DOM MB V5 Diagnosis page

Board ID:

V5 000289

Source:

Micheal Harris

Symptoms:                            

August 5: In STF 2, fADC baseline, pedestal, and pulse STF tests fail
November 8
November 17: Fails local coincidence loop-back test
November 20: Serial ADC 0 tests bad in the standard cold test.

Analyst(s):

G. Przybylski

Analysis Procedure(s):

August 5: Observed STF test failure. Probed fADC input voltages, reference, and clock. All OK.
Probed fADC data pins [D2..D11]  No output.   => FADC U76 faulty. (Replaced by Helen 11/8/04)
November 8:   Local Coincidence Loop-back test failed
November 17: Board also fails Local Coincidence test.  Found intermittent associated with post TB7. Recommend jumper from TB7 to JP3-11.
November 20: Recommend replacing serial ADC 0, then route
Ran low temperature STF test profile from -40°C to -75°C. Results:
STF@-45°C through -75°C: many serial ADC - failures
STF@-60°C through -75°C: Fail local coincidence loop-back test
STF@-70°C through -75°C: Fail ATWD B Ch1 Baseline test
STF@-75°C: Fail ATWD A Ch1 Baseline test
No boot failures during about 800 reboot tests, once every 2 min, while cycling the temperature from -55°C to +65°C every 90 minutes.

Root cause:

Faulty fADC chip.
Faulty PCB trace.

Mitigation:

Replace chip.
Patch with green wire.
These faulty traces are worrisome, in this production run... however, in future production, the connectors will change.

Disposition:

Not for deployment into either IceTop or in-ice DOM.

Any Other Information:

Traveler August 5
Traveler November 8
Traveler November 17
Traveler November 20
Traveler Replaced components log