Fake Switching IC Necessitated Transplant And Modification In IBALL SMPS MODEL SPS252
From the caption you all would have guessed that this is not a case where I just replaced the caps and did dry solder patch up to bring the SMPS back to a crank start! This is a case, where I spent a lot of time in blinking ignorance after doing all tests to locate the fault in the primary switching section. Let us start the story from the beginning, like long, long time ago……………
The SMPS was among the four brought to me in dead condition. The capacitors in the secondary stage were seen bulged, though the fuse was intact! After doing a ring test, which showed all the three transformers very healthy, with a full glow of LEDs, did a thorough dry solder patch work along with replacement of all the electrolytic capacitors, as the 470uF/200V cap itself was reading just 210uF to quote an example. Then cleaned the board thoroughly using IPA and allowed it to dry up before applying power. Then connected the SMPS tester unit, a 12V 25W Bulb as load and the fan. To my dismay, there was no output when I applied the power. The tank capacitors were full and remained like that even after switching off until the bleeding resistor did its part. This was a clear indication that oscillation was not starting. Then discharged the caps and combed the primary area for any open resistor, shorting diode, man-made shorting etc. I even removed one leg of a few suspected components to check its value. Every test showed ok. Then checked the secondary section similarly. Everything was found perfect. The startup voltage was reaching, but the IC did not start oscillation. I ordered for a replacement of the IC – SDC606P. Let us have a look at the boards before proceeding further:
I received a replacement of the IC and I soldered an 8 pin socket in order to avoid the need for desoldering and soldering again and again, should there be a need. Then inserted the new IC and switched on to notice that the adamant dismay was still hanging to reward me, ignoring what all efforts that I had put in. Very cruel indeed! (LOL) This time, I replaced the Startup resistors of 1.2 Meg (510K x 2 in series) which was connected to the 230V AC Line. According to the datasheet downloaded and studied, this IC generates the startup voltage within. Then powered to check with same result. Each time, I did something on the primary, I had to apply power to see the result and remember to discharge the tank capacitors before proceeding further. Then replaced the run DC diode (FR107), its disk capacitor, the wave shaping and smoothing capacitor that is connected to the ground from the drain and the protection diode (IN4007). But nothing worked! I even went to the extent of replacing TL431 and opto-coupler, 817. That exposed the naked fact that this was yet another case of fake IC. I removed the IC and did a resistance test using my analogue multimeter and compared the reading with the original IC.
Both showed same reading. Then why was it not switching? No idea at all! Before proceeding further, I used my good old trick of connecting a three wire module like I have done in many services, especially CRT TVs. I normally do not connect the green pin. Black wire gets wired to the hot ground and red wire to the B+ return from the SMPS transformer. I adjusted the pot to minimum in the module. Then, when I powered, all outputs were normal. It proved that all secondary circuits were fine and the problem indeed was in the primary switching side. Just see the following pictures, which are screen shots of videos covered by me:
Then I looked for a similar IC in my old collections and located two boards which were using this type of IC for primary switching of standby voltage. But the IC number used in both were UTC 7608D, connections of which were different. So I had to rewire and replace the components suitable for the 7608D, for which purpose I drew another drawing of it and kept it side by side of the drawing of SDC606P which I had drawn earlier, for a comparison:
Then removed the UTC7608D from the other boards. Then removed its corresponding transformer also, as the winding could most probably be matching the UTC7608D IC circuit. This is important and also the wiring of the primary and secondary. The beginning pin and ending pin of the SMPS transformer should be connected exactly as it was whenever we put it in a new board, as otherwise the switching will not take place. There is also a possibility of fresh damages if we do not bother about this aspect. I learnt this from my past experiments of SMPS transformer testing, covered in another article already published long back. Here you can see the donor board along with the donated organ: (Don’t worry, I had already looked into the legal papers and found that the donor SMPS had clearly agreed for organ donations after its death (LOL))
The rewiring done was just for testing purpose and it looked crude as you can see from the following images. The pins of transformer had to be interchanged to fit the 7608D while fitting for testing. In the original transformer pin 1 was used for run DC and second was grounded. But in the other one, pin 1 was grounded and 2nd was providing the run dc. Similarly, in the secondary pin 7 and 8 had to be interchanged. (But my drawings do not reflect this change, as I noticed it only while transplanting the transformer) Then inserted one of the UTC7608Ds and rechecked all connections. As you can see, a lot and lot of work had to be done to satisfy my quench to learn more and more of different kinds of experiments.
In fact, we, technicians rejoice from such jobs and consider these as boons amidst our monotonous and tedious repair works. Are we not? I joined extra leads to the transformer and wired it appropriately to match the donor board and kept it on top, without cutting the tracks on the solder side, as I did not want to cut the tracks and reroute it at this testing stage. Now, let us look at the crude wiring done for test:
Then after rechecking thoroughly, I applied power and noticed that there was not even a trace of the ‘dismay’, as the outputs were on and provided a perfect voltage reading at the load of 12V/25W bulb and the SMPS fan. So, I enacted the part of that age old ‘Eureka’ with some changes; I ran inside the house, wearing clothes, ensuring that my wife was not around to dial up the mental asylum! You all can very well imagine how happy we will be when we toil and toil to get a positive result and we get it at the end! So, the old adage; ‘try, try, until you succeed’ helped me once again and I got reinvigorated to make the connections perfect and fit the transformer with modified tracks at the bottom. I cut the tracks suitably and wired it underneath to match the donor board and drilled holes at appropriate places to provide components from the top instead of from the bottom. As the width between pins of the transformer varied, I drilled there too to insert the transformer without bending its leads. These odd jobs boosted my spirit and provided me a lot of thrill and enthusiasm. Such ecstatic feelings cannot be transcribed into words and one need to experience it himself! (In the meanwhile, I also tested the other 7608 and found it to be defective. The SDC606Ps were stored for future tests.)
