Rebuilding the Roland CR-78 Logic Board
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- čas přidán 12. 09. 2024
- In this video we examine and replace a damaged logic PCB from the classic Roland CR-78 drum machine. We will be using the replacement board designed by Akira Honda. (Thanks for the beautiful boards Akira!) CR-78s are famous for damaged PCBs caused by leakage of the rechargeable battery. Save your CR-78 from the trash and get it working again!
Contact Akira Honda at synthsrepair@gmail.com for enquires about the board.
(FYI: this video is not sponsored by Synthsworkshop, the boards were purchased at full price)
I was lucky enough to find a CR-78 with the later, lower voltage 3.6V batteries so there’s no leakage in these machines (872900 and higher serials) but indeed had caps leaking so I did a full recap. Other faults included 74LS going bad (almost all of the latches had to be replaced) and CPU/ROM failing because of humid conditions and rusted pins. Finally went with the Tauntek which has been a lifesaver and I couldn’t be happier, even step programming the CR from the front panel.
Sounds like your story has a happy ending. The next video will feature the Tauntek kit and discuss how it compares to others. Spoiler: I think it is the best kit out there, at least it ticks all the boxes for me.Thanks for watching!
My CR-78 has fairly small but somewhat annoying problem: there appears to be what I'm guessing is some kind of clock noise bleeding through to the audio path. It's a faint ticking sound that runs while the unit is playing: turning the tempo knob up and down results in that ticking also increasing or decreasing in frequency, and stops when the unit stops playing. Not a big deal when using a fairly busy sounding pattern that would kinda cover up that noise, but it's more evident with more sparse patterns obviously. Do you think this could have anything to do with the power supply (it's never been recapped as far as I know) or could it be something else? I'm broadly assuming it's some capacitor somewhere that's going out.
Hi mate, it`s me again. After bringing my CR-78 back to life a small but little annoying issue occured - after powering up, 3rd and 4th track LEDs in the programming section remain permanently lit. To be more specific LED 4 lights up immediately whereas LED 3 after like 20 seconds of dim flashing. This doesn`t affect the functionality of this section. All sustain pedal-programmed tracks can be cleared, recoreded and played back. Do you think it might be sort of an aftermath of the voltage overload? Is there any safe way to fix it or should I rather leave it as it is?
I am going to have to spend a we while examining the schematic to try to figure this out... will get back to you!
@@telefunkian Thank you my friend, I highly appereciate your afford. It seems like some kind on shock-issue.. why" Because now the itme of litttin` up te 3rd LED takes like one minute. Interesting, isn`t it. guess it`s an aftermath of 240V uggin` shock that my belover CR-78 received...
@@telefunkian Any update on CR-78/MS-10? Still waiting. Cheers!
@@lenochod7950 Sorry about the wait, I got busy with work and haven't had too much time to look into this. It is possible that the IC 116, a 74LS175, that drives these LEDs, is damaged, but it could be due to other more serious issues like your CPU being damaged (corrupted MASK ROM, or your RAM (less serious)) I am speculating as I am just going on your description of the faults I would have to have it on the bench to really diagnose something like this properly.
Where can I get this board? My CR78 is completely damaged because of the leak :(
I can"t find anything about that "Akira Honda" board neither.... Any information Mr Telefunkian?