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Pioneer SA-8100 protection issue

Philsound said:
I was too optimistic...
After changing all small transistor on the right channel on the power amp board, the relay did not work.
I compared the 2 channels and the realized that I don't have any voltage on pin 23 on the amp board, nor on pin3 and 4 on the protection board.
I started to check the way of the 34v that is present on pin 16 (protection board), and found that after R14, I still have 34V but after R13, I only get 3.7V!!!
I've removed the resistor and they are both ok at15k....
I am lost again ...
Click to expand...

With zero volume, there SHOULD BE ZERO (0.000v +/- 0.020v) VOLTS on those pins!! Those pins are what are being adjusted TO 0.000v.

IGNORE the R13 and R14 voltages. I HOPE you did NOT change the AWM-027 (protection) Q3 and Q4 transistors. They are CORRECTLY reacting to their INPUT voltages on pins 2 and 4.

In fact, I have to infer that there IS (unacceptably high) VOLTAGE on pins 3 of the awh-022 amp board, and on pins 1 and 4 of the protection board BECAUSE the protection is not clicking the relay. WHAT IS that voltage? Pin 3 of the awh-022 amp board?

somehow in working on the right channel (awh-022 pin 23, AWM-027 pins 3 and 4) there probably was damage caused in the LEFT channel (awh-022 pin 3, AWM-027 pins 1 and 2).

You are "lost". You had better let ME drive....

I am NOT following my usual format of listing the EXPECTED voltages, you would be tempted to "take the wheel back".'

A reading of 34v is NOT acceptable, a reading of 34.0v IS acceptable. Strive for 3 digits of accuracy. 0.1v IS significant in some cases.

1. measure and report the awr-030 power supply voltages on pins 4,5,9,12,13,14,15,16,17,18,19

2. measure and report ALL voltages on the pins of the AWM-027 protection board - 1 through 17

3. measure and report ALL voltages on the pins of the AWH-022 amplifier board - 1 through 37

you think MAKING these readings is tedious, think about me EVALUATING them.
 
Thanks for your help; as I said, i was too optimistic...sorry.

So,i measured all voltages and it was not tedious, it is the minimum that i have to do, of course.

Power supply : AWR-030
pin 1 : 0.2mv
pin 2 : 0.5mv
pin 3 : -5.6mv
pin 4 : -38.2v
pin 5 : 38.4v
pin 6 : -7.1mv
pin 7 : 3.9mv
pin 8 : 5.6mv
pin 9: 51.2v
pin 10 : 0.0v
pin 11 : 0.0v
pin 12 : -41,10v
pin 13 : -23.60v
pin 14 : -17.14v
pin 15 : -13.07v
pin 16 : 12.93v
pin 17 : 17.48v
pin 18 : 24.20v
pin 19 : 34.00v

Protection board AWM-027
pin 1 : 37.00v
pin 2 : 37.00v
pin 3 : -2.5mv
pin 4 : -1.3mv
pin 6 : -13.1v
pin 7 : -0.3mv
pin 9 : 37.4v
pin 10 : 37.0v
pin 11 : -19.2mv
pin 12 : 22.1mv
pin 14 : 34.1V
pin 15 : 34.1V
pin 16 ; 34.2
pin 17 : 7.8v AC
one complementary information, i have 0.0v at the base of Q3 and 1.44v at the base of Q4

Power amp AWH-022
pin 1 : 37.4v
pin 2 : 37.7v
pin 3 : 37.5v
pin 4 : 0.0v
pin 5 : 51.9v
pin 6 : 22.5mv
pin 7 : -0.5mv
pin 8 : 0.0mv
pin 9 : 0.0mv
pin 10 : -0.2mv
pin 11 : -41.2v
pin 12 : -13.18v
pin 13 : 12.9v
pin 14 : -0.1mv
pin 15 : -41.3v
pin 16 : 0.0v
pin 17 : 0.0v
pin 18 : 0.0v
pin 19 : 0.0v
pin 20 : -4.3mv
pin 21 : 51.4v
pin 22 : 1.3mv
pin 23 : -1.6mv
pin 24 : 8.9mv
pin 25 : -21.8mv

pin 26 : 0.6v
pin 27 : 38.6v
pin 28 : 14.7mv

pin 29 : -0.63v
pin 30 : -38.9v
pin 31 : -22.4mv

pin 32 : 34.7v
pin 33 : -37.2v
pin 34 : 35.1v

pin 35 : 37.8v
pin 36 : 38.8v
pin 37 : 36.3v

Done !
If i am right, i realize that when i was thiniking that the right channel was wrong...in fact it was the left one that has a problem, no?

thanks again!
 
I don't know if it may help, but I've removed both Q11 and Q13 to test them and the relay is clicking when they are out of the board. They both passed the test analyzer and are ok.

