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P O L Y T E C H . N U

surplus service (FM-3600/FM-4600)

Nederlandse introduction
Despite the fact that the RT-3600 and RT-4600 is no longer used in 'heavy conditions' such as in the army, it is wise to maintain the equipment well. Maintenance is conservation! The advantage is that the RT-3600 and RT-4600 are built solidly and watertight, making maintenance fairly easy. Below are tips for maintaining such surplus equipment.

Nederlandse cleaning
The FM-3600 and FM-4600 equipment is waterproof, so 'wet' cleaning is the best choice. It is wise to check first whether the equipment is properly watertight. A visual inspection is always a good idea to detect leaks. The next logical step is to spray the equipment with a soap/water solution and pressurize the equipment. These transceivers has a bare metal slotted cylinder head bolt that is removable. By blowing compressed air into this opening will pressurize the equipment and any leaks will become visible as the soapy water will bubble. A little overpressure is enough to find leaks. Do not put too much pressure on the housing to avoid damage.
If the device is watertight, it is wise to rinse the device with water first. I have had the best cleaning results by rubbing water and an abrasive cleaning agent over the unit with a brush. Dirt is well brushed away and the parts become a bit more matte again so that it looks like new. Any light oxidation is also polished away. I often scrub the housing with a brush and brush the more vulnerable parts with a paintbrush. Keep in mind that plastic parts can also become dull. Pre-masking plastic parts with tape is a possible solution to prevent matting the plastic. I have chosen to polish the plastic parts afterwards with a polishing agent and a cloth. After scrubbing, it is wise to rinse everything well with water so that the residues of dirt and abrasive cleaning agent disappears. It is wise to blow dry the connectors and cavities with compressed air so no water remains in the connectors ans cavities. After wet cleaning, it is wise to remove the two modules from the housing so that any moisture that may have penetrated can evaporate. The result is a nice clean device. A video of cleaning such equipment is below.

Cleaning of FM-3600/FM-4600 equipment.

Cleaning of VRC-8000 equipment.

Nederlandse RT-3600 locking oiling
The FT-3600 is equipped with mechanical latches to lock the frequency setting. This lock is less relevant for non professional use, so that the lock is used little or not at all. As a result, the lock is likely to get stuck due to lack of movement and drying of the oil due to ageing. It is wise to pull the lock out and drip a few drops of oil into the mechanism as shown in the photo below. By moving the lock for a while in all possible directions the oil will spread well and lubricate the moving parts. It will appear that the movement becomes increasingly smooth as the oil spreads in the mechanism. I once bought small bottles with a 'luer lock' cap that fits an injection needle. By means of a blunt 'needle' it is possible to get oil quite accurately at the desired place. Sewing machine or WD40 oil works fine for this application. Be aware that oil can 'creep' and leave a stain on the front panel. So cleaning afterwards with a cloth is maybe needed to remove the oil stain. The 'creeping' is visible in the photo below. In a lot of light (such as when photographing with a flash) it will be more noticeable than in 'natural' ambient light.

Oiling of the frequency locking mechanism of the RT-3600.

Nederlandse RT-3600 illumination oiling
Over time, it is possible that the lighting button becomes increasingly heavier or even sticks. The moving plunger contains the light bulb which can be moved back and forth. A rubber sealing ring has been used to make this construction watertight. This rubber ring moves in a cylindrical cavity of aluminum so that a watertight situation is achieved. This rubber can move stiffly and the rubber can also wear as a result. It is wise to lubricate the ring with a little bit of oil. And where there is oil, there is no water. So oiling is also good to maintain water resistance. The necessary steps are as follows:

Remove the metal ring by unscrewing it counter-clockwise;
Pull the 'plunger' out of the cavity;
Clean the cavity from which the plunger comes out using a cotton swab with a little oil to remove metal residue and contamination;
Drip a little thin oil (such as sewing machine oil or WD40) on the rubber ring as shown in the photo below;
Place the plunger back into the cavity and depress the plunger a few times to disperse the oil;
Drip some oil on the screw thread on which the metal ring is to be screwed;
Screw the metal ring back onto the front panel;
Maintenance has now been completed and the lighting is ready for use again.

Drop a little bit of oil on the rubber ring of the plunger.

Replace the plunger in the cavity of the front panel.