[bikerhifinut]

Originally Posted by Michael Maurice

It is generally considered not good practice to have the value of the output capacitors larger than the power supply reservoir capacitors. The original output capacitor is 1500uF and the reservoirs 4000uF.


So by putting in 4700uF's in the output stage, you'd need at least 10000uF or even 15000uF as the reservoirs. That would put a strain on the bridge rectifier which was not designed to feed into such large capacitances. It might even affect the mains transformer and the mains fuse.


If I were you I'd put in 2200uF's for the output stages and 4700uF or 5600uF or maybe 6800uF for the reservoirs.

I don't know where you got 4000uF for the reservoirs Michael as the original user manual shows it as 1000uF and that was what was fitted on the amp.
So I have ordered up new Nichicon caps in values as close as I can get, as per the owners manual. its a full wave rectifier using a pair of silicon diodes and a CT transformer on the ravensbrook series2 just for reference. Its a bit different to its big brother. The circuit is completely capacitor coupled right through with a transformer phase splitter/driver for the output pair.
I remember, going back to my younger days when I blew the original pass transistor in the regulator ( an early lesson in why hi fi amps do not make good instrument amplifiers, I was young and daft, now old and daft) I thought it might be a good idea to increase the value of the reservoir. All it did was to make the sound seem very bass heavy and anything above a very moderate volume caused the 1A PSU protection fuse to blow on transients, caused I assume by the extra reserves ability to deliver a high instantaneous current.
So I am leaving things as they are. In any case I merely want it to work much as it did when new, which was very well indeed.

Andy.