I picked up a TA-500 DC Integrated Tuner Amplifier recently that was described as blowing fuses. Sure enough all 5A fuses were blown. Also C01 had completely come off the board but no obvious signs of heat damage. Possibly just deteriorated from glue corrosion.
I replaced CO1/CO2 330uF/50V Nichicons I had to test. Put new fuses in. DBT showed still short. So pulled Left side Outputs TR05/TR07 and they both tested bad C-E shorts. Now the unit powered up and relay clicks on. Tested Right side with single input on AUX-R and lightly turned up the Right side independent Volume. So that seems to be working.
I wanted to see if the AN7070 was bad offer reading posts that it is failure prone. I am getting some obvious different voltages on several pins and hope I g someone can help me determine if indeed the AN7070 is toast.
Here are the discrepancies and pics of circuit below.
Output to TR05/TR07 should be 0.6 V getting 10v
P-10 = +10V
P-14 = -10V.
Bias circuit inputs.
P-11 = 7.4V. Should be +1.2v
P-13 = 4.9V. Should be -1.2v
I pulled TR03 tested good. VR03 = good, R31/R35 both good.
P-5 = 3.64. Should be about 5.6v
Could be a misprint as R side has 5.6v P5 and both have 25v on P6.
All other voltages match.
Schematic F-3016 amp section
AN7070 drawing.
Any help greatly appreciated.
I replaced CO1/CO2 330uF/50V Nichicons I had to test. Put new fuses in. DBT showed still short. So pulled Left side Outputs TR05/TR07 and they both tested bad C-E shorts. Now the unit powered up and relay clicks on. Tested Right side with single input on AUX-R and lightly turned up the Right side independent Volume. So that seems to be working.
I wanted to see if the AN7070 was bad offer reading posts that it is failure prone. I am getting some obvious different voltages on several pins and hope I g someone can help me determine if indeed the AN7070 is toast.
Here are the discrepancies and pics of circuit below.
Output to TR05/TR07 should be 0.6 V getting 10v
P-10 = +10V
P-14 = -10V.
Bias circuit inputs.
P-11 = 7.4V. Should be +1.2v
P-13 = 4.9V. Should be -1.2v
I pulled TR03 tested good. VR03 = good, R31/R35 both good.
P-5 = 3.64. Should be about 5.6v
Could be a misprint as R side has 5.6v P5 and both have 25v on P6.
All other voltages match.
Schematic F-3016 amp section
AN7070 drawing.
Any help greatly appreciated.