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
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
Parts you will need : flat head screwdriver for removing top, board with
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
threshold (probably between 10 and 50mV)