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Dead Vacuum Sealer

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vne147

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Hello everyone. I was hoping I could solicit some help in fixing a vacuum sealer I have which recently crapped out. The vacuum sealer is the Tilia Foodsaver professional II pictured here:

View attachment 66564 View attachment 66565

When the vacuum sealer is working properly, the user presses the vacuum button which kicks off the following sequence. First, an electric motor drives a set of latches closed which hold down the lid. Next, an electrically driven vacuum pump sucks out the air. Then, a heat sealer strip melts the end of the bag to create the seal. Last, the same electric motor re-opens the latches.

When the vacuum sealer failed, the latches were stuck closed. It is because of that I believe the problem has to do with the electric motor that drives the latches.

I took apart the vacuum sealer and located the motor which drives the latches. It is a single phase (I assume because there were only 2 wires going to it) 115 VAC synchronous motor. When the vacuum sealer first gets powered on, it attempts to drive the latches. I can tell because the motor vibrates and hums indicating that it’s receiving power. However, it does not turn. After about 5 seconds or so the command times out and the vacuum sealer stops trying to drive the motor.

I removed and disassembled the motor. All the gears inside looked good, I measured about 500 ohm across the windings, and when I applied 115 VAC to it, it would spin as long as I started it moving by hand first. Since the motor did run when I started it spinning by hand first, I’m thinking that the problem has to do with the start circuitry.

Looking at the control board there is a large capacitor wired is series with the motor windings. It is shown here:

View attachment 66566

I looked it up and it is an interference suppression film type capacitor. Here is the data sheet:

View attachment 66567

So my questions:

1. Is that capacitor the start capacitor?
2. Does anyone think that’s the most likely culprit based on my description?
3. Is there anything else I should check or test?

Thanks in advance for any help you might be able to provide and please let me know if I can provide anymore info.
 
Why not replace both film capacitors? One may be for starting and the other for phase control during run.
 
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If the motor only has 2 wires then any start circuit will be inside the motor. If it had external start components then there would be at least 3 wires.
 
Unless the latching mechanism is complex I don't see how the same motor can both open and close the latches without reversing the motor rotation. Are you sure it is a synchronous motor? I'm not aware that a 2-wire synchronous motor (or any 2-wire AC, or brushless DC, motor for that matter) can be reversed.
 
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Why not replace both film capacitors? One may be for starting and the other for phase control during run.

The larger capacitor is in series with the motor. That's why I thought it had something to do with starting it. The smaller capacitor is in series with the input to the 7805 linear voltage regulator which powers the DC portions of the board.

If the motor only has 2 wires then any start circuit will be inside the motor. If it had external start components then there would be at least 3 wires.

That makes sense. I didn't see any other components inside the motor aside from the permanent magnet around the rotor and the stationary windings. Any idea then what kind of failure could cause the motor to not spin up on it's own but continue to rotate after being spun up by hand?

Unless the latching mechanism is complex I don't see how the same motor can both open and close the latches without reversing the motor rotation. Are you sure it is a synchronous motor? I'm not aware that a 2-wire synchronous motor (or any 2-wire AC, or brushless DC, motor for that matter) can be reversed.

The motor had a label on it which said 115 VAC and that it was an AC synchronous motor so I'm pretty sure about that. And, the latching mechanism is complex. The motor drives a cam that's connected to a lever arm which opens/closes the latches. The direction of motor rotation for both open and close is the same. There is a microswitch that the lever arm depresses that tells the controller board when the latches reach a certain position.

Is the consensus that I should try and replace that capacitor or look for something else? Anyone have any ideas?

Thanks for the input.
 
You haven't shown us a picture of the motor or the complete PCB so it's very hard to say. I think it's posible that another component could be at fault such as a triac, scr or diode.
 
The motor had a label on it which said 115 VAC and that it was an AC synchronous motor so I'm pretty sure about that. And, the latching mechanism is complex. The motor drives a cam that's connected to a lever arm which opens/closes the latches. The direction of motor rotation for both open and close is the same.
You've convinced me!

I'm not convinced, however, that the caps are in series with the motor/regulator.
A 0.039uF cap can pass only about 1.5mA when the mains supply is 115VAC, and a 0.01uF cap only ~0.4mA. That's surely not enough to power the motor or DC supply?
 
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The larger capacitor is in series with the motor. That's why I thought it had something to do with starting it. The smaller capacitor is in series with the input to the 7805 linear voltage regulator which powers the DC portions of the board.

I'm wondering if you know what in series means?
In series with the 7805 should surely be in parallel No? Its a dc component no current would pass through a cap in series
 
The motors brass bearings are probably dried up, oil them to get the motor to spin freely.
 
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