Samsung SMPS Woahs and Obscure Off-Line PWM Controllers SQD3011K

[denimdragon]

I heard that SMPS or a pain, but I never thought it would be like this. I've been fighting this thing for 3 weeks (off and on of course) and I have finally decided to come to the forum and seek the experts! Any input is greatly appreciated.

This unit comes out of a Samsung Giga-Beat MX-HS8500 home audio system. It's a SMPS made by a Dongquan Solytech Enterprise Corporation (China) and I have the schematics, which would be great if I knew what the hell I'm doing (I am smart enough not to fry the little bit of hair I do have left though). The SMPS board sits adjacent to the main motherboard and they are connected with 24 pin connectors and a male to male wire harness.

I checked the voltages on the SMPS side and there is no voltage present. I started by checking the ST5.3V Stand By power rail and there is no voltage present. From what I have learned so far about these Samsung SMPS is that if the stand by voltage isn't there, then it's most likely the SMPS and not the MICOM chip at fault or its external crystal. Plus, Stand By must be activate for the remote/power button to turn the SMPS on to produce the higher voltages. So, from there I put the main board to the side and I can just focus on the SMPS.

The first thing I did was a visual inspection. I noticed that the bridge rectifiers looked a bit shady on the top side of the board and I did some measurements at the solder joints were the meet PCB. There were some intermittent connections when I apply a little pressure. I touched those up pretty good. This fixed that connection issue. I figured I'd look around a bit more at the solder joints on the entire board. Be anal retentive, I end-up touching up anything that had the vague indication of being cold or "iffy", and that was about 75% of the board. No luck.

Next, I checked all the caps for damage, however it was in-circuit with my MESR-100 ESR meter. The caps all looked in ship shape. I do want to go back and desolder two 1500uF 10V Elecs that are on the 5.3V line just for good measure since they are on the suspect rail. They could be fooling me while in-circuit. After I check the caps, I went to the OPTOs next which I measured with the diode function on my 87V and they look suspect. I changed all but one out because it looked good. I later found the ones I replaced to be good as well (Don't give me the red-ass, I'm still a rookie learning the pitfalls of in-circuit measurements).

I then moved on to the TO-23 mosfets and transistors around the OPTOs and desoldered them and they tested good. I also removed the relays that get the signal to turn on the main power and tested them with one of my bench PSUs and the relays are fine as well as the BAV70 dual switching diodes (DB851, DB852) and the 2N7002BK MOSFET (QQ804). Also all fuses have been checked.
I have yet to check the other mosfets because from what I can tell, they don’t come into play until after I have the ST5.3 Volts Standy By and the 5.3V PS_ON. Next, I decided to check the voltages at the component junctions and there is live voltages on the board. On the schematic below, I have marked some of the voltages that I checked on the cold side.

Any instruction or ideas would be appreciated. This is my first time tackling a SMPS other than a computer PSU, and that has always been a capacitor issue. I only found one reference to this Samsung SMPS and it was a guy on Facebook who said he repaired it by touching up a bulk capacitor that had a shorter leg, so it had wiggled loose. Everything else I’ve found is TV SMPS, and this boards’ layout is like there’s 3 power supplies, because the audio amplifiers have their own section, in addition to the primary and secondary.

P.S. Believe me I have watched a ton of YT videos on Samsung SMPS whether it was a TV, monitor, projects. Also, what is this obscure SQD3011K (I believe this is the special Samsung part number for common a IC they sell that access a) Power IC   It’s a Saken IC, but I haven’t been able to find any datasheet on this part number. I found some similar IC datasheets from Saken (uh… I downloaded them all  ) that I believe might be the same but it’s only a guess. STR3A100 Series looks to be the closest thing I can dig up as for as naming conventions that may be similar in denoting the parts characteristics. It’s a hunch.

Big schematic. (Right Click "New Tab") I will upload actual pictures soon.

[denimdragon]

Any ideas? Here are more pictures of the smps. Click for bigger view.









Here's The Power IC. I think it's a Sanken STR3A161HD, STR3A162HD, or STR3A163HD





Thanks in advance 

[denimdragon]

Better schematic shots also:

[coromonadalix]

Only thing i've found it is made by Sanken, no pdf available ?

EDIT : just found this   
http://monitor.net.ru/forum/topic52357-160.html   they link another part number ... STR3A100

[denimdragon]

Only thing i've found it is made by Sanken, no pdf available ?

EDIT : just found this   
http://monitor.net.ru/forum/topic52357-160.html   they link another part number ... STR3A100

Yes, that's the one. I found out that it was just given a custom PN for Samsung. They also have a D2011K which is the 67KHz version. This one is the 100KHz version. What a PITA  It seems that a good majority of their SMPS have these Power ICs branded this way. I don't think it's the chip but I'm not sure. I'm starting to lean toward it being the PFC chip, gleaned from reading another thread here with a similar issue here which I'm going to check here in a bit.

I changed the Elec @ CB816 because it measured 1.73Ω. The other Elecs measured good in circuit, but I my have to remove all those as well. In fact, that's what I'm going to do. I'm not sure if I have all the values. I can grab those that I don't have from Fry's in the morning. I just don't like the NTE stuff. I can always swap them out later with good quality caps if it proves to be a cap issue. I'm just ready to find out what the root cause is.

