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vaccum cleaner repair

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libyantiger

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hello

the problem is that the motor spins for half second then stops

i opened it and tested all components in board looks like every thing is ok

i direct replaced the bta16-600 triac with bta2416400


nothing works ? can i by pass the triac circuit and feed the 220 directly to the shown motor?

also there is another small signal triac that i have not replaced? could it be the cause?


by the way i trouble shooted and concluded that all switchs cords ok so it not gonna be easy fix


pleaaaaaaaaase help me 87.jpg7.jpg
 

Before condemning the components on the board, are you sure the motor brushes are in good condition?
Working for half a second then stopping sounds more like an overload problem than the triac.

Brian.
 

Before condemning the components on the board, are you sure the motor brushes are in good condition?
Working for half a second then stopping sounds more like an overload problem than the triac.

Brian.

any easy steps for verification of thier condition?
 

Hello libyantiger,
Just out of curiosity, what are the values printed on the side of those two capacitors? (Please see modified pic below)...
Also, the slider as marked in blue; Is it a speed controller or a stepped switch?
Regards,
Relayer

Vacuum Cleaner00.jpg
 

any easy steps for verification of thier condition?

It's a good idea to test the motor with no control circuit intervening. Apply reduced voltage.
When I have wanted to do this I install a low-ohm resistor (or light bulb, etc.) in series with the appliance. It requires a high-watt component. Your motor is probably several A, which makes it difficult to find a suitable resistor.

A variac is really handy in these situations, although expensive. I purchased a 2A type on Ebay for a few dollars.
 

The motor is labeled 20-240V and you can test it directly by connecting to the house power supply. It is an universal motor and hence will have highest speed when connected directly. Also check the motor body is not short with any winding (use a multimeter or a line neon tester).
 

The motor is labeled 20-240V and you can test it directly by connecting to the house power supply. It is an universal motor and hence will have highest speed when connected directly. Also check the motor body is not short with any winding (use a multimeter or a line neon tester).



i am stuck with contradictions from other replies that say" dont over pass the triac that will burn the motor"

it is all arise from the fact that i really understand what the triac is doing at the first place?!

- - - Updated - - -

Hello libyantiger,
Just out of curiosity, what are the values printed on the side of those two capacitors? (Please see modified pic below)...
Also, the slider as marked in blue; Is it a speed controller or a stepped switch?
Regards,
Relayer

View attachment 139317



the slide thingy is just a varible resistor i tested it it is really fine going from 0 ohms to almost one mega or so

the value of the capacitors is ...one is 0.47 mf ...other is 0.15 mf both 270vac!

the small signal transisors one is

pnp works good

other is variac which i cant test and i have not replaced to be honest ....the caps and the small variac are just the last things to replace

before determining that i do have problem in the motor

either the motor is bad or its brushs are bad
 

OK, I'll explain as simply as possible:

The triac is like a super fast acting switch.

If you fed AC mains directly to the motor it would run at full speed. To reduce the speed there are two options, to reduce the voltage or to keep full voltage but reduce how effective it is by pulsing it on and off. The idea is if you feed it short bursts of power with long gaps between them, the average power will be low and the motor will turn slowly, if the bursts are made longer, the average power goes up and the motor goes faster. As long as the bursts occur rapidly enough, the mass of the motor keeps it spinning and you don't notice it is actually getting little 'kicks' to keep it turning instead of steady power. I just grossly oversimplified how it works but hopefully you get the idea.

The triac is what controls the bursts, the slider control adjusts the burst lengths and hence the motor speed. Technically, it's called phase control. The busts will be at a constant rate, twice the AC line frequency so they are at either 100 or 120 times a second depending upon your country's power lines being 50Hz or 60Hz.

I would still check the brushes first, they wear out over time and are designed to be replaced. Somehow the two connecting points on the motor will be removable and underneath them will be a spring and a carbon block. The block is the brush and the spring keeps it in contact with the moving part of the motor (rotor). Carbon is conductive so the power on the two wires passes down the spring and brush where it touches the rotor and feeds power to it while it is still free to spin. To replace the brushes, first get replacements, they are not expensive then open the black connecting points and pull the old brush out. Do the reverse to re-assemble it using the new brushes.

The danger with bypassing the control board to see it it is faulty is that if the brushes are the problem, there is nothing to stop the motor being damaged.

Brian.
 

The danger with bypassing the control board to see it it is faulty is that if the brushes are the problem, there is nothing to stop the motor being damaged...

Most likely it is a series wound universal motor; if the brushes are making poor contact, the motor will simply not run (the brushes are spring loaded so that they run till they are almost completely used up) but I do not see how the motor will be damaged if we apply the line voltage directly on the motor.

I am quite sure that the triac regulator (my vacuum cleaner does not have any speed control) applies the full line voltage onto the motor when at the max setting.

It is also possible to test with a multimeter (use the continuity mode) whether the brushes are ok; if the brushes are fine the motor will read close to zero (Ohm) else they will read open or close to infinity.
 
Last edited:

Sometimes, at the point of complete failure, the brushes contract when cold and connect to the commutator, as soon as it starts up, the combination of heating and vibration moves one or both far away enough to break the connection. I can't be certain in this instance but I know it does happen that way. The danger of direct AC connecting is mechanical damage to the commutator if the brushes shatter or are worn down to their bases.

