Maintenance—492/492P Service Vol. 1 (SN B030000 & up)
Fig. 4-28. A15 and Memory board address decoder outputs.
Exceptions for Firmware Version 8.2
1. The external Mixer bias is turned oft for bands 1
through 5 whenever frequency span or band is changed;
however, the indicator remains lit. If an external mixer is
used for these bands, EXTERNAL MIXER must be can
celled and then reactivated after every FREQUENCY
SPAN/DIV or band change.
2. The microcomputer may not maintain a calibrated dis
play when AUTO RESOLUTION and AUTO TIME/DIV are
selected if a WIDE or NARROW VIDEO FILTER is also se
lected. This is evident when the UNCAL indicator lights.
Change the RESOLUTION BANDWIDTH or increase
TIME/DIV (if not set to AUTO) for a calibrated display.
3. The REFERENCE LEVEL may hang up above
+ 30 dBm in the ΔΑ mode. For example: with a REFER
ENCE LEVEL of +30 dBm in MIN DISTORTION mode, se
lect ΔΑ mode and increase the REF LEVEL for a readout of
+ 1.00 dBm, then switch out of ΔΑ mode by cancelling
FINE. The analyzer will not respond now to changes of REF
LEVEL. Normal operation can be restored by selecting ei
ther 10 dB/DIV, LIN, MIN NOISE or EXTERNAL MIXER.
4. The input attenuator may not set to 60 dB on power-
up, even though the RF ATTEN readout shows 60 dB. The
attenuator is correctly set, however, when the REFERENCE
LEVEL is changed and it now matches the readout.
4-40
REVJUN 1983
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