Inverter Dac
Inverter Dac
Voltage Testing - Every Repair Technician and Engineer Should Master This Skill
By only knowing how to read electronic schematic diagram and testing electronic components were not enough to make us a good electronic repairers. Many faults can’t be detected even if you know how to accurately test and check all the electronic components because those faults only can be detected by simply performing a voltage test. Do you know that quite a numbers of Monitor problems I have to perform a voltage test in order to locate the defective components? Yes, if without voltage testing, I might end up can’t find the fault and the Monitor have to be return back to customers. What if you return many Monitors back to the same customers? Of course your business reputation would be affected and worst if your competitors (other electronic repairers) be able to repair it. You would definitely lose out the customers and is very difficult to get back his trust again about your capability to repair Monitors.
I do know lots of electronic repairers especially newbie’s do not have the courage to perform the voltage test especially Computer Monitors and Television because they were afraid of the high voltage and get electrocuted. Well, if you want to work in this line and choose not to learn about voltage testing (because of afraid), then you are truly missing something that can help you to repair any equipment fast. After all, voltage testing is not that as dangerous as you thought to be. With some guidance from repair friends or even you test it on your own (practical) and protection from isolation transformer, I don’t see any other reasons you don’t want to do the voltage testing. Besides this of course you must know the safety guidelines first in this electronic servicing field.
The real challenging question now is even though you know how to perform the voltage testing; this does not guarantee that you will definitely being able to solve the electronic problems! As to why you can’t solve the problems depends on many factors such as:
- How well you are in understanding the functions of electronic circuit (assuming I’m talking on the Monitor circuit). Some Monitors circuits can be very complicated to understand it.
- How good you are in tracing the electronic circuit (assuming you are tracing from the source to the faulty components) because many electronic repairers will lost track and can’t go further to detect the fault.
- How knowledgeable you are in understanding each function of the electronic component. For example, if no signal flowing to the base of a transistor, of course there would be no current flowing between the collector and the emitter. Another example, what do you expect the output voltage will be if 100 volts is passing through between a 10 ohm resistor and a 10 k ohms resistor?
- Sometimes in order to solve a problem we accidentally create even more problems due to that we do not have the capability to hold tight the meter’s probes causing it to touch on other pins while measuring a components (says is an IC or a transistor). This would cause the whole equipment to shutdown or even burnt the components. How many of you have done that before?
- We must also know what the range of the meter setting is in order to test the electronic circuit accurately. For example, would you test the secondary output voltages when your meter is set to AC range? Or would you expect a reading when your meter’s red probe touches on a cold ground?
From above, these are the things that you should know if you want to be successfully able to perform a voltage test on any equipment. It is not that easy to absorb everything that I’ve just mentioned above but if you have the passion to do it (I mean learn everything from reading electronics books, visiting forum, doing your own practical test and etc) then you are giving yourself a chance to learn something that will truly benefit to you.
In this week’s article I’m going to show you how by performing a voltage test has helped me to solve an unusual problem in a Computer Monitor.
Well, this monitor with the brand name of MIMOS (this is an OEM Monitor) came in with the complaint of can’t adjust horizontal size (there’s totally no changes when the horizontal size control was pressed). The display width (size) was large and both sides of the display curved inward (pincushion out). For your information, the horizontal size and pincushion circuit were located in the same area and both circuits were working together in order to achieve a desire display. If one component in a circuit fails, it would affect another circuit as well! That’s why, when the horizontal size circuit have problem, the pincushion circuitry was affected too (the display curved inward).
Normally when I see this kind of problem, I would usually check and test all the components in the horizontal size and pincushion circuits’ area with my ESR, analog and digital meter. Most of the time, I could solve the problem fast. The common faulty parts for horizontal size width problem in a Monitor were usually dry joints, shorted modulation diode and pincushion transistor and capacitor opens along the horizontal size coil’s line. But somehow I could not locate the faulty components in this Monitor because all of the components that I’ve checked were all tested okay!
