NOTE
Do not perform the 91AE04 adjustment on modules with serial numbers B01 0118 and up. New circuitry on these modules has eliminated the need for this adjustment.
91 AE04 modules with lower serial numbers may also have been modified at a service center to include the new circuitry. R495 is removed from the module during the modification. Modules without R495 do not require the adjustment.
To meet high-speed clock specifications, 91 AE04 modules must be adjusted to the master 91 A04A or 91A04 module's clock.
The 91AE04 adjustment should be performed under the following conditions:
• Installation - The 91AE04 clock adjustments should be performed when the 91AE04 modules are first installed in a mainframe. If the 91AE04 modules were installed at the factory, the adjustments have already been performed. If the 91 AE04 modules were ordered separately from the mainframe, perform the adjustments after you have installed the 91 AE04 modules and connected their cables to the 91 A04.
• Cable Connection Changes - The validity of the 91 AE04 clock adjustment depends on the clock-cable connection used during the adjustments. The 91 AE04 clock adjustments need only be performed once, but the cable transmitting the clock from the 91 A04 to the 91 AE04 must al-ways use the same connectors that are used during the adjustment. You must perform the ad-justments again if you use connectors other than those used in the original clock-cable connection.
The adjustment requires the equipment shown in Table 3-6. The location of the test pOints and trim-mer potentiometer used in the adjustment is shown in Figure 3-12.
Table 3-6
EQUIPMENT REQUIRED FOR 91 AE04A ADJUSTMENT
EQUIPMENT
Tektronix DM502A Digital Multi-meter with TM 500 mainframe Positive lead, 012-0426-00; neg-ative lead 012-0426-00; retract-able hook tips, order two of 013-0107 -00
003-0301-00
Operating Instructions--DAS9100 Series 91A04A/91AE04A Service
TEST POINT A . - - - ,
R495 TEST POINT t l - -_ _ ..,
FRONT VIEW
BACK VIEW
TEST POINT A . - - - . . ~ TEST POINT B
111111
'-~
TOP VIEW
~,--:l
_ _ _ _- R495
4254-10
Figure 3-12. Location of trimmer potentiometer R495 and test points on 91AE04 modules.
To make the adjustment, you must first install all 91 AE04A modules in the mainframe, and connect them to the 91 A04A or 91 A04 master module. Then use the digital multimeter to monitor the voltage between two points while adjusting trimmer R495.
Perform the following steps to accomplish this adjustment:
~
Do not install or remove modules in
a
DAS mainframe while the mainframe power is on. Doing so may damage the module or the mainframe.1 . Turn off the DAS mainframe.
2. Install the master 91 A04A or 91 A04 module that will be driving the 91 AE04 module if it is not currently in the mainframe. Be sure to follow any installation restrictions noted earlier in this section under Configuration Requirements.
3. Install all 91 AE04 modules to be adjusted in the desired locations of the DAS mainframe (following any installation restrictions).
4. Locate the two a-inch coax cables and the 3.5-inch threshold jumper cable that come with each 91 AE04 module. Connect these cables between all of the 91 AE04 modules and the 91 A04 module. Directions for these cable connections are found in the Module Installation subsection of these Operating Instructions.
NOTE
Do not connect P6453 probes to the 91AE04 modules during these proce-dures. The probes are disconnected to prevent the DAS from triggering during the adjustment.
3-31
3-32
5. Turn on the DAS mainframe. All the 91 AE04 modules should pass the diagnostic tests. If the di-agnostics do not pass, check all cable connections between the 91 AE04 modules and the master module.
6. Turn off the DAS mainframe.
~
Failing to tum off the DAS mainframe at this point may result in damage to the 91 AE04 module being adjusted.
7. Turn on the DMM. Set the DMM to 200 mV dc full range.
8. Choose the 91 AE04 module you want to adjust. Locate the two test pOints on the back (solder side) of the module as indicated in Figure 3-12. These test pOints are each located at the junction of a capacitor and a resistor soldered to the back of the board.
• Test point A is located between a capacitor and a resistor pn the solder side of the circuit board. The lead running between the capacitor and the resistor is a short, exposed solder connection.
• Test point B is also at the junction of a capacitor and a resistor, but the resistor lead is long and covered with insulation.
9. Connect the positive gripper-tipped lead of the DMM to test point A, as shown in Figure 3-12.
Connect the negative DMM lead to test point B as shown in Figure 3-12.
10. Turn on the DAS mainframe. Enter the Trigger Specification menu. Set the MODE field to 91A04 ONLY. Set the 91A04 CLOCK field to 3 ns.
11. Fill the TRIGGER ON field in the Trigger Specification menu with all Fs. This, in combination with the disconnected data acquisition probe, prevents the 91 AE04 module from triggering during the adjustment.
12. Press the START SYSTEM key to let the clock enter the 91 AE04 module from the 91 A04 mod-ule. The DAS screen shows the message WAITING FOR 91 A04 TRIGGER.
I
WARNINGI
Do not place your fingers on components while the mainframe is turned on.
DAS circuit boards and components can become very hot during operation.
Do not allow metal jewelry to come in contact with circuit components. A short between components could cause the jewelry to become very hot.
13. Locate trimmer potentiometer R495 on the component side of the 91 AE04 module (as indicated in Figure 3-12). Using the plastic-bladed screwdriver, adjust R495 until the digital multimeter reads between -5 mV and +5 mV. Optimally, the DMM should read 0 mV.
14. Turn off the DAS mainframe.
Operating Instructions--DAS9100 Series 91A04A/91AE04A Service
~
Failing to tum off the DAS mainframe at this point may result in damage to the 91AE04 module being adjusted.
15. Disconnect the DMM test leads from the back of the 91AE04 module.
16. If you have performed this adjustment on all of the 91 AE04 modules in your system, you may turn off and disconnect any test equipment used during the adjustments. If any 91 AE04 modules have not yet been adjusted, return to step 8 and perform all subsequent steps on that module.
All of the 91 AE04 modules in your mainframe have now been matched to the master module. To maintain the adjustment, do not change the order in which the clock cables are connected between the modules.
3-33
Section 4--DAS9100 Series 91A04A/91AE04A Service