You can’t tell from just the appearance of a head if it has been well-maintained. On very old heads, it is quite common for the paint to have worn away, particularly on the left-hand side where operators / cinematographers rest their hands when operating. This doesn’t impact the performance of the head nor does it mean that the fluid head has not been well-serviced throughout its life. Here are some of the things to look out for when buying a second-hand fluid head:
The brake levers themselves can develop looseness / play over the life of the product. In general, this is nothing to worry about as these parts are inexpensive to replace. However, if when the brakes are locked, you can still move the head up and down or left to right a little, then this indicates that the brake housings have deformed over time. This repair, especially in pan, would be prohibitively expensive. Also over a very long time it is possible that little dents in the hardened brake discs can appear on both pan and tilt. Again this repair is easier in tilt than in pan.
On a good pre-owned OConnor fluid head, it should be possible to crank the counterbalance from 0 to 99 without it becoming stiff, and before the clutch slips. If not, it means that the counterbalance screw is worn and probably needs replacing along with the block. This repair can cost up to $1000 so you should consider this in your purchase price.
When tilting, check for noises (clicks and knocks). If the head appears to have pronounced noises when tilting fore and aft, this could indicate one of two potential issues – a broken counter balance bearing washer or, a side load bearing has broken free of it fixed position. The first issue is not costly in terms of spare parts but is quite time-consuming so could cost in the region of $750. The second issue is more costly, and the repair can be as much as $1500.
Ensure that the drag feels smooth and that there is no initial breakaway force necessary to get the head to move. There should be no flat or high spots throughout rotation of pan or tilt, and there should be no play when you reverse direction on pan or tilt.
Test the head repeatedly with pan and tilt moves and feel for witnesses of any sticky silicone grease around the base of the head (take off the 150 or Mitchell base), around the pan brake knob, drag knobs or the right-hand side housing. Often a leak can indicate that a seal has worn and this can also be an expensive repair.
Make sure this is present and has not broken off, if it has, it is prohibitively expensive to replace as it is part of the main housing. If the bubble is working correctly, you should be able to level the base of the head and rotate it through 360 degrees of the pan. The bubble should stay within the reticule when you remove your hand in any position.
Ensure the platform can be adjusted so it can hold the camera plate securely.
If you choose a head, that is in very poor general condition. A complete refurbishment and paint job from a 3rd party can cost between $2,500 and $5,000 depending on vendor and condition of the head.