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

RF Detectors
detector element, make sure that the center conductor is centered in the housing and then reinsert
the element.
CAUTION
Do not twist the element as you insert it. Doing so could damage the detector
element pin or the center conductor of the detector housing assembly.
4. Remove and discard the old PROM. Use the instructions furnished with the PROM Programming
Accessory Kit to program the new PROM.
5. Insert the new PROM into the PROM PC board so that pin #1 is in the position marked on the
PC board (see Figure D-4).
D.5.3
Reassembly of Detectors
Follow these instructions to reassemble the detector (see Figure D-4).
CAUTION
Do not twist the detector element while inserting it. This can damage the detector
element pin or the detector housing assembly center conductor.
1. Make sure that the detector element leads are straight. Screw the detector housing assembly into
the cap assembly. Be very careful not to damage the leads of the element.
2. Insert the element leads into the proper holes in the Pre-Amp board as shown in Detail B of
Figure D-4. The lead from the center pin goes to hole 1, and the other lead goes to hole 2. Solder
the leads in place.
3. After the element has been installed, it may be necessary to readjust the pulse response of the
amplifier due to a possible difference in the video resistance of the new element diodes in
relationship to the old element diodes.
To adjust the pulse response, connect the detector to a pulsed microwave source of about 0 dBm. The
pulse must be very clean as this procedure assumes a perfect input pulse. The rise time of the pulse must
be less than 6 ns, and it should have no overshoot or ringing. If the shape of the pulse is not perfect but
is accurately known, this will do.
Set the PPM in the Graph mode with the Internal Trigger at -10 dBm. Autoscale the display by pressing
[GRAPH] and set the window to a width of 0.1 µs. If the pulse shape is wrong, adjust C3 on the
Pre-Amp board in small increments and wait for the trace on the screen to redraw. After finding an
optimum setting for C3, adjust R9 until the best shape is obtained. Do not move either control very far
from the original setting. The end result for this procedure is to set the maximum rise time consistent
with no overshoot or ringing. If the rise time cannot be set below 15 ns, a small overshoot of less than
5% is acceptable.
4. Slide the sleeve onto the cap assembly. Replace the sleeve holder plate. Insert and tighten screws
(1) and (2), and return the detector to service.
Manual No. 20790, Rev C, November 1998 D-9
Superceded by Revision D, March 2009