I am new to electronics and these SCRs so they are called seem to be hard to find. I would rather not screw up the whole attempt, so I am here wondering if anyone can give insight as to A).Will a S2055M replace? B).If not, why? It seems some people are unsure if NTE5539 is truly equivalent because of its 400V whereas the S2055M would be my choice being that it is a 200v.

A little info these are used to drive the wire feed in a welder (to lessen the V headed there?), there is a thread mentioning them in a battery charger by the same company that seems to have never been finished.

Any insight is and will be greatly appreciated since this welder seems to have found a corner in my shop.

 

Maybe these sites will help you.

This one shows that the STMicro BTW69-600 is a direct replacement http://www.cross-parts.com/news/html/2008111818/0000054538.html

This is STMicro's web page for that type of SCR. And it shows that the part is an "active" one still being made. http://www.st.com/en/thyristors-scr-and-ac-switches/btw69.html

 

Check out Digikey, there are a few options.
e.g. CLA50E1200HB-ND
Max.

 

Maybe these sites will help you.

This one shows that the STMicro BTW69-600 is a direct replacement http://www.cross-parts.com/news/html/2008111818/0000054538.html

This is STMicro's web page for that type of SCR. And it shows that the part is an "active" one still being made. http://www.st.com/en/thyristors-scr-and-ac-switches/btw69.html

Understood, I actually saw that particular part my question there is why would I replace a 100v 55A scr with a 600v when it seems the s2055m would be more equivalent.

 

Mind you the s2055m is available I just don't understand why I would choose the 400v vs 200v replacement. Looking at the electrical specifications in a teccor datasheet (SCRs 1-70A) the s1055m and s2055m only seem to differ at the 2055's "Repetitive Peak Off-State Forward and Reverse Voltage" 200V

 

NTE products are all sold as replacements for repair, not as OEM components. All are intended to be "at least equal" to the parts they are said to replace. A 400 volt part will replace a 200 volt part provided there is compatibility with critical specifications. For an SCR, trigger current, hold current, maximum rate of voltage rise, etc. are important. The higher voltage part costs a little more, but NTE stuff is typically much more expensive anyway.

What I question is why one would want a 55 A SCR for a wire feeder, unless we are talking about a huge automatic welding machine. But if the same company uses the 55 A part in something else, they may have just decided that reduction in inventory is worth it even if the cost of the goods is a little higher.

 

So my idea of a s2055m as a replacement is fine, I'll order them today. Also it does seem peculiar, in this welder these are used I think to knock down excess A or V to drive a small by comparison motor slowly. I am also replacing an MOC3021 optocoupler which I have been told could be a culprit.

 

So my idea of a s2055m as a replacement is fine, I'll order them today. Also it does seem peculiar, in this welder these are used I think to knock down excess A or V to drive a small by comparison motor slowly. I am also replacing an MOC3021 optocoupler which I have been told could be a culprit.

Thank you guys so much! I have literally the exact same issue!!!!! I tested each of the SCR's (Out of circuit of course) and it appears they are ALL dead, and two are complete shorts. It appears the S2055M is now obsolete, so I'm going to use a S4055M, and since I saw your recommendation, I also will replace the opto. I had a resistor turn to powder too, and if anyone ever reads this or cares, it is a 100Ohm 1/2Watt 5%. So free welder, 50 bucks in parts, should be all fixed up, and I save something from the trash heap!

Thanks again, I created this account to just to post this

-James

 

Most SCRs are equivalent to each other. There are three parameters to check:
Blocking voltage (choose the same or higher)
Maximum current (choose the same or higher)
Gate current - look for one that the same or slightly lower. You don't want one that's too sensitive or it might trigger when it's not supposed to.
All the SOT223/TO220/TO247 package devices have the gate on the right and the cathode on the left.
IF you test with a meter, it should look like a diode between gate and cathode.
When they fail, they almost always fail short circuit.

 

Check out Fairchild AN-3006 also AN-3003., for circuits and components

 

Most SCRs are equivalent to each other. There are three parameters to check:
Blocking voltage (choose the same or higher)
Maximum current (choose the same or higher)
Gate current - look for one that the same or slightly lower. You don't want one that's too sensitive or it might trigger when it's not supposed to.
All the SOT223/TO220/TO247 package devices have the gate on the right and the cathode on the left.
IF you test with a meter, it should look like a diode between gate and cathode.
When they fail, they almost always fail short circuit.

But if two of the 8 are direct shorts, there is a fair assumption the rest are toast too, correct?

 

Check out Fairchild AN-3006 also AN-3003., for circuits and components

Thanks for the info, I already ordered the others, they claim to be compatible, am I wrong?

 

If they are equivalent it should be OK.