Some more findings on the amp board:
40.2v at Q5 and Q7 collector,
40.6v at Q6 collector,
40.1v at Q6 emiter,
40.6v at Q11 base and collector and 8.0mv on emiter (all values measured on the board without Q11).
 
inductor said:
Mark-ever thought of asking for donations for all this work you do on behalf of people and their amps ?
Click to expand...

No, that would defeat the purpose - good karma!!!

If pressed, I used to (and still) say; donate to AK to keep the server(s) on the "air".


p.s. look UP at the stickies, (there's one with my name in the title..) when I was in deep Kimchee, AK'ers stepped up to the plate and swung for the bleachers. Other "good karmas" have happened that are not mentioned in any of the threads.

It started with an older Dell laptop of mine that relatives brought to the hospital, with a ventilator on/in I couldn't talk, so I needed it to communicate - even with people next to me, no less with AK.. THEN it died. (later after I was out, I got another hard drive which revived it - but at the time I was in no condition to troubleshoot, no less FIX it). The thread details what happened next.

OK back to our regularly scheduled program...
 
Philsound said:
I don't know if it may help, but I've removed both Q11 and Q13 to test them and the relay is clicking when they are out of the board. They both passed the test analyzer and are ok.

Some more findings on the amp board:
40.2v at Q5 and Q7 collector,
40.6v at Q6 collector,
40.1v at Q6 emiter,
40.6v at Q11 base and collector and 8.0mv on emiter (all values measured on the board without Q11).
Click to expand...

Please don't make it worse....

pulling transistors (what did you do about the outputs and the need for negative feedback to stabilize the amplifier channel?) is not the way to troubleshoot if you do not understand the circuit.

first the amplifier has 2sa726 and 2sc1451 transistors. They are VERY failure prone. They are automatically replaced, even on a good channel.
I replace them with:

(q1,q3,q7) 512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.07 ea
(q5) 512-KSC1845FTA (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.07 ea
and
(q9)512-KSC3503dstu to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe $0.28 ea
although
512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.40
might do in a pinch.

(q13)512-KSA1220AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.39 (R=60-120, O=100/200, Y=160/320)
(q11)512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.40

pay careful attention to the voltage ratings, I use the 1220A and 2690A transistors which have the 160v rating.

these or their substitutes will probably be harder to find. Some of the transistors intended for the driving of CRT guns in color TV's might be suitable.

I have not yet completely analyzed the voltages, but when I saw the 1451 and 726 transistors I knew exactly what had happened. It IS common. the 1451 has been failing in many different manufacturer's equipment.

It is now past dawn here locally and I saw the sunset, so I am now going to sleep for a few hours before I am back. I will look in then...
 
Mark, some good news.
I went again downtown, and bought what i found...none of the reference listed above were available but, searching in their equivalence book, they gave me :

2SA726 : BC557
2SC869 : BF422
2SA628A : BC556
2SC1451 : BF420
2SB527 : BD244C
2SD357 : BD243C

I replaced them all, except the drivers and...it clicked !!!
I can't really say which one was faulty as the replaced ones were ok when testing...!!

Thanks again for your support and time, and I really wish you a lot of great things, starting with a good health, for this new year.

I have learnt a lot with this amp in terms of methodology, starting with the power supply board, then the protection board and the amp board.
As you said, don't assume, check and recheck, that is the key.
 
that bf420 might be getting reallly hot, destructively so...

That's why a to-126 cased transistor was specified. For heat dissipation.

So, a search for a more heat tolerant transistor would be a prudent move. At least check to see if it gets very hot.
 
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Yes you are right, I do agree; I did not check if it was running hot or not.
It is working fine for now, sounding great, more than 50 hours of listening but not playing loud.
What would you suggest as a good replacement with an int'l reference (can't find here Mouser or Digikey, etc...)?
thanks,
 
2SC1451 : BF420
Click to expand...

(q9)512-KSC3503dstu to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe $0.28 ea
although
512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.40
might do in a pinch.
Click to expand...

answered already, see above specifications...
 
Hi, Can't get none of them, but after a long search, i found this one quite close in specifications but not the same case :
2SC1904 : ecb 150v. 0,05A. 1W. 130MHz.

Does it look good for you?
Thanks again
 
Thanks MarktheFixer (if you are still around) for the help in this thead.

I'm going to attempt my first repair on a SA-8100 I've picked up, it also goes into protection. I've got it open and doing a deox first, cleaning fuse contact points, checking for the easy stuff, the low hanging fruit.

Heh, I may be back in this thread (or another) asking for help, we'll see. I do have most tools and skills needed but haven't used them in this application before (or it's been so many years, it doesn't count).

I think it was this thread someone mentioned they couldn't get the relay out for cleaning but I've attached a pic... if you are play with the wires a bit, it can pulled out and twisted up for access.
 

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The first suspects to be replaced are the 2sa726 and 2sc1451 transistors in each amp channel. As well as the trimpots!!
THEN we measure the power supply and protection voltages, IF it isn't behaving.

