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Louie
Louie, Technician
Category: Home Theater-Stereo
Satisfied Customers: 1083
Experience:  Have been in the business 25+ yrs., down to component level.
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Louie, I have a panasonic sa-pt956 that wont power on.

Customer Question

Hi Louie,
I have a panasonic sa-pt956 that wont power on.
Submitted: 7 months ago.
Category: Home Theater-Stereo
Expert:  Louie replied 7 months ago.
Hi Chris and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, can you please try posting back with clear/closeup picture of this board? Click HERE.
Customer: replied 7 months ago.
Can you see this?
Expert:  Louie replied 7 months ago.
Appreciate the picture.Please locate D5896 and determine if there is +6V at its cathode?
Customer: replied 7 months ago.
I got 5.26 at the silver end relative to the chassis
Expert:  Louie replied 7 months ago.
This is the SYS6V and is the standby/housekeeping voltage. Its presence tells us that most likely, the power supply is good BUT another circuit has a fault and the system is inhibiting the power supply from fully turning on.Can you please try locating connector CN5801 and temporarily disconnect it? ...and then attempt to turn on the Panasonic?
Customer: replied 7 months ago.
I can find a CN5802, but no CN5801.
Customer: replied 7 months ago.
what kind of cable is it? flat flex or ribbon?
Customer: replied 7 months ago.
OK - I found it on the controll panel board
Customer: replied 7 months ago.
OK - everything is connected except the CN5801 connector, the unit is plugged in, but everything is dark.
Customer: replied 7 months ago.
as I look at it, it may say CN6801 - it is hard to see.
Customer: replied 7 months ago.
I also tried connecting everything but the CN5802 (with the CN6801 reconnected) and nothing happens.
Expert:  Louie replied 7 months ago.
I understand and please reconnect everything.Using again the chassis as reference ground, determine the voltages each pin of CN5802. Please do this twice; i.e. when just plugged in (standby condition) and again when attempting to turn on.Thanks.
Customer: replied 7 months ago.
with the machine plugged in, everything connected, the voltages. relative to the chassis, of the 5802 connector are :
1) 3.55V
2) 5.89V
3) 0.01V
4) 0.63V
5) 0.24V
6) 0.01V
7) 0.01V
8) 0.01 V
9) 0.01V
10) 0.01 V
11) 0.01V
these voltages did not change when I pressed the power button on the control board. I measured all the pins, then went back and pushed the power button while nmeasuring each one a second time.
Expert:  Louie replied 7 months ago.
The voltage (or lack of it) particular at pin 10 is very significant as it is the PCONT or power control. This voltage should show a change when attempting to turn on and would trigger the power supply to fully power up and provide the other voltages.Please trace where pin 10 wire is connected to the main circuit. Likewise trace and check the voltages of pin 2 and where it leads to the same main circuit.
Customer: replied 7 months ago.
they go over to the FP2901 board, and then they run all over. the #2 wire goes to an inductor... the # ***** goes through a very small SMT resistor and then runs all over the place
Customer: replied 7 months ago.
I went back and tested again and the 10 pin did show a brief pulse of about 4.5 volts when i first pushed the power button. but later presses did nothing.
Expert:  Louie replied 7 months ago.
Interesting and again significant "...tested again and the 10 pin did show a brief pulse of about 4.5 volts..." These however would point to several possibilities and would require (very) patiently checking the main circuit board and still also the power supply on a component level.There is a "trick" of fooling the power supply into turning on. This is brute force bypassing the protection circuitry BUT may also be destructive in the sense that whatever is wrong may/would burn and together with it other components.Which would you be comfortable with proceeding; 1 component at a time or bypass?
Customer: replied 7 months ago.
lets try the bypass
I can get a replacement for $50 on Ebay, so it is not worth the 1 by 1 time
Customer: replied 7 months ago.
I need to run some errands today before stores close. so this may have to lag.
Expert:  Louie replied 7 months ago.
I understand; later then when able.This would also give me time to re-check the schematics and work out how to hopefully lessen the impact of the bypass.
Customer: replied 7 months ago.
ok
Expert:  Louie replied 7 months ago.
Cheers.