Manual - 8500A Series Peak Power Meter - Giga-tronics

Maintenance
6.3 Troubleshooting
The information in this section should enable a technician to locate a malfunction and determine
specifically which PC board is causing the problem. The instructions given in this section trace a problem
to a specific board. Then, the electrical description of the board contained in Chapter 5 and the applicable
diagram in Chapter 8 can be employed to assist the technician in circuit tracing the suspected board.
Ensure that devices or components external to the PPM are not the cause of the problem before starting
the Troubleshooting procedure.
In general, troubleshooting of the PPM is divided into three parts. First, the display is observed for any
error flags (numbers) that might pinpoint the specific faulty section of the circuitry (after performing the
self-test function). Second, a known and specific pulse or CW signal is applied and varied as required to
allow a general determination of the severity and parameters of the problem. Third, suspect PC boards are
placed on extenders, and waveform and dc voltage indications are traced and checked. By following the
initial approach, the steps in this section can help to isolate and locate the PC board causing a particular
problem.
6.3.1 Equipment Required
The equipment in Table 6-1 is also required for the Troubleshooting procedures in this section.
Additionally, the Giga-tronics Extender board (P/N 17075) or equivalent is needed for troubleshooting the
A2 Power Supply PC board, and the Giga-tronics Extender board (P/N 17076) or equivalent is required
for troubleshooting the A3 GPIB/Cal, A4 CPU, A5 Digital Delay, and A6/A7 Analog PC boards to
component level.
6.3.2 Power-On Failure
1. No indication that the power is turned on when the ON button is pressed (fan not running and no
lights on the front panel.)
a. Ensure that the power cord is plugged into an ac source with the correct voltage and
frequency for the PPM. (See Power Requirements in Section 2.2 of this manual.)
b. Check the ac input fuse (F1) on the rear panel to be sure that it is in place and not blown.
c. Ensure that the ac Select Plate is installed in the rear of the instrument.
d. Ensure that the A2 Power Supply Regulator PC board is properly seated in its socket.
e. Check the thermal shut-off switch located on board A2. (Also, see step 1 of Section 6.2)
f. Check the 5 V (CR1) and 15 V (A1CR1) Bridge Rectifiers.
2. Front panel apparently works (the display turns on and lights flash when power is applied), but
the fan is not running.
a. Check the 15 V supplies.
b. Check the fan motor.
c. Check the Fan Filter Circuit consisting of A1R1 through A1R4, A1C13, and A1C14.
3. Fan is running, but nothing on the front panel is working.
a. Check the +5 V and -5.2 V power supplies.
b. Ensure that the A8 Front Panel Interface PC board is properly seated in its socket.
4. Front panel lights are flashing and the display is dark.
a. Ensure that the A4 CPU PC board is properly seated in its socket.
Manual No. 20790, Rev C, November 1998 6-3
Superceded by Revision D, March 2009