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Sansui 4000 issues.

Stereoboy70

Stereoboy70

Active Member
Hello all. Been awhile since I’ve posted. I’m having some issues with my 4000. No sound from any inputs, AM or FM. I rebuilt both amps (1150) the EQ board (1169) preamp board (1149) MPX board (1185) protection board (1176). New caps and new transistors. Also new filter caps etc.. The 2SD213 output trans are checking ok.
DBT shows no issues. Input voltage and DC voltage is correct. I’m missing something. I’ve checked most all of the resistors and all within spec. Level adjustment pot is all the way CW. Cleaned all pots and switches. What’s next??
 
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Check that the tape monitor button is disengaged ( out ) and your function switch is properly aligned to each function. Ken
 
Hi,

If you haven’t already done so - check that you are getting the correct voltages out of the Protector PCB F-1176 on the underside of the chassis. You should have approx +24VDC on pad 9C, and approx +64VDC on pad 9G (both measured to ground/chassis). If you don’t have any voltage at 9C, that you have approx 25VDC at lad 9A, if ok then check the protector lamp, and the SCR’s on the pcb for anode to cathode shorts.

Cheers
John
 
skippy124 said:
Hi,

If you haven’t already done so - check that you are getting the correct voltages out of the Protector PCB F-1176 on the underside of the chassis. You should have approx +24VDC on pad 9C, and approx +64VDC on pad 9G (both measured to ground/chassis). If you don’t have any voltage at 9C, that you have approx 25VDC at lad 9A, if ok then check the protector lamp, and the SCR’s on the pcb for anode to cathode shorts.

Cheers
John
Click to expand...
Thank you. I did find a bad transistor on the ripple filter board though. I’m hoping it’s the issue. I will check the other. I’ll definitely let you know.
 
skippy124 said:
Hi,

If you haven’t already done so - check that you are getting the correct voltages out of the Protector PCB F-1176 on the underside of the chassis. You should have approx +24VDC on pad 9C, and approx +64VDC on pad 9G (both measured to ground/chassis). If you don’t have any voltage at 9C, that you have approx 25VDC at lad 9A, if ok then check the protector lamp, and the SCR’s on the pcb for anode to cathode shorts.

Cheers
John
Click to expand...
I replaced the TR 001 transistor on the ripple filter board and now I get a constant hum from both speakers and it increases to a pulsing hum that gets louder and my DBT gets brighter with the pulsing.
 
skippy124 said:
Hi,

If you haven’t already done so - check that you are getting the correct voltages out of the Protector PCB F-1176 on the underside of the chassis. You should have approx +24VDC on pad 9C, and approx +64VDC on pad 9G (both measured to ground/chassis). If you don’t have any voltage at 9C, that you have approx 25VDC at lad 9A, if ok then check the protector lamp, and the SCR’s on the pcb for anode to cathode shorts.

Cheers
John
Click to expand...
Checked all V at 9a c and g. All good. Humming went away but still no sound. Had to replace an rca jack at the Aux input also. Replaced T001 on 1187 board which was bad and that’s when the humming started. Protection bulb is good. Still hunting the issue. I haven’t replaced a couple of transistors on the 1176 board but they tested good. All diodes on 1187 board are testing good. Checked T002 and it passed. I’m not the best at reading schematics but I can at least see where things are going.
 
skippy124 said:
Hi,

If you haven’t already done so - check that you are getting the correct voltages out of the Protector PCB F-1176 on the underside of the chassis. You should have approx +24VDC on pad 9C, and approx +64VDC on pad 9G (both measured to ground/chassis). If you don’t have any voltage at 9C, that you have approx 25VDC at lad 9A, if ok then check the protector lamp, and the SCR’s on the pcb for anode to cathode shorts.

Cheers
John
Click to expand...
 
Stereoboy70 said:
Checked all V at 9a c and g. All good. Humming went away but still no sound. Had to replace an rca jack at the Aux input also. Replaced T001 on 1187 board which was bad and that’s when the humming started. Protection bulb is good. Still hunting the issue. I haven’t replaced a couple of transistors on the 1176 board but they tested good. All diodes on 1187 board are testing good. Checked T002 and it passed. I’m not the best at reading schematics but I can at least see where things are going.
Click to expand...
All voltages on protector board are ok. I’ve double checked wiring and components. I did replace TR903 and SCR 901,902. Also TR901,902. NOTHING….. no sound. I’ve checked all the SD 213 Outputs. All good. I tested all the switches on board 1176,1184 and 1149. Ohmed out the level adjust on back. I’m missing something here. Selector switch is working correctly also. I’ve repaired many receivers and this has me baffled for some reason. Thanks for your help.
 
Sorry if I missed it - was the issue occurring before you rebuilt those boards?

Did you test after you worked on each board?
 
mikiekimi said:
Sorry if I missed it - was the issue occurring before you rebuilt those boards?

Did you test after you worked on each board?
Click to expand...
Unit was dead. A buddy dug it out and plugged it in and no sound. He gave it to me. I have tested every component on both amp boards. All resistors are ok. Diodes are ok. Transistors were replaced except the metal ones but I pulled them and tested them. Ok. The outputs were pulled and tested ok. I have good V everywhere. I’ve checked the speaker switch, the volume pot , the level pot on the back, the selector switch, all of my VR,s on the boards etc…. I rebuilt the amps, the EQ board, the protector, the preamp board, the the MPX board , the ripple filter, and a new resistor on the H/L filter board.
 
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