|
QUESTION NO. P082803-5: Nec MULTISYNC 95F monitor is missing R31A, I need the value. |
Assuming this NEC is chassis N9902, R31A appears to be 0.33 Ohm, 1 Watt, fusible. |
QUESTION NO. P71103-4: NEC V520(B) monitor without FCC #. The power is ok and LED indicate green but no display. No HV and relay does not click. Checked HOT it's ok. Checked all resistors, diodes and transistors at power supply and deflection area and looks all ok. |
Try resoldering tube connections, especially G2. |
QUESTION NO. P72103-10: NEC multisync FE700+ monitor, all digital alignment controls work except width and pincushion. If problem is processor please mention source for same. |
In many digital monitor it happens that there width and pincushion control doesn't work other all controller functioning ok. This problem is due to the Transistor which control the Horizontal Size. mostly it is located on the center of the circuit board. Look for the Transistor B649A and replace it. Some time there are more then one so if there are then check them all and replace the defective one. |
QUESTION NO. P60503-8: NEC P1250 monitor with vertical field collapse. i.e. a horizontal line is visible in the center of the screen. I have replaced the IC104 but the problem remains. |
No vertical deflection has a specific troubleshooting procedure. 1st. Check vertical yoke winding connections on PCB and measure. resistance of winding with yoke unhooked from PCB (expect 8.2-11 ohms). 2nd. Locate B+ pin of Vertical Output IC and check for DC voltage typical 25-27VDC. 3rd. Locate vertical sync input pin of OUTPUT IC and check for sync in lack of sync means VERTICAL drive missing from further back in circuit typical cause is 2.2 uf cap @50 vdc series coupling. 4th. Look for a 100uf cap at cathode of B+in diode negative will go to pin labeled PUMP or RAMP if this cap has low ESR no vertical defl will occur and output DC reference voltage will be 50-70% of documented value. 5th. Some vertical circuits use a series defl cap in the range of 1000-3300 UF. if this cap is open no deflection will occur. Other variations use less than 1 ohm resistors from NEGATIVE of this cap to ground. Poor solder (heat stress) oropen resistors take cp out of return line and thus NO DEFLECTION. |
QUESTION NO. P60603-7: Nec pn7701 monitor with open R304. Can't read the color code. |
R304 is 3.3 Ohms. |
QUESTION NO. P100202-10: NEC MultuSync 95 monitor had initially dead HOT and fusible resistor. After replacing them HV first reaches about 15 kV then switches off. HV and H outputs from processor tda 9111 disappear. Looks like X-ray protection, but Vcc for processor is only 10 volts (should be more than 10.8). Replacing of processor doesn't help. |
Check that the value of R155 (0.22 ohm) is exact. |
QUESTION NO. P100202-7: NEC V920 Monitor. Need Flyback VCC resistor value (R31A) color not recognizable looks like 0.--?? ohms 1 watt fusible, silver middle code only readable. |
R31A is 0.33 ohms fusible (flameproof) 1 watt. Also replace caps and resistors on FBT supply back to secondary p/s especially 0.22 ohms 2w will be partially open. |
In NEC chassis# N9902, R31A is 0.33 ohm. |
QUESTION NO. P51402-7: NEC Multisync C500 monitor (JC-15W1VMA). No control over horizontal width or pincushion/barrel from onscreen menu even though the menu appears to function correctly. Screen picture OK but only 1/3 in width. |
Check for shorted base emitter Npn transistor in horizontal drive stage. Also review answer for Question P5002-10 Packard Bell A720 monitor which will explain how these systems work. |
QUESTION NO. P319-5: NEC/Multisync 2A monitor, is dead. Green LED on front panel does not light. Clicking sound coming from power switch. Fuse is OK. Resistors, caps and diodes all check out. No signs of heated components other than Q502. |
Normally H.OUT transistor faulty, replace with BU2525A or BU2508A and resolder all areas of FBT. |
QUESTION NO. P41102-3: NEC Multisync 70/pn 7701 monitor. Three months ago replaced F101, Q101 burnt, ZD101 shorted, C119 burnt when Q101 blew, C156, and U101. Now F101 blew and Q101 and ZD101 shorted again. |
