I bought a Channel Master 6430 Reel to Reel, which is the Sanyo 929E. It has a problem of weak volume output when play tape or using line in. The volume knob works but the maximum volume only gives below normal audible volume.
However, if I plug an audio lineout into the mic input, I get loud output. And it can produce audible sound when volume knob turned to 10 or 11 o'clock, where become very loud at maximum.
Initially, I am thinking the problem should be in the preamp section (left section in the schematic) and the power amp section (it can output to speaker directly) should be good? I took out the 2sb186 PNP GE transistor (TR-2, TR-8), it tested OK (With 0.15v drop and OL in correct direction).
So, it is, probably, not due to the transistors? Any suggestion which parts I should focus on instead of testing everything?
Thanks
However, if I plug an audio lineout into the mic input, I get loud output. And it can produce audible sound when volume knob turned to 10 or 11 o'clock, where become very loud at maximum.
Initially, I am thinking the problem should be in the preamp section (left section in the schematic) and the power amp section (it can output to speaker directly) should be good? I took out the 2sb186 PNP GE transistor (TR-2, TR-8), it tested OK (With 0.15v drop and OL in correct direction).
So, it is, probably, not due to the transistors? Any suggestion which parts I should focus on instead of testing everything?
Thanks