Last week I finished restoring the above Pioneer SX-450. I was surprised at how well this unit sounded after a little bit of restoration.
These 450 units have a history of “browning out” with flickering lights when you power them on. The contacts in the power switch get oxidized (dirty) and begin to arc, causing the flickering lights. This one was just beginning to flicker so I decided, for the first time, to clean the switch.
Since this was my first time cleaning the switch, I did not do a good job of taking photos or video to show how it can be done, but I have another 450 with a dirty switch that I can use for a tutorial. Just know the switch is hard to get to and requires a lot of patience to clean and reassemble. I mistakenly reassembled the switch multiple times which was very frustrating. Once I got it back together properly though, it worked great.
Once the switch was cleaned, I noticed a loud thump when powering on the unit. Again, this is common with 450s and I found advice on AudioKarma on how to bypass the thump without having to recap the power supply. The bypass can be seen in the video below:
I decided to go ahead and recap the power supply which was quick and easy to do.
It only required the below caps to be replaced:
- C303 – 100 uf/50 volt
- C304 – 22 uf/50 volt
- C305 – 220 uf/50 volt
- C306 – 220 uf/50 volt
- C307 – 100 uf/25 volt
- Two Large Filter Caps: 4700 uf/35 volts
After the recap, the unit still has a slight noise when powering up but it’s a lot less noticeable than before.
I also installed new LED lights, which require wiring in new bases to fit the LEDs. I chose a cool white LED which make it looks nice and clean without being too bright.
These vintage units often lose their original veneer on the panels so I went ahead and installed new veneer which looks great.
After a few hours of listening, I was impressed with how well this little unit sounds. I bet recapping the entire unit would improve sound further. I might try recapping more on the next 450.
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Aaron Hartley 