If Q101 and ZD101 shorted, you should replace U101 once again; also check on the condition of TH101, the 4-Amp inrush current limiter. TH101 should be roughly 5 ohms when cold (25캜). These units can get bad solder on the board, so check/repair solder, and they get bad caps, incl. C107, C117, C121, C122, C156, etc, so check generally for leaky or open/shorted caps. There is also a stand-up resistor there, near a diode on a heatsink, that will short out Q101, if its lead touches the heatsink. If Q101 still blows, try ringing the SMPS transformer primary. |
I found filter C105 across the bridger no good . Replaced it along with Q101, Zd101,and U101. TH101 read 5.5 ohms, but replaced it anyway. |
QUESTION NO. P40202-5: NEC Multisync 6FG monitor. The led is green, when I turn on click, click (about 5 seconds, the Led is blinking) and then the led is normal. The HOT (C3998) is too hot and then burnt, I guess that the HOT (C3998 ? Volt, 25 Amp, ? Watt). Can I use C3997 (20A) to change the C3998? Or can you tell me the equivalent of C3998? |
The 2SC3998 should be readily available, but 2SC5047, 2SC5444, or 2SC5453 might substitute. I don't recommend using a 20 Amp HOT, to replace a 25 Amp HOT. If your HOT was too hot, check or replace Mosfet Q5G6, it is probably bad. Also check capacitors, like C571, C572, and C573. |
QUESTION NO. P1228-4: NEC Multisync A700 monitor, the HOT, FET, Q601 (K2645), Current Mode Controller, IC621 (KIA3842P), and ZD601 that goes to pin 6 of IC621 (KIA3842P) are all blown. I need to know the voltage rating for this Zener. |
Since ZD601 is off pin 6 (output pin) of the 3842, see if it is a gate-protection zener for Q601, connecting between the gate & source pins of the FET. If yes, the precise voltage rating will not be very critical. Generally, zener values from 12V to 20V will work for gate-protection, in circuits that use a 3842 IC to drive a standard-type FET, like your 2SK2645. Many techs simply use an 18 Volt zener as a universal replacement. |
QUESTION NO. P1016-1: NEC Multisync 70 monitor (model PN 7701), R323 is slightly burnt and I want to confirm its value. |
R 323 is 1K Brown/Black /Red. |
QUESTION NO. P1016-10: NEC Multisync70 P/N PN7701 monitor is dead. The fuse is open; th101 broke; q101 is burnt w/o markings, also zd101 also burnt. I need their values. |
F101 = 3.15 Amp fuse, Q101 = Mosfet 2SK2645 (600 Volt, 9 Amp, 50 Watt, N-channel), and ZD101 = 18V Zener. Since ZD101 and Q101 burned, also replace IC101 (UC3842). TH101 is an inrush-current limiter device, rated at 5 ohms with no load, and 4 Amps max.; a Thermometrics type CL-150 (Mouser cat.# 527-CL150, or Digikey cat.# KC015L-ND) could substitute for those specs. |
QUESTION NO. P1012-3: NEC jc 200 2vma-1 monitor. I replaced the horizontal transistor HPA 150. It works well with the horizontal york plug off the motherboard. The minute I put it back it, blows the transistor. Checked for any leaks into the chassis, it seems to be fine. |
On NEC's, when the HOT blows, the B+ regulator FET generally also is damaged, and if both are not replaced at the same time, the damaged FET will blow the new HOT, from excess B+. There's a couple board versions in JC2002VMA-1; usually the regulator FET is Q5P0 = 2SK758, but may be Q5G6. Also check H. drive cap, C541 = 100 uF/35V. Be sure your HPA150 has an internal damper, despite the presence of D561 & D562. |
QUESTION NO. P921-1: NEC MultiSync P750 (JC-1744UMA-1) monitor, I need to find a replacement for Q591. It is shorted and causing the power supply to cycle. The only numbers on the device are "J306" and "7G2" Of course no help from NEC. Cannot find any info on their website (used to have parts lists online). |
I believe the number you need is 2sj306 which is a mos p fet 250v, 3a, 25w. A 2sj307 will substitute ok. |
QUESTION NO. P911-3: NEC JC 1531-vmr model 4fg monitor has drifting horizontal sync. Adjusting horizontal hold pots vr501 & 502 will fix sync for a short time then it fails again. Replaced LA7850 and assoc caps- no change. |
