PNI BPL505S Manual De Usuario página 7

Fig.6
3. Fix the boom support (16) to the ground. Adjust the heightas the bubber
pad (17) touches the boom when the boom is at horizontal position.
Fig.7
Setting springs' balance and boom weight
Attention: The springs are set to be balanced in factory. Do not replace the
bbom with a longer or heavier one if not necessary. However, if you need to
replace the boom with a longer or heavier one (for example, the weight may
change if a STOP indicator is needed in the middle of the boom), the spring
balance must be adjusted.
7 User manual