Since I have checked all the components in the horizontal size and pincushion circuit area to be okay, now the only way to solve it is through using voltage test. Generally, whenever if you want to perform voltage testing, one must start from the source first. However if you are experience enough you can always skip some section and start tracing the circuit that you think would fail. As there are many electronic repair newbie’s in this ERG member site, I would show all of you how to trace from the source first.
Now think carefully, what makes the display to become small or big whenever the horizontal size control was pressed through the On Screen Display (OSD)? There must be a signal sends out from somewhere to the horizontal size circuit in order to control the display. Am I right? The pincushion transistor has a base pin and if this voltage varies (because of the horizontal size control either set to minimum or maximum) the display will change too. You can choose to trace backward starts from the base pin of the pincushion transistor or start from the source. I will guide you to trace from the source because once you know how to trace from the source, you would be able to troubleshoot and repair other Monitor problems too such as can’t control the brightness, contrast, vertical and horizontal height. You may use this method that I’m about to show you in TV and other electronic equipment as well.
First you must understand what is the function of digital to analog conversion (DAC) circuit. Since most of the modern Monitors are using digital signal (communication between the CPU and EEPROM and other circuits as well) there must be some circuit to convert the digital signal to analog signal in order to drive the pincushion transistor and others electronic circuits too. Our normal multimeter can’t measure digital signal, it can only read analog signal. Older Monitors have the DAC IC located out site the CPU (such as the TDA8444 IC used in NEC XV 14 Monitor) while for modern Monitors the DAC IC is built into the CPU. I guess you are now understood why a digital circuit needs a DAC as part of it complete circuit. In other words, the DAC is required to communicate with the analog world!
In this faulty Monitor, I don’t see any DAC IC nearby the CPU so I presumed that the DAC was already built into the CPU. Now, this is the most challenging part where you have to carefully adjust the Monitor position and yourself so that when the Monitor power is switch “ON” you can perform the voltage test on all the pins at the CPU. Assuming you have taken all the necessary safety and precautions now is the time to switch on the Monitor and start to do voltage testing.
After you got hold of the Monitor, select the horizontal size control through the OSD screen. You could see when the “+” and “-“ buttons was pressed at the front panel, the number in the OSD display indicates the minimum and maximum value representing the size of the display being adjusted. Since this is a faulty Monitor, although the number in the OSD screen is changing (because you are pressing the “+” and “-“) there is no effect on the display and the display remains big and curved. But somehow you could measure the pins at the CPU to locate which one of the pins the voltage is changing when the adjustment button is press! Try one by one of the CPU pins until you saw one that has effect when the horizontal size control was pressed. The voltage is about 0 to 5 volts (depends on the design of Monitors) and should go up or down momentarily when the horizontal size adjustment is changing. Congratulation! You are now have determined the source of the horizontal size circuit. One word of advice, a defective CPU or a corrupted EEPROM data could cause no signal at the horizontal size source pin!
Once you have known the pin then it is relatively easy to find out the fault. Start tracing from the pin and see at where the voltage had missing as shown in this photo. Surprisingly the voltage remains okay even till pin 5 (inverting input) of the quad operational amplifier LM324 IC. Since this is an OP-AMP IC, it requires two inputs (inverting and non-inverting input) to produce an output at pin 7 but the voltage at pin 7 would not vary. And if this output won’t vary definitely it can’t control the horizontal size. Pin 5 voltage of the LM324 IC varies and pin 7 don’t varies then most probably the problem is either in the IC itself or components that are related to pin 6 (non-inverting input). I saw a wire coming from top of the board and upon inspecting it; it was from B+ voltage (about 66 VDC) and passing through a resistor before reaching pin 6 of the OP-AMP IC. Using my analog meter to measure across the high ohms resistor (820k), I found it to be zero voltage. In order to really confirm is the resistor fault, I desoldered one of the lead and check with my ohmmeter. Guess what? The resistor has open circuit! Unbelievable and it was true! Replacing with a new resistor restored the display back to normal.
