power supply problem

[goodsguys]

Hi And thanks for reading this post.

The ac output on my quad 405-2 amplifier's transformer is 71 volts but keeps going up and down by approximately 0.1- 0.3 volts everytime i measure it. Is this normal and is this the correct voltage.

Many thanks in advance. John.

[Firebottle]

Hi Mark, that's no problem at all, the incoming mains voltage variation is the reason that is happening.
70 volts is correct, there is a centre tap on the winding also so in reality you have a 35-0-35 transformer output. When rectified this gives the +/- 50V supply rails.

Cheers, Alan

[goodsguys]

Thanks so much for the reply.

For the smoothing capacitors i have the old caps from the 1970's still installed. I am thinking of replacing with panasonic fc caps 1000uf x 10.

Do you think this is a good idea or should i use one large capacitor. I am a little worried about so many soldering joints but it may pay off with lower esr.

I have tried the panasonic fm's before in a dac and loved the results but unfortunately they are only available up to 50 volts.

Many thanks in advance. John.