- LED TV T-Con Board Problem
- 471k MOV Cracked In LED TV Repaired
- Flash Rom IC Caused Standby Problem in LED TV
- LED TV No Sound Repaired
- No Display In Samsung 32″ LED TV Repaired
- No Power In LED TV Solved
- How To Repair Toshiba LED TV With No Power Symptom
- Samsung LED TV Auto Change Channel Repair
- How To Repair LED TV Backlight Problem – No Picture
- How To Repair LED TV No Picture- Singer Brand
Innovative Modification in Servicing of Electa DVD Player Model EDVIX-740MIC
This DVD Player was brought to me with the complaint that there was no audio or video from it, but front Red LED is lit. When I checked it up, the complaint was same. I opened the cover and did a thorough cleaning of the inside, as it had collected a lot of dust. On checking the DC voltages, I noticed that -12V was around 6V and others like 5V and +12V were ok. I removed the SMPS board and checked.
Voltages were ok and no ESR variations in any of the Electrolytic Capacitors. I just retouched all the solder joints. As you will notice, this board had the keys, sensor and standby LED along with mains on/off switch in it, which is very unusual. Normally, the front panel will have a separate board with another key input data conveying IC. This DVD player does not have any display. Turned my attention to main board. Removed it for checking and found that ESR of most of the five Electrolytic capacitors, had already crossed the limit or at the brim. So, replaced them. Checked components like diode, transistors etc.
Found that two IN4004 diodes were leaky. Replaced these two. There were no dry solders. Connected the board to Drive unit and SMPS externally and tried. DVD started working very well, with audio normal, but no video! Disconnected and removed the DVD board. I had already cleaned the eye unit and all connectors, and also had lubricated the contacts. In order to track the video, I had to remove the RC sockets of composite and S video outputs. See the board below:
Removed one three pin SMD component which had the marking A7. Checked data online and found that it was a series diode and confirmed by my PEAK Atlas DCA. The composite output was given through this. So, this was not defective. Traced the video path and noticed that it was directly from the IC itself, passing through two very tiny resistors, which were also ok on checking. The Control IC used was MT1389. No transistor or other ICs were used in the board for video, as the IC itself was doing the function. Moreover, the IC was getting extremely hot, indicating that all was not well with the IC. (Note: In order to remove the heat zinc on the IC for reading its number, which is stuck with a sticky heat zinc compound, either we need to use a sharp blade and cut it in slowly or use a small nose plier, hold the heat zinc firmly without applying too much force, then twist it horizontally. It will come off. This is what I did.) Since, removing this 256 pin tiny IC without causing damage to the surrounding components, was extremely difficult and further that replacement could perhaps be not available, I did not proceed further and decided to replace this DVD board. And it is here, where the twist starts in this case!
Proper working, when replacing a DVD board depends on various compatibility issues, most important of which is the eye unit. The old board had the flexible connector facing inwards, whereas in the new board, it was facing outside. This is important! If we do not connect the interfacing EYE unit properly, both the DVD board as well as the eye unit might get spoiled! I had two DVD boards with me, with Remotes bought separately. I took one and studied the connections of Power Supply, outputs for DVD unit and 5.1 audio, inputs of data/sensor, USB, Data Card Reader and Mic, i.e., the order in which the various pins are located as printed on the main board. (Caution: Many times what is printed on the other boards such as power supply, front panel etc. may not match with the DVD board!
We have to strictly follow what is on the DVD board.) Most importantly the flexible ribbon connector that goes to the eye unit. The connector pins of Sliding Motor and Loading Motor were different. So, slid out such pins from these connectors and inserted again in the correct place. As the sizes of the connectors were ok for the drive unit, it was easier. Checked the connection of the eye unit and found that if we connect a flexible ribbon cable with both ends on the same side, it will be suitable. The old ribbon cable was having the connections at opposite sides. The SMPS had + 12V, which is not used in the new DVD board. So, I removed it and tided it safely away:
Then interchanged the pins of the connectors at the DVD board side, matching it with the prints there. The old DVD board was not using the limit switch from the sliding connector of the Drive Unit. Please see picture below:
In some DVDs, the program is written in such a way that after sensing presence of a disk, the sliding motor rotates to look for the startup point of the disk. In such cases, no limit switch on/off is required. This was such. In the new Board, the limit switch is required for sensing reach of the startup point. The gear that is engaged to the sliding motor pushes the leaf switch, to make contact with ground (or any other sensor point as the case may be). Only after touching this leaf switch, does the sliding motor reverse to enable locating the startup point on the disk. So, after matching with the minimum requirements of the DVD board for a trial function, I kept my tweezer inserted into these two points and switched on. After the eye unit moved in to the startup point, I removed the tweezer, simulating the function of a leaf switch. It worked very fine with video and audio.