Conclusion- Imagine if I didn’t use the voltage testing method, I don’t know how long that I’m going to spend on troubleshooting this kind of problem. And worst still, I may end up can’t solve the problem and return the Monitor back to my customer. With constant learning and practice in electronic repair you will have no problem in tackling any electronic faults in the future. Just don’t give up and continue to learn from the ERG member’s page. Thank You for being my member.
About the Author
Find out more at the links below. You will be very surprised to discover that LCD and Electronic Component Repairs can make thousands of dollars even for a novice. You can find out the repairing secrets.
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Gateway MA8 ML6720 LCD Inverter Board DAC-08N006 $3.95 |
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Gateway 6000 MX6000 Inverter DAC-08N006 AS023217003 $6.43 |
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New Genuine Inverter HP Compaq Laptop DAC-08B061 08N007 LCD Screen OEM $8.99 |
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Toshiba Satellite M35X LCD Inverter Board DAC-07B037 PK070015900 K000019440 $19.99 |
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New Lcd Inverter dac-07b046 For Dell Inspiron 610m 630m $2.99 |
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GATEWAY LAPTOP MA2 MA3 MA6 MA7 LCD INVERTER DAC-08N006 $4.99 |
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MICRON MPC X3000 INVERTER DAC-O8B03 1B 76-036502-1B $8.95 |
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COMPAL CL50 INVERTER DAC-07B032 2334718900 $8.95 |
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SYSTEMAX 755II0 LCD INVERTER DAC-08B031 2994719500 $8.95 |
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Acer Aspire 3610 Laptop LCD Inverter Board DAC-08N011 $10.85 |
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Advent 7098 LCD INVERTER DAC-08N001 AS023172051 $53.00 |
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Gateway MA2/MA6/MA7 Inverter P/N-AS023217011/DAC-08N006/2995301900 $23.52 |
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NEW Gateway M1200 M1300 Inverter DAC-09B020 PK070017110 $8.03 |
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GATEWAY MX6930 INVERTER BOARD DAC-08N019 AS0232170380 $27.00 |
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Brand New NEC Versa E6000 LCD Inverter DAC-07B043 IV14142/T AS023J75041 US $12.50 |
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Lot of 4 GATEWAY M675 PA1 M675PRR LCD INVERTER BOARD DAC-07B039 2994724000 $34.99 |
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ORIGINAL HP ZD7000 LCD INVERTER 2994722000 DAC-07B036 $16.15 |
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LCD Inverter 4 Acer 3000 3200 3400 5000 DAC-08B034 $5.99 |
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Brand New NEC Versa E6000 LCD Inverter DAC-07B043 IV14142/T AS023J75041 US $13.00 |
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Compaq Presario 2100 LCD Inverter DAC-08B034 $2.99 |
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HP Pavilion zd7000 Laptop LCD Inverter Board DAC-07B036 $7.99 |
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New LCD Laptop Inverter Backlight DAC-07B037 2994722401 PK070015900 PK070015900 $13.69 |
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ACER TRAVELMATE 4400 INVERTER BOARD DAC-08N011 192106900160207282VD00 $3.00 |
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HP / Compaq 15.4" LCD INVERTER DAC-07B035 336994-001 $12.39 |
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76G031033-1B DAC-08N033 ADVENT 9115 5511 5611 INVERTER $14.87 |
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76G031033-1B DAC-08N033 ADVENT 9115 5511 5611 INVERTER $14.87 |
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Gateway MT6000 MX6000 Inverter DAC-08N006 2994743500 $8.78 |
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Inverter For HP Pavilion DV1000 Backlight DAC-08N007 $15.85 |
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HP/Compaq 2100 ZE5000 ZE5600 LCD inverter DAC-08B034 $6.79 |
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For Inverter 4-Lamps Delta Power Supply Unit Board DAC-19M005 AF $26.40 |
