PC fault finding and upgrade tips
Home ] Up ]

 

  Monitor Repair

Please select your monitor brand: Acer AST CTX  Compaq Dell Fujitsu Sony  IIyama Samsung

Updated 09/02/04  - usually only high end monitors are listed on this page but there are a few tips for crappy ones. Tip of the day; if your monitor uses a Samsung or Chunghawa CRT, the best method of repair is to hit the CRT neck with a large hammer. Don't forget your eye goggles! :)

 

Sony

 

Multiscan 100sf

 

Dead - If the PSU transistor type IRFIBC40G is short circuit check the diodes on the secondaries of the transformer as these often go short. Note that the transistor MUST be the same type as the original. You will probably find that the 0.1 ohm fusible resistor feeding it has gone too. This also must be replaced with a fusible type otherwise it will be a fire hazard. If you can't find an 0.1 ohm resistor, a 0.22 or 0.33 ohm resistor works well. As for the diodes on the secondaries, the only two that I have found to go faulty so far are D650 (UF3ML) and D654 (3DL41A). These diodes are unavailable from most suppliers but however a BYT77 and a UF5408 will do as respective replacements and seem to work fine. I have been using a monitor for 3 months with these substitute components.

 

Top

 

Fujitsu

 

E154 - this is a Acer built monitor; cross reference is 7154

 

Dead but power light on - Sync IC TDA4858 and R214 (15K) Also check C335 (220pf 2Kv, replace with 3KV)

Dead power light flashing green - C335 S/C, L304 S/C 2SK2161 S/C also BU2520AF may be faulty.

Dead Power light flashing green - C335 O/C, BU2520AF S/C, L304 off value / Short Circuit.

Excessive EHT - Line output transformer

Looses settings when switched off - Memory IC (next to microcontroller)

Blows 2SK2161 again after a few mins or as soon as signal is connected - L304 S/C

All lights on under flap, no display - Microcontroller

 

E141V (old type PCB) This monitor is equivalent to Samsung HX4838E

Dead - check line output transistor 2SC4769, If short circuit, You will probably find that the 2 2SC614 transistors located in the middle of the board have gone as well. They are mounted above each other. There is also a resistor nearby that sometimes goes open circuit. It is either 1 or 10 ohms depending on the model. Also check the electrolytic capacitors in the line output transistors base drive circuit. If they drop by a couple of uf, the line output runs very hot leading to failure of the above components again a few hours later. Sometimes it is the line output transformer has failed causing the above components to blow, in this case the monitor is BER because the LOPT is unavailable.

E141V (new type PCB) This monitor is equivalent to Samsung HX4838SE

Dead - the entire PSU has usually blown up requiring replacement of about 20 components. Check the line output transistor as well and the base drive circuitry. The line output transistor is a 2SC4769 but can be replaced with a BU2508AX or a 2SC5297 both transistors are used in ICL 142Vs. They seem to work fine as a replacement for a 2SC4769.

Dim display - If fitted with a Samsung CRT, these are notoriously unreliable and they usually fail within a year or two. I have found that the Orion CRT's seem OK.

 

E142

 

Dim display - Faulty CRT, especially the Samsung tubes; they are very unreliable.

Stuck in powersave - dry joints on the CRT base board are a common problem with these monitors. The dry joints tend to be on the CRT connector itself and on the VGA cable connector. 

Display jumping intermittently - This looks like a typical dry joint symptom but first check the four 2.2uf 450V capacitors just below the line output transistor heatsink as these often fail. Usually you get a slight ticking noise from the line output transformer every time the screen jumps which may suggest a duff LOPT but this is not the case. The line output transformers rarely fail in this model.

Dead PSU chip UC3842 and 330K resistor (0.5 watt) in series with pin 4.

Dead - Dry joint on mains input VDR. Usually this results in the surrounding PCB being burnt.

