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Brandnew HDMi 3 to 1 switch box behaving erratic from strangly behaving bad led port 2

By on November 12, 2023
how to repair andonstar microscope

Most of you probably may have read my previous article about fixing the only HDMi port on my heavily used 27 inch Philips monitor. It was successfully fixed after all ordered products were received. The excellent uv hardened epoxy coating and the copper rework sheets to repair all 19 broken off tracks and my good G600 LCD microscope made it possible! Although I recently replaced my tiny 4.7 inch G600 for the bigger 7 inch Andonstar LCD HDMi Microscope with decent led side lights and better lenses. Mainly because the G600 made for this task too dark snaphots. Those superclear Andonstar photos to show the fine HDMi repair result can be found on my FaceBook link :

Because those 19 tracks were so close to each other in only about 10 mm of space I made the repair much easier by only replacing all 12 signal lines and the +5V track (pins 1,3,4,6,7,9,10,12,13,15,16,19 plus the +5V track on pin18). And ground pins 5,8,11,17 and the track to pin 2 were bend up on the HDMi connector so they were not needed on the board. They were wired with 2 thin wires. And track 14 was nc so that connector pin was also bend up and left unconnected.

Constantly switching HDMi cables on the one HDMi port in the end broke the inside plastic, why I also mentioned ordering this HDMi switchbox to prevent this problem from ever happening again:

However, soon after my monitor was fixed this hardly been used switch box started to behave very erratic as this short Youtube video shows:

This problem suddenly started happening showing very bright green leds on port 1 and 3 and most of the time the no longer working led on port 2. Although the switchbox HDMi output selector still worked fine, superbright leds 1 and 3 also got a too high voltage of about 3V instead of the usual expected 2V.

And when measured with my recently repaired VC200 DMM all leds seemed to work although the resistance measured over led 2 was very low. It was an unsteady about 54 ohmic value. And also when this led was taken out of the circuitboard the resistance was there. But it tested fine when a 2V dc voltage was applied.

repair hdmi

Showing practically no flowing current and a bright lit up led. As also next photo shows. And after this test was done the low ohmic resistance was strangely for a short period completely gone! And this resistance when measured was never the same value either! Very strange! But before I started suspecting this bad led, let me explain that I first had examined all chips that were used in this switchbox. Thinking they were internally damaged somehow never expecting that this led was the culprit.

how to fix hdmi

Mainchip U4 in the circuit is a 64 pins LK391 HDMi switcher chip that also drives each of the port leds. A sot23-5 JW5250a chip U2(smd code JW30) provides the about 1,8V DC voltage for the mainchip out of the by each HDMI port provided 5V. Why I at first suspected the mainchip because smd sot23-5 chip U2 worked. A 10 page datasheet of U2 can be found here: (Other datasheet links only showed one page!)

The function of chip U8(can also be an U7 chip) with smd code _G2009 is still unknown.

All diodes and resistors measured fine.

So in next photo I located the track that went from mainchip U4 to led 2 and cut it open (U4 pin 16). Which I did with my new USB-C chargeable Smart Electric Sharpening Pen I also used in my HDMi repair. And it is that track that now is repaired and afterwards was coated with the great working uv epoxy coating in next photo.

With the no longer connected led 2 I concluded that the low ohmic resistance in led 2 was still there. So this ruled out that the mainchip U4 was causing this.

And since no other tracks connected to this port 2 led it only could be the led itself! So to summarize this unexpected culprit, it only was this erratic behaving led that was the reason for the erratic functioning of this switchbox as the Youtube video clip showed. Following photo shows mainchip U4 with all port leds D5,D6 and D8. And also U2 and U8 with all 3 HDMi input ports.

andonstar hdmi

Below photo shows on the left my old G600 LCD microscope and my new Andonstar 246S LCD Microscope.

Andonstar 246S LCD Microscope

Naturally I previously also had contacted the Aliexpress seller that his product already had a very annoying failure even after hardly been used. But since my 15 day buyer protection just no longer was valid I was left with a brandnew but bad product. Which is certainly not the first time something similar on Aliexpress happened! Previously it was a useless 4TB SSD that never worked trustworthy. Sadly again money wasted because of a corrupt seller! And before that a never working XBOX360 dongle, that I, even in protection time did proof with excellent video that the Wifi dongle never worked. However the seller never accepted my claim on his stupid definition that the Gamepad online test website is a joypad safe test. Because as I noticed only on a real XBOX360 it is a definite safe test of proof!

andonstar view ic

Happily both Switchbox and my trusted 27 inch monitor are repaired. All I had to do to fix my brandnew 3to1 HDMi switchbox was replacing erratic behaving led 2/D6.

3to1 HDMi switchbox

Above photo on the left shows unknown chip _G2009, and photo on the right chip JW5250S. This repair shows that even if leds do work they still can behave very erratic in a circuit causing a mainchip going berzerk by flashing and showing too bright working leds.