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LCD SCREEN INVERTER DELTA 76-030562-1B DAC-08B031 -FAST SHIPPING $16.00 |
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New LCD Inverter HP DAC-07B045 AS0231720D2 2995300700 2994736900 2994742300 AS02 $11.91 |
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New LCD Power Inverter AS023172182 DAC-08N010 AS0231720A8 PWB-IV10150T/G1, IV101 $11.91 |
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HP COMPAQ INVERTER DAC-08N004 E232940 WITH VIDEO CABLE $6.99 |
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Toshiba Satellite M60/M65 LCD Inverter Board DAC-09B029 PK070018200 K000026560 $19.99 |
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HP/Compaq ZE5000 ZE5600 inverter DAC-08B034 AS023165020 $5.50 |
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Gateway LCD Inverter Board for 15.4" 2994746400 DAC-08N019 m-series $20.00 |
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LCD Inverter HP AS023172018 DAC-08N007 2994729902 $5.49 |
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Delta 1 CCFL LCD Inverter Board DAC-07B037 PK070018800 K000029120 K000027770 $29.99 |
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Gateway MX6000 MX8000 MX9000 MA3 MA7 MA8 LCD Inverter Board DAC-08N006 - Tested $3.95 |
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new advent lcd inverter board DAC-08N001 z14 $23.51 |
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GATEWAY M675 PA1 LCD INVERTER 2994724000 DAC-07B039 $8.95 |
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17" LCD Inverter For HP Pavilion DV9000 dv9500 dv9600 DAC-08N016 2995301600 $9.58 |
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15" HP Pavilion zv5000 zv5100 zv5200 LCD Screen Inverter DAC-07B037 2994722401 $4.92 |
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Gateway SA8 M M-6318 Series LCD Inverter Board 2994746400 DAC-08N019 AS023217038 $19.99 |
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HP Compaq nc4200 tc4200 LCD Screen Inverter PK070017700 383532-001 DAC-09B024 US $5.63 |
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LCD INVERTER HP nc4200 tc4200 383532-001 DAC-09B024 $11.99 |
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Fujitsu N6010 N6210 Inverter DAC-10N001 CP231661-02 NEW $10.00 |
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Toshiba Portege M800/805 LCD Inverter Board A000025870 AS023216000 DAC-08N035 $29.99 |
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Gateway M685 MA3 MA6 MA7 PA6 LCD Inverter DAC-08N006 $6.95 |
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New LCD Power Inverter AS023172182 DAC-08N010 AS0231720A8 PWB-IV10150T/G1 $11.30 |
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Gateway M675 Inverter Board DAC-07B039 New 2994724000 $38.00 |
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NEW Advent 6441 6551 6552 6553 6650 6651 6652 lcd INVERTER DAC-08N033 $22.74 |
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ADVENT 5511 5611 5612 5311 INVERTER DAC-08N033 $29.01 |
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New LCD Inverter board HP Compaq G50 G60 CQ50 CQ60 CQ70 DAC-08N011 486556-001 US $8.47 |
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New LCD Power Inverter Board Backlight HP M2000 M2100 M2200 DAC-08N007 AS0231721 $6.95 |
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New Laptop LCD Inverter Board for HP AS023172018 DAC-08N007 2994729902 USA $5.49 |
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Acer Aspire 9500 HP Compaq Presario A900 DAC-09B026 laptop LCD screen inverter $17.98 |
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laptop LCD Screen Inverter 4NJE101473 IV-11150T E131735 DAC-098026 dac-09b029 $16.84 |
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laptop LCD Screen Inverter DAC-09B029-A0F K000009570 K000018860 PK070018600 $16.82 |
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Toshiba Satellite P35-S629 DAC-09B026 PK070017600-A0F laptop LCD screen inverter $16.79 |
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NEC Versa 2760MT Inverter NEW DAC-07B020 $21.20 |
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NEC Inverter Board Versa 2400 DAC-08B001 $30.00 |
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3811064301 Rev B1 Inverter Board Assy DAC-10B005 $28.00 |
