed down the other two potential culprits to be either the “Mixer 3” op amp or the accompaniment “Start/Stop” switch.

Has anyone run into this issue and does anyone have any other ideas? Thanks!

• Model & revision/OS:
• Symptoms (what changed, when):
• Tests already done (voltages, parts replaced):
• Photos / audio clips:

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Hey @nomadicrust, though I can’t help with your problem. Here is a link to a pdf of the Casio CT-605 owners manual.

Hope it helps!

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Thanks Jeremy! Appreciate that. I have (most likely) narrowed it down to a faulty tempo fader—but unfortunately have had no luck sourcing the slide pot i need to replace it. Updated post is available here: