BT150 Thyristor equivalent(BT151) has just exploded !!!

[Elecbegginner]

I made abig boob when I suggested limiting current with a car headlight bulb. I thought you were running at 12V

To check the motor, put a filament bulb (mains) in series to limit the current.
To check the thyristor, use a light bulb as a load.

It looks as if you have a dead motor. What sort is it? Does it contain brushes running on a commutator?
Is there any connection across the input terminals? If not, then turn the motor by hand and see if there is an intermittent connection.

The thyristor works by chopping the sine wave so that the average power is reduced. The output voltage measured will depend on the way the meter works.

The problem is that the motor that i checked the previous card with is working fine , but on this card i get very weird output voltages , i am suspecting the Thyristor is not working as it should be .
And what is more weird is that the motor does not turn even with for example 189 volts at output .

 

[Elecbegginner]

Ok guys after analysing the card with DMM , i found a bad resistor , i changed it but nothing has changed in the output voltage i still get 180 volts at the lowest speed position.

 

[(*steve*)]

As has been suggested. Connect a light globe in place of the motor and see if it dims appropriately.

 

[Elecbegginner]

Hi everybody , i connected the filament bulb , and here is what i see :
First of all i have 6 positions to chose from and the pulse position , i only see light in the pulse and the last 2 positions . the 1,2,3,4 are not working .

 

[(*steve*)]

It sounds like the fault in your motor may have taken out more than just the SCR.

Time to start looking for more damaged components...

Perhaps you could start with some sharp pictures (we recommend indirect light like that in shade outdoors, NOT flash or direct sunlight). We will need to be able to read the writing on components. Images of both sides of the board are often useful.

 

[Elecbegginner]

Yes that's what i think , i have already found one bad resistor before testing with the bulb , i will check for more and see where this goes .

 

[Elecbegginner]

One more thing guys i just want to know how to make a check circuit for the thyristor , i want to make sure its working .

 

[CDRIVE]

This is the point where we usually request some clear photos of the device and PCB.

Chris

 

[Elecbegginner]

This is the point where we usually request some clear photos of the device and PCB.

Chris

I will do it .

 

[CDRIVE]

One more thing guys i just want to know how to make a check circuit for the thyristor , i want to make sure its working .

This is a logic level SCR so you can try this simple test.

Place your DMM on Diode Check
Connect the Red (+) probe to the Anode.
Connect the Black (-) probe to the Cathode.
Using a jumper short the Anode to the Gate momentarily.

The SCR should fire and the meter should drop to near zero and remain so until disconnected.

Alligator jumpers will help.

Chris

 

[CDRIVE]

If you want something more permanent you could put this together.

Chris

 

[Elecbegginner]

If you want something more permanent you could put this together.

Chris

Yes that's nice schematic , thanks

 

[Elecbegginner]

And would this circuit work also with triacs ???

 

[Elecbegginner]

OK guys i checked two types of Triacs before checking the Thyristor , and i found a conductivity between gate and terminal using diode test mode , is that a sign of faulty triac ???

 

[CDRIVE]

Yes that's nice schematic , thanks

Your welcome.

And would this circuit work also with triacs ???

As is it will test a Triac in only one direction. I'll draw up another print for you.

OK guys i checked two types of Triacs before checking the Thyristor , and i found a conductivity between gate and terminal using diode test mode , is that a sign of faulty triac ???

You're confusing me. The BT150 is an SCR.

Chris

 

[(*steve*)]

Elecbeginner, an SCR and a Triac are both thyristors, but SCRs and Triacs are different. (Like a car and a bus are both vehicles, but a car is not a bus)

 

[Elecbegginner]

Elecbeginner, an SCR and a Triac are both thyristors, but SCRs and Triacs are different. (Like a car and a bus are both vehicles, but a car is not a bus)

Your welcome.

As is it will test a Triac in only one direction. I'll draw up another print for you.


You're confusing me. The BT150 is an SCR.

Chris

Thanks steve for this new information.
CDRIVE , i don't really know if its ok to put this here or create another topic but its in the same subject .

Well i have some coffee expresso machines that come with two TRIACS a BT131 and a BT139 , i wanted to test them too , so i googled and the way to check them is similar to thyristors , the difference is that TRIACS conduct both ways .

So my question is about the jumper for the triac : am i supposed to connect the gate with a specific anode (anode 1 or anode 2) ?

 

[CDRIVE]

You can try this to test Triacs with a DMM. I show a push button switch but you could use a momentary jumper.

Chris

EDIT: Diode/Continuity mode is not the same as the Rx (Ohms) ranges!

EDIT2: This circuit is only suitable for small signal (logic type) thyristors. Please read mea culpa in post 43.
https://www.electronicspoint.com/bt...-has-just-exploded-t262310p5.html#post1565306

 

[Elecbegginner]

Thanks for this useful test circuit , i will do a bunch of tests on my SCRs and get back here

 

[Elecbegginner]

Thanks to the pictures given by CDRIVE i checked the thyristorsi got and also all triacs , and they are all working good , as for the output voltage variation problem , am sure there is something wrong with card , i will try to put high quality shots for you guys to see it clearly .