CR-78 remote repair

Today, Steen and i will show you a quite interesting small project. Steen has a broken Roland CR-78 and sits in Denmark, i have the knowledge to repair it and sit in Germany. He could send the unit to me to have me repair it, but we tried a different thing, as Steen thought that he could do the job if i guide him through the steps.
So i told him what material he needs to replace the potentially failed latches for the instrument triggers, he got the material, i told him a bit how to solder and desolder, created the desoldering video recently, and after those preparations, we started all this.
So enjoy this video and see, how everything worked out. From those 8 hours of work, i just have 25 minutes of video material which i had to cut down to 10 minutes for YouTube. So lots of fun is missing there, but we hope, you enjoy it anyway.

DISCLAIMER: because of legal reasons and very limited spare time, i can't help you with your electronics problems, so just don't ask - your questions are likely to be ignored.

Category:

Music

Tags:

• CR-78
• DIY
• repair
• Roland
• skype
• soldering
• webcam

[Ni5ei]

Awesome. You're lucky to have one if those later boards. My CR-78 is one of the first batch and there are no plugs on the mainboard, everything's soldered so I can't take out the mainboard at all.

[MusicMiK]

@Ni5ei I don't have any CR-78 :( But it seems that you really have a very old CR-78. I have not yet seen other versions than those with the connectors, i even didn't see the old version with the higher voltage battery yet.

[sgtpepper1138]

fantastic work, what kind of camera are you using, looks really nice

i'd like to have one of those drum machines just to do the "in the air tonight" pattern

[MusicMiK]

It's a Panasonic FZ-8. Very recommendable for all internet purposes. Can record videos in 640x480 up to 15 minutes (maybe longer), post-processing is done with Apple iMovie, where it goes directly to YouTube.

[mklndrs]

Very neat idea !

Which ic's did he replace ?

[MusicMiK]

Those 4 near the triggering connector - 1x74LS174, 3x74C175 (we put HC175 in there, as C175 aren't made any longer).

Those ICs are the most common problems of the CR-78, the symptoms are missing instruments or random triggers in high speed.

[Ni5ei]

@MusicMiK Oh yes, I read that you don't have one.

Mine is serial # 821179. I have no idea when they changed the board connections to separate connectors but looking at the serial number I guess it's from november 1979? (no idea if the number is related to a production date).

I could send you some pictures of the mainboard if you like. The soldered connections make it a lot more difficult to repair or mod because you can't take out the mainboard.

[donpepperoni0]

Great to get another of those fantastic machines back in action! Good work!

[Laurentius84]

Hi Micha,

very impressive videos you got there, my compliments! :)

Cheers from Esslingen, :)

Lars F.

[laserbeak43]

that's what i call using your resources. bravo.

[lesingemonotone]

Great effort, thanks for sharing!

/kroffe a k a Le Singe Monotone