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No voltage on pins 8-19 on SX-1050 awr 103 board????!!!!

I unfortunatly did not buy extras. However I double shecked the board and all connections are clean and all diodes ,transistors, and the two 10 Ohm resistors, were replaced. R 19 does get extremely hot
 
Steve 1050 said:
I unfortunatly did not buy extras. However I double shecked the board and all connections are clean and all diodes ,transistors, and the two 10 Ohm resistors, were replaced. R 19 does get extremely hot
Click to expand...

I was editing info into my post, it's probably the power amp drawing so much juice, the pre-driver transistor has the only direct connection to the 60 v supplies, all the rest of the connections have resistors in the way that won't allow that much current to flow, but a bad output section will, depending upon what's blown away. It is understandable that R19 gets hot...

I forgot to add my usual advice about getting extras, especially transistors, just in case, because they are so cheap. I suspect you will also find that Q5 is probably shorted and Q6 blown. You can remove Q5, Q6 and Q7 and do a quick power up to see if the +60v regulator is working, after pins 8, 16 & 17 are disconnected from the rest of the unit.

You could also check (by removal and diode testing) Q13 through Q20 on the power amp board. Some are most assuredly blown up. AND check the power amp board and the power transistors for goop shorting them. Q16 - Q20 are in a row across one side of the board, while Q13 - Q16 are the two leftmost and rightmost (outer)transistors of the two clusters of transistors on the board.
 
Mark, it's been a long day and I work better with a few couple of hours sleep. I will perform the required checks and surgery tomorrow, and let you know whats' happening.
 
My =60V readings are around 75 V kinda high?, as are all of the voltages. I did buy a replacement for Q5, and the original Q6 appears Good thru diode check
 
Hindsight is always so darn accurate... I should have INSISTED on pulling those wires. You need to check ALL the transistors Q1 - Q8, and post the results.

You will need to order some more transistors ( full set?), and I'll come up with some additional resistor numbers to put inline with the power leads which will limit any short circuit currents to a level closer to the rated load. First guess is about 2000 ohms at 2 watts or so.

I MAY also specify a few different transistors with a higher voltage rating than the original design, which may be more tolerant of faults, avoiding cascade failures. Of course if the emitter to base voltage gets over 5 volts, most are toast anyway.

We have until monday to sort out the numbers and details. IF we have the Q13-Q20 results we may be able to order those as well at the same time.

Power supplies blow for many reasons, and sometimes it isn't the power supply's fault. It's just that a lot of the time with Pioneers, it IS just an overheated power supply.
 
Q1
black=base, red= emitter 1.478 [same formula used for all transistors]
red= base, black= emitter .611
black=base, red= collector .658
red=base, black= emitter .609
black=emitter, red=collector 1.041
red= emitter, black= base 1.424
Q2
base,emitter=1.608
base,emitter=.659
base,collector=1.56
base,collector=.653
emitter,collector=.659
emitter.collector=.609
Q3
base,emitter=.661
base,emmiter=2.00
base.collector=1.34
base.collector=1.92
emitter,collector=1.67
emitter,collector=.655
Q4
base,emitter=1.789
base,emitter=1.988
base,collector=1.265
base,collector=.646
emitter,collecter=.714
emitter.collector=1.68

Q5,6,7 out of circuit, all bad

Q8
base,emitter=.637
base,emitter=1.792
base,collector=.625
base,collector=1.64
emitter,collector=1.87
emitter,collector=.673


all Xsistors checked in circuit.
 
I'm sorry, i ASSumed that you had read EchoWars' testing post, and that you knew the tests must be done out of circuit, to eliminate external influences. My bad....

Those numbers show oodles of external influences.

This thread details the testing of bipolar transistors, plus it explains why the readings must be made out of circuit.

You should follow the thread down to the 11th post, where I posted a pair of examples, feel free to copy the examples and edit in your own results. (with a familiar order a short glance is all that's needed to tell good, bad or marginal)

Darn, I gotta remember to check closer, you were doing such a good job that I was lulled into a sense of security.

Ok, now for the Q6 & Q7 question, this was the original part substitution:

q6,q7 2sa628 to-92 ??? pnp 25v .1a .15w 100mhz
replacement part # 512-ksa733clta @ $0.05 ea (ebc layout) 50v .150a .250w 180mhz
replacement part # 512-ksa733Clta @ $0.05 ea (ebc layout) WRONG!!! (ECB layout)


Q6 & Q7 : new replacement part # 522-ZTX795A @ $1.51 each TO-92L (e-line) 120v 1.0a 1.5w 100mhz

we're trotting out the "big guns", with high voltage and high current capability, along with oodles of gain.
Of course there's a price to be paid... and it's only cash, as opposed to some other parameter in the transistor.
 
