Tech. Bulletins (click here to return to list)

1. OVERVIEW

Lamphouse adjustments performed following the procedures outlined in the Gretag Service Manual will result in higher than the rated settings recommended by Phillips. When adjusted by the procedures in the book, the Printlamps will be driven at approximately 285 Watts instead of 250, which will significantly reduce the life expectancy of the lamps. Further, exploding lamps may result in additional damage to lamphouse mirrors and lenses.

The reason for this dicrepancy is not totally clear, but may be caused by a change of specifications of the Phillips # 6958 bulb (ANSI EVC.FGX), as the resistance of the bulb is approximately 8 percent less than expected (resulting in a lower voltage drop when driven at the rated current).

The following describes the Lamphouse adjustment procedures for an initial setting of 250 watts power (per bulb). The new settings will result in a longer life expectancy of your printlamps. A slight reduction of printing speed may be experienced, but this should be outweighed by the reduction of lampchanges and additional (QC) stability.

2. ADJUSTMENT PROCEDURES

2.1. NOMINAL SETTINGS

The nominal power rating of 250 Watts per bulb is achieved when the current is at 10.85 amperes, which will result in a voltage drop of 93 Volts accross all 4 lamps (23.25 Volts each). With proper function of the LAMPO and LAMCO pcbs the maximum power allowed should be around 285 Watts (24 Volts, 11.86 Amperes) when Copy light low is reached.

2.2. FIMES ADJUSTMENTS

Temporarily remove the Pre-Filter from it’s position (to prevent damage while the filters are fully retracted (see FINISys bulletin FNS-3141-001). Install a new set of printlamps in the Lamphouse (insure that the pins are sanded with 400 grit sandpaper for optimal contact). Place both filmarms towards the in position so that Film-End is generated, then power up the printer. Enter MTEST, then connect a voltmeter across the top and bottom terminals at the power strip at the right hand side of the lamphouse. The voltage with filmend should be around 75 to 85 volts.

Enter OCLV and get ready to hit the Stop Button when the voltage across the 4 lamps reaches 93 Volts. Use the "U" (up) or "D" (down) keys of the keyboard to fine adjust the voltage. Observe the filters of the filter unit, which should be open most or all the way. (If 93 volts cannot be reached, adjustment of the LAMCO current may be required.)

Connect the ground lead of the voltmeter to the FIMES pcb testpoint TP2 (ground) and adjust the Blue, Green and Red cell readings to 9.35 Volts. Check all 3 readings and repeat adjustments if necessary (as the filters may not all have been out initially). Hit "enter" at the keyboard, when done. A number will be displayed now, which is the equivalent to the OSLV value. Leave MTEST by entering "bye", then perform an OSLV, to let the computer establish the new Light Value (as adjustments to the FIMES have been made).

2.3. LAMCO CURRENT ADJUSTMENT

The purpose of the (maximum) current adjustment is to limit the current to a safe range, that will produce "COPY LIGHT LOW" before the lamps are driven in a range that might explode them. This same adjustment will also determine what the initial OSLV number will be when new printlamps are installed. The initial number should be in the range of 1.90 to 2.10 (with a clean lamphouse and new printlamps). The maximum number will be 2.55 (which results in COPY LIGHT LOW instead of the 2.55 display). The maximum power allowed should be about 285 watts (equivalent to a current of 11.86 Amps and 96 volts accross all 4 printlamps).

To adjust the maximum current, first perform the steps outlined in 2.2 above (including pre-filter removal), then perform an OSLV. The number should be around 1.90 to 2.10. Numbers lower show that the maximum current could reach unsafe levels, numbers higher may indicate that the lamphouse may need cleaning. To adjust the maximum current:

• OSLV number too high turn LAMCO potentiometer clockwise
• OSLV number too low turn LAMCO potentiometer counter-clockwise

Turn the potentiometer no more than ½ turn each time, then enter OSLV and observe number obtained. When the number is in the range of 1.90 to 2.10, the maximum current needs to be checked. Connect a voltmeter across the top and bottom terminals at the power strip at the right hand side of the lamphouse. Block the light at the FIMES measuring cell while performing another OSLV. The current should raise to maximum (equivalent to approximately 96 Volts accross the 4 lamps). Be ready to power down the printer immediatly if this number is raising higher than 100 volts !!! This may indicate a problem with the LAMCO/LAMPO pcbs. If all adjustments are performed correctly, "COPY LIGHT LOW" should be displayed, and the voltage accross the 4 printlamps should be approximately 96 volts.

Adjustment of the maximum current should only be required for the recalibration to correct power rating described above and is not normally needed as a routine adjustment. If the LAMPO or LAMCO pcb is changed, new calibration is required. To perform initial calibration, turn potentiometer on LAMCO fully counter-clockwise.

Re-Install the Pre-Filter when work is completed.

3. VERIFICATION (OTFI)

To verify the lamphouse adjustments the OTFI (Order Test Filter) command can be used. This command is available with MTEST active. No data is stored by the computer. Proper Lamphouse (FIMES) calibration is pre-requisite to correct execution of this command.

LV: The number of steps needed for full light (equivalent to OSLV)

zero: This data will tell how well the FIMES is calibrated. If values are within +/- .05 the calibration of the FIMES is adequate.

max: Gives the maximum attainable filter densities. Values should exceed 1.5, usually 2.0 or greater. Note that maximum filter densities of less than 1.5 may cause filter failures. The FIMES measuring block or one of the dichroic filters may be of insufficient density and should be replaced.

4. PRINT-LAMP CHANGES

Replacing old or failed printlamps should normally not require balancing the FIMES pcb. In fact if this is done, running a test and re-balancing the printer will be required. Printlamps should normally be replaced in a set of 4 so that lampchanges can be scheduled. Prior to insertion the contacts of each bulb should be sanded with 400 grit sandpaper to insure removal of any oxide buildup. This will help prolong the life of the lamp and the printlamp sockets. After new lamps are installed, perform an OSLV immediatly, as the computer still has the old value (2.55 if lamps were changed because of copy light low), which would be too high for new lamps. After a warm-up and burn-in time of about 10 to 15 minutes perform another OSLV.

Verification of the OTFI ZERO values (MTEST) will show whether the FIMES needs to be calibrated:

• If the ZERO values shown are within +/- .05d, calibration is adequate and printing can continue without balancing changes.
• If the ZERO values for BLUE and/or RED are outside these values, adjust them but NOT the green channel (which avoids changing the printlamp intensity). A test must be made.
• If the ZERO value for GREEN is outside these values, adjust GREEN first an then BLUE and RED. A test must be made.

4.1. COPY LIGHT LOW

Assuming all calibrations have been performed by the above procedures, a "copy light low" display or OSLV values higher than 2.10 after a printlamp change may indicate that the Lamphouse, all Pre-Filters and the Beam-Splitter Mirror should be cleaned, as too much light may get lost prior to reaching the measuring cells. Maintenance should only re-calibrate the FIMES after this has been assured.

5. LAMVO READINGS

The percentage readings of the LAMVO are incorrect after the printlamps are adjusted to 23.25 Volts (each). Either ignore them or recalibrated the LAMVO so that 23.25 Volts equals 100%.

This page last modified: May 08, 1997
copyright FINISys Inc. 1997, author: R. Ganahl