Check IC 74xx86xx somewhere on the main board close to the cable coming from the crt bd. This ic takes the horizontal and vertical signals from the computer and feeds to the required ccts. It can be influential in resolution changes. |
QUESTION NO. P411-7: NEC 5FG monitor switches on with green light lit , no EHT but have outputs from power supply as follows: brown/184v red/90v orange/28v, unsure if these voltages are correct. |
If this 5FG is JC-1741UMA, and you are measuring at K1, K2, K3 of power connector CN-K, I'd expect to see 180V, 90V, 30V nominal. |
QUESTION NO. P427-1: Nec Multisync 4FG monitor powers on with solid GRN LED. Bad static crackle on power up as the display flashes for a split second. Part site might also help. |
Start by checking under the electrolytic capacitors for leaked fluid, conducting voltages to various places and eating PCB traces. For that symptom, start with C557, C556, & C793, but many can leak. Other common leakers include C561, C554, C564, C516, C517. Clean up any leakage well, and repair any blackened traces that got eaten by fluid. |
QUESTION NO. P418-8: Cornerstone color 21 [nec,jc-2142umw] monitor. I replaced Q581-2sc3998 and Q5g6- 2sk758. The high voltage is back but now the side pin can only be corrected a little bit. |
Assuming this brand is like the NEC 6FG, try checking the pincushion daughterboard, on the left side of the main board. First check for any leaking electrolytic capacitors at this board, or where the input connectors are located. Check if +12V and -12V are present on pins SA4 and SA5 of the connector. Also check IC5S3, an LM324A-type op-amp, on the daughterboard, as this can sometimes fail. |
QUESTION NO. P10803-6: I need the part number and sub for Q2001 (N1l4M K34XM) of NEC XV17+ monitor. |
That marking corresponds to AN1L4M, an NEC PNP digital switching transistor. There are two series 47K resistors between its base and emitter leads, which will make this device test differently from normal transistors. The NTE/ECG 2360 is a possible sub. |
QUESTION NO. P130-6: Nec Multisync XE15 monitor. I need the value or any information of transistor J306. |
"J306" is 2SJ306, a P-channel MOSFET, rated at 250 Volts, 3 Amps, 25 Watts, Rds[on] < 2 ohms. There are not many substitutes, due to the 250V rating; the possibilities include 2SJ306 itself, 2SJ307, 2SJ449, and IRFI9634. Try Dalbani (www.dalbani.com), MCM Electronics (www.mcmelectronics.com), LJ Enterprises (www.ljent.com), or B&D Enterprises (www.bdent.com) for these devices. |
QUESTION NO. P112-8: NEC multisync 70 monitor will intermittently not turn on from cold start. The led is amber and there is a constant clicking. |
I just fixed one of these - it sure felt like X-ray protect but is apparently a power supply issue. Adjust the SMPS output setting, you will probably find that it has drifted out of spec (there is a pot for the adjustment). |
QUESTION NO. P816-8: NEC Multisync 70 7701 monitor (Dec98). High Voltage shuts down after extended periods of use. If it is shut off for a few seconds and turned back on, you can hear the HV come up then shut down again. If power is shut off for about 10 minutes it comes back up and runs for another extended period. |
You might try heat & freeze, to see if the Weltrend IC (has markings like WT60Pxxxx) has become heat-sensitive. If yes, try glueing on a (grounded) copper plate to it for a heatsink. If not the IC, check/resolder the main board for (intermittent) bad solder joints. |
QUESTION NO. P58-10: NEC JC-1531VMA-3N monitor. Q510 is shorted. Installed is 2SJ306. I have seen publications listing this as a IRF9610 and/or IRF9620. What should it really be? |
I would stay with the original if possible. This part is available from most part suppliers. |
QUESTION NO. P516-8: NEC Multisync 5D JC-2002VMA monitor. I need to identify and a sub for Q5T0A, marked NEC K1271. |
2SK1271 is rated 1400 Volts, 5 Amp, 150 Watt, Rds[on] < 4 ohm @ 3 Amps, MP-88 case. 2SK1271 is listed by B&D Enterprises (800-458-6053; www.bdent.com); MCM Electronics (800-543-4330; www.mcmelectronics.com); and Union Electronics (800-648-6657; ued.net/index.html); getting the original is probably cheaper than the other suitable FET's. |
