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 142V’s. 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) Won’t
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. |