Saving Mr Food Saver - Part 1

Projects /  Repairs  Original post date: 07/26/2017

I bought a Food Saver from the Thrift shop a while back.  I have been using it to make small plastic bags for storing parts.  After grocery shopping I have decided to use it for portioning meat that goes into the freezer.

I guess it wasn't heavy duty enough.  The case was barely warm when it gave up half way leaving me still have stuff to pack.  :(  So I opened it up and carefully cut open the plastic insulation tapes on the primary side of the transformer winding.

It would seem that the transformer wasn't fixable, so I have decided to mod the food saver.  I did a quick trace of the schematic of the controller board.

That's a 115C thermal cutoff fuse that protects the transformer from overheating and catches fire.  It did its job and is now open circuit.

I have decided to take some measurements to figure out my options.  I wired up an AC transformer to feed power into the secondary side.

The open circuit voltage of the primary side would give me some idea what the ratio is.  16V input to 67.9V out means that the output is around 120V * 16/67.9 = 28V assuming the windings are not shorted.

I have decided to take a measurement of the current.  Bare in mind that this is in series of an inductor, so not all of the it ended up as losses.  It is 1.92 V*A.  It probably means that the thermal fuse kicks in early enough to prevent the magnetic wire insulation from burning up.

So I ordered some thermal fuses from the usual place.  I am hoping that's something similar size and would work.  It looks like it is a knock off of the Alpha Therm GmbH - Tamura E3F part.  The dimension is very close to the one I have.  Found ebay ordering for the original part.  It's a bit too late as I ordered from China.

It probably going to take the full 2 months to get here.

I found a Hammond 166G25 transformer that has the same core size and similar output range.  The rating for the secondary is 25V 0.5A.  The food saver transformer is for very light duty cycles and the NiCr heating wires can easily use 2-3A.

I hooked up an external transformer for some more testing.  At 15V, the pump draws 1A (AC) and the heater wires draw 4.85A.  I think that it is already on the high side as the motor is running off a 1A rectifier diode and the transformer wires are 22 AWG which is rated for 5A maximum. What this means is that there might be a short circuit in the transformer primary winding and as a result the wrong transformer voltage is calculated.

At 10V AC, the motor current dropped to 0.7A or so while the heater to about 2.85A.  That's probably the right ballpark. The heater wires are controlled by a TRIAC which requires AC to operate correctly.  I might be able to modify the circuit with a MOSFET and run the unit from an external 9V to 12V DC supply.