Phono Stage Diffficulty SX-737

Panamafred

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After months of enjoyment and recently replacing output transistors I have encountered a new problem with my SX-737.:sigh:

Was listening to music minding my own business when all of a sudden left speaker just totally goes to a windy scratchy noise. Sounded almost like a microphone picking up wind sounds. The music was barely audible through this noise.

Left speaker only suffers this condition when input is turned to "phono", and when speakers are both plugged into A as well as B. Even with the turntable disconnected from the receiver this noise persisted in the one channel, so it must be in the receiver.

Note: after leaving receiver off for a few minutes I was able to get both speakers to work fine for about 30 seconds untill noise returned:tears:

Any ideas?
 
Phono transistor let loose. 2sa725, they do that...

we have a list of pre-emptive replacements in the unit, that will "get it over with, once in and out"
and they (2sa725, 2sa726, 2sc1451, trimpots, then 2sc1312 and 2sc1313) are at the top of the troublemaker list.


recap/rebuild parts list:
http://www.audiokarma.org/forums/showpost.php?p=6414212&postcount=5

for convenience (mouser.com) :
AWF011 PHONO
AWF011 c1 1 25 cssa 647-UKL1H010MDDANA
AWF011 c2 1 25 cssa 647-UKL1H010MDDANA
AWF011 c7 330 6 cea 647-upw1c331mpd
AWF011 c8 330 6 cea 647-upw1c331mpd
AWF011 c11 3.3 25 ceanl 647-UKL1H3R3MDDANA
AWF011 c12 3.3 25 ceanl 647-UKL1H3R3MDDANA
AWF011 c17 100 25 cea 647-UPW1H101MPD
AWF011 c18 220 16 cea 647-UPW1V221MPD
AWF011 Q1 2sa725 512-KSA992FBU
AWF011 Q2 2sa725 512-KSA992FBU
AWF011 Q3 2sc1313 512-KSC1845FTA
AWF011 Q4 2sc1313 512-KSC1845FTA
AWF011 Q5 2sc1313 512-KSC1845FTA
AWF011 Q6 2sc1313 512-KSC1845FTA

$3.49 at current prices, all in stock...

Have you replaced the 2sa726's in the control amp and the power amp, as well as the Fuji 2sc1451 's in the power amp along with the adjustment trim pots?

IF NOT, STRONGLY consider doing them and the protection board while you are in there - WHEN - NOT IF - the 2sc1451's cut loose, they will take the outputs with them. The replacements are already in the list on that post.
 
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Wow, thanks for the informative reply. Is the link you gave me the "once in once out" list, because that looks pretty intense to me.
I am confident I can replace a few transistors though, maybe you could direct me to the trouble makers list? Thank you so much for the help
 
Fred. The "ALL INCLUSIVE LIST" is broken down to boards. It looks formidable, but when you break it down to boards it's not bad. But get the whole thing and then separate the new parts down to individual boards. The caps are 40 years old and were really good for about 20 years or so. It's surprising at times that these units are still running, as I don't think PIONEER really thought about 40-50 years down the road.

Listen to Mark. When (not IF) one of the trouble children start acting up the rest will get into the act. Best to just dig in and go for it. It's cheaper this way as you pay shipping only once, and have all the parts in hand. It's a proven list. I did mine last year with it and it's run hard and put away wet (so to speak) with no problems at all.

The 2sa725,2sa726, and 2sc1451's are the worst of the lot, causing all kinds of problems. The trimmers are old and weak with the possibility of the wiper lifting and then you blow the output transistors. The 1312's and 1313's just go bad. It's inevitable that they will go bad. And it's about that time. Think of it as a 100,000 mile overhaul.

Get the parts and then take it one board at a time. If you get stuck HOLLER!!! We'll be here to catch you.

Larry
 
A journey is intimidating, but it is taken one step at a time.

As long as you can successfully replace one transistor and one capacitor, you have the essentials to conquer the whole job.

as for the "trouble makers list", I NAMED them already, the worst of the worst is the small list in one sentence. find it's members in the bigger list. The bigger list is ALSO trouble makers.

The detraction of doing piecemeal corrections is that repeated flexing of wires and desoldering / resoldering causes damage, and soon you will be spending as much time if not more fixing that damage, as fixing the faults that bring you back in there time after time.
 
