Topics

Front panel knob removal on 2225 (or 2xxx series)?

David Slipper
 

I managed to remove the"cal" knobs (grub screws) and the "v/cm and
sec/cm" knobs (easy pull off) for cleaning and repair but I cannot budge
the remainder.

So, can anyone suggest the best way to remove the likes of the position,
focus and intensity knobs which don't have grub screws and don't seem to
want to pull off :-(

Some of these are damaged and I need to replace them but I need to get
the old ones off first without wrecking the switch or the shaft.

TIA
David

tekscopegroup@...
 

Gently applying some heat to warm up the stuck knobs usually seems to work wonders. Use a heat gun, but be careful not to overheat them. So far I never had to do this procedure myself, but there are messages out here in this group and elsewhere that recommend this procedure.

David Slipper
 

I can imagine the mess if you get it wrong!!!

Given the knobs have a pair of "pegs" that engage with PCB mounted pots (assumed from photos I have found of the knobs and assemblies), heating the knobs on the outside of the front panel may not help -- the warmth needs to be applied to where the knob engages with the pot itself between the PCB and the front panel - not much room there.

See the pictures of the FP and knobs<http://vondervotteimittiss.com/belfry/?p=216>

TIA
David

On 23/02/2019 16:45, tekscopegroup@...<mailto:tekscopegroup@...> wrote:

Gently applying some heat to warm up the stuck knobs usually seems to work wonders. Use a heat gun, but be careful not to overheat them. So far I never had to do this procedure myself, but there are messages out here in this group and elsewhere that recommend this procedure.



.

Chuck Harris
 

It isn't that you need to make the knob expand, it is
simply a matter of warming the plastic a little so it
isn't quite so brittle.

You must, I repeat must, pull the knob straight off of the
shaft. I recently started using a pair of fine pointed
needle nosed pliers. I pull the knob up to clear the panel,
then stick the points to the knob's skirt's outer edges
and pry up gently. They come off very easily.

-Chuck Harris

David Slipper wrote:


I can imagine the mess if you get it wrong!!!

Given the knobs have a pair of "pegs" that engage with PCB mounted pots (assumed from photos I have found of the knobs and assemblies), heating the knobs on the outside of the front panel may not help -- the warmth needs to be applied to where the knob engages with the pot itself between the PCB and the front panel - not much room there.

See the pictures of the FP and knobs<http://vondervotteimittiss.com/belfry/?p=216>

TIA
David


On 23/02/2019 16:45, tekscopegroup@...<mailto:tekscopegroup@...> wrote:

Gently applying some heat to warm up the stuck knobs usually seems to work wonders. Use a heat gun, but be careful not to overheat them. So far I never had to do this procedure myself, but there are messages out here in this group and elsewhere that recommend this procedure.

Roy Morgan
 

Inspired by watch repair methods:

A couple pieces of hacksaw blade, de-toothed and shaped on a grinding wheel, then bent into short armed L shape, could make a fine pair of levers to get the knobs free. Apply pressure equally on both sides, with the tips well in toward the shaft/center of the knob. Fabric or even paper towel layered under the pivot point prevents panel damage.

Roy

On Feb 23, 2019, at 6:21 PM, Chuck Harris <cfharris@...> wrote:

It isn't that you need to make the knob expand, it is
simply a matter of warming the plastic a little so it
isn't quite so brittle.

You must, I repeat must, pull the knob straight off of the
shaft. I recently started using a pair of fine pointed
needle nosed pliers. I pull the knob up to clear the panel,
then stick the points to the knob's skirt's outer edges
and pry up gently. They come off very easily.
Roy Morgan
K1LKY since 1958
k1lky68@...

Colin Herbert
 

From my experience with hacksaw blades, I think that any attempt at bending
them will result in breakage. Then again, if the metal was annealed before
bending..., but wouldn't that defeat the object?
How about a couple of similar-sized hex-keys used in the same way?
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Roy
Morgan
Sent: 17 March 2019 17:23
To: TekScopes@groups.io
Subject: Re: [TekScopes] Front panel knob removal on 2225 (or 2xxx series)?

Inspired by watch repair methods:

A couple pieces of hacksaw blade, de-toothed and shaped on a grinding wheel,
then bent into short armed L shape, could make a fine pair of levers to get
the knobs free. Apply pressure equally on both sides, with the tips well in
toward the shaft/center of the knob. Fabric or even paper towel layered
under the pivot point prevents panel damage.

Roy

On Feb 23, 2019, at 6:21 PM, Chuck Harris <cfharris@...> wrote:

It isn't that you need to make the knob expand, it is
simply a matter of warming the plastic a little so it
isn't quite so brittle.

You must, I repeat must, pull the knob straight off of the
shaft. I recently started using a pair of fine pointed
needle nosed pliers. I pull the knob up to clear the panel,
then stick the points to the knob's skirt's outer edges
and pry up gently. They come off very easily.
Roy Morgan
K1LKY since 1958
k1lky68@...

Chuck Harris
 

Cheap hacksaw blades are hardened steel, through-and-through...
and break easily.

More expensive hacksaw blades are bi-metal, and as such have
hardened teeth, and a less hard, more flexible back.

Bimetal blades bend without breaking, which is the point behind their
use.

Either type can be bent without breaking if you apply a torch.

Regardless, a pair of needle nosed pliers does a dandy job of
removing snap on tektronix knobs. Use them as a prying tool,
not a gripping tool. Position them so that their points are
straddle the pot's shaft, and are under the skirt of the knob.
Lever up carefully, and the knob will pop right off.

-Chuck Harris

Colin Herbert via Groups.Io wrote:

From my experience with hacksaw blades, I think that any attempt at bending
them will result in breakage. Then again, if the metal was annealed before
bending..., but wouldn't that defeat the object?
How about a couple of similar-sized hex-keys used in the same way?
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Roy
Morgan
Sent: 17 March 2019 17:23
To: TekScopes@groups.io
Subject: Re: [TekScopes] Front panel knob removal on 2225 (or 2xxx series)?

Inspired by watch repair methods:

A couple pieces of hacksaw blade, de-toothed and shaped on a grinding wheel,
then bent into short armed L shape, could make a fine pair of levers to get
the knobs free. Apply pressure equally on both sides, with the tips well in
toward the shaft/center of the knob. Fabric or even paper towel layered
under the pivot point prevents panel damage.

Roy

On Feb 23, 2019, at 6:21 PM, Chuck Harris <cfharris@...> wrote:

It isn't that you need to make the knob expand, it is
simply a matter of warming the plastic a little so it
isn't quite so brittle.

You must, I repeat must, pull the knob straight off of the
shaft. I recently started using a pair of fine pointed
needle nosed pliers. I pull the knob up to clear the panel,
then stick the points to the knob's skirt's outer edges
and pry up gently. They come off very easily.
Roy Morgan
K1LKY since 1958
k1lky68@...