Philips 37PF7321/98 cannot turn on

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

7102 in the circuit diagram indicates STP6NK60Z. But the actual component on the board is STP3N60ZFP.

Which should I get, the 3 or the 6?

[budm]

Re: Philips 37PF7321/98 cannot turn on

"there seems to be a polyester 100pf 5% 1kv in line on the 12 volt line and just out of the transformer" Are you talking about C2507 (100p) connected to transformer T5500 PIN 6?
The 11V in the SCH generated by D6140 (connected to transformer pin 7) that is showing 80V, is that the one?

[stj]

Re: Philips 37PF7321/98 cannot turn on

use the 6, it has half the on-resistance so it will generate much less heat aswell as handling more power.

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

7102 in the circuit diagram indicates STP6NK60Z. But the actual component on the board is STP3N60ZFP.

Which should I get, the 3 or the 6?

either will work depending on availability
the 6 is rated at higher watts so it should be a bit tougher

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

"there seems to be a polyester 100pf 5% 1kv in line on the 12 volt line and just out of the transformer" Are you talking about C2507 (100p) connected to transformer T5500 PIN 6?
The 11V in the SCH generated by D6140 (connected to transformer pin 7) that is showing 80V, is that the one?

yes, that is the capacitor I mentioned
D6140 is an SOD-57 2a 600v avalanche diode (We do not know if the 80v is there or in the other line yet) have to wait till power gets back up to check this

I am thinking the voltage is in the other line because it looks like the D6140 circuit is running to the cathode end of a diode at 6148 ??

PS: this is probably only the second time that I have actually had a schematic to work with, so I could be reading something wrong ??
I have done over 1000 boards, but all old school

[budm]

Re: Philips 37PF7321/98 cannot turn on

On that 11V line right at the Cathode of D6140, it only has 470nF filter so it will be very high frequency pulsing DC, it is not filter to steady DC unil it passes through 10K R3175 and filtered with C2140 10uF, so his meter will not show correct reading at the Cathode when he tries to measure that point.
Q7531 +5_SW MOSFET is turn on and off by Q7532 whis is part or the PS_ON/OFF circuit Q7506, Q7507.
Q7532 is normally on (it is OFF when TV is ON) when TV is OFF which will route the bias voltage through resistor R3121, 3153 for Q7531 through ground through D6133.
THE 100PF 1KV cap is part of the RCL snubber network for D6504 which is for 35~50VDC (I do not exact value) which is used for Tuner.

[budm]

Re: Philips 37PF7321/98 cannot turn on

If you redraw the circuit, then you will see the function of that C2507 100p 1KV cap, it is part of the snubber circuit.

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

How I wish I can understand what you guys are talking about.

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

Replaced 7101 and 7102. Fuse 1315 still popped.

The voltage at 1306 on main power board is 140vDC on pin 1 and -140vDC on pin 2. Negative probe to negative pin on big Cap.

But from post #37, it used to be 140vDC and -80vDC.

Looks like 7102 survive. Gate to Source is 9.35Kohm, Gate to Drain is 1Mohm, Source to Drain is 2Mohm.

7101 also looks ok.

What is wrong?

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

Something else in that area must have gone
Did you check all the resistors and diodes in that area before you reinstalled the parts ?

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

check to see if 2152 is showing shorted

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

a thought
if you bought the power mosfet with a bare metal large tab instead of a all black plastic one, Did you install an insulator behind it ?

like this
http://www.ebay.com/itm/100Pcs-TO-22...-/161076565624

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

a thought
if you bought the power mosfet with a bare metal large tab instead of a all black plastic one, Did you install an insulator behind it ?

like this
http://www.ebay.com/itm/100Pcs-TO-22...-/161076565624

Yes, there is a bare metal large tab behind the mosfet. I did not install an insulator behind it. So this is causing the short.

I have checked the 2 resistors and they are 470 ohm. The diode's resistance 10 Kohm only showed in 1 direction.

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

Yes that is a big problem and hopefully the only one
Slide a piece of thin cardboard behind it for now

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

Yes that is a big problem and hopefully the only one
Slide a piece of thin cardboard behind it for now

We got the power!

What can I say, you are the genius!

Ok. 7531 mosfet pin1 is 6v, pin 2 is 5v and pin 3 is 5v. The pad on the right of the trace cut is now 96vDC. The ground ref is the black circle in post #56.

7501 optocoupler's pin1 is 1v and pin 2 is 0v.

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

I assume that 7531 was the original ?
That should not have power to all pins with the gate wire disconnected
SO, As I mentioned, when you grounded that to check it, you probably managed to get it to stick like the last one (right now it is stuck to on so your power supply relay probably won't turn off with the switch)
This is why I said you should order another

on the 96v !
Start checking red circles for voltage
greens are ground

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

I assume that 7531 was the original ?
That should not have power to all pins with the gate wire disconnected
SO, As I mentioned, when you grounded that to check it, you probably managed to get it to stick like the last one (right now it is stuck to on so your power supply relay probably won't turn off with the switch)
This is why I said you should order another

on the 96v !
Start checking red circles for voltage
greens are ground

All red circles are 95v except one 125v.

I have replaced a new 7531. Pin 1 is 6v, pin 2 is 5v and pin 3 is 5v. Same as old 7531.

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

125 is too high since the 2508 cap is only rated for 100

but I do not know why it is that high
try checking the 5110 resistor

5110 is not a resistor-- It is a 10Uh inductor or choke so you won't be able to read it for ohms

[bammbammfran]

Re: Philips 37PF7321/98 cannot turn on

All red circles are 95v except one 125v.

I have replaced a new 7531. Pin 1 is 6v, pin 2 is 5v and pin 3 is 5v. Same as old 7531.

silly question
are you sure it is 125 and 95 or did you maybe not see a decimal point which might make it 12.5 and 9.5 ?

[john_doe]

Re: Philips 37PF7321/98 cannot turn on

125 is too high since the 2508 cap is only rated for 100

but I do not know why it is that high
try checking the 5110 resistor

5110 is not a resistor-- It is a 10Uh inductor or choke so you won't be able to read it for ohms

Is the supply coming from the transformer?