Triac Q4004F42

[Phiyedough]

This is my first post here. I am a domestic appliance repairer. I don't know much electronics but I do try to repair circuit boards where the fault is easy to diagnose, like a shorted triac or burnt out copper strips. I have been asked to look at an old massage device with a faulty motor controller. I think the fault lies with the triac, Q4004F42 but I've not been able to get a new one. I managed to get a Q4008LT but I think that won't be suitable as it's a triac / diac dual device. I can get the BTB range of triacs quite easily, would one of those be suitable as a substitute for the Q4004F42?

 

[MrAl]

Hi there,


They have that part at Digikey, so you could do a search for that.
It's a 400v, 4A triac, but triacs gate specifications vary quite
a bit so i would try to get the exact part unless you feel like
looking up the specs and trying to find a match with a different
part number.

 

[Phiyedough]

Thanks for the reply, Mr Al. I don't mind looking at specs but I don't know which parameters need to be matched to get a satisfactory equivalent. I'm in UK and did look at the UK part of the Digikey site but it looks like I would have to buy 500 triacs I tried to give a link to the Digikey site but apparently that is against the rules

 

[MrAl]

Hi again Phi,


You have to match the max current, max voltage, and the gate current for
all four quadrants. The gate current spec varies wildly so you have to be
careful there and check each quadrant. Of course if you are doing a
repair and not a new design you have to match the package type too
or it might not fit into the exisiting product without massive mechanical
modification

I found what looks like a cross reference: NTE5629
which Mouser carries. You could try there or call Digikey and see if they would
part with a quantity of 1 piece.

BTW, what is the shipping price from USA to the UK? I ask in case i can
get one myself, but in the past i had problems mailing to various places
in the world. For example, i was mailing a special serial port AD converter
chip to Australia, and found that the shipping was high for priority, but
only about 2 bucks for first class, but the guy would have to pay me in
US dollars (USD) because my bank charges 50 dollars for conversion from
AU dollars to US dollars. I ended up sending it for free or it would have
cost me 40 dollars for conversion ha ha.

 

[Phiyedough]

Thanks again, the NTE5629 also seems to be hard to get over here but I can get a BTA08-800C from Farnell. It is a 600V 8A device but it seems to have the correct 25mA gate currents. I was hoping to be able to get something from Connect Distribution as I order from them about twice a week. They have one they list as BTA08-400C-ST which might be OK but I don't know what the letters ST signify.

 

[MrAl]

Hi again,


Well, when i look up the specs on the NTE part i see that it has a gate drive
current of 3ma max. This is much different than a typical triac that has a gate
drive spec of 25ma for three quads, and higher for quadrant 4. These kind
of triacs are often called "sensitive gate" triacs, and are used when the
drive circuit can not put out the normal gate current that a regular triac
needs.
Because of this, i would suggest looking up 'sensitive gate triacs' and see what
you can find that is 400v and 4 amp if that's what you need.

There is a chance that the data sheet isnt right i guess, so if you do order
that 25ma gate triac and it doesnt work at least you would have an idea
why it doesnt work. If it doesnt work then most likely the drive circuit
can not put out more than 5ma or so, so you will have to go with
a sensitive gate triac.

 

[Phiyedough]

I fitted the BTA08/400C triac from Connect (The ST bit must just be the manufacturer as it was not marked as part of the number). The massage device speed control now works so it must be a good enough match

 

[MrAl]

Hi again,


Oh that's great news. Glad you got it working again.
Good luck with it.