Electronics > Repair

Tektronix Camshaft repair guide

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BlownUpCapacitor:
Today, my Tektronix 7A26 has suffered the common issue of camshaft disease. The plastic around the aluminum has shrunk and cracked itself into multiple pieces.

This won't do for me as I don't like to spend extra money to buy parts and instead like to make do with what I have. So here is a guide on how to fix it.

Stuff needed:

-Cyanoacrylate or some kind of glue

-A file or sandpaper with a high-grit

-Needle nose pliers

-Elbow grease and patience

This guide will only cover the failure where the plastic bit that actuates the camshaft and connects to the rod is broken. This is the most common failure.

1
The first step is to disassemble the device that holds the camshaft. The method will vary depending on the model so I won't cover that.

You will need to safely extract the damaged camshaft by itself. There will also be a C-ring near the front, remove that, and don't lose it! This clips onto the actuator so parts may start falling out.

Refer to image 6 for an example of what you should have. In my case, the rod and the actuator fell out of the cam. This may not be the case for you.

2
Use your needle nose pliers to gently remove the copper springs near the end of the cam. These are spring so they might jump out! (image 5)

Then remove the broken actuator and the aluminum rod. (image 1)

3
Use the glue to glue back the pieces of the actuator together. Refer to image 2&3. Ignore the yellow and the silver wire on the actuator. This was a mistake I made while experimenting.

Note: You should keep the actuator the same size as it was originally! This means no adding extra mechanical reinforcements! The cyanocrylate is enough to hold it together! This is important as the tolerances are quite tight.

After gluing and curing the glue, use your file/sandpaper to remove excess dried glue.

In image 2, the silver wire part is where the C-ring retainer goes. Make sure that slot is clear for you! Do not get glue into that.

4
Now slide the rod and glued actuator back into the cam as shown in image 4

Then reassemble the white cam holder with the springs and cam.

The other cam holder should attach back and the retainer C-ring slid back onto the actuator.

At this point, the repair is done and the unit should be reassembled.

Check for operation and if all is good, give yourself a nice pat on the back.

BlownUpCapacitor:
Images

BlownUpCapacitor:
Update: This method will not work for camshafts that have dual cams ei dual timebases like the 7B53A, however, I am actively working on a solution, and it seems very very promising, stay tuned!

BlownUpCapacitor:
Here's how to fix the dual time base camshafts, again, this is only if the cam actuator has failed:

Stuff needed:

-Cyanoacrylate or some kind of glue

-A file or sandpaper with a high-grit

-Needle nose pliers

-exacto knife/metal spudger

-Elbow grease and patience

1
The first step is to disassemble the device that holds the camshaft. The method will vary depending on the model so I won't cover that.

You will need to safely extract the damaged camshaft by itself. (image 11) There will also be a C-ring near the back, remove that, and don't lose it! This clips onto the cam itself.

Refer to image 11 for an example of what you should have. No actuator parts should be falling out. If they are, save them. They're tiny and are a pain in the ass to find again.

2
Use your needle nose pliers to gently remove the copper springs near the end of the cam. These are spring so they might jump out! Image 1 is what you should have now

3
Remove the upper lid part of the cam using an exacto knife or spudger. The method I used was to gently push the tip of the blade into the gap until I heard a click or the blade stopped. I did this the full 360 degrees around the cam lid. (image 2)

The cam lid should now be loose, and you can use needle nose pliers to pull it out. What you should have is image 3

Check to make sure you didn't damage the lid, look at image 4, that is what holds the broken cam actuator

4
Split the lid open using your needle nose pliers. This is done by squeezing the base of the lid. The lip portion is where your pliers should rest on while you squeeze to crack it open like a nut.

Refer to image 5

5
You should see black pieces of the cam actuator inside the lid. DO NOT LOSE THESE! (image 6)

Make sure you have all of them. Try reassembling them loosely on the smooth part of the aluminum rod. (image 7)

If you are missing pieces, time to bend your back over and start searching the ground!

If you really cannot find all the pieces, the most important ones are the pieces with the wings or tabs on them.

6
Find the etched part of the rod for the cam, not the knob. (image 8 )

Glue the broken cam pieces back on that etched part of the rod. (image 9)

It should be like a rocket ship, and it should be pointing towards the front. Make sure the glue cures completely! This part will be under a lot of force when in operation! So make it strong, whilst keeping the original dimensions.

Use your file/sandpaper to grind away the extra glue.

7
Glue the lid back together so it looks like image 4 again.

Then slide the rod with the glued actuator back into the lid. Make sure it fits and rides smoothly. If it doesn't, repeat the last line in step 6.

You should have what looks like image 10.

Remove the rod from the lid.

8
Glue the lid back onto the cam, it should look like image 1. Don't use too much glue to the point you will never be able to open the cam again in the future. Apply just enough to keep it together strong, but little enough that you can still open it back up.

After gluing the lid on and curing the glue, slide the rod through the back of the cam. The cam actuator should be small enough to fit through the back and go in. Try getting the actuator back into the lid and seeing if it actuates the cam properly.

If it does, remove the rod and reattach the back so it looks like image 11. Then insert the rod. It should look like image 12.

9
Reassemble the whole thing again (image 13).

Don't forget the retainer ring while doing so!

Then check for functionality (image 14).

Job well done.

BlownUpCapacitor:
images

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