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WE88 94v-0 Inverter Board DAC-10B006 $28.00 |
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ORIGINAL Gateway SA1 M-6885u LCD Inverter Board AS023217038 DAC-08N019 $17.10 |
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HP Pavilion ZD7000 LCD Inverter DAC-07B036 $3.99 |
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MPC Micron Transport T3000 X3000 LCD Inverter DAC-08B031 B1 $9.95 |
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Toshiba Satellite M300/M305 LCD Inverter A000025870 AS023216000 DAC-08N035 $29.99 |
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DELL lcd inverter board DAC-07B046 A118 $9.25 |
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ADVENT 5511 5611 5612 531 543 INVERTER DAC-08N033 $29.01 |
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15.4" LCD Screen Inverter for DAC-09B017 6001709L-E $2.99 |
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LCD Screen Inverter for Acer Aspire 2000 5720 5110 14.9" PK070018510 DAC-09B017 $6.99 |
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New Lcd Inverter dac-07b046 For Dell Inspiron 610m 630m $7.95 |
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New Lcd Inverter dac-07b046 For Dell Inspiron 510m 600m $7.95 |
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Lcd Inverter HP dv1000 Series dac-08b061 as023172018 $3.99 |
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Lcd Inverter For HP Pavilion dv5000 dac-09b017 iv13154 $4.99 |
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Lcd Inverter e131735 ynv-c02 For HP Pavilion dac-09b017 $4.99 |
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Inverter dac-08n011 For Acer aspire 3020 3610 5020 Lcd $8.98 |
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GATEWAY M675 INVERTER AND CABLE DAC-07B039 DD0PA1LC201 $5.99 |
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Gateway MA3 MT6452 LCD Inverter DAC-08N006 $3.99 |
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MPC Transport T2400 LCD Inverter Power Board DAC-09N014 $12.95 |
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GATEWAY M675 PA1 M675PRR 17" LAPTOP LCD INVERTER BOARD DAC-07B039 2994724000 $8.99 |
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Gateway M360 M460 M465 NX500 MT6400 MX6000 LCD Inverter DAC-08N006 AS023217011 $9.50 |
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Inverter DELTA DAC-12B165 REV: A0 GateWAY 610 Media $22.00 |
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Gateway laptop LCD Screen Inverter DAC08N006 board $17.99 |
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laptop LCD Screen Inverter DAC-09B017 6001709L-E DAC-C9D017 YNV-C02 PK070018510 $13.97 |
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laptop LCD Screen Inverter IV13154 DAC-07B035 IV13154/T T51I056.03 PK070018120 $13.95 |
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laptop LCD inverter TW9394V-0 DAC-0713037 PWA-TF041 $9.92 |
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laptop LCD Screen Inverter DAC-08N011 2994740801 board $12.95 |
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LCD Inverter PK070018800 DAC-07B037 541380000002 $2.99 |
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For HP Pavilion dv7-1200 LCD INVERTER PK070006T00 E198444 403831-001 DAC-09B026 $14.38 |
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Delta DAC-09B020 Inverter 7 Pins Connecter PK070017110 $15.00 |
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laptop LCD backlight inverter AS023170023 DAC-08N004 $15.98 |
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HP Compaq DAC-08B061 laptop LCD Screen Inverter $17.98 |
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HP Compaq DAC-08N007 laptop LCD Screen Inverter $17.97 |
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Compaq NC4200 NC4400 TC4200 LCD Inverter DAC-09B024 $8.99 |
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GateWay MA8 MA3 15.4" LCD Inverter Board DAC-08N006 $8.10 |
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LCD Inverter for HP Compaq NX7000 NX7010 NX9100 ZV5000 $11.65 |
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NEW Gateway M1200 M1300 Inverter IV12103T T51I059.00 PK070017110 DAC-09B020 $13.50 |
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