Roland R70 Repair - Advice needed!

Johnny333

I hope it's alright to post here (being a drum machine rather than guitar amp) but I'm seriously stuck and know there are a few very knowledgable individuals on here that might be able to help!) 

I'm attempting to repair a Roland R-70 drum machine. I bought it at a flea market in supposedly "full working condition", though when getting home and testing it found the headphones output was very weak and no audible signal from the stereo L/R outputs.

I've tried to fix it with the help of GPT but it's confidently sent me down numerous rabbit holes and consistently provide incorrect advise, so I'm reaching out for some real human help! 

I've so far replaced the following capacitors: C2, C5, C7, C10, C11, C12, C13, C16, C32, C33, C34, C35, C36, and C50. This significantly improved the headphone volume, but the stereo outputs are still silent. The screen and main sounds/program is all running as it should and working perfectly through the phones output so I'm convinced it could be a relatively simple fix. 

Service Manual PDF: https://www.synthxl.com/wp-content/uploads/2019/05/Roland-R-70-service-notes.pdf

GPT was pointing me to IC42 being the problem but I'm not convince this is correct. Any advise would be hugely appreciated and I can provide multimeter readings of anything that might be helpful.

Cheers!

Funkfingers

Is IC42 mounted via a socket or soldered to the board?

Danny1969

One of the quickest ways I would approach a fault like this is to get a little headphone amplifier and and use the input as a probe … connect the Earth of the headphone amplifier to the common ground of the circuit you’re working on and work your way backwards on the input of the various opamps until you find the signal. Then  you can see where the signal disappears and why. 

Johnny333

Thanks so much for getting back to me guys and appreciate the tip on the headphone amplifier! I ended up managing to solve it by changing the caps between IC2 and the stereo outputs.