I also checked what will happen, if these two pins are not shorted at the time of switch on. The disk got ejected showing Disc Error. Then I soldered these two joints together at the Drive Unit side and tried. The disk, after spinning, got ejected out. So, a momentary contact and then release was absolutely necessary. These tests provided clue for Disc Error problems in future trouble shooting; i.e., loose contacts in these leaf switches! Located a spare leaf switch from a salvaged DVD drive unit:
As you will observe, one of the leaves has a plastic piece attached to it. The pushing has to be exactly on this spot. Now, the next task was finding a suitable place for fixing it. Undoubtedly, it has to be on the path, in which the eye unit moves and touches the spindle motor side. I studied other salvaged drive units and found out that there was a slot in which this leaf switch is pushed in, and it was the plastic body of the eye unit that touches it, when it moves in. In this case, that was not possible, because of fixing problems. So, I decided to place it at the point, where the tip of the gear (white in colour) that moves back and forth, engaged to the motor, touches. See the picture:
I manually slid the eye unit, keeping the leaf switch in the small slot that was available near the eye unit mounting screw and rubber, and marked two lines on the outer ring, after locating the point, where the gear pushes the leaf switch for closing it, and gets released when the gear moves out. Then using my tile cutter, I cut that area, in order to push the leaf switch in, placed the leaf switch in, and by trial held it in a suitable position, and applied Fevibond, followed by Super Glue. Waited for a few minutes, holding it in position for the glue to bond together tightly.
Laid the two wires of the leaf switch neatly inside the groove and soldered the other ends on the sliding motor connecting PCB. Slightly bent the other leaf away, to enable momentary contact and release as the gear moves in and out; rather fine-tuned it! Gave all inter connections and tried. The player worked very well.
Next task was to interface the connector from the control section, where, sensor, standby LED, function keys were all located. This was difficult, firstly due to change of order of the connections in the DVD PCB and secondly due to the size of the socket, which was smaller than the connector. So, dug out a suitable connector from my collections, and cut the wires a little far away from the connector. Then soldered suitable leads (collection of leads that are cut after replacing capacitors, resistors, LEDs etc.) that will fit into the other connector that comes from the control side. Then inserted these into the connector at the appropriate places, to match the requirement of the DVD board.
You will notice that I had marked what should go where in order not to make a fatal mistake! Then bent the tips in a zig zag way, to ensure that these do not short , and fixed it with Fevibond, and allowed it to get dried overnight, as it was almost 11PM, before I could finish all these tedious and time consuming works!
Next day morning, I rechecked the connections and inserted the connector and switched on the unit. It worked very well by using the Remote Control. The keys were not functioning, as this DVD board requires an interfacing IC for data signals. I even tried replacing the 8 PIN Program IC from the old board (it is mounted on a socket). But when I tried with the old Program IC, the player did not work. So, put the original program IC back. The customer has to compromise on this; there is no other go! Likewise, I readjusted the connectors of Card Reader and 5.1 audio out. Fixed the DVD Board and SMPS Board. When trying to insert the Drive unit, I noticed that the new DVD board is slightly larger in size, and the unit cannot be placed straight. Fixing it straight is important as the disk holding tray has to move in and out without any hindrance. So, using my soldering iron, I made dents on one of the legs of the drive unit.
Fixed the Drive unit, and used a screw that did not have a wider head, in order not to go over the DVD board. Tried the player once again and it worked very well:
Fit the cover, after playing several DVDs and CDs for hours together.
I believe that a technician’s job is not just finishing a repair work, but find out alternative solutions, when met with a dead end, and accomplish the result! So, this was a very satisfying and refreshing service work, though mind boggling and tedious!
This article was prepared for you by Parasuraman Subramanian from India. He is 66 years old and has more than 30 years’ experience in handling antiques equipment Valve Radio, Amps, Reel Tape Recorders and currently studying latest techs classes conduct by Kerala State Electronics Technicians’ Association. He was a BBA graduate, retired as MD of a USA company.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S-If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
You may check on his previous repair article below: