Sony KDL26S4000 no standby

[Dannyx]

Good day folks. I'd like some thoughts on this Sony bastard which doesn't turn on. Actually, it's totally dead: no standby at all. I added the schematic for the supply. Problem is, where it says 3.3v on the right, at CN6200, I get a jumbled mess of an output: jumps around between 4-5v and dies whenever the main board is connected. I traced back the standby supply to IC6100 MIP2h2, but couldn't find too much about this IC, other than a pinout which indicates pin 4 to be VCC but offers no other info to see what voltage should be expected there. Funnily enough, you can just about see a 1 on the right side of the pin just where the image is cut off - what a troll , so I'm expecting around 15v knowing how most of these standby ICs operate. I'm not getting anything close to this on pin 4: all I get is a messy 4-5v just like on the output, so I traced back even further and I believe VCC is supposed to come through D6103 and R6106, from pin 3 of transformer T6100 - "AUX winding" as we usually call this. The diode appears to test fine in diode mode and the diode reads 2.6ohms which is a bit higher than the 2.2 the schematic indicates, but should be good enough.

Another colleague before me had already replaced and reflown many of the components there, as you can see in the close-up, including all the caps and even the IC itself - it still doesn't work. My colleague suggested the large IC at the top (IC6202 MCZ3001), is faulty, which I can accept to a degree, except I presently don't get any standby, which should come BEFORE that IC is even operational. NorCal on YT did an excellent video on MCZ3001, which I don't dismiss as being faulty at this point, but I must first get the standby circuit up and running so we get stable 3.3v on that output...any ideas ? The problem lies in the primary I believe, the giveaway being the unstable input I get on pin 4 of IC6100.

EDIT: also yes, I am aware there's two different ground points of sorts - I'm not measuring on chassis ground, I'm measuring the 3.3v output relative to pin 3/4/9 of CN6200, which are NOT chassis GND !

[R_J]

Re: Sony KDL26S4000 no standby

pins 3,4, & 9 ARE chassis ground via R6121 0Ω and L6103, IC6202 has nothing to do with standby
You might have a faulty opto (PH6100) or reference ic (ic6101)

[budm]

Re: Sony KDL26S4000 no standby

So as usual, are C6104, C6107, C6108 OK? Since you are getting Voltage on the cold side, it means the IC is at least switching otherwise you will not have any output on the cold side at all.
MIP2H2 SMPS IC
Pin 1 - VDD
Pin 2 - FB
Pin 3 - OLP
Pin 4 - VCC
Pin 5 - D
Pin 6 - not present
Pin 7 - S
Pin 8 - S

[R_J]

Re: Sony KDL26S4000 no standby

This is from one of the manuals I found

[Dannyx]

Re: Sony KDL26S4000 no standby

About grounds: this is a weird one, because putting one probe of my meter on one of the lugs used to attach the board to the chassis and the other probe on pins 3,4 or 9, I get nothing - no continuity at all. This is kind-of indicated in the manual, because notice how the GND symbol after R6121 (which is fine BTW) is different than the symbols for GND used, say, higher up, at GND_1. These other GNDs DO connect to the chassis. It doesn't matter, because I had a look through the whole schematic and located the connector where the loom from the supply plugs into the main board, and there the two GNDs come together, so I did the same for now and just added a wire between "STBY GND" let's call it (pin 3,4,9) and "chassis GND" on one of the lugs, which is a real stupid way to describe them, but that's how it is.

About the parts: both the caps mentioned and the parts R_J mentioned were replaced by my colleague the first time around and are assumed to be OK, though I'm not sure exactly which were new and which were salvaged. I know for a fact the caps are new, since he's not the type to reuse old ones, plus he's got a stock on hand ready to go and doesn't bother. He told me that he even replaced the MCZ IC....which was not cheap ! I wish he would've consulted me first One thing I haven't tried is heating up the board to see if anything changes.

Now this other colleague I'm working with has presently replaced IC6101, the MM1530, by botching a SMD package to the bottom of the board, but hasn't tried it out yet. I can't remember what the part is exactly, but care was taken to ensure it's still got a REF of 1.25v, or real close, because a simple TL431 wouldn't suffice - it's got a ref of 2.5v...I guess it would still work to a degree, but the output would overshoot, so it would then require modifying the feedback network, which would certainly be doable.

Now on the primary, I salvaged a diode from another similar Sony board to try and also replace D6103 just in case. I'm not liking the looks of the values I get on pin 4 though - only an unstable 4v...

My colleague needs to brush up on his SMPSs (not to sound like an ass), but he said, even argued, that it's the MCZ that powers IC6100 (not sure how he tried to demonstrate that to me), which I do not agree with. He even believes the Vsense pin (pin 1) is what powers the MCZ via those resistors in series with the main cap...just because it comes from the main cap...where there is power...or something - not correct either. Some major brushing up to do there, which ultimately leads to arguing and an unpleasant work environment...whatcha gonna do

[Andrew F. Ali]

Re: Sony KDL26S4000 no standby

so as usual, are c6104, c6107, c6108 ok? Since you are getting voltage on the cold side, it means the ic is at least switching otherwise you will not have any output on the cold side at all.
Mip2h2 smps ic
pin 1 - vdd
pin 2 - fb
pin 3 - olp
pin 4 - vcc
pin 5 - d
pin 6 - not present
pin 7 - s
pin 8 - s

+10k

[R_J]

Re: Sony KDL26S4000 no standby

I guess those pins 3,4 & 9 are a seperate ground that is not connected to the chassis/panel ground, does seem a bit strange, but it is what it is, so make sure your your 3.3 is stable using pin3 as ground.
Seems to be 3 grounds, Hot or P-ground, chassis ground and that special ground for the standby? which I can't seem to see anywhere else in the manual except for the power supply.

I do se a lot of fuses on the B board

[Andrew F. Ali]

Re: Sony KDL26S4000 no standby

.

[Dannyx]

Re: Sony KDL26S4000 no standby

It does get connected to the chassis eventually, but only through the main board. I tied the two together anyway now so we should be good - it wasn't the problem to begin with. The problem is on the primary somewhere and my money is on that diode I mentioned TBH...I had a fairly problem in the past on a Samsung TV which drove me nuts and I eventually gave up: it had an ICE3BRxxx IC and this thing wouldn't turn on the AUX output (hence no STBY since it was handled by the same X-former if I remember correctly) until I touched my meter probes between GND and its DRAIN pin...completely and utterly stupid and I couldn't fix it even after trying out a new IC...most illogical ! :|

[R_J]

Re: Sony KDL26S4000 no standby

Do you get the power_on signal from the main to turn the rest of the board on?

[Dannyx]

Re: Sony KDL26S4000 no standby

No, and it would be impossible given that 3.3v standby is not the right value and drops to 0 once the board is connected, so there would be nothing to switch. I would've tried strapping that to PS_ON, but I doubt anything would happen....though I'll try it anyway to rule it out.