SX-525 Refurb
- Thread starter Rockmore
- Start date
PM me with a real world address. Postage is what, 44 cents now?
Because Pioneer factory mounted the 390 ohm 2-3 watt resistor
right on the board. The right side was charred black from heat and everything in that area except for the standard resistors got replaced (caps, transistor, diodes).
usps first class mail from casa markthefixer, arranged by PM...
Mark- got the zeners- thanks!
PM me your Paypal email address again.
B1 still at 52vdc
B2 jumped to 26.7vdc
B3 still at 5.88vdc
all the ac's the same-
except checked ac5 this time and
its at 7.5vac
transistor-
E jumped to 33.8vdc
C lowered to 32.3vdc
B jumped to 39vdc
Noticed this last time also- with WRONG
12v zener in wz-320 and 12v zener correctly
in wz-120, i had signal strength and reception.
(still no audio yet). With NEW correct 30v zener
in wz-320, no signal strength and reception..
??
PM me your Paypal email address again.
B1 still at 52vdc
B2 jumped to 26.7vdc
B3 still at 5.88vdc
all the ac's the same-
except checked ac5 this time and
its at 7.5vac
transistor-
E jumped to 33.8vdc
C lowered to 32.3vdc
B jumped to 39vdc
Noticed this last time also- with WRONG
12v zener in wz-320 and 12v zener correctly
in wz-120, i had signal strength and reception.
(still no audio yet). With NEW correct 30v zener
in wz-320, no signal strength and reception..
??
With just 5.88 v the tuner itself, and specifically the ta7060p chip, doesn't have enough voltage to operate.
B3 really hasn't changed much, huh?
How about taking that 12v zener that you pulled out (we KNOW that one works), and putting it in place of that other "12v" zener.
If that doesn't help:
Disconnect the wire at B3 and see if it comes up to 12 volts. Something may be pulling too much current out of the 12v power line. But I don't expect that (12v on disconnecting b3) to happen.
It probably is another zener with the wrong voltage controlling B3, because we went from 12v to 26v on B2 without b3 budging. That's called "regulation". and swapping with the zener you took out that we know is 12v with this other zener that looks like it is a "6v" zener should fix it.
It's kind of hard filling in the blanks with only a partial service manual available. Because it doesn't explain how the tuner was working when there was 9v at B2 and 6v (or so) at B3.
B3 really hasn't changed much, huh?
How about taking that 12v zener that you pulled out (we KNOW that one works), and putting it in place of that other "12v" zener.
If that doesn't help:
Disconnect the wire at B3 and see if it comes up to 12 volts. Something may be pulling too much current out of the 12v power line. But I don't expect that (12v on disconnecting b3) to happen.
It probably is another zener with the wrong voltage controlling B3, because we went from 12v to 26v on B2 without b3 budging. That's called "regulation". and swapping with the zener you took out that we know is 12v with this other zener that looks like it is a "6v" zener should fix it.
It's kind of hard filling in the blanks with only a partial service manual available. Because it doesn't explain how the tuner was working when there was 9v at B2 and 6v (or so) at B3.
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OoooKkkk.
Think we've finally got the PS where it needs to be. Please verify:
B1 52v
B2 26.7v
B2 at exactly 12v
Got the tuner reception signal back and it's string across the band.
ECB v on the sd313 all the same as in previous post. All a little low but think it's OK.
NOW- on to the amp board to see if I can finally get some audio out to the speakers. Trying to go through this thread from the start, and determine which transistors (again) merely need to be switched 180 degrees from bce to ecb, correct?
Its going to be a hassle with the amp board wires all soldered, and flipping the entire chassis back and forth to get to the amp top and bottom.
MARK- PM me your paypal email address again.
Think we've finally got the PS where it needs to be. Please verify:
B1 52v
B2 26.7v
B2 at exactly 12v
Got the tuner reception signal back and it's string across the band.
ECB v on the sd313 all the same as in previous post. All a little low but think it's OK.
NOW- on to the amp board to see if I can finally get some audio out to the speakers. Trying to go through this thread from the start, and determine which transistors (again) merely need to be switched 180 degrees from bce to ecb, correct?
Its going to be a hassle with the amp board wires all soldered, and flipping the entire chassis back and forth to get to the amp top and bottom.
MARK- PM me your paypal email address again.
33&athird
Turn on & Tune in
Great...good news!, i'll still get my project back to you, on this thread, since it may help some poor soul later:yes:
:sigh: no audio?...almost definately the transistors. I don't think you could just flip them 180 degrees, since then the heatsink wouldn't be on the correct side...the transistors on the 525 I belive are board-mount, correct?:scratch2:. However, other than that technicality, your thinking is correct, the c is alright, but e and b are flipped.
