Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old January 7th 19, 08:32 PM posted to sci.electronics.repair
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Default Calibrated dial knob repair

I recently bought an old Eico 955 In circuit capacitor tester. It worked
right away, but I am going to recap it. But there is a problem. The
Calibrated dial knob wont clamp to the shaft. Someone apparently over
tightened the set screw and cracked the part that fits around the 1/4"
shaft. Someone also must have glued it, then broke it again. That only
makes gluing it again a worse option because the old glue is gooped all
over the pieces, so they wont fit together properly anymore.

Finding a replacement is likely not an option.
Knob Part number - Eico 89678

How would you fix this?

I do have one thought. To carefully grind away the entire center part of
that knob with a dremyl tool. Then take a new smallish knob with a set
screw and drill out the 1/4" hole thru to the face of that knob, and use
JB Weld to glue that new knob inside the old one. Of course the set
screw has to line up with the original set screw hole. (there is room
for a small knob inside). I might even have a solid aluminum knob that
will fit in there, but I have to find them....

However, grinding out that center will be tricky and time consuming,
since the new knob needs to be centered very precisely.


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Old January 7th 19, 09:09 PM posted to sci.electronics.repair
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Posts: 272
Default Calibrated dial knob repair

On Monday, January 7, 2019 at 2:33:24 PM UTC-5, wrote:
I recently bought an old Eico 955 In circuit capacitor tester. It worked
right away, but I am going to recap it. But there is a problem. The
Calibrated dial knob wont clamp to the shaft. Someone apparently over
tightened the set screw and cracked the part that fits around the 1/4"
shaft. Someone also must have glued it, then broke it again. That only
makes gluing it again a worse option because the old glue is gooped all
over the pieces, so they wont fit together properly anymore.

Finding a replacement is likely not an option.
Knob Part number - Eico 89678

How would you fix this?

I do have one thought. To carefully grind away the entire center part of
that knob with a dremyl tool. Then take a new smallish knob with a set
screw and drill out the 1/4" hole thru to the face of that knob, and use
JB Weld to glue that new knob inside the old one. Of course the set
screw has to line up with the original set screw hole. (there is room
for a small knob inside). I might even have a solid aluminum knob that
will fit in there, but I have to find them....

However, grinding out that center will be tricky and time consuming,
since the new knob needs to be centered very precisely.





The knobs all look different, the number of shaft configurations is very limited...
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Old January 7th 19, 11:20 PM posted to sci.electronics.repair
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First recorded activity by DIYBanter: Jul 2007
Posts: 3,797
Default Calibrated dial knob repair

On Mon, 07 Jan 2019 13:32:51 -0600, wrote:

I recently bought an old Eico 955 In circuit capacitor tester. It worked
right away, but I am going to recap it. But there is a problem. The
Calibrated dial knob wont clamp to the shaft. Someone apparently over
tightened the set screw and cracked the part that fits around the 1/4"
shaft. Someone also must have glued it, then broke it again. That only
makes gluing it again a worse option because the old glue is gooped all
over the pieces, so they wont fit together properly anymore.

Finding a replacement is likely not an option.
Knob Part number - Eico 89678

How would you fix this?

I do have one thought. To carefully grind away the entire center part of
that knob with a dremyl tool. Then take a new smallish knob with a set
screw and drill out the 1/4" hole thru to the face of that knob, and use
JB Weld to glue that new knob inside the old one. Of course the set
screw has to line up with the original set screw hole. (there is room
for a small knob inside). I might even have a solid aluminum knob that
will fit in there, but I have to find them....

However, grinding out that center will be tricky and time consuming,
since the new knob needs to be centered very precisely.


A few questions:

1. Which knob?
https://c1.staticflickr.com/4/3834/11055642634_e5daa78fe7_b.jpg

2. What part of the knob is cracked? Is it the plastic part or the
brass center insert? I haven't seen too many knobs without this brass
insert as threading the plastic doesn't last very long on small
diameter knobs.

I'll assume it's the brass insert. These are very much the same for
all similar sized knobs that use a 1/4" dia shaft. I've actually done
what you're proposing. I used a lathe to insure that everything was
centered. Instead of trying to totally drill out the brass insert, I
used a smaller drill (or end mill) that left a thin brass annular
ring. I removed that with a pair of pliers.

The replacement brass insert was provided by a random knob from my
collection. I inserted a 1/4" steel rod into the knob, gouged two
grooves 180 degrees apart in the plastic (being careful to NOT hit the
brass insert), and split open the knob.

