LaserwriterII NTX - fixing the AC Power block

#1 Wed, 3 Dec 2014 - 05:56

I have a couple of Laserwriters that I am working on and troubleshooting led me to the issue of a triac at q101 on the AC Powerblock (just under the fan).

Anyway - I have no idea how to uncover what to get for a replacement, here are the specs that I know:

1) Its a Mits with the following markings

BCR8DM

12L 87

2) my multimeter reports it as a PNP, CEB (no other value)

3) Here is a marginal picture of it, without the heatsink

Any suggestions for a replacement, or how to go about finding one of these - I have tried the obvious searches, but the closest I got were some partial matches on the numbers, no solid replacement.

#2 Wed, 3 Dec 2014 - 06:55

As far as I remember, a Triac is a pair of transistors tied together serially. The 12L 87, I believe is a Date Code.

Searching the Internet, I found a pin out:

http://www.pinout.net/element_browse.php?conid=40642

Specs (in .pdf):

http://www.alldatasheet.com/view.jsp?Searchword=BCR8DM

And it looks like it is no longer made, but there is a equivalent: NTE5638 TRIAC-400VRM 8A TO-220

http://www.weisd.com/test/GenericParts_WEISD_view.php?editid1=BCR8DM-8

I searched Newark.com following a false lead, some other forum said they had them, they don't but thy do have equivalents:

http://www.newark.com/webapp/wcs/stores/servlet/Search?catalogId=15003&langId=-1&storeId=10194&categoryId=800000005452&st=triac%20BCR8DM&pageSize=25&showResults=true&pf=810021709,810050159,810087357,811880813,811880814

DigiKey, Mouser, others should have equivalents as well.

#3 Wed, 3 Dec 2014 - 13:16

Triacs usually don't go bad unless they're shorted

#4 Fri, 5 Dec 2014 - 03:07

Thanks for the responses.

I'll let you know how it goes.

#5 Thu, 11 Dec 2014 - 04:31

I have a couple of lw ll that I am going to recycle. I can send you a power supply from one if you want

#6 Thu, 18 Dec 2014 - 04:30

That would be very helpful - pm sent.

Thanks oldappleguy