 

X154 (Samsung chassis, equivalent model unknown)

 

Wont switch on when warm and loud buzzing noise This was a weird one, the fault was eventually traced to IC TDA9109 (sync chip)

 

Poor focus, cannot be corrected - Faulty CRT.

 

E156 (Samsung chassis equivalent DP15H)

 

Display too bright - R522 (1 meg ohm) high in value; its located near the line output transformer. This can be R508 (1.5meg ohm) on some board revisions. 

 

E155 (Acer 7255e)

 

Out of focus - This monitor is a complete pile of crap and should be disposed of. Uses Samsung CRT's (enough said)

 

E178 (Hyundai V700 chassis)

 

Intermittent won't power on / takes a while to come on / dead when cold - C123 330uF 25V Fault symptom is usually accompanied by a brief buzzing or fizzing from the Line Output Transformer but its not faulty.

 

Top

 

Acer

 

7154

 

Dead but power light on - Sync IC TDA4858 and R214 (15K) Also check C335 (220pf 2Kv, replace with 3KV)

Dead power light flashing green - C335 S/C, L304 SC, 2SK2161 S/C also BU2520AF may be faulty. 

Dead Power light flashing green - C335 O/C, BU2520AF S/C Also check L304 - if this has gone it is usually discoloured. I don't know where to get these from but the value is 2.2mH. These inductors are often fitted in other Acer models so a raid on your scrap boards pile may turn up a suitable replacement.

Blows 2SK2161 again after a few mins or as soon as signal is connected - L304 S/C

Excessive EHT - Line output transformer

Looses settings when switched off - Memory IC (next to microcontroller)

All lights on under flap, no display - Microcontroller

Stuck in powersave - dry jointed sync pins on VGA cable connector (CRT base board)

 

Top

 

CTX

 

1569DSE

 

Dead with tripping PSU - Check IC701 (TL431), R717 (12K) and capacitor C721 (1uf 50V). If the capacitor has blown apart and the resistor burnt, check the line output transformer before replacing any components as in my monitor the transformer had literally melted at one side and a crack surrounded the transformer's middle. Obviously this transformer had developed a EHT to pin 11 short with catastrophic results. Replacement transformers are available but due to the cost it is usually more economical to scrap the monitor.

 

Top

 

Compaq

 

P50

 

A weird one - the display had vertical wrinkles running down the left of the screen which became less severe as they got further to the right. The wrinkles were the same distance apart and weren't affected by the image size, position etc i.e. they were on the raster itself. Not having a circuit diagram for this model, I first suspected there was noise being introduced in the line stage but on further inspection, the convergence was distorted where the wrinkles were. After much head scratching the fault was traced to shorted turns in the scan coils. This was not fixable so the monitor ended up in the bin.

 

P1100 (Sony G1 chassis)

 

Excessive brightness and / or flyback lines - this seems to be a common problem with these monitors and the only way to repair them is to either adjust the G2 voltage using the Sony DAS software and jig or if this is not available, some component changes. There are two 10meg ohm resistors in series on the tube base board that provide feedback to the G2 regulator and lowering either or both of these resistors will reduce the brightness. Try replacing one with 4.7M ohms first then 6.8M ohm but this depends on how bad the excessive brightness is. The component locations are R457 and R459 if I remember correctly. This monitor uses a custom version of the Sony G1 chassis but most of the parts are the same. Note that the resistors must be rated at least 1KV and 0.5W or they will not last very long and could burn up. The resistors are easily available from www.farnell.com or raid your scrap boards pile like I did.

 

Colour tint / coloured flyback lines - Use the Colour return option in the options or colour menu in the monitor's on screen display (depends on firmware revision). You will have to leave it an hour to warm up first. If this does not improve matters, suspect the CRT.

