Toshiba 55SV670U No standby light with 5 standby volts

[jhbox]

Re: Toshiba 55SV670U No standby light with 5 standby volts

@R_J

Unless you know something I dont, there isnt any cap at C898, C890 or C895.
No voltage on the coil of SR81 or R853. Hard to tell from looking at the board too.

[R_J]

Re: Toshiba 55SV670U No standby light with 5 standby volts

I was looking at the bottom view of the Shopjimmy board, I guess some of the locations don't have caps in them, I was trying to see if there was any voltages on the secondary of that circuit of T880

[jhbox]

Re: Toshiba 55SV670U No standby light with 5 standby volts

This board is not very clear near the relays, hard to tell where anything is going to, or maybe its just my inexperience talking again.

[jhbox]

Re: Toshiba 55SV670U No standby light with 5 standby volts

I did my best to follow the circuit, ended up finding what i think is a diode at Q862 (directly above Q832) that appears to not be getting any juice through it. Both are reading about -7 on one side, but only Q832 is showing anything on the other, about 7. Any opinions on this? I can't get a reading on either out of circuit.

[Doc38343]

Re: Toshiba 55SV670U No standby light with 5 standby volts

You need to try and find a known good reference point following the paths of input.
what i mean is for example we know you have mains so go to the nearest DC on the OTHER SIDE of the isolation coil.. it is marked COLD / AC high voltage side is marked HOT, since you have some voltage showing you can stay out of that side. For example a coil can have two or more secondary's putting out different voltages. they will be lower voltage AC then they go thru another set of diodes to rectify and some smoothing filter caps... all this leads to some control circuits that do a lot of different things... try to find the last common part that is still good.
Another way would be to follow the working Pin like your 5v backwards to the source.. then you can see where the other missing voltages come from and begin to find whats not working... Q marked parts are transistors D marked parts are diodes and they can look alike when the 3 leg SMD. Q transistors act as switches to turn on or off bigger current carrying IC's or Mosfets that basically look for a condition then turn on to supply power. the engineers do all that for safety so hopefully nothing burns...
In your case something is failed that is not allowing the IC to trip on the Mosfets to supply power to a particular rail. R_J is the man he has helped me solve many a riddle.
Also what they are telling you is when you have your 5v standby power it tells the main board to look for an ON command from your remote or the power button. that is commonly 3.3v then when you press power it turns on some of those little Q transistors and sends a signal back to the power supply to turn on even more transistors. try to be sure what happens on each pin of the connector when you press power with the meter on it. I have to get my wife to help me on that part because i'm old and shaky and don't want to short anything.

[R_J]

Re: Toshiba 55SV670U No standby light with 5 standby volts

The only reference I have are the shopjimmy pictures, you have the board in front of you. Q862 is a 4 leg optocoupler (white), Q832 must be the other one (top number is blocked by cap) There are about 4 seperate smps on this board, It looks like the one for standby +5 (Q840,T840) is working and supplying voltage to turn on SR80 which powers up the ciruit around Q880

Q862 & Q832 look like they could be for the +24 volts, one to turn it on and one for feedback? maybe?

On PJ90 pin 7 is the POW_TV You had 3.23 volts, correct. Does this voltage change when the power button is pressed?
On PJ91 Pin 2 POW_SIG does this pin change when power button pressed?

It looks like Q813 is what might produce the 3.3 volts for the POW_TV pin
---------------------------------------------
With meter negative on C880, what are the voltages on Q880, also what is its number? (STR-Y6456)?

[budm]

Re: Toshiba 55SV670U No standby light with 5 standby volts

What dcv do you have on the connector PJ91 on pins:
AC_DET: it should be about 3V when power switch is activated.
POW_PRT: it should be around 3V when power cord is plugged into the wall.
POW_SIG: it should be about 3V when power switch is activated.

There are 3 power supplies for the board.
Relay SR81 is for the PFC Voltage booster and 24V power supply (transformer t860).
Relay SR80 is for the 18V_AUDIO and 12V power supply (Transformer T880)
5V1 Standby power supply (Transformer T840).

[jhbox]

Re: Toshiba 55SV670U No standby light with 5 standby volts

@R_J
Yes, 3.28 on POW_TV.
No change on POW_SIG , showing 0

@budm
AC_DET : nothing when power switch is activated or otherwise
POW_PRT: 3v
POW_SIG: nothing when power switch is activated or otherwise

[jhbox]

Re: Toshiba 55SV670U No standby light with 5 standby volts

Also, I took a look at those Q transistors. Looks like I'm getting continuity across the cathode and anode pins of Q881, Q841, and Q852. Getting no continuity across Q813 and Q832. Looks like those last two need to...be replaced? Not going to lie folks, I'm lost here. Thanks for all your tutelage so far.

[budm]

Re: Toshiba 55SV670U No standby light with 5 standby volts

To me at this point the POW_SIG is the key, I believe if it is not present then the whole power supply will be on, but then again I am not 100% sure since we do not have the diagram for the board.

[R_J]

Re: Toshiba 55SV670U No standby light with 5 standby volts

Why did you replace Q880? Have you even checked that circuit?

[jhbox]

Re: Toshiba 55SV670U No standby light with 5 standby volts

@budm
I'll see if I can track down POW_SIG. Still not getting a standby light on the front though.

@R_J
In my research I saw that R851 and Q880 often go bad together, or that was the jist I got. either way, I've got steady volts coming off of it, so its doing its job.

[budm]

Re: Toshiba 55SV670U No standby light with 5 standby volts

BTW, what are the coil Voltage rating of the relay SR80 and SR81?

[budm]

Re: Toshiba 55SV670U No standby light with 5 standby volts

I did more research about the power supply PE0702A.
I found some info for PE0702, it is not the same power supply as PE0702A but it has the same pin out Voltage readings of the connectors. As you can see, right now the main board is not sending the POWER_SIG to turn on the power supply.
I believe you are having problem with the main board since you also indicate that you are getting the Standby indicator light either.

[jhbox]

Re: Toshiba 55SV670U No standby light with 5 standby volts

I did more research about the power supply PE0702A.
I found some info for PE0702, it is not the same power supply as PE0702A but it has the same pin out Voltage readings of the connectors. As you can see, right now the main board is not sending the POWER_SIG to turn on the power supply.
I believe you are having problem with the main board since you also indicate that you are getting the Standby indicator light either.

I'll take a peek at the main board tonight, have to admit I haven't given it any real attention. I'll be relieved/annoyed if it turns out to be something dumb there.

[budm]

Re: Toshiba 55SV670U No standby light with 5 standby volts

So what are the DCV coil rating of those two relays (SR80, SR81) I asked about?

[jhbox]

Re: Toshiba 55SV670U No standby light with 5 standby volts

@budm
Sorry its taken me so long to reply. 4.92on SR80 and a flat 0 from SR81.

[budm]

Re: Toshiba 55SV670U No standby light with 5 standby volts

@budm
Sorry its taken me so long to reply. 4.92on SR80 and a flat 0 from SR81.

I need the DCV rating as printed on the relay's body.

[jhbox]

Re: Toshiba 55SV670U No standby light with 5 standby volts

Pardon me. 12 on SR81, 5 for SR80

[jhbox]

Re: Toshiba 55SV670U No standby light with 5 standby volts

I was unable to detect anything obviously wrong with my main board, though perhaps I don't know what to look for. I'll try to ID the fuses and caps there and start going through them, lacking any expert guidance from the sages here