LeCroy 2228A

External

 LeCroy
 2228A
 TDC
 
 COM STOP
 COM START
 STOP
 0
 1
 2
 3
 4
 5
 6
 7
 CLEAR
 63348

 FULL SCALE COUNT
 TEST POINT
 
 PICOSEC./COUNT SELECT
 250
 100
 50
 
 LeCroy
 MODEL 2228A
 CURRENTS
 -6V 550 mA
 +6V 600 mA
 -24V 140 mA
 +24V 25 mA
 LeCroy RESEARCH SYSTEMS
 
 LAM SELECT
 END OF CONVERSION (EOC)
 EOC AND ADDRESSED CHANNEL VALID
 OC AND ANY CHANNEL VALID
 OFF
 
 Q SELECT
 EOC
 EOC AND ADDRESSED CHANNEL VALID
 EOC AND ANY CHANNEL VALID
 
 CAUTION
 CRATE POWER SHOULD BE TURNED OFF DURING INSERTION AND REMOVAL OF UNIT
 TO AVOID POSSIBLE DAMAGE CAUSED BY MOMENTARY MISALIGNMENT OF CONTACTS

Internal

Key ICs:

• MOTOROLA MC10102P: input quad 2 input NOR gate
• mixes test trigger?
• RCA CA3046: NPN transistor array
• NE NE521N: dual differential comparator / sense amp
• LeCroy SC100: ADC?

2015-06-04 repair

11 bit ADC (0x600 full range) but values were as follows for the two units I tested:

Slot 9 (broken knob)

 CH0: 0x000632
 CH1: 0x000644
 CH2: 0x000632
 CH3: 0x000358
 CH4: 0x000637
 CH5: 0x000525
 CH6: 0x00062A
 CH7: 0x00063A

Slot 11 (good knob)

 CH0: 0x000699
 CH1: 0x000691
 CH2: 0x00069D
 CH3: 0x000353
 CH4: 0x000696
 CH5: 0x00069F
 CH6: 0x00068C
 CH7: 0x000686

Both units seem to have constant offset errors, possibly the test pattern generator. Also, CH3 is flaky on both units...coincidence?

Ran a 14 hour burn in test in test mode (slot 11 / good knob):

You can see considerable drift on channel 3 (yellow), the channel with a bad reading. Other channels were pretty stable, within +/- 1 DN over the entire period. Swapped some ICs around and issue seems to have gone away.

More measurements after swapping:

Took about 1200 seconds (20 min) to settle.

Test code: https://github.com/JohnDMcMaster/uvscada/blob/master/lecroy_6010/2228a_cal.py