Since both the plastic knobs and brass inserts were knurled, there was
no way these were going to fit together without some modification.
After some careful measurement, I put the original knob back into the
lathe, and enlarged the hole slightly so that the new brass insert
would fit. I then roughed up the plastic with sandpaper to give the
glue something to grab onto. I stuffed a grease covered steel (not
brass) screw into the set screw hole, smeared the brass insert with
epoxy, and let it harden. The nylon screw was easily removed, but if
there has been some difficulty, I could easily have removed it with a
little brute force.

Good luck.
--
Jeff Liebermann

150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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Old January 8th 19, 10:44 AM posted to sci.electronics.repair
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Posts: 1,840
Default Calibrated dial knob repair

On Monday, January 7, 2019 at 11:33:24 AM UTC-8, wrote:
I recently bought an old Eico 955 In circuit capacitor tester. ... Someone apparently over
tightened the set screw and cracked the part that fits around the 1/4"
shaft.


A lathe and some aluminum to make a metal fitting, and some creative hollowing-out
of the old knob, can fix it. Old plastic with cracks and glue just won't be a part of
the solution (it needn't look like the original, IMHO).

If the shaft is fully round, consider a lock fitting as used on old trimpots: the
knob can grab that shaft like a collet, but still come off with the right wrenches.


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Old January 10th 19, 03:09 AM posted to sci.electronics.repair
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First recorded activity by DIYBanter: Dec 2018
Posts: 23
Default Calibrated dial knob repair

On Mon, 07 Jan 2019 14:20:44 -0800, Jeff Liebermann
wrote:

On Mon, 07 Jan 2019 13:32:51 -0600, wrote:

I recently bought an old Eico 955 In circuit capacitor tester. It worked
right away, but I am going to recap it. But there is a problem. The
Calibrated dial knob wont clamp to the shaft. Someone apparently over
tightened the set screw and cracked the part that fits around the 1/4"
shaft. Someone also must have glued it, then broke it again. That only
makes gluing it again a worse option because the old glue is gooped all
over the pieces, so they wont fit together properly anymore.

Finding a replacement is likely not an option.
Knob Part number - Eico 89678

How would you fix this?

I do have one thought. To carefully grind away the entire center part of
that knob with a dremyl tool. Then take a new smallish knob with a set
screw and drill out the 1/4" hole thru to the face of that knob, and use
JB Weld to glue that new knob inside the old one. Of course the set
screw has to line up with the original set screw hole. (there is room
for a small knob inside). I might even have a solid aluminum knob that
will fit in there, but I have to find them....

However, grinding out that center will be tricky and time consuming,
since the new knob needs to be centered very precisely.


A few questions:

1. Which knob?
https://c1.staticflickr.com/4/3834/11055642634_e5daa78fe7_b.jpg


The CALIBRATED one with numbers on it.

2. What part of the knob is cracked? Is it the plastic part or the
brass center insert? I haven't seen too many knobs without this brass
insert as threading the plastic doesn't last very long on small
diameter knobs.

No brass parts, the set screw is in plastic, part of the piece that fits
on the 1/4" shaft is broken away (opposite set screw).

I'll assume it's the brass insert. These are very much the same for
all similar sized knobs that use a 1/4" dia shaft. I've actually done
what you're proposing. I used a lathe to insure that everything was
centered. Instead of trying to totally drill out the brass insert, I
used a smaller drill (or end mill) that left a thin brass annular
ring. I removed that with a pair of pliers.


Like I said, there is no brass in it. not the best quality knob in my
opinion..... even if it is 50 years old.........

The replacement brass insert was provided by a random knob from my
collection. I inserted a 1/4" steel rod into the knob, gouged two
grooves 180 degrees apart in the plastic (being careful to NOT hit the
brass insert), and split open the knob.

Since both the plastic knobs and brass inserts were knurled, there was
no way these were going to fit together without some modification.
After some careful measurement, I put the original knob back into the
lathe, and enlarged the hole slightly so that the new brass insert
would fit. I then roughed up the plastic with sandpaper to give the
glue something to grab onto. I stuffed a grease covered steel (not
brass) screw into the set screw hole, smeared the brass insert with
epoxy, and let it harden. The nylon screw was easily removed, but if
there has been some difficulty, I could easily have removed it with a
little brute force.

Good luck.




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