Thrustmaster F-22PRO Spiking Fix

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Feb 6, 1999, 3:00:00 AM2/6/99
Hi everybody,

after a long fight against the infamous F-22 pot spiking, I
finally came across a durable and effective solution.

The two suggestions against spiking F-22 pots mentioned most are to

a) clean the pots with something like tuner cleaner, WD-40 etc.
b) open the pots, remove the grease in them and bend their contacts.

Both methods are not completely satisfatory for me. Method a) did fix the
problem, but only for a very short time. After a few weeks I had to repeat
the process again and again. Method b) was effective but reduced the
lifetime of the pots to - in my case - about 3 months.

The only way to get out of this dilemma was to find suitable replacement
pots. This proved to be a problem because the pots used by Thrustmaster are
quite unique. Their electrical travel (the range of movement where the
change from 0 Ohm to the full 127K Ohm of resistance takes place) is only
ca. 60 deg. while standard potentiometers have an el. travel of ca. 270 deg.

a) I do not accept responsibility for any harm you may do your
joystick, your computer, yourself (a soldering iron is HOT, believe me :-) )
or anything else etc. etc. etc.
b) There's a very small amount of jitter in the F-22Pro analog readout when
the stick is not sleeping. This is not affected by the following. AFAIK this
jitter is so small that it will not cause any trouble in sims. To completely
switch this jitter off for testing purposes run the F22RESET.EXE from
c) I don't know if the keyboard mapping of the analog joystick movement
(JSX, JSY statements) is negatively affected by this solution. I never used
this feature.

To replace the pots with some standard ones you may want to try this:

1.) Find potentiometers with the following properties:

- best quality you can get hold of
- 0,25W or higher
- linear (NOT logarithmic)
- resistance 100K - 200K Ohm (200K will make things easier),
perhaps even 500K (didn't try)
- fit into the F-22Pro (compare them to the orginal ones).
- 6,3 mm shaft WITHOUT standard flattening.
The shaft has to be made of a material that you can easily work with
(like plastic, brass etc.)
- minimum shaft length 22mm (including the length of the thread)
- el. travel ca. 270 deg. (like almost any pot)

2.) Shorten the shaft of the new pots to a length of 22mm (including the
thread, just like the original ones).

3.) Shut down your computer.

The procedure described below is a bit involved and can be shortened
drastically if you know how the pots are connected to the F-22Pro (the two
pots are connected in opposite rotational sense) and you have instruments to
show the pot readout without having to connect them to your computer. Decide
for yourself...

4.) Open the base of the F-22Pro (you may lose your warranty). The bottom
plate is hold by 4 Phillips screws under those little rubber elements (if
you remove them carefully you may be able to re-use them, if not - your
local electronics dealer probably carries them). Make yourself a plan of the
potentiometer wiring (the wires are color-coded).

5.) Desolder one of the original pots (I suggest you start with the one for
the horizontal axis) and solder one of the new pots to the open wires. Do
not try to install the pot now but see that it has the same spatial
orientation as the original. Hold the new pot in a way that no part of it
has contact to the interiors of the joystick.

6.) Restart your computer and enter the Thrustmaster TMScope software. If
you have a throttle make sure to bring it into idle position before you
enter TMScope.

7.) Adjust the new pot to the absolute MINIMUM value (turn it until the raw
values in the window don't change any more).

8.) Turn the new pot 30 deg. in the opposite direction and hit the "Recal
TMS" button in TMSCope. This is the NEW CENTER position.

9.) Turn the new pot 30 deg. to the left and to the right. The cursor should
move at least to 4th notch on the scale in both directions. The raw numbers
should not stop changing inside this 60 deg. range of movement. If they do
adjust the center position a tiny bit and try again (don't forget to press
"Recal TMS").

10.) Look at the orientation of the flattening of the original pot shaft
when in its center position. Mark this orientation on the new pot shaft in
ITS NEW center position.

11.) Take the old pot out of the F-22Pro (The L-shaped mounts are held in
place by those little Allen screws on top of the base. Be careful with the
strong springs of the F-22Pro). Draw the black plastic gear from the old

12.) File the flattening into the shaft of the new pot. The length of the
flattening is ca. 6mm. Make sure it fits perfectly into the black plastic
If you want to desolder the new pot for the filing temporarily, switch off
the computer first!

11.) Install the new pot in the F-22Pro. Check the gear alignment with

12.) Repeat steps 5.) - 11.) for the other axis. Do not solder anything
while the computer is running. Remember that the orientation of the shaft
flattening will be different on the two pots!

13.) Recalibrate the stick in the Windows control panel.

Hope this helps,



Feb 6, 1999, 3:00:00 AM2/6/99
Nice work, but better to send this mail to TM ;)


Ritchie, Kelvin

Feb 6, 1999, 3:00:00 AM2/6/99
Does this problem occur on F22's that are currently shipping or just with the
models that first came out?


Robert B. Kasten

Feb 7, 1999, 3:00:00 AM2/7/99
Scorpio <> wrote:


What an excellent post. This should be up on a website

Opinions expressed herein are my own and may not represent those of my employer.

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