 

P700 (custom Sony chassis made for Compaq)

 

Dead - EHT comes up then after about 10 seconds shuts down with orange light flashing - This was caused by a faulty eeprom, there was line and frame scan and all voltages were OK. Replacement of the IC (8 pin SMD) with one from a scrap board proved the fault. Note you cannot fit a blank eeprom as this chip contains the monitor's firmware as well as the settings. The Sony DAS software may be required if the greyscale etc is out after IC replacement; this unit uses a Sony chassis similar to the CPD-200E which I believe also suffers from eeprom and microprocessor failure quite often. Luckily my monitor did not need adjusting as the greyscale was acceptable but not perfect.

 

P900 (Sony F99 Chassis)

 

See the Dell P991 as this uses a similar chassis. The video boards are different between models but the rest of the components are the same. The P900 has two inputs and the P991 only has one.

 

P110 (Sony N3 chassis variant)

 

Display squashed vertically and 'frilly' edges to image & rolling intermittent - Many deflection problems including loss of sync and geometry distortion is caused by the surface mounted deflection processor IC CXA2043Q. This IC is a real pain to replace and its easy to damage the circuit board when removing. Only managed to replace one successfully.

 

Top

 

AST

 

Vision 7L

 

Blows horizontal output transistor intermittently - L403 (4uH) defective, also check C446 and C451 both 10uF.

 

Top

 

IIyama

 

Vision master Pro21 (model MT-9021T)

 

Image severely distorted and squashed into a 2 to 3 inch wide strip down the middle of the screen (partial line collapse) - Replace the line output transistor 2SC5294 with preferably an exact replacement otherwise it may fail in a month or two. This is a 20 amp HOT and there are not many equivalents. Also, you must check for dry joints as this is very common in this monitor and dry joints are likely to be the original cause of the line output transistor's demise. Also check the transistor to the right of the HOT (2SA1959?) as I have had one test okay on diode test but it had a 400kohm leak from base to emitter causing the HOT to burn up quickly.

 

No display (EHT OK) - Check / replace the green video power amplifier that drives the CRT and the nearby circuit protector in its +V supply rail. Note: There seems to be two chassis fitted in this model; one has the video output IC on the tube base board, the other on the video PCB beneath the main PCB. The version I had was the one with the IC on the tube base board.

 

Vision Master 21 (model MF-8221T)

 

Very poor convergence on edges of screen - Remove the sub PCB from the CRT yoke and re-solder all connections / dry joints. Note where the wires came from as its easy to get them mixed up. 

 

Vision master Pro 410 (model A702HT)

 

Dead (LED green, no EHT) - check the circuit protector feeding the B+ supply rail (I can't remember the component reference, its between the chopper transformer and the regulator diode, rated at 3 amps) This appears to fail for no reason. The protector is a 3A bussman fuse; do not replace it with a wire link!

 

Vision master 400 (model S701GT)

 

Dead, power supply chirps at switch on, LED briefly flashes - check for cracks in the main PCB around the LOPT and the edges particularly where the mounting holes are. The PCB in IIyama monitors seem to be made from poor quality SRBP and are consequently flimsy and break easily. It is often easy to damage a PCB if its not removed with care when servicing. This fault can also be caused by faulty capacitors (see below)

 

Powers up but goes off when signal is connected - replace ALL the low value electrolytic capacitors in the primary side of the power supply. These are mostly 10uF 100V and measure OK with a meter but are faulty. Also check the capacitors on the secondaries especially the voltage rail that feeds the feedback circuit for the power supply as this model seems to suffer from lots of bad caps. 

 

Severe power supply regulation problems (image brightness / size varies with display content) - as above, check / replace the capacitors on the outputs of the power supply as these can be bad (high ESR) even though they measure OK for capacitance. Often some can be seen with bulged tops and / or leaking. These 400 series monitors seem to have poor regulation when new as I have one myself so don't expect it to be perfect after the repair.