Yeah, about the only bad part of working on these units...as Mark pointed out, pioneer stuff got easier to work on going up the chain, and later in the years. Remember this was I think their first series of solid state stuff, with their first being the sx-1000tw(or td, one had a tube rectifier), the earlier sx-## series was tube-based. The 525 is a bit of a pain (especially the stream of wires at the bottom), but even the 727 is a pain to get to the amp board.
Which amp board wires are being soldered?
i'll get back to this soon, I hope (stupid programming logic design...:grumpy
From my recollections, the original a726's were bce while the replacement a992's are ecb.
This is referenced to the flat of the transistor, and the lettering on it, facing you, and with the leads pointing down, then the a992 has ecb left to right.
Since you copied exactly, these are the only transistors you would have had trouble with. Q1, Q2, Q3 & Q4.
Now, what I do in that case is stand the cabinet on end, transformer (heavy end) down, and I use a pair of wooden "feet" that are mounted "cross ways" to stabilize it, attached in the middle (countersunk hole so it's flat) by the cabinet screws into the cabinet screw holes. I also have the additional assistance of a "lazy susan" turntable the whole thing is setting on.
This is referenced to the flat of the transistor, and the lettering on it, facing you, and with the leads pointing down, then the a992 has ecb left to right.
Since you copied exactly, these are the only transistors you would have had trouble with. Q1, Q2, Q3 & Q4.
Now, what I do in that case is stand the cabinet on end, transformer (heavy end) down, and I use a pair of wooden "feet" that are mounted "cross ways" to stabilize it, attached in the middle (countersunk hole so it's flat) by the cabinet screws into the cabinet screw holes. I also have the additional assistance of a "lazy susan" turntable the whole thing is setting on.
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First and foremost, PLEASE forgive the size of the pictures I am about to post, the size is incidental and not in any shape or form an editorial or comment. they are pre-existing attachments used in other threads.
This is a to-126 transistor with an ECB lead arrangement. And a visible symbol, correctly inserted in a board.
You can see how the first lead , the E, goes into the hole with the arrow,
and how the LAST lead , the B, goes into the hole that's connected to the flat surface that the arrow "protrudes" from. In a straight line.
The C is the only one left - the "odd man out", that is bent forwards or backwards to get to the leftover hole.
The physical trick is to just remember the first and last letters, find the hole for the first letter, put it in the hole to act as the pivot point, and then pivot the transistor around that hole until the last letter lines up with it's hole. Put it in. Then bend the leftover center lead to the leftover hole.
edit: a good place to store and reference this:
This is a to-126 transistor with an ECB lead arrangement. And a visible symbol, correctly inserted in a board.
You can see how the first lead , the E, goes into the hole with the arrow,
and how the LAST lead , the B, goes into the hole that's connected to the flat surface that the arrow "protrudes" from. In a straight line.
The C is the only one left - the "odd man out", that is bent forwards or backwards to get to the leftover hole.
The physical trick is to just remember the first and last letters, find the hole for the first letter, put it in the hole to act as the pivot point, and then pivot the transistor around that hole until the last letter lines up with it's hole. Put it in. Then bend the leftover center lead to the leftover hole.
edit: a good place to store and reference this:
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I turned into a moron overnight- those pics are great. Stating and showing the physical board markings and determining 2 out of the 3 is exactly what I needed! This post as it is and as it continues has got to be a definitive for anyone recapping or replacing everything on a SX-525. What a gold mine of info. AND with baby pictures LOL. Can't beat that.
Double Edge Sword
Believe it or not, had Q 2 and 3 in correctly. All the 992's in Q 1 2 3 4 are now in correctly with their ecb orientation..
Audio! But... (here we go again), amp is extremely distorted. Had the volume pot all the way down on power up, and already was getting a little out to the speakers. Even slightly turning up the volume, the audio starts distorting and is loud.
I deoxe'd all the pots about a month ago. Going from left-right on the balance has no effect on this problem either other than correctly going from one speaker to the other. Barely "touching" the volume up the amp seems to have excessive gain. Switched speakers to some old 8 ohm beaters I had and tried to get the volume up to 1/4. Naturally the amp almost cut out from distortion, especially on the right channel.
Used the tuner, and a CD for a source in, no change.
Believe it or not, had Q 2 and 3 in correctly. All the 992's in Q 1 2 3 4 are now in correctly with their ecb orientation..
