Fan in Tektronix 556


rateick@...
 

I just acquired a Tektronix 556 with Type D and Type 53/54A plugins
and probes for $15.00. To my surprise after replacing the missing
tubes in the Type D plugin, the scope appears to work. The only
problem is that the cooling fan is inoperable. It spins freely when
no power is applied. After power is applied, it hardly turns at all.
Spinning manually it is no use. I found the rebuild procedure listed
here for motors with 1/4 in. dia shafts, however, this one has a
shaft of about 4mm dia. Does anyone know if this motor sounds
repairable? Any suggestions on a source for a new motor? I have
considered replacing the assembly with a box fan, any thoughts on
this? Thank you for your help.

Rick Rateick


dhuster@...
 

Rick, I'd imagine that there's all kinds of replacement fans you
could use in the 556. Just remember that you have to move a LOT of
air. Make sure that the CFM figure for any fan you substitute is
really high. Also make sure that the fan you install is shrouded so
that you're pulling air in from outside and not just moving it around
inside the box.

Dean


Phil (VA3UX) <phil@...>
 

At 03:55 AM 10/12/2001 +0000, you wrote:
I just acquired a Tektronix 556 with Type D and Type 53/54A plugins
and probes for $15.00. To my surprise after replacing the missing
tubes in the Type D plugin, the scope appears to work. The only
problem is that the cooling fan is inoperable. It spins freely when
no power is applied. After power is applied, it hardly turns at all.
Spinning manually it is no use.
Was this a one time occurrence after initial start-up or does it still exhibit the same characteristics (ie. spins with no power, doesn't spin with power; or seized after first power-up) ?

I've had some stiff fans on scopes that had been sitting for years. What I've found to work is squirting an anti-seize compound (the spray stuff for loosening rusty nuts and bolts) into the lube holes and turn the fan MANY turns in both directions by hand until it starts to loosen. The "anti-seize" compound (I can't think of the proper name, but it's like WD-40 which would probably also work) appears to gradually dissolve and loosen tar and gum deposits in the bearing surfaces which restores the clearances. As it starts to loosen, I spray more of this stuff into the hole to flush-out what's been loosened and continue. I just keep repeating this until the fan spins freely in both directions with a flick of the finger. This can take quite a while : in one case I let the fan sit overnight with this stiff in the holes and there was a huge difference the next day. Use lots of paper towels/rags. Eventually I actually run the fan for a minute or so with this stuff still in it. Finally, I flush all the anitseize out of the bearing by liberal and repeated application of thin, light oil suitable for plain bearing motors. It's more mess but it ensures that all the antiseize stuff is removed because it doesn't have the necessary properties for long term lubrication.

Let us know how it goes

Phil


I found the rebuild procedure listed
here for motors with 1/4 in. dia shafts, however, this one has a
shaft of about 4mm dia. Does anyone know if this motor sounds
repairable? Any suggestions on a source for a new motor? I have
considered replacing the assembly with a box fan, any thoughts on
this? Thank you for your help.

Rick Rateick




To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@egroups.com



Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/


John Rehwinkel <spam@...>
 

I just acquired a Tektronix 556 with Type D and Type 53/54A plugins
and probes for $15.00. To my surprise after replacing the missing
tubes in the Type D plugin, the scope appears to work. The only
problem is that the cooling fan is inoperable.
[...]
Any suggestions on a source for a new motor?
I have an old 500-series fan I used to use to keep the dust
moving the right way when working on my house. I'd vaguely
seal off the dust-generating activity in one room at a time,
and exhaust that room out a window, creating a slight vacuum.
That way, air came in from the (relatively) dust-free rooms
instead of the other way 'round. If I can find it, I suppose
I could ship it to you. It still has the shroud and frame,
and I can attest as to its ability to move plenty of air.

-- John Rehwinkel KG4L
spam@fgm.com


Miroslav Pokorni <mpokorni@...>
 

Rick, do not forget that open frame fans are available from number of
sources, not only fans for electronics makers but general manufacturing
suppliers, like Grainger. The latter also carry low fractional horsepower
replacement motors.

Regards

Miroslav Pokorni

-----Original Message-----
From: dhuster@pb.k12.mo.us [mailto:dhuster@pb.k12.mo.us]
Sent: Friday, October 12, 2001 5:03 AM
To: TekScopes@yahoogroups.com
Subject: [TekScopes] Re: Fan in Tektronix 556

Rick, I'd imagine that there's all kinds of replacement fans
you
could use in the 556. Just remember that you have to move a
LOT of
air. Make sure that the CFM figure for any fan you
substitute is
really high. Also make sure that the fan you install is
shrouded so
that you're pulling air in from outside and not just moving
it around
inside the box.