QUESTION NO. P515-10: Nec 2051 mh monitor. I need the equivalent of stk 730-080. |
The NTE equivalents for the STK730-series only cover the lower-power STK730-010 and STK730-020 devices (110 Watt, 145 Watt). No NTE equivalent is listed for the 210 Watt STK730-080 device. However, B&D Enterprises (800-458-6053; www.bdent.com), Union Electronics (800-648-6657; http//ued.net/index.html), and MCM (800-543-4330; www.mcmelectronics.com) do list the STK730-080 device itself, and B&D also has the datasheet on-line. |
QUESTION NO. P52-3: NEC jc2002vma monitor. Q560(hpa150) shorts repeatedly. Cannot find any other problems. |
There are a couple versions of this NEC, so these location numbers may not be exact. Replace the B+ regulator FET, probably a 2SK758 (location Q5P0 or Q5G6), on a heatsink at the front of the main board. Replace capacitor C541 = 100 uF, and check D561 & D562; an older board might have a single D560 installed in place of both D561 & D562. |
QUESTION NO. P228-10: NEC 6FG 21" monitor, when turned on, I can hear the sound of H.V. charging the tube, but after 1-2 seconds, the H.V shuts down. Before this symptom, the monitor just worked at 640x480, not accepting more than this. |
See if the deflection transistor Q581 and regulator Q5G6 are leaky or shorted. For the modes problem, you might ask if your customer has been trying to run this older monitor on a newer video card, with scan rates that are too fast (also stressing the deflection circuitry). |
QUESTION NO. P21-9: NEC JC-1402HMA monitor. R632 was blown beyond recognition, I need the value of this. R623, R624 were blown also. |
NEC's tech website lists R632 as 1.2 K ohm, 1/4 Watt, 5%, carbon, part# 40175175. |
QUESTION NO. P16-3: NEC JC1743UMA monitor (XP17) turns on but no HV or picture. |
Check Q541 (HOT) and Q572 (P-FET). |
QUESTION NO. P122-9: NEC Multisync 4FG, JC-1531VMA monitor dead, power light does not light. Disconnect leads from power supply to main board, check power supply out on 24, 80, 150 all fine. Connect all leads except 150 back to power supply, everything works including power led. Seems to be shorted out on 150 side. |
Very common with this model. Check Q505, Q510 (replace IRF9610 with IRF9620), D506, D507, ZD502 and C520. Also check for bad electrolytic caps in the horizontal/HV section. |
QUESTION NO. P922-6: NEC Multisync 5fg JC-1741UMA monitor operates normally with sync on green. With separate sync, modes with horiz. freqencies less than approx. 35kHhz are not recognized. Have substituted new control PCB, with same result. Appears to be problem with sync selection processing which is located on video PCB (inaccessible when control PCB is installed). |
After obtaining schematic of video PCB, was able to trace problem to defective capacitor C8H2, 4.7uf 50V electrolytic, which had decreased in value. This, along with very high ESR, prevented it from coupling discrete horizontal sync to the input of sync processor chip, IC8G3 (except at high horizontal frequencies). |
QUESTION NO. P728-8: Where can I buy a circuit board for an NEC 2143 monitor? It is the front panel control board<pwe-404b> or Q25-157MS. I am not sure which one is the part #. NEC will not sell to anybody. |
Does not surprise me about NEC after what they have done to their consumer base. I'd contact their customer relations devision and voice my opinion to them about not supplying parts. They stranded millions of cunsumers when they dropped their consumer electronics line a few years ago. I personally do not buy any of their products due to these facts. |
QUESTION NO. P628-1: I need a description of q5e4 in mainboard of nec multisync xe15 monitor. |
Q5E4 = 2SD1763. An NTE2576 would be a close substitute for that type. |
QUESTION NO. P526-5: Nec JC1741UMA monitor, the power light is on and the tube sounds like it is charging but there is no picture on screen. |