MAKE AND USE a DBT. You are mucking around in prime DBT territory.
 
markthefixer said:
The first suspects to be replaced are the 2sa726 and 2sc1451 transistors in each amp channel. As well as the trimpots!!
THEN we measure the power supply and protection voltages, IF it isn't behaving.

MAKE AND USE a DBT. You are mucking around in prime DBT territory.
Click to expand...

Roger that! I've just built the DBT. Finished deox on the all the controls, cleaned relay and all switches. Cleaned fuses and fuse holders.

Turned the unit on, on DBT. Light is dark, unit goes in and out of protection at random intervals with no input.

Protection Board:
Voltage between pins 2 & 4 very jumpy, between 1v and occasionally 34 vdc!
Less than a volt at pin16.

This thing is whacked! At any rate, the problem must be in PS or the PA - I don't have a transistor tester yet, tho I do have a nice scope and meter as well. But I will order up the 2sa726 and 2sc1451 transistors and trimpots and change those to start with.

I have the SM.pdf but it doesn't have component locations? And the boards aren't marked? I feel dumb already, don't tell me I need to follow traces on the board?
 
The sa-8100 manual is a bit less helpful than others - they were learning.

Download this one if you haven't, it's 90 meg and readable.

boards have a zzz-999 designation to identify them, then there are the C1, Q1 etc designations.

Each board is broken out in the second half of the manual, showing schematic with component identification, then a board diagram (from the bottom!) also with component identification.

I will have to teach you about the three transistor leads, and how to use the symbol on the board to correctly install each transistor, avoiding the 5 incorrect possibilities and getting the 6th (and correct) installation.

The symptoms you describe is the classic power amp transistor failing model (most likely the 2sc1451). DON'T run it, it CAN spontaneously turn itself into a smoking ruin that needs many high powered components including output transistors.
 
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markthefixer said:
The sa-8100 manual is a bit less helpful than others - they were learning.

Download this one if you haven't, it's 90 meg and readable.

boards have a zzz-999 designation to identify them, then there are the C1, Q1 etc designations.

Each board is broken out in the second half of the manual, showing schematic with component identification, then a board diagram (from the bottom!) also with component identification.

I will have to teach you about the three transistor leads, and how to use the symbol on the board to correctly install each transistor, avoiding the 5 incorrect possibilities and getting the 6th (and correct) installation.

The symptoms you describe is the classic power amp transistor failing model (most likely the 2sc1451). DON'T run it, it CAN spontaneously turn itself into a smoking ruin that needs many high powered components including output transistors.
Click to expand...

Thanks alot Mark, I have run it for maybe 10 minutes (no input, no output) to see if it would settle out, and it did somewhat.

Thanks for that manual, I had found broken links to it yesterday. It does show what I need.

I'll go ahead and re-educate myself on transistors - I sure don't expect for you to take your time for it! I knew this stuff 25 years ago, but like they say - if you don't use it, you'll lose it. Well, I've lost it. :tears:
 
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.

markthefixer said:
markthefixer said:
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


attachment.php


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.



attachment.php



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

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....
attachment.php


and two transistor layouts, ebc and ecb with the same triangular target hole arrangement
attachment.php
Click to expand...
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

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
Click to expand...


attachment.php
Click to expand...
 
OK, I'm good to go on transistors.:smoke:

Pulled 2 of the 2SA726 - both OK.
Pulled the two 2SC1451 - the datasheet always shows the flat side up, correct? So the webpage name indicates "BCE" but the image shows "ECB"???
NTE290A.jpg


Here's how the test came out, with both pinouts. If they are OK, then the only thing I've found bad is R54 (attached to Q10). Oh, and the Service Manual specifies R53, R54 as being 1.5K, while both resistors are actually 15K. Which is correct, what they installed or what they spec'd? (EDIT: dumb question, I guess the SM isn't a spec book - it's intent is as a "as-built". Except it's wrong).
 

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Until they fail utterly, the noise faults will not show up on the gross tests. Also the low voltage of the diode test won't induce it as well as full working voltage.

PLUS Those aren't Fiji 2sc1451's - I cant read the numbers, but the 1451's to-5 type case WITH integral heat sink is unmistakable - and those ain't them.

In fact on the one I can make out, it starts with an "A" which is the OPPOSITE of a C.

I think you may have the wrong transistors.

The foil diagrams are viewed from the BOTTOM (non-component side) of the board.
 
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I am completely ready to believe I got something mixed up - but I did take good pictures before I started.
Here is the foil not matching the SM - I have pics in high-res if you want me to send them via email.
UPDATE - my board is an AWH-022-B - notice the "B" version as opposed to the SM which has the "A" version.

I've included a full board pic, this is after I've removed those transistors and resistors, I've highlighted it to show you what I see.
Now that I am looking for differences, I see that I am probably off-track - the SM "A" board appears to be significantly different than the "B" board.
LAST EDIT ON THIS POST AT 7:05 AM - UPDATED PICS WITH TEXT
 

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