16) optiquest 수리내역

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QUESTION NO. P72503-1:  Optiquest V95 Model vcdts2183 monitor FCC GSS1900 the horizontal sync is way out, the picture is only 4 inches wide.  I think LM1292N IC is bad but can't locate one. I used to purchase IC's from LJ but his site is no longer there.

LJ Enterprises' new web address www.ljecc.com/

QUESTION NO. P50503-8:  Optiquest Q71 monitor powers off immediately.  I need the specs on burned voltage regulator Q429.  The board is version VCDTS21348-2M.

Q429 is 2SC5248, rated 160 Volts, 1.5 Amp, 20 Watts, 150 MHz, DC gain 60-200, Cob 20pF, TO220F case. A 2SC3298 also might substitute for 2SC5248.

QUESTION NO. P42203-6:  Optiquest Q71 monitor FCC GSSJ 17001 came from another shop. I replaced the shorted HOT.  It is working fine now but too wide.  Width control does not work.  Pincushion ok.

Check or replace D422, Q429, and Q411.

QUESTION NO. P117-10:  Optiquest V73 VCDTS21433 monitor is dead, the led stays amber.  All the caps are ok with ESR.

Check Q550, Q881, T823, and IC841.

QUESTION NO. P10703-10:  Optiquest Q71.  R457 was burned, I need the value.

The resistor is 680 ohm 퐓 R457in circuit.

There are several different chassis used in the Optiquest Q71, but if R457 burned, yours is probably the Jean chassis, where R457 is 680 ohms, 1/2 Watt. Also replace the defective disk capacitor C449 (220pF/2KV), which caused the R457 to burn.

QUESTION NO. P95-2:  Three Optiquest 1769DC monitors with same problem:   Replacement HOT shorted after two days usage.

Check for bad solder and cracks, especially at the horizontal driver transistor and transformer, and check the ESR of any electrolytics in the drive circuit.  Also, if there is any of that notorious glue on the horizontal or high voltage components or heatsinks, scrape it away; that glue has sometimes caused the HOT to overheat and short.

Upon removing the horizontal driver transistor found the goo that had overheated around the Horizontal Transistor.  It was impossible to read the part number.

QUESTION NO. P55-5:  Optiquest V775 monitor with a raster only about 2 inches wide.  The raster is not trapezoidal or distorted & video is present.  I checked all caps on the main board with an ESR meter & they seem O.K.   I replaced the H.O.T., no change.

I would think "Eeprom".

QUESTION NO. P421-5:  Optiquest 4000DS 17" monitor, does not have High voltage. Power supply voltages are OK per printing on board. Led lites indicating a vga signal present. The wave trace at base of HOT is not a good sawtooth signal.

You should not expect a sawtooth at the base of a HOT.  Drive to B of HOT looks more like a rectangular with negative spikes on falling edge

__ ___ .... hilevel ~+0.7V

!____! !__ .. lolevel ~-2V

! !

! ! <-- 1st neg. spike below -5V

If signal to base of hot is other than rectangular waveform check drive (which is often done by a transformer - check the signal on its primary - it is rectangular again). If drive to hot (as shown above) is present scope C of hot.- ATTENTION ! Make sure your scope can handle >1200volts peak.  You should see needle like pulses starting at falling edge of hot-B drive.  If no trace there or scope not able to safely display 1200Vpeak, check the DC voltage at the collector print with HOT DISMOUNTED. Maybe the supply voltage (+b) to or through the flyback is missing.  If so and you find a burned fuse or fusible resistor in the supply path, check HOT for CE shorted.