20
Subject to change without notice
4. Troubleshooting of the HM5014-2
Caution: Security advice!
The following procedures assume that the
HM5014-2 is connected to mains / line via a safe-
ty transformer. Only qualifi ed personnel who are
aware of the danger of electricity should execute
the following procedures.
If cables or connectors have to be disconnected, the instrument
must be switched off before removing. Before continuing, ob-
serve the remarks in chapter 2.1 “Test instructions”.
See paragraph 5.1 “Opening the instrument” how to remove
the rear cover and the casing of the instrument.
Item Behaviour of the HM5014-2 Possible cause / What to do Remark
1.1 No front panel LED light, no trace
and no readout visible on the CRT
(dark screen)
Blown fuse: Pull out fuse holder at the
rear and check the fuse. If blown, re-
place with same rating only and switch
the instrument on again. If the fuse is
intact, continue with item 1.2
The instrument must be disconnected
from mains / line before changing the
fuse.
1.2 LEDs will fl ash one short time,
nothing else happens
Power supply detects overload Continue to isolate fault, execute 1.3 to 1.6
1.3 Pull KEY conn Does the CRT light up (will display an
error message) ?
Short on KEY Board – replace board and
repeat test 1.2
1.4 Pull XYZ conn Do the LEDs on the KEY Board light up
(CRT is not active) ?
Short around XYZ-Board – replace board,
and repeat test 1.2
1.5 Pull CPU conn Measure the voltages on the cable. Replace CPU Board and repeat test 1.2
1.6 Pull IF-Unit conn Does CRT light up? Replace IF-unit.
2.1 Check amplitude at “1”, must be
–31 dBm
Attenuator malfunction, replace ATT 1 thru 3 are the hex marks in the block
diagram
2.2 Check amplitude at “2”, must be
–15 dBm (±3 dB), frequency 29,7
MHz for center peak
RF Box malfunction, replace RF Box
2.3 Check amplitude at ”3”, must be
–14 dBm (±3dB), frequency 10,7
MHz for center peak
IF Unit malfunction, replace IF unit
3.1 Filters not equal in amplitude IF Unit defective, replace IF unit
3.2 No noise on baseline Replace IF Unit as a test, if still no sig-
nal, replace CPU Board
Digitization working, but no signal voltage
applied
Interface not responding Replace interface Board
No probe power Replace KEY Board Voltage regulator is located on KEY Board
4.1 RF ampl has dropped Perform checks 2.2 to 2.4 to determine
cause, follow instructions
Possible ATT, RF Box, IF Unit faulty
4.2 RF ampl not linear Perform checks 2.2 to 2.3 to determine
cause, follow instructions
Possible ATT, RF Box faulty
4.3 Full band ampl check fails Perform checks 2.2 to 2.3 to determine
cause, follow instructions
Possible ATT, RF Box faulty
5.1 No TG sig Replace TG Board and test if error per-
sists, check connection to CPU Board
and RF Box, switch TG ATT in 10 dB
steps and listen for sound of relays
Also check the connectors to TG Board. Is
it powered?
6.1 No test sig Replace CPU Board as test, check ca-
ble to jack
The signal is derived from the 96 MHz sig-
nal on CPU Board
7.1 No audio Replace KEY Board Is the jack damaged?
4. Troubleshooting of the HM5014-2
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