Audio! But... (here we go again), amp is extremely distorted. Had the volume pot all the way down on power up, and already was getting a little out to the speakers. Even slightly turning up the volume, the audio starts distorting and is loud.
I deoxe'd all the pots about a month ago. Going from left-right on the balance has no effect on this problem either other than correctly going from one speaker to the other. Barely "touching" the volume up the amp seems to have excessive gain. Switched speakers to some old 8 ohm beaters I had and tried to get the volume up to 1/4. Naturally the amp almost cut out from distortion, especially on the right channel.
Used the tuner, and a CD for a source in, no change.
33&athird
Turn on & Tune in
:headscrat...it's not the pots, so don't worry about that. Sounds like a output device problem, although it could be something else. I know if half a push pull is incorrect, a amp will only output half volume at high distortion, but it sounds like this is a bit worse. :scratch2:...i'll try to think of something, and report back-i've heard of this problem before on a different unit...
mtf here from Robie's AK get together.
I think the backwards 992's got hurt.
got spares?
I think the backwards 992's got hurt.
got spares?
Spares? What am I a parts store?!? Hard enough even getting the correct 33v zener remember LOL...
No. No spares. Ordered 4 of the KSA992FBU Korean PNP transistors in the original order.
- Am I NOW going to have to pull all 4 of these 992's again?
- How would they get damaged? Heat?
- How can you test them? Ive got the transistor tester on my DMM now for hfe.
- Is what i described, having audio with the volume at 0 and distorted and loud at small volume levels saying a 992 or more is defective?
33&athird
Turn on & Tune in
Heh, some of us around here are parts stores
, not as glamorous as it sounds, though:sigh:Nope, not exactly...the small silicon juntions inside the transistor can get damaged by reverse-biasing, ocassionally. Even electro-static discharge can sometimes blow junctions on transistors, and IC's. Accumulated heat could have done it as well, though.
I think the hfe could help, but more imortantly, the diode function, I would think:scratch2:...
Almost all bipolar transistors cannot withstand more than 5 volts from emitter to base, and a reversed insertion could satisfy that condition.
The two transistors form a differential amplifier, a strange beast with two inputs, two outputs, and a propensity to compensate for the other transistor.
Add to that the rest of the power amp circuitry and it is reasonable the slightest input sends it flying from it's positive limit to it's negative limit as it unsuccessfully tries to find a balance it can never attain.
I should have mentioned spares, especially with the minimal cost for these compared to the postage. For penance I still have your address.
If your meter has the diode test, reading this should shed some light on transistor testing. Knowing the lead arrangement will allow you to do Hfe tests with the meter, if the 6 diode tests show no obvious faults.
http://www.audiokarma.org/forums/showthread.php?p=432830#post432830
This thread details the theory, and post #11 details an explicit procedure by the numbers..
The two transistors form a differential amplifier, a strange beast with two inputs, two outputs, and a propensity to compensate for the other transistor.
Add to that the rest of the power amp circuitry and it is reasonable the slightest input sends it flying from it's positive limit to it's negative limit as it unsuccessfully tries to find a balance it can never attain.
I should have mentioned spares, especially with the minimal cost for these compared to the postage. For penance I still have your address.
If your meter has the diode test, reading this should shed some light on transistor testing. Knowing the lead arrangement will allow you to do Hfe tests with the meter, if the 6 diode tests show no obvious faults.
http://www.audiokarma.org/forums/showthread.php?p=432830#post432830
This thread details the theory, and post #11 details an explicit procedure by the numbers..
Not interested in theory anymore. Interested in tangible, timley fix(es) after this nightmare that I all did by the book. Sheesh. Im putting in a order with Mouser, will get "spares" of these supposedly good 992's and get a couple of the 512-ksc2073tu for the PS sd313 that Goat recommended.
Looks like I'm going to have to pull the 992's regardless so WTF. I'll just replace them. But I'm sick of this s$$t, believe me.
ANYTHING ELSE?
Let me think on it, we have until Sunday evening for the Mouser order.
I WILL be thinking about this. I'm not a big football fan... although if the Bears were in the fray, I might work up a little enthusiasm...
But I'm not willing to sit through it just to see the clever commercials.
So other things (like this) will occupy my thoughts.
Usually things like this are learned in an electronics school lab, with a pile of really cheap transistors at your side...
I WILL be thinking about this. I'm not a big football fan... although if the Bears were in the fray, I might work up a little enthusiasm...
But I'm not willing to sit through it just to see the clever commercials.
So other things (like this) will occupy my thoughts.
Usually things like this are learned in an electronics school lab, with a pile of really cheap transistors at your side...