Steve 1050
Active Member
I went back and checked trans layouts and found a couple flipped will resolder correctly after checking their "health" and report back tomorrow
No voltage on pins 8-19 on SX-1050 awr 103 board????!!!!
- Thread starter Steve 1050
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Steve 1050
Active Member
relay problem broken wire-fixed relay working. still no voltages on pins 7 thru 17, Damn! there is voltage at power Amp pins- -64.5v could the protection circuit be causing problems?
Ok, there's a few gaps in communication here... There are two relays in the sx-1050. One toggles within a second or two of power on, it is called the soft start relay and it tames the massive inrush of current that happens when the unit is turned on and the big capacitors charge. The other happens usually several seconds later as all conditions stabilize and it is safe to connect the speakers to the amplifier outputs.
The soft start relay in this model is connected to the +76v raw dc that runs the +60v and +30v regulators. The fact that a power supply problem kept the soft start relay from engaging says that a large amount of current was flowing through the fault, probably a damaging amount.
You have re-checked the five fuses on the AWR-104 board to be sure that they are ALL ok?
Also what method did you use to determine that the flipped transistors survived?
To do troubleshooting of the regulator circuits, it may be necessary to at least remove Q4 and Q8 at first, and to isolate the +60v and -60v regulators from a load that may be shorted somewhere off of the regulator board.
The fact that after caps, diodes and transistors have been changed that the regulators still don't function means that either something fundamantal was overlooked, or there is some basic misunderstanding that happened during the rebuilding or testing of the transistors.
The soft start relay in this model is connected to the +76v raw dc that runs the +60v and +30v regulators. The fact that a power supply problem kept the soft start relay from engaging says that a large amount of current was flowing through the fault, probably a damaging amount.
You have re-checked the five fuses on the AWR-104 board to be sure that they are ALL ok?
Also what method did you use to determine that the flipped transistors survived?
To do troubleshooting of the regulator circuits, it may be necessary to at least remove Q4 and Q8 at first, and to isolate the +60v and -60v regulators from a load that may be shorted somewhere off of the regulator board.
The fact that after caps, diodes and transistors have been changed that the regulators still don't function means that either something fundamantal was overlooked, or there is some basic misunderstanding that happened during the rebuilding or testing of the transistors.
Steve 1050
Active Member
The soft start relay is working the second relay is not, transistors were remover and tested with DMM diode function the appear to be good. All fuses test good.
Ok, what are the 3 voltages on each of the transistors?
Steve 1050
Active Member
sorry i took so long to get back to you which transistors
All of them, down to a tenth of a volt, metal chassis ground referenced:
and don't cheat, probe each voltage AT the transistor's leads as you identified them!!
There are MANY levels of tests and things I am looking for here, including your lead
identifications and component polarities....
-------- Positive regulator -------
Q1 Collector
Q1 Base
Q1 Emitter
Q2 Collector
Q2 Base
Q2 Emitter
Q3 Collector
Q3 Base
Q3 Emitter
Q4 Collector
Q4 Base
Q4 Emitter
ALSO, the voltage at the common connection point of of C1, R2 and R3.
------ negative regulator --------
Q5 Collector
Q5 Base
Q5 Emitter
Q6 Collector
Q6 Base
Q6 Emitter
Q7 Collector
Q7 Base
Q7 Emitter
Q8 Collector
Q8 Base
Q8 Emitter
ALSO, the voltage at the common connection point of of C9, R10 and R11.
I assume the voltages at the output pins 5 & 6 are 14 volts...
and don't cheat, probe each voltage AT the transistor's leads as you identified them!!
There are MANY levels of tests and things I am looking for here, including your lead
identifications and component polarities....
-------- Positive regulator -------
Q1 Collector
Q1 Base
Q1 Emitter
Q2 Collector
Q2 Base
Q2 Emitter
Q3 Collector
Q3 Base
Q3 Emitter
Q4 Collector
Q4 Base
Q4 Emitter
ALSO, the voltage at the common connection point of of C1, R2 and R3.
------ negative regulator --------
Q5 Collector
Q5 Base
Q5 Emitter
Q6 Collector
Q6 Base
Q6 Emitter
Q7 Collector
Q7 Base
Q7 Emitter
Q8 Collector
Q8 Base
Q8 Emitter
ALSO, the voltage at the common connection point of of C9, R10 and R11.
I assume the voltages at the output pins 5 & 6 are 14 volts...
