8711A-04
SUPERSEDES: None
DATE: 1 November 1993
8711A RF Network Analyzer
Serial Numbers: 0000A00000 / 3325A00941
Intermittent Memory Loss on the 8711A
Parts Required:
Part No. Description
0811-1088 Resistor 680 ohm 3 watt
Situation:
Several 8711A customers have reported that they “randomly” lose data, instrument states,
and programs that were saved to internal non-volatile memory. The problem actually
occurs when line power is removed from the 8711A while it is turned on. This would
occur during a power outage or by removing the line cord. The problem does NOT occur
if the instrument is turned off using the line switch and THEN the line voltage is removed.
The problem only occurs if the line voltage is removed while the switch is on. The problem is worsened by low nominal line voltage and low line frequency (50Hz).
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AUTHOR: JV
ENTITY: 5300
© 1993 AGILENT TECHNOLOGIES
PRINTED IN U.S.A.
SERVICE NOTE
ADMINISTRATIVE INFORMATION
MODIFICATION RECOMMENDED
SERVICE NOTE CLASSIFICATION:
ACTION
CATEGORY:
LOCATION
CATEGORY:
CUSTOMER INSTALLABLE
ON-SITE
SERVICE CENTER
AGILENT RESPONSIBLE UNTIL: November 1995
ADDITIONAL INFORMATION:
IMMEDIATELY
ON SPECIFIED FAILURE
AGREEABLE TIME
AVAILABILITY:
PRODUCT’S SUPPORT LIFE
RETURN
SCRAP
SEE TEXT
SERVICE
INVENTORY:
RETURN
SCRAP
SEE TEXT
USED
PARTS:
STANDARDS:
Labor 1.0 Hour
Continued
Page 2 Service Note 8711A-04
Solution/Action:
The problem has been isolated to improper timing of the power-fail line in the A6
power supply. MID now has a field repairable solution for existing units. A 680 ohm
resistor can be soldered across the +13 volt standby supply. This resistor should be
attached to the power supply board directly. Remove the power supply/display assembly, then remove the four screws that hold the power supply. Locate the power supply
connection cable attached to J5 of the 5062-3416 board. This is the only 16 pin connector in the supply. Unsolder pins 9 and 16 of J5. Pin 9 is directly across from pin 1
(square pad) and pin 16 is diagonally opposite pin 1 (at far end of connector). Both are
located at the edge of the board. Position the resistor, then shape and cut the leads to fit
the holes. Insert the resistor from the NON-component side of the board and solder in
place making sure nothing can short.
The recommended resistor is 0811-1088, but any 1-3 watt resistor in the 560-750 ohm
range should work if it physically fits.
Re-assemble the unit and don’t forget to re-attach the power-on switch interconnect
cable. Verify operation by storing a state, then removing power while the switch is on.
Power up again and verify the state was indeed saved. This should work for virtually all
instruments; if not, replace the A6 power supply with part number 5062-3437. All
power supplies with serial prefix 3341 and above have been re-designed to eliminate
this problem. All 8711A’s serial number 3325A00942 and above, either incorporate the
added resistor or have the newly designed power supply board.
All 8711A’s (below s/n 942) returned for service should be tested for this problem and
repaired if necessary. Cost of this repair will be covered under warranty; reference service note 8711A-4 on the CSO. If there are any questions, contact the service engineer,
John Vallelunga.
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