Thread: Yamaha CA-400
View Single Post
Old 17th Nov 2022, 9:27 pm   #1
EF80TVVALVE
Octode
 
EF80TVVALVE's Avatar
 
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,431
Default Yamaha CA-400

Hi all,

Well I thought I'd make a relevant thread for this amplifier. I bought it locally and it caught my attention being a nice bit of 70s teak finished kit and I could do with a good amplifier for my hifi. It was sold as having one channel missing but in reality the faults were much more severe.

I have now replaced all of the rectifiers, some were burned up and others were short so it wouldn't have worked very well in that state. One of the large 4700uF capacitors had a hole in the side and the other although in good physical condition was a dead short. I also had to replace the 10R 2W resistor which had burned up.

With all of the above done I applied a bit of power via the Variac, a suspicious warm smell soon eminated and I traced this to the replacement 'D705' rectifier getting hot. As this supplies the output transistors this will be my next area to investigate as something in this circuit is drawing excessive current. I believe the transistors fitted are known to be problematic so I'll start there and check the surrounding components.

It seems to be a very well designed amplifier so I look forward to hearing it working especially having never heard a yamaha amplifier of this age either.
EF80TVVALVE is offline