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

Maintenance
then reset to unity gain, and the second stage is tested, then the third, and then the fourth in the same
way. The tolerance for each stage is 2% of the gain.
1. Check the amplifiers in the Analog PC board.
2. Check the Analog Switches A6U22, A6U15, and A6U13.
3. Check the PPI chip A6U1.
Self-Test #5 (Error Number 05): Excessive B Channel Offset
Use the same description and Troubleshooting procedures as given in Self-Test #3. All reference
designations are changed to A7. Applies only to the Model 8502A.
Self-Test #6 (Error Number 06): B Channel Gain Error
Use the same description and Troubleshooting procedures as given in Self-Test #4. All reference
designations are changed to A7. Applies only to the Model 8502A.
Self-Test #7 (Error Number 07): A Channel Analog Output DAC
This test routes the output of the Analog Output DAC circuit to the input of the Analog A/D Converter.
The DAC is stepped through 81 steps from low to high (each step is 0.1 V). The tolerance is
0.5% ±10 mV.
1. A6R47 (LIN GAIN) is not adjusted properly. See Section 5.3.6.
2. Check DAC circuit A6U8, A6U14A, and A6U21A.
3. Check analog switches A6U20 and A6U13C.
4. Check the PPI chip A6U1.
5. Check the decoder circuit consisting of A6U2C & D, A6U3C, and A6U5D.
Self-Test #8 (Error Number 08): B Channel Analog Output DAC
Use the same description and Troubleshooting procedures as given in Self-Test #7, preceding. All
reference designations are changed to A7. Applies only to the Model 8502A.
Self-Test #9 (Error Number 09): Delay 8255s
This test writes a hex AA to the first port of A5U6 and reads back the data. It then writes a hex 55 to the
same port and reads back the data. These tests are then performed on the remaining two ports of A5U6,
and on all three ports of A5U7.
1. Check A5U6 and A5U7.
2. Check A5U4.
3. Check Address Decoder A4U34.
Self-Test #10 (Error Number 10): Delay Time Error
This test sets the PPM into the Peak Mode with a delay of 200 ms. It then triggers the delay circuit and
measures the time until the delay is complete. The tolerance is 7 ms.
Make a thorough check of all circuits on the A5 Digital Delay PC board.
Manual No. 20790, Rev C, November 1998 6-5
Superceded by Revision D, March 2009