Mission accomplished providing greatest satisfaction ever, which proudly and legitimately entered into its collection home! Following is the picture of the toll in this war for justice: (LOL)
This article was prepared for you by Parasuraman Subramanian from India. He is 74 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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Albert van Bemmelen
April 20, 2024 at 2:25 pm
Thanks for sharing this great and complex repair! All the rewiring at first was done just for testing purposes and afterwards made permanent when the adjustments were successful. But what I do not get is who and why would sell you those fake ic's that only match pinsetting and ic marking? Was there only one seller who provided these fake controller chips?
If such illegal and corrupt sellers really exist they should be brought to Justice!
PS: if you could as another test uncover the plastic casing (or remove the outside material with for instance acetone?) you maybe could reveal the actual chip layout to confirm the fake chip layout. That probably at least would involve less work and time than all the made adjustments took.
Yogesh Panchal
April 20, 2024 at 3:02 pm
Albert,
There are sellers in the market who sell near by matching material with reprinting on it..i also faced this problem, sometime you find out-of 10 pieces, 5 pieces are working properly and another 5 are waste....
just Read this ---https://ieeexplore.ieee.org/document/6856206
Parasuraman S
April 20, 2024 at 11:49 pm
Yes, very true!
Hollis LuQuette
April 28, 2024 at 5:29 am
Thank you for posting the article , that was published in 2014 .... Just think how many counterfeit chips etc in the last 10 years have blossomed out... I have bought many parts from Aliexpress in the past , all of them are genuine parts ..... I know what parts to buy and what not to buy ...
If I need a 25 dollar part and the price is 3 dollars for 10 of them , I will not buy that item .... There are honest stores on Aliexpress and dishonest ones .....
Paris Azis
April 20, 2024 at 3:37 pm
Hello Albert! Although I totally agree with your sayings, keep in mind that it is almost impossible to suspect the new part at hand right from the beginning of the repair procedure. Sentimentally you trust it! It’s your new replacement part! The sad conclusion comes only if and when all the following repair attempts are already failing one after the other! Only then you start questioning your “new” part! As for your reference about justice in this business, you’d better forget the idea...”There are no fishing nets for the big fish”...And the repairs technician is definitively the last person who can fight the case. He (or she) is rather another victim of that fact...
Parasuraman S
April 20, 2024 at 11:49 pm
Absolute truth!
Parasuraman S
April 20, 2024 at 11:48 pm
1) Fake ICs are flooded in the market and nothing we can do about it.
2) I could not follow your instructions.
Many thanks for your expert comments!
Imoudu.O
April 22, 2024 at 4:40 am
You really went extra mile to lay hold ur satisfactory.Thanks
Parasuraman S
April 22, 2024 at 4:23 pm
Many thanks, dear!
Hollis LuQuette
April 28, 2024 at 6:05 am
I lost the 5 volt rail and needed a 5 volt regulator for my HP 8656B signal generator, which is the latest model almost the same as the 8657A model.... the LM338K is a variable regulator .... I have no idea why that part was in there , it came from the factory with a 5 volt fixed regulator ...... Anyway I looked at DigiKey and the price was 79 dollars , Yes I did a double take on that one ... LOL Almost all the reputable parts houses were about the same price , I sourced a couple of them from a parts house in Texas for 12 dollars each plus shipping, while I was on the phone , yes talking to the owner on the phone which is a rare thing nowadays, I ordered a few op amps and sockets for the IC's , the owner of the store was selling his stock from years back ..... I put the regulator in with new thermal paste and it was a victory win for me ... The signal generator was brought back to life ..... OK now to the point ... I saw many of those parts on ebay and stores in aliexpress selling for 10 dollar for 10 pieces , there is no way I would pay someone so I could cause damage to my own test equipment .... There are videos on YT that show those fake parts with the top of the TO-3 off...... Not the same parts and the new fakes are not 5 amps , more like 1 amp ... I could go on and on about this ,but I know that all of ya'll already know about this plague that is going on .....
Yogesh Panchal
April 20, 2024 at 2:49 pm
Sometime we found the culprit but conclude the job because part is not available.
Joy is on different stage when we succeed after mental torture & Harassment of unavailability of proper Parts & meanwhile found solution another way.
of course sometime it cause mental instability for few Moments because this relief can't be expressed in words....Ha Ha Ha......
Good effort! Sir.
Parasuraman S
April 20, 2024 at 11:48 pm
Yes, very true!
Paris Azis
April 20, 2024 at 3:47 pm
Hello Parasuraman! This is another “learning by torturing oneself” case! Not at all unusual in our days, unfortunately. Nevertheless what counts is the final result which should always be (as it is here) positive!
My respect to your rational persistence on such cases!
Parasuraman S
April 20, 2024 at 11:51 pm
Yes, very true! The final thrill is what drives us on! Many thanks for your comments!
Anwar Yunas Shiekh
April 21, 2024 at 5:31 am
Great work, but I would be nervous abourt liability.
Parasuraman S
April 21, 2024 at 11:01 am
Since the hospital does not incur any expenses, as I am doing it as a completely free service, we can forgo the worry! Many thanks for your comments!
Waleed Rishmawi
April 22, 2024 at 1:45 pm
yes totally agree on this complex repair but you came on top providing us with a successful result and experience to gain. thanks for sharing and have a blessed day.
Nilton Cezar Vieira
April 23, 2024 at 7:33 am
Sir, this repair was an "epic battle"! I read the article like I was watching a film, anxious for the end. Congratulations for wining!