If there is power and high voltage, but no video, one cause is forgetting to put the Sync switch on the back panel to its "on" position! Also, check that the BNC/D-sub selector switch on the front panel is set correctly. |
QUESTION NO. P430-4: Nec 5D monitor with no power LED, no heater in picture tube, but has hi-voltage present on front of screen. Power supply checks out, 170v, 85v, and 24v are present. |
The NEC 5D gets its filament voltage (6V) from the Video input board, that is the board nearest the back. If you trace the twin ribbon cable from the CRT board to this board you will see where it is fed from. The six volts is fed through a resistor which ultimately derives it's supply from a 12 volt source. I think you will find a 12 volt regulator on this board that is supplied from the 24 volt source coming into the board. This is a common problem. Also check all components from the 12 volt regulator to the 6 volt feed. A schematic REALLY helps, since this board has circuit traces on both sides. The power LED also will not light when this circuit does not work. |
QUESTION NO. P415-8: NEC XP17 monitor that powers up but immediately loses HV (I can see a picture very shortly and Green LED is OK). All transistors around the FBT seems OK. Also vertical Def seems OK. |
I figured the problem out my self. It was the FBT that was defective. |
QUESTION NO. P317-7: NEC monitor JC-1733VMA which displays a green LED but no video. Items that checked good were heater, HV (stays on) and power supply output voltages. |
Check the CRT board for a high-ohm resistor, I think R906, 1.5 Mohm, that goes bad. |
QUESTION NO. P225-4: Have a few NEC XV17 model JC 1734VMA monitors, FCC #A3DJC-1734VMA. Two units had poor focus that could not be adjusted with fbt pots. Replaced cracked fbt with good units, and now cannot properly adjust focus. Is there a secondary adjustment/part replacement to calibrate for new fbt? |
If you can go from bloom to bloom you have a bad crt. If it is almost focused at one end, then you need to readjust the high-voltage regulator. |
QUESTION NO. P34-4: NEC 3D monitor that when turned on just has a white line across the center of the picture tube. |
Check for vcc at pin 1, 12volts. and for b+ at pin 7, 24volts. You may need to replace the LA7835 ic. |
QUESTION NO. P223-1: NEC Multisync monitor model no. JC-1734VMA. I need the value of Q541. |
Q541 = 2SC5047. Before replacing Q541, check if Q572 = P-FET (2SJ306 or 2SJ307) has gone leaky or shorted, or else high B+ voltage may blow your new HOT as well. Also be sure R538 on main board is not accidentally touching and shorting to the shield. Parts available from MCM (800-543-4330), or B&D Enterprises (800-458-6053). |
Q541 is marked C5047. |
QUESTION NO. P216-10: NEC 4FG 15" monitor with a focus problem. I can adjust the focus but it will change and need to be readjusted. It constantly changes. |
You need to replace the flyback, they are known for this. |
QUESTION NO. P119-7: NEC Multisync 5D in for repair, model no. JC-2002VMA. The problem is that there are parts missing. Q560 and D560 are gone along with their heat sink. I believe they are the HOT and damper. |
The information you need is contained in the answer to Question P129-4. |
QUESTION NO. P1210-7: Nec XE15 monitor that, after it warms up, it collapses vertically and the power light turns amber, then it comes back up for one second and does it again. It continues with this cycle until turned off. It sounds like the high voltage goes down also during this cycle. |
This sounds like a bad IC881 = TMP87CK42N chip, but these are expensive, so try to confirm first with freeze spray or heat before replacing. NEI (888-634-7278) has had these, be sure to note the suffix code off the IC to get the correct version. |
QUESTION NO. P129-4: NEC Multisync 5D monitor model no. JC-2002VMA. Two components are missing, Q560 and D560. I need help identifying these two parts. |
Q560 is a HPA150R available from L.J. Enterprises, CCS, etc. D560 is not used when D561 & D562 are installed. They are RG2A2. These series diodes with their cathodes toward the collector of Q560 shunt Q560 to ground. To prevent your replacement Q560 from failing again, be sure to replace C541 (100uf @ 50v) & Q5P0 (2SK758). |