Dean



------------------------ Yahoo! Groups Sponsor

To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@egroups.com



Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/


rateick@...
 

Thanks for the response.

The fan exhibits this problem after several turn-on/off cycles. The
bearings in the fan appear not to be in good shape based on the
loosness of the shaft. However, when power is not applied to the
fan, it spins freely. The blades show some damage on the leading
edges which does not correspond to any stationary part of the scope.
Thus, it is possible that the former owner swaped out this fan
service another scope.

I do not as yet have a schematic for this scope, so the following is
speculation. The fan has three wires. Two are at 120V relative to
the third. I am speculating that this fan uses a runing capacitor and
that it may be shot.

Rick Rateick

Was this a one time occurrence after initial start-up or does it
still
exhibit the same characteristics (ie. spins with no power, doesn't
spin
with power; or seized after first power-up) ?


leo.schleider@...
 

Hello Rick,

I checked my 545B on this issue. I once fixed such a fan in my 545B by
taking it completely apart, cleaning the bearings, and relubricating it.
The rotor should move freely forth and back a few millimeter
in axial direction and it must rotate freely in eiter end position.
When the motor is powered up, the whole rotor moves 2-3 millimeters,
in axial direction so that the blades come closer to the motor.
I remember, when I took it apart, some thin spacers or plastic discs on the
axis at
either end. It could be if someone tried a to fix the fan that
those spacers / discs havent been retured correctly. The plastic discs
probably keep the lubricant close to the bearings. If you decide
to take the motor apart, clean the bearings and built it together that
it doesn't block even if you move the rotor in axial
direction to either end.
There is one more important thing. Check the blades that they are all in the
same plane and have all the same angle. If that is not the case, the
fan is out of balance and makes unnecessary noise and the whole instrument
is vibrating. After doing all this the fan in my 545B runs smoothly
and is very silent.

Leo

-----Urspr�ngliche Nachricht-----
Von: rateick@michiana.org [mailto:rateick@michiana.org]
Gesendet: Samstag, 13. Oktober 2001 05:58
An: TekScopes@yahoogroups.com
Betreff: [TekScopes] Re: Fan in Tektronix 556


Thanks for the response.

The fan exhibits this problem after several turn-on/off cycles. The
bearings in the fan appear not to be in good shape based on the
loosness of the shaft. However, when power is not applied to the
fan, it spins freely. The blades show some damage on the leading
edges which does not correspond to any stationary part of the scope.
Thus, it is possible that the former owner swaped out this fan
service another scope.

I do not as yet have a schematic for this scope, so the following is
speculation. The fan has three wires. Two are at 120V relative to
the third. I am speculating that this fan uses a runing capacitor and
that it may be shot.

Rick Rateick

Was this a one time occurrence after initial start-up or does it
still
exhibit the same characteristics (ie. spins with no power, doesn't
spin
with power; or seized after first power-up) ?

To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@egroups.com



Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/


Phil (VA3UX) <phil@...>
 

At 03:57 AM 10/13/2001 +0000, you wrote:
Thanks for the response.

The fan exhibits this problem after several turn-on/off cycles. The
bearings in the fan appear not to be in good shape based on the
loosness of the shaft. However, when power is not applied to the
fan, it spins freely.
Hmm. Well, "spins freely" is a good sign.

I do not as yet have a schematic for this scope, so the following is
speculation. The fan has three wires. Two are at 120V relative to
the third. I am speculating that this fan uses a runing capacitor and
that it may be shot.
You might have something there. The schematic shows this a C1404. It is a 3.75 uF cap. Try swapping it out. This of course will be an AC rated capacitor.

Phil


Rick Rateick

Was this a one time occurrence after initial start-up or does it
still
exhibit the same characteristics (ie. spins with no power, doesn't
spin
with power; or seized after first power-up) ?

To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@egroups.com



Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/


Stan or Patricia Griffiths <w7ni@...>
 

I have never had this type of problem with a 556 fan before but I took a
quick look at the schematic and noticed there is a "starting capacitor"
connected to the motor. I suspect the motor won't start if this capacitor is
missing or bad. I would check that first.

Stan
w7ni@easystreet.com

rateick@michiana.org wrote:

I just acquired a Tektronix 556 with Type D and Type 53/54A plugins
and probes for $15.00. To my surprise after replacing the missing
tubes in the Type D plugin, the scope appears to work. The only
problem is that the cooling fan is inoperable. It spins freely when
no power is applied. After power is applied, it hardly turns at all.
Spinning manually it is no use. I found the rebuild procedure listed
here for motors with 1/4 in. dia shafts, however, this one has a
shaft of about 4mm dia. Does anyone know if this motor sounds
repairable? Any suggestions on a source for a new motor? I have
considered replacing the assembly with a box fan, any thoughts on
this? Thank you for your help.

