silicon controlled rectifier Q10 (CR400Y) equivalent?

[macclassic]

I am following Larry Pina's guide to repair a Mac Plus analogue board power supply, page 23, but I cant find a silicon controlled rectifier Q10 (CR400Y) or an equivalent on Mouser???

 

[cheesestraws]

I can't find a CR400Y but there seems to be quite a lot of other CR400 family SCRs out there or equivalents thereof.  Do you have a photo of the component itself?

 

[macclassic]

Yes attached, only Larry's drawing locates Q10 where Q11 is and vice versa?

 

[cheesestraws]

Hmmmm.  As far as I can see, a C3153 is a transistor not an SCR.  What does Q11 look like?

 

[macclassic]

This

 

[cheesestraws]

Well, a 2N3906 is also a transistor not an SCR, so unless I'm very much confused, you perhaps have a different analogue board to the one the book is referring to?  I am rapidly leaving any area I can even remotely pretend to be competent in here, though...

 

[macclassic]

Ha, Ha, I will double check the page

 

[cheesestraws]

I just noticed you're in the UK (like me)—I believe the analogue boards over here are different from the US ones (presumably for different voltage?), so...  if you like when I get home I can open up one of my Pluses and compare notes.

 

[macclassic]

It seems that The Dead Mac Scrolls doesn't refer to the Plus specifically, and doesn't say much about INTERNATIONAL boards.

The  Macintosh Upgrade & Repair Secrets, also written by Larry Pina, does mention INTERNATIONAL boards in Chapter 6 "Dead Sets" (which is the problem my Plus has, intermittently) yet it still only shows the layout of the the US board, as shown, with the positions of Q11 and Q10 in opposite places to the INTERNATIONAL boards.

So I'm going to follow this book instead.

And finally, my board has the following message printed along the bottom shown in the last image

 

[macclassic]

Doh!,  The spec for component Q10 on the International Mac Plus analogue board was in Addenda D of The  Macintosh Upgrade & Repair Secrets all the time, I just had to find it by using the lesser known skill of "reading"  :blink:

 

[cheesestraws]

Doh!,  The spec for component Q10 on the International Mac Plus analogue board was in Addenda D of The  Macintosh Upgrade & Repair Secrets all the time, I just had to find it by using the lesser known skill of "reading"  :blink:

So yup, Q10 and Q11 there are transistors (T-NPN and T-PNP on the list on the right).  The CR400Y SCR is Q12.

 

[macclassic]

That too! but I have lost a lot of sleep lately.

 

[cheesestraws]

Oh, I really know that feeling.

 

[cheesestraws]

This thread may be useful:

 

[macclassic]

Thanks for that, but thankfully replacing the resistor at R55 solved my intermittent "no bong and black screen" issues