Testing Vicor Power Assembly

This test procedure applies to Vicor Power Assembly (VPA) Rev C Issue assemblies.

Test Setup

Required for this test procedure:

• VPA power supply to be tested
• 24 V (or 48V) 5A supply
• Winchester to Winchester pin to pin cable <= 1m long
• 48HP MCE crate, fully populated with cards including two revision E readout cards
• three 50 ohm MDM jumper boards
• MCE dummy load
• Ubuntu computer with MAS installed
• Create a directory and a logfile with the serial number of the unit under test on scuba2 server as: scuba2:\public_html\sc2mce\system\power_supply_of_all_kinds\psu_Vicor\test_res\VPA_xxx\VPA_xxx_Log.txt
• Oscilloscope

DC Voltages

First, connect the VPA power supply to the MCE dummy load using a < 1m cable and measure the DC voltages. The voltages should be in the range:

• pVa: 6.1 to 6.3 V
• nVa: -6.1 to -6.3 V
• Vlvd: 4.4 to 4.7 V
• Vcore: 2.9 to 3.2 V
• Vah: not connected

With the VPA connected to the dummy load, observe the DC power supply voltages using an oscilloscope. There should be no obvious AC variation on the lines. The AC coupled RMS value of each power supply line should be less than 20 mV.

ECO-074

Make sure ECO-074 is applied and the unit is appropriately labeled as C4 or C5 depending on 24V or 48V version.

LED Test

Make sure the Green LED is on when the unit-under-test is powered on.

Noise Spectrum

Now, connect the supply to a full 48HP MCE with Rev E readout cards. Place 50 ohm jumper boards on all three MDM connectors at the back of the MCE.

Connect the clock card fibres to a MAS computer, and on that computer, run the script 'psu_noise_raw_acq'.

(Note: This script calls spectrum_fit.py, make sure that is present!) This script requires two arguments: readout card number (1 or 2) and readout card channel (1-8). Use RC 1 channel 4 as follows:

> psu_noise_raw_acq 1 4 analyze VPA-xxx

where VPA-xxx is the serial number of the unit you are testing.

This script collects raw data and generates a text report file and a png file of the power spectra in the directory /data/cryo/<date in YYYYMMDD format>/<date_timestamp_VPA-xxx_rcx_x.png. The reported timestream rms in ADC units should be around 4.2 +- 2%. The power spectra needs to be inspected for any unusual noise. The f3dB has to be within +-10% of 2.8MHz.

On the scuba2 server, Copy the report file, the png file and the data directory from the MAS computer to the test results directory on the scuba2 server: (scuba2:\public_html\sc2mce\system\power_supply_of_all_kinds\psu_Vicor\test_res\VPA_xxx\ )

Smooth Startup

Use an oscilloscope to capture a snapshot of each voltage rail at startup. Probe the rails on the Winchester connector. Store the snapshot in the test_res directory. An example can be found here:vpa-016_startup.png