PS-77CS Shredder Repair

After around 7 or 8 years of some tough abuse and shredding my Fellowes PS-77CS Shredder has finally given up the ghost and failed on me.

The machine is getting power, but it doesn’t run the shredder motor. There are signs of power going to the device, because it detects win the bin is open and lights up the red light to say it’s open. The light goes off when you push in the Micro switch so this tells me the sensor circuit was working fine and the problem was more electrical as opposed to mechanical.

I did some dismantling of the actual equipment. Fairly simple, lift it up and remove about 10 screws. Open the lid then disconnect the wire attaching the motor to the PCB. I did a quick look around the circuit and couldn’t find any specific issues.

I finally identified the problem, I went to remove the PCB so I could look up the schematics and when removing it the transformer was literally hanging on a couple of threads of copper wire. So it came off easy enough (picture below)

 

 

 

 

I decided to remove it, as it was evident to me the transformer is what caused the problem. For those who don’t know, a transformer receives an incoming voltage in a circuit and then alters it for the output side (either by increasing or decreasing it). In this case, it’s receiving an input voltage of ~ 220v and outputting it into ~ 15.6v from what I can find online (these are the specs). I’ve wrote them below if anyone finds them useful.

Input Voltage: 220V
Output Voltage: 15.6V / 15.6V
Dimensions ???? : 8 * 11 (On other sites, this number translates as “specification” – so I think it’s the size)
No Idea ???? : 3 + 4 (On other sites, this translates as “stitch / work type” – not sure if this means the number of pins)

Now, when researching online, it seems these transformers are commonly fitted to the Fellowes shredder models and seem to be the weak point of them. The point of failure is usually when the shredder falls over or gets banged about a bit. The transformer / PCB are mounted upside down in the shredder motor. So if the unit falls over it can damage it. Essentially it’s dangling on it’s own internals.

A common fix suggested by one user seems to be fitting an M2730 transformer, which is slightly bigger then hot glue it in place so it doesn’t damage it if it falls. I looked up this product and unfortunately it’s a discontinued product. So I may try places like eBay or Farnells / CPC in the UK to try and source one.

In the meantime I have emailed Customer Support at Fellowes to see if they stock spares. I’m more than happy to fit the equipment myself to get it up and working again. Failing that I’ll source one online if they cannot supply. The equipment by Fellowes is amazing. It’s stood up to some tough abuse from myself, but I’d rather not pay £ 100 for a new shredder if I can fix it myself for around £ 20

I’ll update this post as I go, hope some of you find it useful and helps you on your quest with your Fellows PS-77CS Shredder or others.

PS: If your from Fellowes, I’ll happily receive a new shredder from you if you offer me one. I wouldn’t complain 🙂

UPDATE 2021

I’m actually still looking at this, my knowledge has increased over the years. The problem I’m having is sourcing a transformer with the correct pitch / pin spacing and size enough to fit into the array. I’ll keep this article updated should I find it, as I’ve been wanting to repair it.

For information the Chinese sites list it as follows

Input Voltage: 220V (Chinese sites like this as Enter, I’m guessing entry voltage)
Output Voltage: 15.6V / 15.6V (It is a dual 15.6v transformer – the 15.6 is UNLOADED voltage)
Dimensions ???? : 8 * 11 (On other sites, this number translates as “specification” – so I think it’s the size)

– Still not sure, I think this could be referring to the gauges of wire  (8 gauge, 11 gauge)…. still looking

No Idea ???? : 3 + 4 (this translates to the pin count – 3 primary, 4 secondary)

EXTRA INFO

Pitch – 5mm

Row Spacing – 20mm

There is 20mm between the primary / secondary pins, and 5mm between the terminals of the secondary pins

(On other sites, this translates as “stitch / work type” – not sure if this means the number of pins)

For information – it uses an EI28 transformer core

UPDATE#2 – 31/08/21

This shredder is now FIXED. I basically decided that if the shredder was no longer working, I may aswell not worry about the board and just try to bodge it.

For reference the transformer I used is a Vigortronix VTX-121-3223-215 model.

EDIT – The correct code was actually VTX-121-3023-215 not the one above, as my Amazon order matches this code instead

I’ll be uploading some pictures, because to fix it the way I’ve done it, you need to be prepared to damage/repair your own board in order to fit the transformer.

NEWER PICS UPLOADED 22/04/24, see reference photos at the bottom. This may help others and I’ve given a bit of a written description to help with each

The problem is the pin pitch/spacing on all the modern transformers, I ended up cutting holes in the board and bending pens, then running wires to join them up. I’ll probably upload a Youtube video detailing this for further information

I also had to make my own Capacitor up for testing (which was a bad idea anyway). The capacitor I used was Electrolytic, and 330uF/400V, which turned out to be 55 x bigger than the factory one (but it worked for testing at least). It also explains why my shredder said it was overheating. I’ve since ordered the correct type for my shredder to be fitted.

