FREEING A FROZEN HELICOID ARM HEIGHT ADJUSTER RING ON THE SL-1200
MK2,3,4,5,M5G
The helicoid tonearm height adjuster is one of the greatest features of
the SL-1200. However, over time, and especially if not rotated frequently, this
ring is known to become frozen. Fully restoring the adjuster will usually
require a full disassembly of the toneam. The adjuster ring has 2 different
sets of threads. Against the black trim ring are standard fine pitch machine
threads. against the arm base are a special set of deep cut threads. So far, my
experience shows that it is the deep set threads that become seized.(not what
you might expect). It appears to be a reaction between the brass of the
adjuster ring and the aluminum of the arm base. This happens because when you
lock the arm base, pressure forces one side of the arm base against the
adjuster ring. I suspect over time this squeezes the lubricant from that space
and allows the brass to bond to the aluminum. Operating the adjuster now and
then should prevent this from happening.
Before proceeding with a full dissasembly, you may want to try a simple
test with a heat gun. With the heatgun on low setting, warm the base of the arm
and the trim ring. alternating back and forth between the two, and moving
aroung the arm base. after the arm base is warmed, wait a minute or so and try
to move the ring. You may be surprised to find it frees up. You can do this a
few times and then work the arm through its full range 0 - 6. At this point you
could return the deck and instruct the customer to move the height ring every 6
months or so to prevent it from sticking again.
If you want to fully restore the helicoid to original factory
performance, you will need to fully dissasemble the arm base as follows.
- Remove the 4 footers and the rubber bottom.(21 screws)
- Remove phono cable clamp and metal toneam cover. At this point, you
may want to try putting a few drops of paint thinner or WD-40 on the threads.
let that set up for a little while and see if the ring moves. If it does, I
would stop and save your client some labor charges. If not you will need to
apply some heat to the threaded ring. .
- Using a heat gun on low setting, carefully heat the ring with a heat
gun and it should free up and turn. Heat for about a minute, then try and turn
it. If it is still stiff, heat for another minute and test. do this repeatedly
until it lets go. keep a careful eye on the plastic insert, you don't want to
damage that.
- Unsolder the 5 tonearm wires and remove the cable PC board. leave the
ground wire free.
- With the ring free, locate the base locking mechanism and remove it
by removing the C clip, brass washer and 2 holding screws. flip the table over
and remove the arm base from the ring first.
- Now remove the ring by rotating clockwise. (The threads are
reversed.)
- Clean all the threads of all the peices of all old grease. Odorless
paint thinner works well here.
- Coat the fine threads of the adjuster ring with a thin film of
technical petroleum grease and screw it into the
black base rotating counter clockwise.
- When the adjuster ring seats, reverse rotation one revolution then
continuing until the 0 mark is at 8 0'clock as viewed from the front.
- Coat the deep grooves with a thin coating of
technical petroleum grease. The arm base has three starting points. You
will need to experiment until the arm sets up in the right location. The arm
base is in the right position when it is fully seated and the pointer indicates
just beyond the 0 mark.
- Back in the bottom of the arm, temporarily re install the base lock
with just 2 screws. Flip the table back over and confirm that the arm base
adjusts properly such that when the arm base is all the way down, the indicator
shows just beyond the 0 setting. If not, you need to repeat 9 until you get
that condition. When you have it right, replace the brass washer and the
C-clip.
- If all is good. you can install the cable PC board and re attach the
5 tonearm wires.
- Confirm wires are in the right place in order from left to right
Black, Green, Red, White, Blue. (sometime Brown is used in place of Green)
- Attach a cartridge and preamp and check that both channels play and
there is not hum.
- Now replace the covers and the bottom.
- Clean up all surfaces with Windex.
Return To Service Tips Page