Brian.
 

ok let me add more clues to the probelm


some times it never run at all??

some times it runs for half second then stop

however some times it runs ok but very slow ...in this times i put my fluke mulitemeter on the motor to see what ac we have across it

i saw 40 vac ....such a low voltage !

that is all i have right now....still away from the home ..tommorow i will back and complete my investigations


the pleasure of knowing what is worng some times can be even more rewarding than solving the probelm !

- - - Updated - - -

OK, I'll explain as simply as possible:

The triac is like a super fast acting switch.

If you fed AC mains directly to the motor it would run at full speed. To reduce the speed there are two options, to reduce the voltage or to keep full voltage but reduce how effective it is by pulsing it on and off. The idea is if you feed it short bursts of power with long gaps between them, the average power will be low and the motor will turn slowly, if the bursts are made longer, the average power goes up and the motor goes faster. As long as the bursts occur rapidly enough, the mass of the motor keeps it spinning and you don't notice it is actually getting little 'kicks' to keep it turning instead of steady power. I just grossly oversimplified how it works but hopefully you get the idea.

The triac is what controls the bursts, the slider control adjusts the burst lengths and hence the motor speed. Technically, it's called phase control. The busts will be at a constant rate, twice the AC line frequency so they are at either 100 or 120 times a second depending upon your country's power lines being 50Hz or 60Hz.

I would still check the brushes first, they wear out over time and are designed to be replaced. Somehow the two connecting points on the motor will be removable and underneath them will be a spring and a carbon block. The block is the brush and the spring keeps it in contact with the moving part of the motor (rotor). Carbon is conductive so the power on the two wires passes down the spring and brush where it touches the rotor and feeds power to it while it is still free to spin. To replace the brushes, first get replacements, they are not expensive then open the black connecting points and pull the old brush out. Do the reverse to re-assemble it using the new brushes.

The danger with bypassing the control board to see it it is faulty is that if the brushes are the problem, there is nothing to stop the motor being damaged.

Brian.



great explanations sir ....i will replace them and come back with the result
 

55556.jpg77889.jpg7899999.jpg

that is how brushs looks i wonder if they are ok or not?
 

Sometimes, at the point of complete failure, the brushes contract when cold and connect to the commutator, as soon as it starts up, the combination of heating and vibration moves one or both far away enough to break the connection. I can't be certain in this instance but I know it does happen that way. The danger of direct AC connecting is mechanical damage to the commutator if the brushes shatter or are worn down to their bases.

Brian.

got the burshs pictures sir would you have a look at them please
 

If the other one is the same I would say they are OK. They get shorter as they wear down but there seems to be plenty of length left on that one.

While open, look through the hole at the commutator (copper sleeve with slots in it) and make sure it has no obvious scratches or burned sections. It turns around if you rotate the motor shaft so you can inspect it at all angles.

If the fault is still there after you reassemble it, you have an electrical fault on the circuit board. Check it for poor solder joints first, then I would suspect the capacitors with the black plastic sleeve over them. It would be extremely unlikely to be the yellow block capacitors in the red boxes on earlier photographs.

Brian.
 

If the other one is the same I would say they are OK. They get shorter as they wear down but there seems to be plenty of length left on that one.

While open, look through the hole at the commutator (copper sleeve with slots in it) and make sure it has no obvious scratches or burned sections. It turns around if you rotate the motor shaft so you can inspect it at all angles.

If the fault is still there after you reassemble it, you have an electrical fault on the circuit board. Check it for poor solder joints first, then I would suspect the capacitors with the black plastic sleeve over them. It would be extremely unlikely to be the yellow block capacitors in the red boxes on earlier photographs.

Brian.


so it is now ok to direct connect the motor to ac for checking purpose? then i willl direct replace all suspected componenets and

feedback the resutls in this thread
 

As you have removed the brushes, it is time to clean the commutators- normally that would not be needed but it is a good idea since you are having problem with the motor. Wrap some tissue paper or cotton on the tip of a screwdriver and press on the copper block and turn the rotor by hand. Modern motors are remarkably robust. Check with a multimeter whether the contacts are fine (after you replace the brushes).
 

THANKS FOR ALL ....after i reconnected the brushs ...i conncted the motor directly ..."by passed the driver " works fine! however still woried that my hard working vaccum may fail because there is nothing to lower the stress

i wonder if i can stick a component to limit the current to the motor so it works .with less stress and abit less power


thanks again
 

If you reduce the voltage across the motor terminals, it will rotate slower but also take a higher current. If you increase the voltage, it will run a little faster but take a lower current. Motors get damaged because of "stalling", the rotor is stuck but there is some voltage still present (that happens under low voltage) - that makes rather high current to pass and damage the winding. Therefore my recommendation is not to reduce the voltage on the motor (than the specified) because motors get damaged under low voltage condition.
 

If you reduce the voltage across the motor terminals, it will rotate slower but also take a higher current. If you increase the voltage, it will run a little faster but take a lower current. Motors get damaged because of "stalling", the rotor is stuck but there is some voltage still present (that happens under low voltage) - that makes rather high current to pass and damage the winding. Therefore my recommendation is not to reduce the voltage on the motor (than the specified) because motors get damaged under low voltage condition.

looks like i have to leave it as it is ....is it technically safe?
 

I do not think, based on the information above, that your motor is sick. It is the electronics that is messing the operation. In the worst case, the controller will not send any power (voltage) to the motor and it will refuse to start (no damage). In the other extreme, the controller applies the full voltage to the motor and it runs happily. No motor should grumble at the rated voltage of operation. Modern motors are remarkably sturdy beasts- they refuse to die.
 
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