Okay Okay you guys have talked me into it. Now I have an excuse to inhabit my basement workshop for a while. :banana:

I am going to start slow and replace the "2sa726's in the control amp and the power amp, as well as the Fuji 2sc1451 's"

In addition I'm going to order this list which I presume is what I need to get the phone up and running:
AWF011 PHONO
AWF011 c1 1 25 cssa 647-UKL1H010MDDANA
AWF011 c2 1 25 cssa 647-UKL1H010MDDANA
AWF011 c7 330 6 cea 647-upw1c331mpd
AWF011 c8 330 6 cea 647-upw1c331mpd
AWF011 c11 3.3 25 ceanl 647-UKL1H3R3MDDANA
AWF011 c12 3.3 25 ceanl 647-UKL1H3R3MDDANA
AWF011 c17 100 25 cea 647-UPW1H101MPD
AWF011 c18 220 16 cea 647-UPW1V221MPD
AWF011 Q1 2sa725 512-KSA992FBU
AWF011 Q2 2sa725 512-KSA992FBU
AWF011 Q3 2sc1313 512-KSC1845FTA
AWF011 Q4 2sc1313 512-KSC1845FTA
AWF011 Q5 2sc1313 512-KSC1845FTA
AWF011 Q6 2sc1313 512-KSC1845FTA

and if I can replace all that without electrocuting myself or permenantly damaging the receiver I will dive in and do the rest of it.

also, what do you mean when you say : "adjustment trim pots" which part number is that?
Please advise and I will go ahead and order these parts!
Thanks for the support, I'm really excited about this project!
 
sigh
decoding / prioritizing the list for the power amp:
AWH033 pwr amp
AWH033 c1 0.33 25 cssa 598-DSF050J334
AWH033 c2 0.33 25 cssa 598-DSF050J334
AWH033 c7 220 6 cea 647-UPW1E221MPD
AWH033 c8 220 6 cea 647-UPW1E221MPD
AWH033 c9 47 35 cea 647-UPW1H470MED
AWH033 c10 47 35 cea 647-UPW1H470MED
AWH033 c19 22 10 cea 647-UPW1a220mdd
AWH033 c20 22 10 cea 647-UPW1a220mdd
AWH033 vr1 100 652-3386H-1-101LF <<<<<
AWH033 vr2 100 652-3386H-1-101LF <<<<<
AWH033 vr3 10k 652-3296P-1-103LF <<<<<
AWH033 vr4 10k 652-3296P-1-103LF <<<<<
AWH033 q1 2sa726 512-KSA992FBU
AWH033 q2 2sa726 512-KSA992FBU
AWH033 q3 2sa726 512-KSA992FBU
AWH033 q4 2sa726 512-KSA992FBU
AWH033 q5 2sc1451 512-KSC3503DSTU
AWH033 q6 2sc1451 512-KSC3503DSTU
optional
AWH033 q7 2sd357 512-KSC2690AYS
AWH033 q8 2sc357 512-KSC2690AYS
AWH033 q9 2sb527 512-KSA1220AYS
AWH033 q10 2sb527 512-KSA1220AYS
output transistors, only if needed as replacement parts
AWH033 q11 2sd370 863-MJ21194G
AWH033 q12 2sd370 863-MJ21194G
AWH033 q13 2sb530 863-MJ21193G
AWH033 q14 2sb530 863-MJ21193G
 
Alright, just ordered the complete phono list, as well as all of the problem children you guys have pointed out. If this goes well I am going to redo the whole thing, I love this amp!

Hope everything gets here soon, thanks for the help and encouragement, you'll be hearing from me!
 
Fred; Download the datasheets for all the transistors you order. On each Datasheet will be a pinout and a drawing of the transitor with the pins labeled. They will be different than the original transistors. Make sure you understand which pin is which and which hole corresponds to each pin. 6 ways to install them, only one is correct. A little study will prevent AW SH**'s, and letting the smoke out. There is a good thread here.... http://www.audiokarma.org/forums/showthread.php?t=43186 on testing and installing transistors. Pay particular to post #11.

It's not as easy as it looks, but once you get the drift, it's not hard.
 
replacement transistor installation

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


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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?:


80px-BJT_PNP_symbol.svg.png


80px-BJT_NPN_symbol.svg.png


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.



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-----------------------------------------------------

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....
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and two transistor layouts, ebc and ecb with the same triangular target hole arrangement
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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

attachment.php


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


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Thanks for the helpful info Mark, I've more or less been piecing all of that info together after opening the amp up and noticing the pnp/npn symbols next to the transistors... :scratch2:...I thought that would make way to much sense to print that on the board, but hey sometimes things just work out. Good to know the data sheets for each transistor are readily available, now as long as they arrive in labelled bags I think I can manage!

