Connecting Phototubes to the Board

Plug green signal cables into the connector on the phototube labeled "SIG"

Plug other ends of green cables into two of the inputs on the board

Connecting high voltage supply to divider box and the divider box to the phototube (again, double check that your high voltage is off before continuing with this step!)

There are two types of HV connectors, MHV (left) and SHV (right)
Using the cable with MHV connectors, connect one end to the HV supply
Plug the other end of the same cable into the side of the HV distribution box
Using the cables with SHV connectors, plug one end into the front panels of the HV distribution box
Plug the other end of these cables into the HV connector on the phototube

Setting and Turning on High Voltage

Please note, it is possible to damage the tubes by running them at too high a voltage, so be careful during this step!

Set the power supply to the HIGHEST voltage required by all the phototubes you are using. Note: DO NOT TURN ON HIGH VOLTAGE SUPPLY YET!

Use the voltage divider box to decrease the voltage that will be seen by the other (not highest voltage) tubes in your telescope

Example: you have three tubes which run at 1150V, 1250V and 1100V, respectively. Set the supply to 1250V, and the voltage divider to -100V, 0V and -150V for the three tubes, respectively

You are now ready to turn on your supply.

If your supply is a "Northeast Scientific" supply, set your supply to "STD-BY" and let the vacuum tubes warm up for one minute (skip this step if your supply is a "Bertan")

Turn on your supply

Adjusting Thresholds of your Board

Although the default threshold of 30mV is probably fine for more applications, you may wish to increase your threshold if your tube has a high count rate at a low voltage (1000V) or decrease your threshold if it has a low count rate at a high voltage (1500V)

The procedures for adjusting the threshold are documented in the "electronics instructions"

Parts you will need : flat head screwdriver for removing top, board with power

available, digital voltmeter with probes, jewlers screwdriver
Removing the top of the board housing with power off

Reading threshold voltage (reads 10x actual threshold) as voltage between ground on PMT input connector and test point

Adjusting the blue potentiometer with jewler's screwdriver until you reach the desired

threshold (probably between 10 and 50mV)