QUESTION NO. P1116-1: I have a problem with a NEC 3FG monitor. The picture erratically blinks and the size of the picture suddenly increases and decreases. I have no schematics for this one, I think it is a horizontal sync problem. |
Two possible solutions: No 1 High voltage drive frequency too high. Replace zd508 6.2V 1/2watt zener,C581 10uF/50V,R5C8 39K,IC801 Sync processor HE60020. No 2 Try replacing high voltage adjust control VR15 Intermittent at the 20K to 22K surface area. |
QUESTION NO. P1024-4: Still working on that NEC 3FGx. I have two burned resistors which were in the drain circuit of the MOSFET. Both appear to be 10 ohm 1/2 w flameproof but one measures 150 ohms and the other 180 ohms. They are circuit designations R557 and R558. Are these values correct or are they a different value? Both are quite charred. |
Both r557& r558 are 390omhs 3w at 5% . |
QUESTION NO. P119-3: I have a NEC JC-1734VMB Monitor. When on, it only displays for a second then the HV will shut down. However, the led remains green. Repeating the ON /Off sometime will get it up and it will stay good for the whole day until the next ON /OFF procedure. |
Since it will fire up sometimes, it is not a blown part like a HOT or FET. I think you need to read about IC801 in answer P1027-3 on this page. |
QUESTION NO. P119-8: Have a NEC jc-1741uma need the value of resistor r860 on the video board mounted on the back of the monitor. I believe it is for the 13-volt supply for the cpu board mounted on top of video board. |
R860 =10ohm-1watt. |
QUESTION NO. P1025-5: I am working on an NEC JC1531VMA2 (4fge) that lost highvoltage after I replaced the flyback. The replacement transformer came out of a working set. After replacing the high voltage adj. pot, the high voltage shut down. Smps is good., H.O.T. is good. What should I look for next? |
You probably have a very high high voltage and x-ray protection shuts it down.Try readjusting or change your trimmer pot again. |
QUESTION NO. P113-10: I have a Nec monitor model JC 1532 (3FGX). I need the pin-out of the monitor cable (end to end, not just function). |
The end to end pinout of the 3GFx video cable is as follows: 15 pin computer 11 pin video pcb connector connector 1 1 2 3 3 5 *4 *2 5 7 *6 *4 *7 *6 *8 *Shield 9 N/U *10 *9 *11 *9 12 11 13 8 14 10 15 N/U Pins with an "*" are connected to both the shield and pin 9 on the video connector inside the PCB cable.Basically all are grounds. |
QUESTION NO. P1027-3: I have a NEC monitor (JC1734VMA), when I power it on I get no video. However, if I turn on the monitor before the PC is connected then connect, I have video. I also noticed if the PC is connected and I toggle the monitor on\off\on just righ, it will fire up. |
Check out IC801 = UPD78014YCW-Y22 (or -Y24), see if heat or freezespray on IC801 affects the situation. If bad, not good news. the preprogrammed IC801 IC's are expensive; NEI (888-634-7278) wants $$ for these IC's. |
QUESTION NO. P105-5: I have an NEC Model 3FGx with ZD520 and Q512 burned beyond recognition. What are the part numbersof these two components? |
Q512 is a 2SK752, ZD520 is a RD8.2. |
QUESTION NO. P925-6: I have NEC JC-1531VMA monitor with problem. Both sides of picture are bowed outside ( ). Picture is clean. Adjustment from the front panel in service helps slightly. |
The common problem that causes this symptom is that C561 = 470uF on the main board can leak electrolyte, damaging traces on the PC board. Remove the cap and check underneath: if this cap leaked, you'll need to clean the board well, check all nearby traces carefully for damage, and to jumper any damaged traces. Even with no loss of continuity, leakage onto the trace from the wiper arm of pot VR403 to pin# 8 of board# PWE317E can actively cause problems, so you may need to actually CUT that trace at both ends, and jumper between the cuts. Note, the leaky cap may actually test good, but replace it anyway with a 50V cap. Cap C557 can also get leaky and should get checked, too. A bit of conformal coating or lacquer on the PC board after cleaning well can be a future safeguard. Secondarily to this problem, if it still will not adjust, and you're sure you caught all the damaged traces, check IC4E2 and IC4E4 on board PWE-317E, check that there is 53.5 Volts across resistor R409 on the main board, and check C523. |