Questions:
1. Most of these capacitors can go in either way right?
2. In regards to the pots on the power amp, is there any notation similar to the transistors? It looks like there are a few leads coming off of these.

It took a five page thread for me to replace the output transistors back in May, I'm gonna shoot for under three pages this time! Thanks for all the help!
 
only a FEW of the caps can go in either way.

those "either way" ones will be VERY different in appearance and will be 0.1 to 1.0uf and have DSF or ECQ part numbers

The UPW and UKL caps ARE polarized.

do one at a time, and as you remove each one, check that the polarity of the cap and the markings on the board agree. If they don't - go with what was factory installed and make a note of it.
 
Here's an example of a POLARIZED ELECTROLYTIC. Note the stripe on the side. That will designate the NEGATIVE (-) side. These can be had in Radial and axial configurations. NOTE on an axial the stripe will have an ARROW to denote the NEGATIVE SIDE. These are generally valued above 1uf but there are some values below 1uf. If you have any sub-1uf caps, best to substitute film caps for them. (for example .33uf 25v)

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Here's an example of a NON POLAR/BIPOLAR Electrolytic. It has NO STRIPE, but in most cases it will have BP (BIPOLAR) on the side. These are also available in Radial and axial configurations.

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And finally a non polar Film. This is a Cornell Dublier DME. Orange Drops are similar in shape as are the ECQ caps. They come in RADIAL, and AXIAL lead configurations. This one is Radial. Values are generally less than 1uf but some can be had in values higher than 1uf but size grows exponentially.

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Thank You Larry.

when I do the "everything" thread, a lot of your posts are gonna get quoted (with FULL credit!!)
 
Hey, I'm just backstopping the GRAND SENSEI, with graphics and info.
 
I'm just backstopping the GRAND SENSEI,

If neither of you are the grand sensei then........

I really appreciate all of this info and am growing more and more confident as the shipment from mouser approaches. The last grey area I have left are vr1-4 on the power amp.
 
:banana::banana::banana:
:music::music:
:yes:

Just wanted to say, thanks ALOT! Phono board is totally redone, will be moving on to Power Amp next,
all the sounds that are supposed to be there are there
and those that arent, arent!

This really wasn't that tough once I got inside and plugged the soldering iron in. Thanks again!
 
Make sure you read and understand the thread(Link HERE) on setting the idle current and the bias. The Manual is wrong. Yell if you have problems with it.
 
Sorry I've been absent from this thread this week, I'm getting married this weekend and have not had the time to really work on this project.

Before I adjust the idle current and bias I think I need to replace vr1-4, right?
I can't figure out how these go in-
the legs are labeled 1,2,3

Here are the links to mouser so you could access the data sheets if you wanted:

http://www.mouser.com/Search/Produc...virtualkey65210000virtualkey652-3296P-1-103LF

http://www.mouser.com/Search/Produc...virtualkey65210000virtualkey652-3386H-1-101LF

Based off the symbol on the schematic I'm pretty confident that I know where the leg labelled as "2" goes, (represented as an arrow) but the other two legs are shown as identical squiggly lines.

Are these legs 1 and 3 interchangeable?

Thanks a lot for all the help so far, can't believe what I've accomplished, ordering the rest of the parts to do a total re-do of the inside once I return from my honeymoon.
Thanks!
 
Print out a copy of page 47 of the manual. Practice on this a couple times 1st.

Legs' 1 & 3 are interchangeable. Look at the board (AWH-033) drawing. Find all 4 VR's. They are pretty much in a line across the board. Note that the legs are set in a triangular way, with Pin 2 by itself. The 100ohm pots are set up the same as the board. The 10K pins are in a line. With the pin markings on the 10K pots facing you, bend 1 & 3 toward you, and pin 2 away from you. Make a 2nd bend to allow them to go in the holes. PIN 2 goes in the hole that has the "ARROW" on it. This is the wiper that goes across the resistive element.


!!!!NOTE!!!!:
VR3 and VR4 pins are oriented "upside down" on the board from VR1 & VR2.

MARK WITH A SHARPIE, the side of the pot that the end of PIN2 is pointing to or at. (Orientation trick).
Mark the ACTUAL BOARD with the location of PIN 2 for each VR. A dot will suffice.


Orient the drawing the same way as the actual board. Which ever set of board edge pins are UP, have the same drawing pins UP. Punch some small holes in the board drawing so you don't bend the pins on the pots. Practice orienting and inserting ALL of the pots a couple times. Once you get comfortable with the orientation of each, insert them one last time on the drawing, remove the original from the actual board (keeping the same board orientation as the drawing) and replace it with the new one. Do this for all of them.


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