Yep. The new one's are bipolar film caps. The tantalums are the audio gear equivalents of IED's. So we replace them with Film caps. They go in either way.
Pioneer SX-636 left ch. low
- Thread starter dukeofurl
- Start date
dukeofurl
Active Member
Finally managed to spare a couple hours today to recap the AF Amp Assembly (AWK-035-0). - All seemed to be good.
Got to the transistors Q1: 2SA726: 512-KSA992FBU and Q2: 2SA726: 512-KSA992FBU for the last 2 things to go in.
The sound is now very low. - white (or is it pink) noise becomes apparent when I turn the volume totally down.
Is it possible that the transistors are not put in correctly? (I put them back like the originals) .... is the layout of the new ones different from the originals, perhaps?
Got to the transistors Q1: 2SA726: 512-KSA992FBU and Q2: 2SA726: 512-KSA992FBU for the last 2 things to go in.
The sound is now very low. - white (or is it pink) noise becomes apparent when I turn the volume totally down.
Is it possible that the transistors are not put in correctly? (I put them back like the originals) .... is the layout of the new ones different from the originals, perhaps?
You got them in wrong. Pinout on the new ones is E-C-B, with the FLAT facing you and the legs pointing down. E= Emitter, C= Collector, B=BASE. Not all are ECB. Some are EBC, BCE, CBE. There are 6 ways to install a transistor, but only 1 way. DATA SHEETS are available on the ordering sites provided you are using Mouser, Digikey, newark, etc. Otherwise look up the manufacturer's site and download from there.
Read this thread on how to identify which leg goes where and how to test them. Pay particular attention to POST #11. There are some good graphics that you might want to print out (highly recommended you do!) http://www.audiokarma.org/forums/showthread.php?t=43186
Read this thread on how to identify which leg goes where and how to test them. Pay particular attention to POST #11. There are some good graphics that you might want to print out (highly recommended you do!) http://www.audiokarma.org/forums/showthread.php?t=43186
dukeofurl
Active Member
Yep, I feel stupid. Didn't notice the original orientation of the legs (same as the replacements) but now I have a recapped preamp section that works!! 
Time to button the front end up and proceed to the power supply.
Thanks for your ongoing help!! Oh, and the link about transistors was SO helpful!
Time to button the front end up and proceed to the power supply.
Thanks for your ongoing help!! Oh, and the link about transistors was SO helpful!
It's a rite of PASSAGE around here. Damned near everyone has done it at least once. The 1st time we won't laugh or get on you too hard. But anything after that, and you're FAIR GAME! Just watch out for that 600# gorilla Mark the Fixer has tied up in his back yard.
The gorilla? The neighbors kept confusing the two of us, so I traded him for the hounds of hell.
I'm sorry you fell prey to the assumption, we do TRY to stress that the replacements at times are NOT exactly like the originals... And provide the correct pinouts in the posts that carry data on the transistors.
like this:
512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 300-600hfe $0.17 ea
512-KSC1845FTA (ln)to-92 ecb 120v .05a .5w 100mhz 300-600hfe $0.05 ea
get the data sheet for the transistor from the seller,
Use the symbol silk screened onto the board.
These are your two guideposts.
I'm sorry you fell prey to the assumption, we do TRY to stress that the replacements at times are NOT exactly like the originals... And provide the correct pinouts in the posts that carry data on the transistors.
like this:
512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 300-600hfe $0.17 ea
512-KSC1845FTA (ln)to-92 ecb 120v .05a .5w 100mhz 300-600hfe $0.05 ea
get the data sheet for the transistor from the seller,
Use the symbol silk screened onto the board.
These are your two guideposts.
every Mouser transistor has a data sheet available for download.... download them and look them up. then install as per the symbol printed on the pc board at that location.
never ever use the original transistor to determine how the replacement will go in.
from an earlier post:
First you need to learn about what the three transistor leads are about, and identifying which is which and where it goes according to the symbol. Then you will see that my parts list include lead arrangements - which assume the transistor lettering (and flat) are facing you and the leads are facing down, then go left to right.
Q13 2sc938 150v 0.05a 0.6w
512-KSC2383YTA to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17
The big TO-220's with the metal mounting plate are hard to reverse, but the smaller ones are, but my specified replacements are usually E C B as a rule of thumb BUT we ALWAYS CHECK...
But you really should start here and follow ALL the links...
http://www.audiokarma.org/forums/showthread.php?t=331932&page=5
here's a preview, DO YOU SEE these symbols on the boards you are working on?:
e is always the arrow on one angled line (direction can be out (npn) or in (pnp) towards the base)
b is always the flat line the other two lines come out if at an angle
c is always the angled line without the arrow
letters can be smudged or illegible, while the symbols are hard to mistake and pretty language independent
pioneer doesn't use letters, if there is a symbol. sometimes in a linear hole arrangement, there is only an 'e'.... with no room for a symbol.
