BT139-600G Triac Equivalent

Rob Jarratt robert.jarratt at
Sun Dec 17 13:07:34 CST 2017

Thanks Peter,

Now that you mention it, I have heard that these triacs get used in the auto
voltage detection. I was about to reverse engineer the schematic and that is
now my next step. I would still like to identify possible replacements
though in case I ever need spares for this part.



> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at] On Behalf Of Peter
> Coghlan via cctalk
> Sent: 17 December 2017 13:25
> To: cctalk at
> Subject: Re: BT139-600G Triac Equivalent
> >
> > I have a suspicion that this component may be faulty on the input side
> > of my
> > H7826 PSU. A little tester I have does not recognise it, it is
> > possible that the currents it uses are too low for this particular
> > triac, but I am not sure.
> >
> What is the function of this triac in your power supply?
> I have come across a triac which is used to switch between 115V and 230V
> input in the PSU of a DEC 3000/300.  My triac went short circuit which
> some release of magic smoke when the PSU was used on 230V.  I also had
> difficulty finding a replacement for it so I ended up leaving it out.  The
> worked fine on 230V only without it once I replaced the other damaged
> components.
> If your triac has a different function, ignore the above.
> Regards,
> Peter Coghlan.

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