Servicing the Fast Motors
There are two types of motors. The fast motor and the slow motor. The fast motors seem to need less maintenance than the slow motors because they are larger and better built. Also, the shaft doesn’t have to travel both around and up and down like the slow motors do.
Remove the motor assembly. Separate the slow motor from the fast. Check the fast motor for freedom of spinning. If it spins freely and looks relatively clean, then oil the top and bottom bearings. Notice that inside the small holes around the shafts is a felt material. Soak this felt also which will hold oil near the bearing.
If the motor is unusually dirty or is having problems spinning, then you should disassemble it for a more precise service.Remember, before opening up the large motor, mark the two halves of the outer case so you can get it back together exactly the way it originally was. The large wheel which holds the rubber o’ring should be removed. The pulley should be removed. There is a small “C” clamp on the shaft just below the pulley which should be removed. Remove the four screws on the motor case and slide it all apart. Thoroughly clean the shafts and bearings. Remove any old oil or sludge. You can better see the felt around the bearings from the inside. Soak the felt with oil. Put oil on the shafts and bearings. Reassemble the motor and the wheel and pulley. Clean off any excess oil on the case, shafts etc.
Servicing the Slow Motors
The slow motor usually will have a couple of problems. First, check the shaft for freedom of spinning and moving up and down. On the upper rotor assembly, the slow motor has a spring on the bottom of the armature that will lose some of it’s strength over time. This will allow the armature to “bottom out” when switching to the fast motor. This will cause a “clunk” or even a grinding sound depending on how bad it is. Disassemble it carefully remembering how it comes apart so you can put it back together.
Take the spring and with small needle nose pliers slightly stretch it. Be very careful NOT to over do this. Reassemble and test. You are looking for the armature NOT to bottom out when released. I just hold the shaft up from the top and give it a spin and release it. If it hits the bottom of the frame, then an additional stretching is needed. If not, then you got it. If you over stretch it, the slow motor will have trouble disengaging from the o’ring.
Now clean it very thoroughly. Notice there are oiling holes (on most) on the frame near the top and bottom shaft. Inside is again a felt that needs to be saturated. Don’t get in a hurry here, it takes some time. Also add oil to the shafts and bearings. The slow motor on the lower drum works upside down and usually does NOT have the bottoming out problem. Clean off any excess oil when assembled.
Putting it all together
Reassemble and make sure that the adjustment for the slow motor is set right. Basically if it’s too tight, the slow motor will not completely engage to the o’ring or if it does, will not release from it. If it is too loose, then the slow speed will be “soft” and not have much torque. I like to see the fast motor immediately change to slow when the slow motor engages. If the motor has any slippage while changing to the slower speed, the wear on the o’ring will increase.
Adjusting the Lower Belt
The lower belt is adjustable and should be checked while working on the motors. If too tight, there is no slippage on the belt so when changing from fast to slow for example, a great deal of stress will be applied to the o’ring. Also the operating noise will be greater. If it’s too loose, the rotor may not reach full speed. You adjust the tension by the position of the motor to the drum. Loosen the wing nut on the motor and push it away from the rotor until the belt is taut, but do not force it beyond this point. Tighten the wing nut.
My test for belt tension is this; 5 to 8 seconds. In other words, if I don’t have any o’ring slippage,(which is what I want) then the belt is adjusted so that the time from slow to fast and fast to slow is around 5 to 8 seconds.
Another test is when switching from slow to fast, somewhere about half way to fast, the lower drum motor should brake free and spin all the way up while the drum is still accelerating. a looser belt is OK if you like a slower speed change and no extra wear will occur.
The motors require little lubrication, and usually at yearly intervals. This requirement is relative to the amount of usage, but other factors can be involved; dust and dirt, for example can absorb the lubricant, leaving the bearings too dry to operate properly. An oiling schedule can only be worked out through experience with each individual situation. Generally, there is a tendency to over oil. Thus, all factors should be considered in determining just when lubrication is to be done.
Correct oiling of either of the motor assemblies requires their complete removal from the cabinet. Bearings are located inside the two end covers on each of the motors. These are sleeve-type (Oilite) bearings, and each is surrounded by a felt pad which functions as an oil reservoir.
Both the bearings in the small motor, and the bearing nearest the pulley on the fast motor, can be oiled without disassembly. The bearing near the rubber tire drive wheel cannot be accessed with out separating the two motors and removing the drive wheel.
In applying oil, care should be taken to avoid excessive amounts. Each felt pad can absorb an ample, but Limited, amount of oil. If the Leslie Oil provided is not available, use a good small motor oil like sewing machine oil.
This information is for educational purposes only and no claims are made that this information will lead to any successful repair. Benton Electronics assumes no responsibility to its use.
|The Hammond Story||Servicing the Leslie 122 Amplifier|
|The Hammond Story|
|Servicing the Leslie 122 Amplifier|