Sanyo dp47840 No Standby Voltage

[philliesfan30m]

I checked all the fuses. i have no voltage on the secondary side at all. i replaced ic601 which is for the 5 volt standby section but still didn't fix it. i have 170v across the main caps and 19v on the vcc pin of ic601. i thought then it might be r613 was bad but with it out of circuit it read 333k ohm which it is suppose to be a 330k ohm resistor so thats not it atleast i don't think so. i have 170v on 1 side of that resistor and about 256 on the other side where the drain comes off ic601. i checked all the diodes and caps and they seem fine on both the primary and secondary sides. i also checked the opto's and d631 which also seems fine.i did see that shopjimmy did have a repair kit but they are out of stock. maybe ic602 is bad but i don't know how to check it. i'm stumped any help would be appreciated. here is the schematic compliments of tom66. if pics are needed i will take some but hopefully we can figure it out with the schematic cause my camera sucks. page 43 has the schematic diagram.


[SM].pdf&mfg=Sanyo

[budm]

Re: Sanyo dp47840 No Standby Voltage

"i have 170v across the main caps and 19v on the vcc pin of ic601" OK, something does not make sense here for you to have 19VDC at the VCC pin since that voltage is generated by the the rectifier diode D603 which gets its AC voltage from the winding of the transformer T601 PIN 4 and 5. The IC601 must be driving that transformer for it to produce the VCC for the IC once the IC starts running, that is also why you are seeing 256V switching voltage (if you look with the scope, you will see high frequency pulses, if the IC is not driving then the voltage will be steady 170VDC) on the Drain pin. Please verify again to see if you have 5VSTBY or not.

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

i tried to check the vcc pin to make sure and i slipped now i have to figure out what all i ruined on it. i know better i can't believe i did that!

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

ok now the drain is a steady 170vdc i replaced ic601 and resistor r606 which shorted out. now i don't have any voltage on the vcc of ic601. and before i shorted out ic601 when i took a reading of d603 it read around 500 1 way and ol the other way now when i check it in circuit it reads about 50 both ways but when i lift a leg it reads high 400's 1 way and ol the other way.

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

so from what you said now the ic isn't driving the transformer after my screw up. i have check everything on that 5vstb line and can't seem to find any problem parts. i know it didn't seem right but i did have 19v but no voltage on the secondary side at all nor did the standby light on the front come on. i have to be missing something.

[budm]

Re: Sanyo dp47840 No Standby Voltage

"so from what you said now the ic isn't driving the transformer after my screw up" That is correct. I did not dig deep yet in details in the SCH to tell you where to test next.

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

thats ok any help is appreciated. i did check r611 is that for current sensing? it is suppose to be a 1 ohm 2 watt resistor and when i checked that resistor it was reading around 3 ohms which would put it out of tolerance that was with me subtracting the amount of the 2 leads being touched together. i don't know if that would be enough to cause a problem anyways. i'm imagining it would but i'm not sure.

[budm]

Re: Sanyo dp47840 No Standby Voltage

I would take that out and test it off the board, if the resistance went up that will cause the over current sensor to kick in thinking that it has too much current flowing through that current sensing resistor due to higher voltage developed across that sensing resistor.
BTW, all other components around that IC tested fine?

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

i did take it out and tested it and it was higher than the tolerance so i changed it out. yeah i checked everything around that ic and everything checks ok except i just check d640 and it was reading around 250 both ways in circuit and out so now i have to see if i have a replacement. i don't know if that would cause any problems but i am getting desperate.

[budm]

Re: Sanyo dp47840 No Standby Voltage

D640 looks to be 18V Zener to clamp down the feedback signal, that can cause problem if it has low resistance, I wonder if the opto D605 is also damaged.

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

actually the opto d605 does give a slightly different reading than the other 3 opto's in diode mode from 1-2 then reversed i get around 1290 on the other 3 and i get about 1200 on d605 and ol when reversed on all 4. i don't know if that slightly different reading will affect it or not. i don't have 1 of those zener's laying around i am gonna order some they are tiny. i have donor boards but i can't seem to find any that have that zener or if they do have it i can't read any numbers to verify what it is. i do have other opto's that match up but for some reason they put that silicone under all of the opto's so i have to remove it in order to desolder it i am gonna replace it and see what readings i get with the different 1 installed.

[budm]

Re: Sanyo dp47840 No Standby Voltage

We need to find out if the Photo transistor inside that OPTO also shorted out or not, you can use Ohm meter to measure between Collector and Emitter. Do you remember how you damaged the board because I was wondering how that 18V Zener is damged.

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

i was trying to test the vcc and i think i touched the vcc and the drain together.

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

ok i measured all 4 opto's pin 3 is the emitter and pin 4 is the collector with the dmm on 2000k setting. d605 with black lead on pin 3 and red on pin 4 it reads OL with the leads reversed it reads about 557. d606 reads about 16 both ways. d607 reads about 46 both ways. d608 reads 1mohm both ways. i'm guessing that d605 is bad? or is d606,d607,and d608 bad?

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

bump

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

bump

[budm]

Re: Sanyo dp47840 No Standby Voltage

Since > 165VDC was dumped into the VCC pin and any thing that are connected to that pin, the ZENER is already damaged, I would say the Opto D605 is more likely to be damaged. You should also check all those components in red circles. You have spare IC too, right? If in doubt, replace the parts, that much of the high voltage can damage lots of parts.

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

yeah i put in the spare ic but i don't have any of those zener diodes around. i tried to check all my spare boards but they don't seem to have what i need. i also put in another opto in d605 but i don't wanna try it until i get 1 of those zener cause i don't wanna ruin the new ic. i did check all those components and everything else seems ok i also replaced r612. d603 still reads resistance both ways and i'm positive it didn't prior to my mess up in circuit but if i take it out then it read the way it should so i might just change that also to be safe.

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

i changed everything you had circled and still don't have any standby voltage

[philliesfan30m]

Re: Sanyo dp47840 No Standby Voltage

ok now i have the 5vstb and i have approx. .3v on the ps_on pin and i have 2.3v on the line off pin. i think it is some kind of fault putting it in shutdown mode. none of the led lights on the front come on even though i have the 5vstb. the power switch works when i hit the button the voltage goes from about 0 up to about .7 volts. but the mainboard doesn't seem to be sending the signal. so i tried to jumper the 5v and the ps on and still nothing. i haven't checked the ir board but i think something on the mainboard is causing the problem. what is the line off pin for?