This is an interesting amplifier, a Cyrus 2 along with the optional PSX power supply.
The amp can be used by itself using the built in transformer or you can remove a couple of internal 4A fuses and power it from the PSX (on the right) that has a huge transformer along with four big smoothing capacitors.
When used with the Cyrus PSX, the power supply in the amplifier only powers the preamp section while the PSX provides power for the main amplifier.
This approach keeps the power supply for the preamp clean and unaffected by power supply dips that could happen with the volume cranked up loud. The size of the transformer and smoothing capacitors in the PSX would probably keep the supply stable at any volume!
The amp is pretty minimalist as it has no bass, treble and loudness controls.
So, what was wrong with it?
The main amplifier had a lot of very bad solder joints that I repaired and the LED that illuminates the Cyrus logo in the PSX didn’t work so I replaced it. One of the solder joints was so bad a wire from the transformer could be pulled out of the circuit board!
I also added some wire to share the load going through a somewhat heat stressed copper track (traces as they’re often called) on the circuit board as it could fail in the future.
There was evidence of a previous repair, but that’s not too surprising given its age.
One of the problems with old amps such as this one is the input selector is a mechanical slider switch controlled from the front panel rotary switch.
Those old mechanical switches are almost impossible to repair as the contacts wear out and there’s usually nowhere to spray any contact cleaner unless you take the switch apart.
If you need any electronics or audio equipment repaired please contact me. Info in the link below.