Saving Mr Food Saver - Part 2

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

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.

(Yes, that's literally back of the envelope.  For some reasons, I get a lot of bills. :(  )

It is a very simple design and there are no Arduino nor 555 here.  The first transistor is used to detect the voltage of the RC circuit (13M, 22uF) as it rises slowly when the power turns on.  When it crosses a threshold (VBE + VZener), the transistor pulls its output low.  The second transistor is wired as an emitter follower and is used to trigger the TRIAC.

I have replaced the TRIAC with a MOSFET (BUZ11) that I have in my junk box.  Gate to Gate, A1 to Source and A2 to Drain.  I wired in a 5.6K pull down between the Gate and Source as a pull down resistor.

The wires previously hooked up to the transformer is connected to the terminal block.  The micro-switch (rated for 6A) on the right hand side that acts as an On/Off switch is wired in series to the input.  I got a piece of power cord that was a left over from a cable converter case mod.

I did some testing with my bench supply.  At 13V,  the amount of heat was about right.  The unit draws in 4.7A.  Yikes!  This really limits my options.  I got a 12V/5V power brick (left) and a open frame 12V supply (right) from somewhere else.  It turns out that they are both made by the same company and they uses the same form factor!  The open frame supply is a much newer design and it is rated for 11A.  It requires forced air ventilation at above 6A of load.  I set the output voltage to 13V using the trimpot near the output connector.

I made a retainer clip for the cable on the low voltage side out of the old transformer "E" core.  I used my Dremel tool to cut a deeper groove for the closed end.

This is how the retainer fits.

The old power cord from the cable converter was designed to fit into a U shaped hole in its sheet metal case.   Not much of a strain relief, but the power cord insulation is thick enough and it'll have to do.  The cable looks like it belongs there.  :)

This mod/upgrade should increase the duty cycle greatly.