There is not 53.5 V across R409. It varies with the witdth of pix as low as 27V to 35 Volts. |
QUESTION NO. P826-10: I have a NEC 4FG, Model jc1531 VMA, with bad side pin Cushion )(. I already checked C561 for leaks but do not see any. What else can I check? |
I cannot tell if your inspection of C561 for leaks was good enough. Did you read the Monitor Answer# P527-4, including the part about C561 seeming OK? Did you do everything that answer indicates? Checking continuity of traces and cleaning underneath C561? Jumpering the trace from VR403 to PWE317E? Testing the IC's on PWE317E? |
QESTION NO. P817-3: I need information about an IC (included in a monitor 4FG,15"Nec) VPS08N. I have tried many different sites, there was no information. Can you help me to find datasheet for this IC, it is only for testing purpose, if the ic is OK. |
VPS08 is a Sanyo 3-channel, 80 MHz CRT video output driver. It is obsolete, so the Sanyo website (www.elisnet.or.jp/login-sanyo.htm) does not provide its datasheet. But you might download the datasheet for VPS10, which has similar package and voltage ratings, though rated for 100 MHz. VPS12 and VPS13 also exist. In the meantime, you might also check the traces beneath your VPS08N for corrosion due to leakage from cap C793, which is a common problem in NEC 4FG's. |
QUESTION NO. P726-4: I have a NEC 4fg (jc-1531vma). Someone has worked on this unit before and removed two parts. Need to know values of Q-503 and Q-504. |
Q503 is a K699 and Q504 is a B536 with a heat sink. |
QUESTION NO. P722-5: I have a NEC monitor with the model number of JC-1402HMA and FCC ID of A3D9MDJC-1402HMA. On the power supply board PWE-195, resistors R623 and R632 were burned beyond recognition. I was wondering if anyone could please tell me what value they are supposed to be? |
NEC maintains a tech support page, with listings of the original parts for its JC-1402HMA monitor, at http//cssweb.nectech.com/Original/ms2/parts.htm. According to that site, R623 is 5.6K, 5%, 1/4W, and R632 is 1.2K, 5%, 1/4W. |
R-623 is a 5.6k 1/4 watt and R632 is a 1.2k 1/4 watt. Notice that they are both sitting on pin 14 of IC602 which might also be bad stk 7404. Also check diode D610, transitor TR602 and resistor R624 (1 ohm 2 watt). The DC output at C1 will run anywhere from 53 to 98 volts depending on the mode the monitor is running in. The fixed output voltages at K1 and K2 are +85 and +26 volts respectively. |
QUESTION NO. P630-8: I have an NEC monitor, ModeJC1575VMA, when powered on the HV is ok, I have a green LED and normal raster when the screen control is turned up. The problem is a "NO VIDEO" symptom. Normal video signals enter the LM2405 I.C. on the video P.C.B but no signal is present on the CRT cathode pins. |
LM2405 is a triple CRT driver for R,G, B. I take your comments to mean that there are three video inputs (not blanked) going in to pins 8,9,11, but none are coming out (at pins 5,3,1). This IC is open-loop and fixed-gain, with independent amp circuits for the R,G,B signals. So, if NONE of these signals are coming through, either the IC is bad, or one of its two supplies is down. First, check that you are getting Vcc at pin#6 and Vbias at pin#10; these should be at the very least +60V and +8V, respectively, relative to ground (pins 2,4,7). More typical operating voltages are +80V and +12V, respectively. If either supply is below the minimums, check if there is an internal short in the IC at either of those two pins, if the bypass caps off pins 6 and 10 are good, or if either of the two supplies is not functioning upstream. If both supplies have good voltages, and their bypass caps are good, the IC itself is probably gone. |