-----------------------------------------------------
now a quick lesson on installing a small transistor in a traditional triangular hole arrangement with a symbol printed in the center of the triangle
1. find the LEFTmost lead on the package and identify it's designation (emitter? base? collector?)
2. look at the symbol on the board, find the corresponding hole
3. insert that lead into that hole
4. find the RIGHTmost lead on the package and identify it's designation (emitter? base? collector?)
5. look at the symbol on the board, find the corresponding hole
6. insert that lead into that hole
7. the center lead will now need to bent forward or back to go into the leftover hole.
DON'T THINK "WHERE IS THE FLAT FACING"
think
"outside leads" and THEIR holes...
this one's ecb....
and two transistor layouts, ebc and ecb with the same triangular target hole arrangement
well, you do need to get the parts, first....
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...
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
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
Last edited:
Keep 'em inside during Full moon.
dukeofurl
Active Member
Excellent post(s), thanks again gents!
I've now finished the power supply. - All went well.
Moving on to the power amp (AWH-034-0).
- Regarding the KSA992's, I suppose that these want to be matching, correct? - Q1 through Q4. - Where do the matched pair go? (Q1 & Q2 or Q1 & Q3)
Also, I see that the originals, in my amp are A763 (also stated on the schematic) and the "shopping list" shows:
Q1-Q4 as 2SA726: 512-KSA992FBU, is this correct? (ie: the difference between A763 and 2SA726).
I've now finished the power supply. - All went well.
Moving on to the power amp (AWH-034-0).
- Regarding the KSA992's, I suppose that these want to be matching, correct? - Q1 through Q4. - Where do the matched pair go? (Q1 & Q2 or Q1 & Q3)
Also, I see that the originals, in my amp are A763 (also stated on the schematic) and the "shopping list" shows:
Q1-Q4 as 2SA726: 512-KSA992FBU, is this correct? (ie: the difference between A763 and 2SA726).
50V won't hurt anything. The originals were rated for 35V. Pioneer did substitute higher voltage caps without making notice in the manuals (if they ran outof 35V caps, for example). Use the 35V replacements. There's 14.4v or so on the cap, so it's not a problem with a 35V.
The parts list shows the the 763 as primary with the 726 and the 640 as secondary and tertiary subs). Usually it's the 726 as the primary with the 763 2nd and 640 3rd. In any event replace with the 992's.
Q1&3 are paired, and Q2&4 are paired.
The parts list shows the the 763 as primary with the 726 and the 640 as secondary and tertiary subs). Usually it's the 726 as the primary with the 763 2nd and 640 3rd. In any event replace with the 992's.
Q1&3 are paired, and Q2&4 are paired.
dukeofurl
Active Member
Well, I've finally got a free day (today) to finish everything.
Got the bias sitting nice at 20mv and it "seems" to be working well enough.
One thing that is odd is that when I power the receiver down, the right channel has a little static-like noise (low-ish) and seems to last around 20-30 seconds. - Like a slow discharge? - Any ideas?
Got the bias sitting nice at 20mv and it "seems" to be working well enough.
One thing that is odd is that when I power the receiver down, the right channel has a little static-like noise (low-ish) and seems to last around 20-30 seconds. - Like a slow discharge? - Any ideas?
You could, but i get mine from WJOE.com. Less expensive in lots of ten. And shipping is usually less too. http://www.wjoe.com/all_lamps.htm Get the GF670. 8V 250ma. Then replace all of them.
Without going thru the whole thread again.......did you replace the Main Filter Caps (6800uf/35V) ? Sounds like one of them may be on the way out. It shouldn't take more than a few (3-4) seconds for the sound to bleed off from the caps discharging. With new caps it's almost instantaneous.
647-UVZ1J682MRD 6800uf / 63v Nichicon. It's about 40% of the size of the original. Either use some spacer material between it and the clamp, or gut the original cap and restuff it with these. This is what i used in my 737.
Last edited:
dukeofurl
Active Member
No, I haven't replaced those, although I did ask earlier on.
I'll create another order.
dukeofurl
Active Member
dukeofurl
Active Member
Would any of these work? - Any one better than the other?
http://www.mouser.com/Nichicon/Pass...pxZ1z0j7ks&Keyword=6800uF+63V+Snap-In&FS=True
http://www.mouser.com/Nichicon/Pass...pxZ1z0j7ks&Keyword=6800uF+63V+Snap-In&FS=True