 

Vision master Pro 450

 

Dead - replace the B+ rail smoothing capacitors along with any others that show signs of bulging and / or leaking. You will find that there are up to 6 visibly burst capacitors suggesting a overvoltage problem but this does not seem to be the case, it may be wise to change all of the capacitors anyway to prevent it from coming back as a 'boomerang' repair. Use high quality 105 degree capacitors as replacements. It seems that the capacitors manufactured by Gluxon? are crap, they fail in other manufacturer's units too and it is very common.

 

Vision Master 452 and Pro 452 (MF901U and MA901U)

 

Dead / brief line jitter then dead These use an almost identical chassis as the Vision master 450 above and suffer from the exact same problem. Change any capacitor made by G Luxon in the power supply area.

 

Vision Master 501 (S101GT)

 

Dead, loud whine from PSU (LED green) - Line output transformer. This is the first time I have seen a faulty LOPT in an IIyama monitor.

 

 

Dell

 

P1110 (Sony G1 Chassis version, not Nokia)

 

Excessive brightness (1) - Refer to cause (2) as well - this seems to be a common problem with these monitors and the only way to repair them is to either adjust the G2 voltage using the Sony DAS software and jig or if this is not available, some component changes. There are two 10meg ohm resistors in series on the tube base board that provide feedback to the G2 regulator and lowering either or both of these resistors will reduce the brightness. Try replacing one with 4.7M ohms first then 6.8M ohm but this depends on how bad the excessive brightness is. The component locations are R457 and R459 if I remember correctly. Note that the resistors must be rated at least 1KV and 0.5W or they will not last very long and could burn up. The resistors are available from www.farnell.com .The chassis used in this monitor is very similar to the Compaq P1100 but be aware component references may differ between models, check the feedback circuit to the G2 regulator; the resistors will be there.

 

Excessive brightness (2) - Refer to the above topic as this fault can be caused by the two resistors mentioned above going high in value. Check before substituting components because on one occasion, I found a faulty resistor in a P991 which has a very similar circuit design.

 

Excessive brightness with flyback lines - Defective video output IC. 

 

Colour tint / coloured flyback lines - Use the Colour return option in the options or colour menu in the monitor's on screen display (depends on firmware revision). You will have to leave it an hour to warm up first. If this does not improve matters, suspect the CRT as these early Sony FD-Trinitron tubes seem very poor compared to the older, horizontally curved tubes.

 

P991 (Sony F99 chassis)

 

Too bright / red, green or blue flyback lines - check R053 on the tube base board (G2 circuit) if OK the CRT may be leaky or the monitor requires adjustment due to normal CRT ageing. If the alignment software is not available, replace R053 (22M ohm) with a lower value but don't go lower than 15M ohm. I found that a 15M ohm and 2.2M ohm in series worked well. This 'mod' will reduce the brightness but the greyscale will probably be out (a red, green or blue tint) so this will need resetting. Set the monitor to 9300K and leave it on for an hour then use the colour return option in the user control menu. This will make the monitor do a beam current measurement of each CRT gun and align itself (it will change various shades of grey for about 10 seconds) then the image will re-appear. You should now find the greyscale is OK. If not, suspect the CRT.

 

Colours and brightness drift - Faulty CRT. 

 

Focus suddenly changes - CRT short. Sometimes curable by disconnecting the tube base board and earthing the focus pins of the CRT and switching on. You may get a loud crack as the EHT is discharged through the tube. Often, arcing can be seen inside the tube neck at the securing clamp of the yoke assembly, this usually requires CRT replacement unless the short can be removed with a CRT restorer or the above method.

 

D828FI

 

Frame jitter on lower half of screen when warm - TDA9109 sync IC (very common fault)

 

M770 (Philips CM2300 chassis)

 

Line Output Transistor blows instantly after replacement at power on - Check tuning capacitor .39uf 400V for low value reading or open circuit.

 

Samsung

 

All models

 

Samsung monitors are complete garbage. Throwing them in the nearest skip is the best thing to do.

 

Looking for monitor schematics?

Home