Sansui Sled2453w No Standby Set Is Dead

[Sinfury2112]

Re: Sansui Sled2453w No Standby Set Is Dead

tried replacing the 50v 22uf no change

[jetadm123]

Re: Sansui Sled2453w No Standby Set Is Dead

What's the part number of the 8-legged chip connected to the startup cap that you just replaced?

[Sinfury2112]

Re: Sansui Sled2453w No Standby Set Is Dead

what's the part number of the 8-legged chip connected to the startup cap that you just replaced?

6c12105
5640

[Sinfury2112]

Re: Sansui Sled2453w No Standby Set Is Dead

I need service manual

[CapLeaker]

Re: Sansui Sled2453w No Standby Set Is Dead

Check that thermistor

[dick_barton]

Re: Sansui Sled2453w No Standby Set Is Dead

If the 5640 is an FA5640 then the pdf file is available from:-



Vcc on pin 6 should be a min 11V, typ 14v, max 26V

[Sinfury2112]

Re: Sansui Sled2453w No Standby Set Is Dead

thermistor says 4.7 1136 on it im assuming its 4.7 ohm it tested 5 or 6 ohm cold and dosent drop much when I wave heat around it with my solder iron is that good?
also theres 9.7v on pin 6 of the 5640

[vinceroger69]

Re: Sansui Sled2453w No Standby Set Is Dead

Try heating the powerboard up nwith a hair dryer for about three to four minutes some times if its a bad capacitor this can get the supply tempory working also 9.7 volts on pin 6 seems low its 11 volt minimum according to the pdf

[Sinfury2112]

Re: Sansui Sled2453w No Standby Set Is Dead

I heated the board like you said not much change at all 9.7 to 9.8 give and take

[Sinfury2112]

Re: Sansui Sled2453w No Standby Set Is Dead

could I add a few volts to see if it will fire up would that be safe?

[CapLeaker]

Re: Sansui Sled2453w No Standby Set Is Dead

Hell NOT! Working on the primary is a dangerous thing as you are connected to the mains!

[budm]

Re: Sansui Sled2453w No Standby Set Is Dead

Did you replace the blown 0.22 Ohms resistor R510 with the jumper wire? Looking at your pictures and the board layout, that's what it looks like to me.
That is the fusible resistor for the Main B+ to feed the SMPS section, that blown resistor will not cause you to lose 170VDC on the main filter cap.
There must have been a shorted circuit to take out that fusible resistor and the shorts circuit could have blown open circuit otherwise it will blow the main AC fuse if the shorts is still present.
So for sure you are getting 170VDC between the two legs of the main filter cap?
"Fuse is good I found a blown 0.22 ohm resistor replaced that now have 170v across main cap"
This statement does not make sense at all since the resistor is connected to the + leg of the cap, and the other leg of the resistor is fed to the SMPS section.
That fusible is blown for a reason.

[Sinfury2112]

Re: Sansui Sled2453w No Standby Set Is Dead

yes that is a jumper wire I added the fuse never blew and I do get 170v across the main cap

[budm]

Re: Sansui Sled2453w No Standby Set Is Dead

Check R505 (Source resistor for the MOSFET), it should be <1 Ohms.
Also take the resistance readings of all the pin against the GND pin of the SMPS IC FA5640 and report the readings.

[Sinfury2112]

Re: Sansui Sled2453w No Standby Set Is Dead

its 055.8k

[Sinfury2112]

Re: Sansui Sled2453w No Standby Set Is Dead

1 = 23.74k
2 = 150k
3 = 057.0k
4 = gnd
5 = 088.8k
6 = jumping all over the place
7 = 0.L
8 = 39.69m and climbing

[budm]

Re: Sansui Sled2453w No Standby Set Is Dead

"could I add a few volts to see if it will fire up would that be safe?" The VCC pin 6 is fed by the internal charge pump circuit which through VH pin 8 which gets the High B+ Voltage through the resistors R501, R512, when the charge pump circuit charges up the Startup/running cap connected to the VCC pin till it reaches the minimum startup Voltage, when that Voltage is reached the IC will send the drive Voltage to drive the Gate of the power MOSFET which then the MOSFET willl drive the power transformer, tho provide the output Voltage on the secondary side winding, at the same time the Aux winding of the transformer will provide the running Voltage to keep the SMPS IC running, the charge pump circuit is then shutdown.
So right now you may have bad Voltage at pin 8, bad charge pump circuit, internal leakage on VCC pin that not allow the VCC to reach the required start up Voltage, bad startup/running cap.

[budm]

Re: Sansui Sled2453w No Standby Set Is Dead

its 055.8k

That is blown as I expected, That is the source resistor for that MOSFET Q501, for that resistor to blow up, the MOSFET must have conducted (or shorted out)heavily to take out the fusible resistor and the Source pin resistor, R505 looks to be 0.22 Ohms 1W 5% MOX type.
At this point I would replace both resistors with the correct one not with the jumper, and replace the IC and also the MOSFET Q501.
You also need to check the Gate drive R/D (Resistor-Diode) network which is connected between the drive pin of the IC and the GATE pin of the MOSFET.

[Sinfury2112]

Re: Sansui Sled2453w No Standby Set Is Dead

the 8 pin ic is the one needs replaced?

[budm]

Re: Sansui Sled2453w No Standby Set Is Dead

the 8 pin ic is the one needs replaced?

Yes,the IC FA5640, the MOSFET, RESISTORS, ...