QUESTION NO. P69-1: I have a NEC monitor model 3FGX which had a focus problem so I changed the Flyback. The monitor seemed fine for a while then it would not turn on anymore. |
Check out the HV-adjust pot VR516, a silicone-sealed 20K ohm pot near the flyback. These are factory-preset for each individual unit (hence the silicone), so your new flyback may need that setpoint changed. These pots can also go bad and cause shutdowns. |
QUESTION NO. P518-2: I have 2 NEC 14" multisync 4FG model # JC-1531 VMA monitors with the same pincushion problem. The screen has good clarity and brightness and switches to all modes but the sides of the picture are concave )(. |
Check C561 470uF/25V could be leaking on bottom replace it with a 470uF/50V 105 DEG.C. if it still does not work check IC552 LM2940CT 12V 1.5-AMP regulator. |
QUESTION NO. P428-1: I have an Nec JC-1539VMA that has an orange power light, no high voltage (it only draws about .05 amps of current), I've checked most of the power supply components but can find no bad parts. Does anyone have any experience with this one? |
These units are notorious for having defective IC881 microprocessors, Toshiba TMP87CK42N-4147, which mimic power supply problems when bad. NEI (800-659-3186) or CCS (800-356-1227) may have this IC, but it is pricey. |
QUESTION NO. P36-3: NEC XE15. When turned on, I get the orange (standby mode) power light. It does not change to green when video is applied. There is a high pitched squeal which increses in pitch and intensity as you increase the brightness controll. The horizontal output transitor tests as shorted when the flyback is connected but when it is disconnected it tests good. He suspects a bad flyback but is not sure. |
Suspect the damper diode[s], and any other components around the hot. Try a flyback tester [ringer] if available. The diodes within the flyback [tripler] also may be defective or shorted truns within the flyback. Check external components first before condemming the fbt. Look for any signs of perforation thru the casing of the flyback. |
QUESTION NO. P127-1: Looking for help on NEC Model JC-1433VMA with no video symptom. Powers on but no video. |
Key items were missing in your question. Does the HV cycle on and stay on? This is confirmed by either HV Voltage probe or by hearing the crackle. If HV is present is the filament lit? Either or both would cause no video to appear. |
QUESTION NO. P116-5: Several NEC 2A monitors (JC 1403HMA) with similar symptoms. The display is out of focus when turned on. The picture focus improves the longer the monitor is on. One of the monitors appears to have healed itself, meaning the focus and brightness are good at all times, however, when the computer is turned off the raster is visible (not blanked) and a few of the retrace lines are brighter than others. |
ANSWER 1: How old? Possible crt, suspect crt socket for high resistance path from focus to grnd. Other things may be failure in Focus supply from FBT or focus/screen control assembly. |
ANSWER 2: Sounds like it is temperature related, possibly a bad cap. Try using a hair dryer to heat up components and watch for inprovement. |
QUESTION NO. P129-1: NEC / multisync (3DS) M# JC-1404. The video is fine except there are 2 vertical blue bars about 1 1/4" wide on the right side of the display separated by about1 inch. I replaced the 51387 IC with no difference. I also replaced the 3 1Uf 160 volt capacitors as they were reading low. |
Look at question/answer #P1210-8. The problem and solution are what you need. Replace all 3 caps 2.2uf @50vdc off the video processor. |
QUESTION NO. P1210-8: NEC Multi sync 3DS M#JC1404HMA-2 14" monitor. On the right side of the monitor are 2 blue bars about 1 1/4 inch wide running vertically with a spacing of about 3/4 inch. I replaced the 1 Ufd caps on the video board and the M51387 IC with no change. |
Check the 3 2.2uf 50v ccaps below your 51387 color processor. |
QUESTION NO. P113-10: N.E.C. 4FG monitor has excessive brightness with retrace lines. |
Replace the flyback if your crt is not shorted. |