Rick Rateick


To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@egroups.com



Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/


Stan or Patricia Griffiths <w7ni@...>
 

Hi Leo,

Very good post except the fan blade moves AWAY from the motor while it is
running.

Stan
w7ni@easystreet.com

leo.schleider@t-online.de wrote:

Hello Rick,

I checked my 545B on this issue. I once fixed such a fan in my 545B by
taking it completely apart, cleaning the bearings, and relubricating it.
The rotor should move freely forth and back a few millimeter
in axial direction and it must rotate freely in eiter end position.
When the motor is powered up, the whole rotor moves 2-3 millimeters,
in axial direction so that the blades come closer to the motor.
I remember, when I took it apart, some thin spacers or plastic discs on the
axis at
either end. It could be if someone tried a to fix the fan that
those spacers / discs havent been retured correctly. The plastic discs
probably keep the lubricant close to the bearings. If you decide
to take the motor apart, clean the bearings and built it together that
it doesn't block even if you move the rotor in axial
direction to either end.
There is one more important thing. Check the blades that they are all in the
same plane and have all the same angle. If that is not the case, the
fan is out of balance and makes unnecessary noise and the whole instrument
is vibrating. After doing all this the fan in my 545B runs smoothly
and is very silent.

Leo

-----Urspr�ngliche Nachricht-----
Von: rateick@michiana.org [mailto:rateick@michiana.org]
Gesendet: Samstag, 13. Oktober 2001 05:58
An: TekScopes@yahoogroups.com
Betreff: [TekScopes] Re: Fan in Tektronix 556

Thanks for the response.

The fan exhibits this problem after several turn-on/off cycles. The
bearings in the fan appear not to be in good shape based on the
loosness of the shaft. However, when power is not applied to the
fan, it spins freely. The blades show some damage on the leading
edges which does not correspond to any stationary part of the scope.
Thus, it is possible that the former owner swaped out this fan
service another scope.

I do not as yet have a schematic for this scope, so the following is
speculation. The fan has three wires. Two are at 120V relative to
the third. I am speculating that this fan uses a runing capacitor and
that it may be shot.

Rick Rateick

Was this a one time occurrence after initial start-up or does it
still
exhibit the same characteristics (ie. spins with no power, doesn't
spin
with power; or seized after first power-up) ?
To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@egroups.com

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/


To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@egroups.com



Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/


rateick@...
 

I disassembled the fan and now think that the problem is a failed
bearing. The rotor is wearing on the stator as evidenced by wear
damage and by wear debris. So, unless I want to fire up the lathe,
make a new bearing and then fight the reassebmly problem, I think the
best approach is to install a 120 vac muffle fan. I can make a
simple adaptor from aluminum.

Rick Rateick

--- In TekScopes@y..., Stan or Patricia Griffiths <w7ni@e...> wrote:
I have never had this type of problem with a 556 fan before but I
took a
quick look at the schematic and noticed there is a "starting
capacitor"
connected to the motor. I suspect the motor won't start if this
capacitor is
missing or bad. I would check that first.

Stan
w7ni@e...


Don Black <jeans@...>
 

Hi Rick,
Can you get a small ball race from a bearing supply house and
fit it in place of the worn plain bearing. You should be able to get one to
fit the shaft and then you may have to machine the end plate to take the
outer race, or perhaps turn up a sleeve if it's too big a hole. Use Loctite
or superglue if necessary to secure it.
I think that would be less hassle than fitting a new fan.
The loose bearing allowing the rotor to pole sounds like the problem.

Don Black.
rateick@michiana.org wrote:

I disassembled the fan and now think that the problem is a failed
bearing. The rotor is wearing on the stator as evidenced by wear
damage and by wear debris. So, unless I want to fire up the lathe,
make a new bearing and then fight the reassebmly problem, I think the
best approach is to install a 120 vac muffle fan. I can make a
simple adaptor from aluminum.

Rick Rateick

--- In TekScopes@y..., Stan or Patricia Griffiths <w7ni@e...> wrote:
I have never had this type of problem with a 556 fan before but I
took a
quick look at the schematic and noticed there is a "starting
capacitor"
connected to the motor. I suspect the motor won't start if this
capacitor is
missing or bad. I would check that first.

Stan
w7ni@e...
To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@egroups.com



Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/