In such cases we always may count ourselves lucky that we mostly are able to fix or improve any bad working product. Which makes it all our worth while.

albert from netherlands

Albert van Bemmelen, Weert, The Netherlands.

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Note: You can read his previous article on Green VC200 DMM Lithium Upgrade



  1. Parasuraman S

    November 12, 2023 at 10:15 am

    Vow! Another expert technical information packed article, which normal people like me might feel the head reeling! Aliexpress usually protects the buyers, and I am surprised to see that you had repeated bad experiences. They have even refunded my money in a couple of cases, where the items were faulty without having to be returned. Many thanks for sharing another wonderful article! The moment I see another article from you, a kind of shudder goes through my spine and I cannot be blamed for this feeling! (LOL)

    • Albert van Bemmelen

      November 12, 2023 at 4:13 pm

      Aliexpress is mostly not the problem when a product doesn't work. It are always the sellers that are mostly the reason for not getting the service or refund for their not functioning useless products! Added up to the only 15 days of buyer protection time period after the product was received that is complete nonsense compared to the normal 2 year of warranty on all in Europe bought products!
      Like the time that I bought a replacement tablet touchscreen for my niece that arrived in a in transport completely damaged box after the seller never accepted my legit claim telling me I had damaged the badly packed touchscreen myself.
      PS: you may notice that the Andonstar 7 inch LCD microscope has 6 front pushbuttons like my much smaller G600 LCD microscope. That is as I later found out because they are probably made by the same designer or manufacturer having the same poor constructed firmware design that is not intuitive to say the least. For example it is not possible to return from a bad chosen function with a return, stop or exit button because you are stuck in a function and only escape the wrong choice by chosing another -mostly wrong chosen- bad function. It is just hard to select the right function when you do not know the sequence of pressing the right selection on both microscopes that are completely the same in design when the controlling firmwares are compared. But the Andonstar is made with professional lenses and makes much better brighter HDMi photos. Although it is not chargeable or as portable like the G600 is.

      • Parasuraman S

        November 12, 2023 at 8:39 pm

        Head reeled further!(LOL)

  2. Albert van Bemmelen

    November 12, 2023 at 8:48 pm

    Here a very interesting computer tip about the in the article mentioned previously never useful on any of my computers working and in all tested partition managers as completely bad 4TB SSD marked drive. It was recently placed in one of my DM800HDse satellite receivers and there successfully formatted in only seconds. Although this 4TB SSD afterwards still failed when tested by the Dreambox hdd testprogram it now records all my tv programs and is recognized as being a 4TB hdd. Although it very likely still is corrupt or faulty somehow and even tested bad on my special StarTech USB1to2 copier tester it for the time being is this way functioning useful until it starts to fail at recording my tv programs. This can be a very interesting fact when you have such bad or completely useless and refusing to correctly format SSD too!

    • Albert van Bemmelen

      November 13, 2023 at 1:27 pm

      PS: This bad brandnew 4TB problem SSD is supposedly a WD Green model drive. But even when the WD diagnostic tools were downloaded and started, those utils couldn't even recognize the serial number of this bad fake sold drive! So that seller must have bought a bunch of discarded cheap SSD's to make fast money with to sell!

  3. moshe jacobson

    November 13, 2023 at 5:35 am

    bravo Albert...another very excellent article (& repair job)...massive thank you for sharing!

    • moshe jacobson

      November 13, 2023 at 6:13 am

      Also, which was the new model adonstar that you bought?

      • Albert van Bemmelen

        November 13, 2023 at 1:20 pm

        It was mentioned below the HDMi switchboard photo being the Andonstar 246S LCD Microscope Moshe. They have also other models with larger 10 inch screens and other lenses. But 7 inch was big enough for me.
        Also because this 246S also supports connecting its HDMi video output to a HDMi monitor when a larger view is needed.

        • moshe jacobson

          November 18, 2023 at 7:50 am

 appologies - the danger of skim reading photo captions!!
          but thank you.

  4. Yogesh Panchal

    November 13, 2023 at 3:46 pm

    It is strange to see LED glowing without Current DC Bench Power supply is properly calibrated??

    • Albert van Bemmelen

      November 13, 2023 at 10:16 pm

      It is a 10Amp 30V max adjustable power supply.
      Why the small current probably didn't show in its limited segment display.
      Also because these special very high bright leds need only little current.

      • Albert van Bemmelen

        November 14, 2023 at 3:17 am

        Meaning if the led current is lower than 10mA, so only about 0.009A it therefore won't show on the 10.00Amp DC display.

  5. AdamS

    November 13, 2023 at 7:08 pm

    AliExpress strikes again...

    • Albert van Bemmelen

      November 14, 2023 at 2:04 pm

      True but luckily sometimes also Aliexpress has still some competition from other online websites like Banggood, Grandado, Wish, Miniinthebox, Lightinthebox, and of course last but not least eBay.


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