[fjord]

I had problems with a very similar 60" Samsung LCD TV board. Turned out to be the transistors on the high voltage side. Why don't you check those for proper operation?

[denimdragon]

I had problems with a very similar 60" Samsung LCD TV board. Turned out to be the transistors on the high voltage side. Why don't you check those for proper operation?

Thanks! I'll give that a shot.

[denimdragon]

I've tested all the through hole FETs and the standby circuit TO-23 FETs out of circuit and they all test good. I gone over the entire board with solder in case of faulty joints, changed out the optos, and still no standby power. Anyone have an idea what else to check for? I also checked the rectifier diodes and no issues there. I'm at the point now that I'm about to just start replacing components until it works lol.

[coromonadalix]

When you take measurment  you are on the right ground i hope, you have one for the primary side of the circuit and one for the secondary side .... they are not on the same level

I would automatically change the 3 small capacitors near the ic k3100, sometime one of them is an startup capacitor, it may have changed in value even if its not bulged or leaking and the circuit is sensitive, it may not start. Unless the k3100 is really dead.

You should always have an standby voltage running around, the vss 5v pin, but you have some parts on this line .. check them too.

[denimdragon]

When you take measurment  you are on the right ground i hope, you have one for the primary side of the circuit and one for the secondary side .... they are not on the same level

I would automatically change the 3 small capacitors near the ic k3100, sometime one of them is an startup capacitor, it may have changed in value even if its not bulged or leaking and the circuit is sensitive, it may not start. Unless the k3100 is really dead.

You should always have an standby voltage running around, the vss 5v pin, but you have some parts on this line .. check them too.

Yeap, I'm using the proper grounds. That's the first thing I noticed when I was doing some trace chasing. I will change out those caps you mentioned as well. There is no power right around the ICM852 12V regulator area and the -5V regulator. I've pulled the 12V regulator so I can do a breadboard test and will do the same with the -5V regulator.

I want to test the ICs for PWM and I'm wondering if I can use one of my power supplies or a function generator to send a small voltage (based on the datasheet) to turn them on so I can scope them at the gate drive pins. A low enough voltage should be alright to date or no?

I'm still trying to understand the topology of this circuit. I understand the basic concept on how the SMPS works, but the issue seems to require fine detailed comprehension. After I get this one going, I'm going to practice troubleshooting SMPSs with some old PSUs I have laying around.

[coromonadalix]

To me the k3100 seems to be an open collector smps driver with 1 feedback pin, one with the opto coupler going to pin4 of k3100, i see it like an flyback transformer driver

The big problem is:  you have pfc (power factor correction) section, and with the real smps icp801 ic  section behind it, who will bloc the main dc voltages you should have on the fm801 fuse, i should guess around 400v written on the other schematic section pfc_out pin

If you relays don't close and you don't have this voltage nothing will start on the k3100 smps side.

I would try to isolate the sections, not easy to do,  bypass the relays,  remove connector cn801  just in case,  and unsolder 1 side of d?808 (pfc_out pin)  the relay a and b  close after maybe an given 1-2 secs delay, after the a+b are closed, the a+b is closed together with c  to form the continuity needed to supply the k3100

Do you have an high voltage psu  who does 400vdc current limited      as a start I would have gone around 160vdc and rise it up slowly up to 400vdc to see if the k3100 will start 

Not even sure the problem is around k3100, it may be easily elsewhere ??

Maybe google fuu Ebay to buy a good spare board

[coromonadalix]

oh damn 

You have 2 secondary smps  for the cn801 connector

the first is made with the (icm801) k3100 and the other (ics 801) the ucc25600 ic

And an pic 16f753  who seems to act as an monitoring controller of some sort

It is more complicated as i thought  ....  you have to diagnose the 2 of them and go to the main one ... and to know if the pic controller does its job too, an daunting task for you, even for me

It would try to find an spare board right away

[denimdragon]

oh damn 

You have 2 secondary smps  for the cn801 connector

the first is made with the (icm801) k3100 and the other (ics 801) the ucc25600 ic

And an pic 16f753  who seems to act as an monitoring controller of some sort

It is more complicated as i thought  ....  you have to diagnose the 2 of them and go to the main one ... and to know if the pic controller does its job too, an daunting task for you, even for me

It would try to find an spare board right away

I'm glad I was correct in my assumption. When I saw the Pic16 I knew this was not the normal SMPS! I would love to be able to just purchase another supply, but there are 2 problems. First, I already looked for one    I did find two on eBay, but they were way more than I was willing to pay. And the second reason is I would feel really good if I can repair this one and the knowledge I gain about SMPSs will be invaluable. I am confident that I can do this with help from guys like yourself here on the forum. I'm a patient man, and giving up just leaves a bad taste in my mouth.

Given the information you have told me about the topology, I have a knew perspective on tackling this PSU. I have most of the tools I need to get it done and I have a very good local electronics store where I can source a ton of parts that normally would need to be ordered (plus I have a ton of computer PSU and other PCBs I can snag parts off of if need be). The only thing that I am lacking is a current sniffer and I'm about to construct one of those. I have a couple of LT1028 Low Noise OP Amps, so I'm going to make the Bob Smith model. It will be a lot faster than me using one of my meters and I like the fact that it's audible.

Thanks again for all the help and if you have any more ideas, I'm all ears 

[JimKnopf]

How does the story ended? Have a similiar problem with a D2011K at the moment.