• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Yamaha C-70

E

Enobenetto

New Member
I have both a Yamaha B-2 and the Nelson Pass DIY VFET amp. I bought some NS-1000 years ago and the seller installed dual binding posts for bi-amping (he also upgraded the caps). When I get my Yamaha C-70 fixed, is it possible to use the inverted out and normal out, so that I can bi-amp the Nelson Vfet to the midrange and tweeter, as well as the B2 to the woofers? The manual shows how you can use the inverted jacks with one stereo amp, by using one inverted input and one normal input, so I wondered if you could bi-amp with the other unused inputs?

Also, speaking of the C-70, the input jacks on the pre-out are loose and drop the connection. Could I swap the input jack module from phono 1/2 with the preout ones? They look the same, but not sure, and don't want to mess anything up when I desolder them.

Thanks
 
Register to hide this ad
Thanks Avionic!! I will try both this week.

I really like the B2, which I've only had a couple of weeks. The bass is pretty awesome and the imaging sounds detailed but relaxed. The DIY VFET is similar but the bass is not great. I like the C70 a lot and boy does it have a lot of gain. I'm getting rid of my headphone rig because the headphone amp and eq from the C70 are better. Is the JRC opamp the one for the headphone amp? Would it make a difference to swap it out with a newer opamp?
 
I was able to get the C-70 working again by swapping the rca preouts with the phono 1/2 inputs jacks (not exactly easy for me). The only thing is that the inverted outputs don't produce any output? The wiring in the manual was complex for a single amp but I eventually did it right and still no sound out of the inverted preouts? It works fine out of the normal preouts.
 
Enobenetto said:
still no sound out of the inverted preouts? It works fine out of the normal preouts.
Click to expand...
Has to be either a cold solder connections.. Likely on the RCA jack if the NORMAL works .. Either that or a crack in the PCB around the INVERTED jacks.

Or ........Little orange relay RY504 is not working. Check solder connections on the relay as well.
 
Last edited:
I've been playing the C-70 and its intermittent connection issues now makes me think this unit falls into the relay problem category.
 
Enobenetto said:
I've been playing the C-70 and its intermittent connection issues now makes me think this unit falls into the relay problem category.
Click to expand...
All the C-70's that I work on. Get all eight relays replaced.
 
Enobenetto said:
I've been playing the C-70 and its intermittent connection issues now makes me think this unit falls into the relay problem category.
Click to expand...
Tapping on the relay should make it cut in and out if its a relay contact issue or solder connection issue.
 
Thanks,f both of you!!! I haven't had a chance to get back to it. I will test the relays as you stated. Where can one get replacement relays if needed? Is it a donor C-70 situation for parts?
 
I’ve come across a C-70 that is stuck on Tape-1 and being auctioned as junk. Are the selector switches easy to fix/replace?
 
Sparkplug said:
Are the selector switches easy to fix/replace?
Click to expand...
Solenoid operated switch. Largest switch assembly in the unit.. Could also be a problem with the Tone control /switching logic board.

index.php



https://audiokarma.org/forums/index.php?threads/yamaha-c-70-project.747782/

There is 6 slide switches that may require disassembly and cleaning. If it is stuck in one function -- I'd start with the logic board and make sure your getting the voltages to all 6 solenoids when the function buttons are pressed.
 
Last edited:
avionic said:
Solenoid operated switch. Largest switch assembly in the unit.. Could also be a problem with the Tone control /switching logic board.

https://audiokarma.org/forums/index.php?threads/yamaha-c-70-project.747782/

There is 6 slide switches that may require disassembly and cleaning. If it is stuck in one function -- I'd start with the logic board and make sure your getting the voltages to all 6 solenoids when the function buttons are pressed.
Click to expand...

Thanks, much appreciated. :thumbsup:
 
You must log in or register to reply here.
Back
Top Bottom