TEST BANK: AMP/OHM
Test 600.1 — OHM/AMP
Bank AMP/OHM
Inputs INPUT HI to AMPS Short
Expected Value 0.0095 volts
Limits 0.001 volts
Fault Message 1mA SOURCE
Description This test requires a jumper wire from the INPUT HI jack to the AMPS
jack on the front panel. The +7V reference is switched to the ohms circuit
through U133. Q123 and Q125 are turned on to generate a 1mA current that
is routed to the INPUT HI jack. The signal path for this 1mA current is from
the +14V node through R194, Q125, Q119, Q120, K101 (pins 3 to 4) Q102,
Q101, through the parallel combination of R115, L109, and R324, then to the
INPUT HI jack.
The jumper wire then routes the 1mA into the AMPS jack through K103
(SETK3 control line high so that pins 3 to 4 and 7 to 8 are closed). This puts
R205 in series with R158 for a total of 10.1Ω. The 1mA current through
10.1Ω generates around 10mV which is sensed through S101 and R142 to
the AMPSHUNT node. The AMPSHUNT signal is routed to S6 of U163
where it is switched to the A/D MUX. The A/D MUX is configured for ×1
gain. Measure 10mV at AD_IN.
Bit patterns
Bit pattern Register
QQ
87654321
—U106—
110v1111
QQ
87654321
—U109—
00101111
QQ
87654321
—U134—
1v10111v
—U130—
11101101
QQ
87654321
—U121—
10110010
ACDC_STB
MUX_STB
IC pins: Q8=11, Q7=12, Q6=13, Q5=14, Q4=7, Q3=6, Q2=5, Q1=4
2-54 Troubleshooting
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