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No prob I kind of thought you might want them out of circuit. will pull them now an recheck. I had read the post but had forgotten about it, sorry.
 
reading s for Q1-4 and Q8. format same as test post

Q1 NPN
base black lead, collector red lead=OL
base black, emitter=.594
base red, collector black=OL
base red, emitter black=OL
emitter black, collector red= OL
emitter red, colletor black=.596

Q2 NPN
Base-collector=OL
base-emittor=OL
base-collector=.642
base-emittor=.644
emitter-collector=OL
emitter-collector=OL

Q3 NPN
base-collector=OL
base-emitter=OL
base-collector=.648
base-emitter=.657
emitter-collector=.OL
emitter-collector=OL

Q4 NPN
base-collector=OL
base-emitter=OL
base-collector=.653
base-emittor=.654
emitter-collector=OL
emitter-collector=OL

Q5,6,and7 previosly proved bad

Q8 PNP
base-collector=.622
base-emitter=.634
base-collector=OL
base-emittor=OL
emitter-collector=OL
emitter-collector=OL
 
When you use a variac the idea isnt to slowly apply power its to add some power then check. then add some more then check. and so on till you get up to full power on.
What I do is apply say a quarter of the power and then have a feel around and look around (for rising smoke). BE CAREFUL!!! to see if anything is getting warm or hot. If not then go a bit more and feel and look again. Also you can do some tests to see if things are going to plan.
The idea is to catch something before it blows. You probably could have caught Q7.
Again I say BE CAREFUL feeling around in the unit. Stay away from mains voltage stuff and only contact the plastic casings of transistors etc.
 
Thanks for the reminder, I will definatly be more careful in the future. Its' been a long week and I'm not up to full speed. I know that is no excuse, not offered as one, just an erstwile explanation. sorry.
 
The tests look good, and with a consistent format, we can spot errors (or strangeness, like the report of Q1's readings).

I am going to double check all of Q1's (2sd313/ksc2073) lead designations I posted..

Then I am going to try to reconcile Q1's readings. That may reveal why the +60v regulator with a good Q1, Q2 and Q3 didn't regulate, just passed current.

edit1: they are both base - collector - emitter with the metal tab facing up, and to the rear, which puts the base at the left. A standard TO-220 pinout, and there is no difference between the original and the replacement.
Assuming the readings had the emitter and base swapped, they make sense.

edit2:
Since Q2 and Q3 should be working in the positive regulator, Q6 and Q7 are their complements, thus:

q6,q7 2sa628 to-92 ??? pnp 25v .1a .15w 100mhz
replacement part # 512-KSA910YBU @ $0.11 ea (ecb, opposite layout) 150v .05a 0.8w 100mhz
versus the ksa733's which were 50v .150a .250w 180mhz, so a lot less voltage and a little more current in the old ones, instead of the overkill that the ztx795a 's represented.
 
Hey no worries Steve I understand.
I hope you guys don't mind the occasional 2 cents from the peanut gallery as I'm finding this thread rather riveting and have been following it since day 1.
 
Those transistors are from the pos. regulator aren't they? it seemed that the positive voltages were all there but high, and there were no negative voltages.
 
Musical, Chime in any time, the more the merrier. I used to repair stereos and whatnot years(30+) ago but have since forgotten most of my electronics theory, so comming to this forum has given me a chance to work on my skills and have fun working on my reciever at the same time. when I first aquired this reciever it worked, however if I recall the protection relay (speaker) would sometimes open, that was part of the reason I put it away. that and at the time my rig was not complete. My speakers were cheap low end goodwill specials. I have since then been able to aquire much better speakers, a couple of reel to reel tape decks ,and turntables. I figured I would pull out the Pioneer and having forgotten about having spilled something(soda I think, maybe Scotch and soda) I powered up the unit. the rest they say is on the forum.
 
Q1, Q2 & Q3 are the positive voltage regulator, and while it was passing voltage, it was NOT doing it's job, as the voltage was too high. When the Q1 readings showed a base/emitter lead confusion/reversal, I was HOPING that a cockpit error was to blame for it's non-functioning status, meaning that it was either installed wrong or something else was causing it to turn on all the way, as opposed to turing on partially... which IS the purpose of regulation. I was also hoping that Q1 was NOT shorted or damaged. So far they look good.

The Q5, Q6 & Q7 negative voltage regulator is a mirror image of the positive regulator. The positive and negative regulators are independent in this case (sometimes they aren't!!) and all transistors are "complements" (or opposites) of each other, thus having mirror image specifications, which led me to change my Q6 and Q7 substitution recommendations from some expensive transistors to the somewhat lower amperage parts, of which the higher amperage shouldn't be needed. Both new choices for Q6 and Q7 have much higher voltage ratings than the ksa733's 50v.

The parts that still seem good on the positive side were higher voltage parts than the ones on the negative side, which promptly blew up on the massive overload.

I expect that the overload IS on BOTH the positive and negative 60 volt rails, due to the way the amplifier is designed.

This is why I want to get the power supply working without a load connected, to iron out what is going on that makes the positive supply and negative supply act so differently when they went bad with the overload.

Edit: this is a 3.3k ohm 2 watt resistor (mouser) part number ( 588-OY-3.3K-E @ $1.05 each) , we need to get two, one for +60 and one for -60. IF there is a direct short, the total current is 19 milliamps, about 1.1 watts, and when the short is cleared there will still be a large voltage drop across it, but by then we will know things are working much more closely to normal. Either way we will have a fighting chance at fixing things.
 
Mark you may like these readings for Q1 a little better same test format just results shown

Q1
OL
OL
.601
.603
OL
OL

I realized that I may have been testing Q1 backwards upside down so I rechecked it
So what is the next step
 
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