Reference 450R by Quadraflex

previd01

previd01

Idaho Spud
I ran across this receiver a while back, and since I worked for Pacific Stereo for many years, it caught my eye. I decided to write this post to help anyone else who has run across this problem while trying to restore the output section. The problem, bad output transistors,burnt resistors, NO SCHEMATIC! Since both channels were fried and the same resistors were burnt beyond recognition, I could not determine their value. The Quadraflex brand was a Pacific Stereo mid-level house brand. Entry level equipment was Calibre, high end was Concept. Back in the day, the schematics were on microfiche cards and every stores' service department had them. Mine are long gone. Then it dawned on me. Quadraflex and Concept (and perhaps Calibre) were made by the same company in Japan for Pacific. I looked up (on the AK data base) the Concept 4.5 schematic. Bingo! The output stage is identical. Only the reference numbers for the components were changed. The power supply, phono preamp and protection circuits also appear to be the same. Oh the sweet smell of success!
 
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Someone else pointed out once that the phono board was the same as concept in the quadraflex 450 and the 650. But the amp section the same also, that's good info as I have a 450R in my room setup, love the looks of these receivers. When I got it it also had one bad channel and burned resistors in the amp section. Took a lot of help from the great folks here on ak to get it fixed. I also have a 650 (someday I might get fixed) that I stole the phono board out of to put in the 450.

Also have a fully functional 180R.
 
Reviving an old thread, but I recently acquired a 450 that I need to take in and have cleaned up. Guy has done a ton of amps but never a Quadraflex, thanks for the information.
 
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