1st thing in troubleshooting is CLEANING! If the contacts on the switches, pots, sliders, etc., aren't clean you get either degraded sound or no sound. So grab the Service manual from HIFIENGINE or here and look at the exploded diagram on how to disassemble the front face panel to access the pots and switches. Turn off and UNPLUG the 450.
Tape Monitor button, is #1 suspect. As it doesn't get used it builds up crud on the contacts which loose contact. The Mono switch will sum both channels and then send it to both.
Get the DeOxit (D5 and G-5) and clean the living crap out of every control on the front panel and back panel(including the RCA JAcks with Qtips inside them).
If you can't get G-5 locally you can use CRC 6-26 electronics lube short term. DeOxit available Guitar Center. G-5 may be there also. If not go to Home Depot in electrical Dept and CRC is there.
1.)Give every switch and pot a short spritz with the D-5 (startat one end and work to the other.) NOTE!!!!! POWER SWITCH on the back of the speaker rotary switch DOES NOT GET DEOXIT!!! And keep it away from the TUNER Variable Cap (the big thing with all the fins!). Get DeOxit on that and you'll DETUNE IT.
2.)Turn, push, or flip each 2 times to spread Deoxit inside.
3.) Walk away or 30-45 minutes.
4.) Spritz everything again, one at a time and then EXERCISE each 40-50 times.
5.) Repeat for next until done.
6.) Remove 90% of cotton from Qtip. Soal in DeOxit and swab inside of RCA Jack, spinning Qtip while pushing and pulling a few times.
7.) let dry overnight and TEST!
If ok, button it up. If not then some deeper testing and trouble shooting is needed.
Larry
