Mailmate Shredder - replace the internal fuse with a circuit breaker

I bought a Staples Mailmate shredder some 6 years ago while living in the US. I just love the size and design and the fact that it cross cuts (rather than just stripes) my documents, credit cards and CDs.

After some heavy use last year during tax preparation, the internal fuse blew. So I went to get a replacement. It took some time to find out how to open up the shredder, but eventually I got the job done and the shredder worked again….

…until I prepared this year’s tax.

The fuse blew again, and getting the shredder open just consumed so much time the first time that I decided to replace the fuse with a resettable circuit breaker.

I could have just bought a new shredder and I really was on the verge, but I really love my Mailmate.
It also saves about 37 bucks (the price of a new shredder minus the circuit breaker) and it is environmental friendlier to repair than to replace.

So this time I’ll show you how to open the shredder and how to replace the internal fuse with a circuit breaker.

If you have other appliances including a hardwired fuse, this instructable may help getting an idea on how you can improve the affected appliance.

Warnings:

• Be careful if you follow this instructable and only do this if you are familiar working on electronic circuits.

• The shredder runs on AC, so ensure to pull the plug before opening the unit.

• The circuit board has some capacitors which could carry load. If not handled properly you run the risk of an electric shock.

• When handling the internals of the shredder, be careful with the blades inside to prevent cuts.

• Also, the sticker on the bottom of the shredder’s top indicates that the unit is not user serviceable.

• Do not wear your best clothes. The gears inside the unit are lubricated with some nasty grease.

If you follow this instructable anyway, you do so at your own risk.

Step 1: Tools and supplies

You will need the following tools and supplies for this project:

• Screwdriver
• Soldering iron
• Desoldering pump
• Solder
• Heat shrink tubing
• Cable lugs
• Electrical pliers
• Cable
• Cable stripper
• Circuit breaker (5A as per PCB, anti-surge type)
• Electric drill
• Saw
• Wrench

Some hints and tips:
The screwdriver must be long enough to reach the screws which fasten the waste bin housing to the shredder top (about 6 inch, maybe a little more).
The screw heads are all Phillips recessed heads. As I couldn’t find a screwdriver with the appropriate length, I used a regular flat head screwdriver which was long enough and filed the size of the blade to fit the screws.

The cable must be long enough to connect the main board with the circuit breaker. I used a cable with a length of about 12 inch and later shortened it to the appropriate length.
You can use single conductors, but as space is sparse within the shredder head, I opted for a two-core cable which makes routing the cable through the unit easier.
The wire cross section should be similar to the mains cable’s cross section as it has to carry the same current.

The internal fuse is rated at 5A. Unfortunately, I couldn’t get a circuit breaker with the same rating. So I bought one being rated at 6A. I assume that this will still work in the long term. It’s at least better to give it a try (in my opinion) than to open up the unit every time the internal fuse trips.

Comments

[Raider_SPE]

Man, my mailmate just failed and I was and still am pissed. This thing was a workhorse for a long time. I don't have any experience with soldering but maybe this is a good first proj?

The light still comes on but it will not get going. Would this be the fuse problem or something else?

[Mike73]

If the light still comes on, it's not the fuse. Once the fuse trips, the light doesn't come on any more.
I'd recommend checking the relays.
I've checked by enlarging one of my images, and in my unit, Staples used Tianbo relays. If you check out the picture of the PCB (the one where the 2 arrows point at the screws), the relays are the 3 black little boxes to the left. I don't know how much you know about electronics (you say you don't have experience with soldering), so I'll try to explain. The relays switch the mains power for certain functions of the shredder. One of them will most likely turn on the 120V for the unit, while I'd imagine the other 2 will turn on the motor. One for the shredding, and one to reverse the blades. The signal is given by some low voltage input. The buttons of such units usually run on 12 or 24V. The just provide the signal to the relay. Once the relay gets the signal, the relay's contact gets closed by magnetic force, providing 120V to the motor.
So if your light comes on and you know how to use a multimeter, you can press the buttons of the unit while measuring the voltage on the high voltage pins of the relays. If I didn't explain clearly enough, let me know and I'll try to walk you through. If you check the output voltage of the relays and you don't get a 120V reading (assuming you check the proper pins of the relay), the relay is stuck and has to be replaced.
BTW, I used my shredder now for a week, and it's working like new.

[Mike73]

Duh. I forgot. Whatever you do: be careful. If you work on the open unit with the power connected, it is even more dangerous. So be sure you know what you do. If you don't, don't do it. If you do it, don't do it if you're alone at home ;-)