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

Series 8500A Peak Power Meters
b. Press [RESET] on the rear panel. If this clears the problem, check the output of the Reset
Timer (A4U17) for a pulse width of approximately 750 ms when the RESET button is
pressed.
c. Check the 6 MHz CPU clock at A4TP1.
d. Check the CPU Halt signal at A4U12, pin 17 (low digital level = a Halt condition).
e. Check the Address and Data I/O on the CPU at A4U12.
f. Check the Address Buffers on the CPU at A4U7, A4U8, and A4U9.
g. Check the Data Buffers on the CPU at A4U32 and A4U33.
h. Check the Address Decoder on the CPU at A4U34.
i. Ensure that all of the PROMs on the CPU board are installed in their proper locations.
Self-test Failure Indications & Possible Causes
Information given in this section assumes that the PPM was working properly when it was initially turned
on, that self-test was selected, a failure occurred, and an Error Number was shown in the instrument’s
display window. Note that during the self-test, all of the front panel LEDs are lit.
Each of the self-test checks will be described briefly, and then possible causes of the problem (as
indicated by the displayed Error Number pertaining to the specific test) will be listed.
Self-Test #1 (Error Number 01): -5.2 V Out of Tolerance
This test applies -5.2 V to the Analog A/D Converter (A6U7) through switch A6U13. The -5.2 V must be
between -4.94 and -5.46 V.
1. Check the -5.2 V regulator circuit on PC board A2.
2. Check the switches (A6U13C and A6U20) on the A6 Analog board.
3. Check the PPI chip (A6U1).
Self-Test #2 (Error Number 02): Memory Bad
This test performs a walking 1’s test on the volatile RAM. (Clears the memory, then writes and reads a 1
to each memory location. Then writes and reads a 2, etc.)
Check the volatile RAM chips A4U5, A4U6, A4U30, and A4U31.
Self-Test #3 (Error Number 03): Excessive A Channel Offset
This test sets the A channel on the A6 Analog PC board to its maximum gain of 8192, and measures the
total offset voltage present at the input to the Analog A/D Converter (A6U7). The allowable range for the
voltage at the input to the Analog PC board is 0.5 mV which would mean a range of 4.096 V at the input
to the A/D Converter.
1. Swap the detector and run the self-test again.
2. Check the amplifiers in the Analog PC board.
3. Check the Analog Switches A6U25, A6U20, A6U15, and A6U13.
4. Check the PPI chip A6U1.
Self-Test #4 (Error Number 04): A Channel Gain Error
The self-test sets the first variable gain stage to a gain of 8 and measures the offset. Then, 0.5 V is
applied to the input of the x2 amplifier and the overall gain is measured. The first variable gain stage is
6-4 Manual No. 20790, Rev C, November 1998
Superceded by Revision D, March 2009