Pioneer SX-838 voltage problems???

Tomcow

Active Member
Pioneer SX-838 powers on but no relay.Getting strange voltmeter readings on both power supply board and protection board.PS,pin 1,-21mv,pin 2,plus 20mv,pin 3,plus 20mv,pins 4 and 5,plus and - 41V,pin 6,0mv,pin 7,-43V,pins 8 and 9,-155mv,pins 10 and 11,plus 10V,pins 12 and 13,plus 14V,pin 14,plus 12.7V,pins 15 and 16,0mv,pin 17,plus 49V,pins 18 and 19,minus 187mv,pin 20,0mv,pin 21,7V,pin 22,6mv,pin 23,plus6.2mv,pin 24,-6.3mv
 
Protection Board:pin 1,plus 10V,pin 2,-156mv,pin 3,-12.8V,pin 4,0mv,pin 5 and 6,plus 10V,pins 7 and 8,-12.9V,pin 9,plus 3.8V,pins 10 and 11,plus 14.7V,pin 12,plus 7.4V,(AC)
 
A little clearer format (then I'll try to digest them):

Power Supply:
Pin 1, -21mV,
Pin 2, + 20mV,
Pin 3, + 20mV,
Pins 4 and 5, ±41V,
Pin 6, 0mV,
Pin 7, -43V,
Pins 8 and 9, -155mV,
Pins 10 and 11, + 10V,
Pins 12 and 13, + 14V,
Pin 14, + 12.7V,
Pins 15 and 16, 0mV,
Pin 17, + 49V,
Pins 18 and 19, minus 187mV,
Pin 20, 0mV,
Pin 21, 7V,
Pin 22, 6mV,
Pin 23, +6.2mV,
Pin 24, -6.3mV

Protection Board:
Pin 1, + 10V,
Pin 2, -156mV,
Pin 3, -12.8V,
Pin 4, 0mV,
Pin 5 and 6, + 10V,
Pins 7 and 8, -12.9V,
Pin 9, + 3.8V,
Pins 10 and 11, + 14.7V,
 
Last edited:
Check the voltages on the PS board Pins 1, 2, 3, 18, 19, 22, 23, & 24 on an AC volts scale.
 
Ok.pin 1,37.5V,pin 2,31.7V,pin3,31.7V,pin 18,38.9V,pin 19,38.9V,pin 22,7.5V,pin 23,7.7V,pin24,6V all read with voltmeter on AC.
 
So the updated measurements are:

Power Supply:
Pin 1, 37.5VAC,
Pin 2, 31.7VAC,
Pin 3, 31.7VAC,
Pins 4 and 5, ±41V,
Pin 6, 0mV,
Pin 7, -43V,
Pins 8 and 9, -155mV,
Pins 10 and 11, + 10V,
Pins 12 and 13, + 14V,
Pin 14, + 12.7V,
Pins 15 and 16, 0mV,
Pin 17, + 49V,
Pin 18, 38.9VAC,
Pin 19, 38.9VAC,
Pin 20, 0mV,
Pin 21, 7V,
Pin 22, 7.5VAC,
Pin 23, 7.7VAC,
Pin 24, 6VAC

Protection Board:
Pin 1, + 10V,
Pin 2, -156mV,
Pin 3, -12.8V,
Pin 4, 0mV,
Pin 5 and 6, + 10V,
Pins 7 and 8, -12.9V,
Pin 9, + 3.8V,
Pins 10 and 11, + 14.7V,
 
Is that the little square black box with the 2 arrows on top pointing at each other?3 pins going into the board? What should it read?
 
That's the square box. The two arrows each represent one diode. Those can be tested for resistance in the forward/reverse direction using the center (common) lead as a reference for each diode. The resistances should be around 500Ω in the forward direction and at least 1,500Ω in the reverse direction for each half.
 
Is this the SR3am-8 rectifier?It could certainly cause all the voltage problems on the PS board,I would think.Could it be replaced with a 512-1N5404?
 
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