A few notes along the way to help you out as these may be also questions you’re searching

Does the Shredder use a start capacitor or a run capacitor?

• • The Fellowes PS-77Cs uses a “run” type capacitor

What value is needed for the capacitor?

• • It should actually be printed on the Motor of the model (6UF/450V), the model that was fitted to my shredder was YY9050-2M23
  • If you need to work out the manual way however, here is the formula
    • Motor Wattage x Efficiency x 1000 / (AC Voltage x AC Voltage x AC Frequency)
    • In this instance (180W x 80% x 1000) / (230 x 230 x 50) (Motors are around 80-85% efficient FYI just input this range)
    • 14.4 Million / 2.645 Million = 5.44 Micro Farads (round up to 6)

Reference Photos

The transformer I used for the repair, Vigortronix VTX-121-3023-215 (affiliate link for Amazon), special thanks to Frank for contacting me to query this article too. As it helped me to add some content to update the article

The underside of the transformer, incase you’re having problems with the orientation, the (2 pins) go to the AC voltage side (3 pins) of the board, I never had a central pin. The central pin is simply used to help secure it to the board. I modified my board for the pin to fit through, then soldered it all down to help secure it (Right hand side of the picture is the underneath, AC, Voltage side)

A couple more reference photos for above and below the board

In terms of the board, the side closest to the safety capacitor (yellow cap), is the AC voltage side where the 2 pins go

The opposite die is the DC voltage side (DC voltage is done through a full bridge rectifier, via the 8 diodes), I cut a wider hole here, then soldered each pin to the relevant rectifier diodes. They run in pairs, so it’s just a case of soldering one pin to each applicable pad for a diode pair

Final picture showing above and below , so you can see how the Transformer looks on the board, it’s orientation, and what the pins look like below. It’s not shown, but I ended up using hotglue to help secure it too iirc. The board was secure due to the way I soldered it, but wanted ot make sure. Since when the machines get dropped is when they tend to dislodge.

 

Photos

LEFT PHOTO – Underneath the board, you can see I’ve soldered one pin to one track via the hole in the centre. It looks weird, but all that side are connected via the same pad, so the extra copper wire and soldering was just to help secure it.

You can also make out the diode pins that I’ve soldered to as well for the other 2 pins. It’s easier if you shine a torch underneath to see the tracks (or use a multimeter), but basically every diode arrangement, is connected to +1 pin away from the one next to it. So if you numbered the pins 1 – 8, it would be connected as such (1+3, 2+4, 5+7, 6+8)

RIGHT PHOTO – Just a top down over view of the board. I noticed after the repair that the Triac was sparking and getting a burning spell. This could be from a poor trace, bad board, bad triac, faulty transformer, or any other choice. It did end up going away however, so figured it was probably something due to it’s age (as it had been sitting broken for about 7 years).

If you do this approach, I recommend not leaving it switched on, and just simply running it as needed then turning it off like any other electrical device. If you notice any smoke, then yeah it could be goosed. For me I didn’t care, as the machine worked, and I only shred when needed anyway. It’s mainly just a warning for others, I personally don’t understand how this could affect the Triac and figured something had just gone wrong due to age, because the transformer is connected to the board. And providing I’ve chosen the right one it should function as needed

 

FURTHER PHOTOS AND UPDATES (from Frank)

Another succesful repair, thanks to Frank for following up with me. He has managed to fix his shredder too with help from this article, and allowed me to post the photos too.

 

It’s ok if you use my photos. I would be happy if this saved even one
more device from the trash.
My Fellowes model is “W-5Cs”

Greetings
Frank

Hi,

as promised, I wanted to send you my success report, along with a big
thank you. Without your blog I probably wouldn’t have been able to solve
the problem, especially since it was the only page I found about it. I’m
good with a soldering iron, have measuring devices and tools and have
repaired many things, but unfortunately I often don’t have the depth of
knowledge to find out for myself what the problem is or what
specification the spare parts have to have if it’s not obvious. I had
already thought about going to a repair cafe where a few retired
volunteer technicians try to help people. But I don’t think they would
have been able to identify the part without technical documentation, as
it is nowhere listet by the number printed on it.

I rejected the idea of using a cable and chose your method of drilling
into the circuit board. However, it didn’t quite fit and a ceramic
capacitor was in the way. I simply removed it and installed it on the
back of the board as there was enough space at the bottom of the
housing. In addition, the wire of a fuse was in the way. Here it was
enough to unclip the plastic housing a little at one point. If you are
interested I have attached photos.

It worked well straight away and it runs. No defective capacitor or smell.

Thank you again and all the best wishes!

Frank