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SX1010 Transistor orientation

S

Smwilli

Well-Known Member
I've got the pinouts for the new transistor replacements as found on a sx1010bom list. The replacement pinout is easy, as the data sheets show a 3-D image of the transistor. Problem is reading the SM for original transistor lead orientation. I can't tell if I'm looking at the bottom/top or front/back of the transistors as shown in the SM. Here are the pics for:

2sa726
2sc1451
2sd313+2sb507
2sc869
2sa628a
2sc1384

I'm sure some are shown each way, because some of the images have solid lines, others dotted. Thanks for any help!
 

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The manual can be wrong. The key is that Pioneer silkscreened the PC board with collector, emitter, and base symbols, so if you're replacing a transistor we don't really care what the pinout of the old part is, as long as we know the pinout of the new one.
 
Hmm...Well, I'll go by the board then. Wasn't sure if they were sometimes mis-silkscreened like the + - symbols on some sansui boards.
 
This might help, but the LETTERS are not usually on the board. The to-92 and to-126 transistors on that list are all ecb, leads down, left to right, lettering facing you:
NOTE the direction of the arrow!!!
pnp, in, 2sa,2sb,ksa,ksb
npn out, 2sc,2sd,ksc,ksd

When there's doubt, LOOK AT whatever other components are connected to that pad's trace... But I haven't run into any of that crud on the 1010 amp boards, and I just did some recently...
(and I/we check the silk screen before pulling the original one, assuming that if it worked from the factory, everything was correct.)

markthefixer said:
well, you do need to get the parts, first.... :D

and when ordering the transistors, mouser has links to the transistor's data sheets, DOWNLOAD the data sheets!!! THEY are your BEST guide as to the correct lead connections for THAT particular transistor.

Do you understand the transistor symbol? enough to identify the emitter, base and collector from it? Because most boards (Pioneer) have the symbol printed on it, with holes around it, and it is orientated so there is an emitter hole, a base hole and a collector hole. And obviously, only the transistor's emitter goes into the emitter hole, the base into the base's hole and the collector into the collector's hole. IF you want it to work... :D

oh, and by the way, the symbol usually DOESN'T have the E, C and B letters ON on it... :stupid:
there are two flavors,
pnp: arrow pointing in, 2sa,2sb, ksa, ksb part number prefixes
npn: arrow pointing out, 2sc,2sd,ksc,ksd part number prefixes

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hint: if "rotating" it in your mind is a puzzler, orient it in the hole this way(transistor hole arrangements are usually triangular):

choose the leftmost lead, use the data sheet to identify it... for example it is the emitter
put it in the emitter hole

choose the rightmost lead, use the data sheet to identify it... for example it is the base
find the base hole, rotate the transistor line of leads around the inserted leftmost lead to point at the base hole
put the rightmost (base) lead in the base hole.

the THIRD hole is now either in front of or behind the transistor, in this example the collector is "left over"
bend the center lead forward or back to go into the hole.

easy...

notice that this example had the lead order of emitter, collector, base which is a common lead arrangement

that means that:

looking at the transistor, with the leads pointing DOWN, and the flat part (or lettering in the case of some zetex transistors) FACING YOU
going from left to right has the lead order of emitter, collector, base
Click to expand...

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Thats what I just did. I wrote downthe symbols for NPN and PNP along with the transistors designation on a print of the foil side of the board to reference. I really appreciate everyones help!
 
Just remember that the foil side will be 180* out when you are looking at the component side. That's what threw me when I did my 1010. I ended up replacing everyone of the transistors on those two boards. But when I got done, it was 1000% better than it was before the recap/re-transistor. I think Mark still cringes about that 1010 rebuild.
 
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