Steve 1050
Active Member
Q1 emitter .959v
Q1collector 2.04v
Q1 base 1.45v
Q2 Emitter 1.45v
Q2 Collector 2.04v
Q2 Base1.85v
Q3 Emitter .941v
Q3 collector 1.83v
Q3 base .42v
Q4 Emitter .03v
Q4 Collector .94v
Q4 base .49v
Q5 emitter -1.16v
Q5 collector -1.62v
Q5 base -1.24
Q6 emitter -1.24v
Q6 collector -1.62
Q6 base -1.42
Q7 emitter -.14v
Q7 collector -1.16
Q7 base -.86v
Q8 emmiter -.14v
Q8 collector -.14v
Q8 base -.6v
common point = 1.96v
Q1collector 2.04v
Q1 base 1.45v
Q2 Emitter 1.45v
Q2 Collector 2.04v
Q2 Base1.85v
Q3 Emitter .941v
Q3 collector 1.83v
Q3 base .42v
Q4 Emitter .03v
Q4 Collector .94v
Q4 base .49v
Q5 emitter -1.16v
Q5 collector -1.62v
Q5 base -1.24
Q6 emitter -1.24v
Q6 collector -1.62
Q6 base -1.42
Q7 emitter -.14v
Q7 collector -1.16
Q7 base -.86v
Q8 emmiter -.14v
Q8 collector -.14v
Q8 base -.6v
common point = 1.96v
Yecch... stone cold dead...
What are the voltages on pins 2 and 3 and then later check the resistance of R1 and R19.
There should be at least +65 volts on the collector of Q1 and -65v on the collector of Q5.
With the power off:
Do a resistance test FROM pin 2 to the collector of Q1
and
Do a resistance test From pin 3 to the collector of Q5.
What are the voltages on pins 2 and 3 and then later check the resistance of R1 and R19.
There should be at least +65 volts on the collector of Q1 and -65v on the collector of Q5.
With the power off:
Do a resistance test FROM pin 2 to the collector of Q1
and
Do a resistance test From pin 3 to the collector of Q5.
Steve 1050
Active Member
resistance Pin2 to coll Q1 3.09Mohm
resistance pin3 to coll Q5 OL
R1 = OL
R19 = OL
Pin 2 =80.6v
pin3 = -80.6v
measured with Fluke 77 Multimeter
resistance pin3 to coll Q5 OL
R1 = OL
R19 = OL
Pin 2 =80.6v
pin3 = -80.6v
measured with Fluke 77 Multimeter
They should BOTH read ten ohms. They are definitely blown, Depending upon the room available, if you (i) can find 10 ohm 5 watt resistors and use them, it would be better.
Can you take an in-focus picture of the component side of the board?
At the very least, I need to know the dimensions of the board's width and length.
The resistors should have been mounted some distance over the board.
Edit: radio shack has a pair of 10 ohm 10 watt resistors part number 271-132 @ $1.79 ea, that with a little ingenuity should fit (vertically, there shuld be enough clearance)
Steve 1050
Active Member
Idont have a digital camera with macro capability. However those resistors are original (or so it appears). height from board is aprox. 1/2 in.
Board is 4.75 in. wide by 3.75 in tall
Board is 4.75 in. wide by 3.75 in tall
A fault radical enough to destroy these resistors is nothing to fool around with, before trying to power up the board again, the load has to be removed and re-applied carefully, watching the current drains on the supplies.
I will have to think a bit before posting a step by step method.
The measurements are fine. Unfortunately Radio Shack doesn't list the resistor's dimensions.
We can live without pictures.
edit mouser # 588-33J10RE @ $1.12 ea is 10 ohms 3 watts and is a good choice. either one (r/s or mouser) is fine.
I will have to think a bit before posting a step by step method.
The measurements are fine. Unfortunately Radio Shack doesn't list the resistor's dimensions.
We can live without pictures.
edit mouser # 588-33J10RE @ $1.12 ea is 10 ohms 3 watts and is a good choice. either one (r/s or mouser) is fine.
Steve 1050
Active Member
Mark thank you for your help so far. I have to go to bed, (have an early day tomorrow. will check in tomorrow. Later.
I'm not sure how much it will help, with a short on a low wattage regulated power supply as opposed to a short on the big unregulated power suppliers, but a dim bulb tester seems to be the best balance of precaution versus opening up a bunch of wires in case of short circuits.
A dim bulb tester is a incandescent lamp in series with the power cord, in the same way a fuse is. If there is too much current capable of being drawn (by a short) the balance between it and the bulb will cause the bulb to glow brightly, limiting the current available to do damage in the receiver.
Normally the bulb will glow brightly as the filter caps charge, then almost completely dim out as the receiver drops back to it's low idling current.
The lower the wattage of the bulb, the less energy there is to do damage, but the longer it takes to charge the main caps.
Considering the situation, I would try to find 20,40,60 and 100 watt bulbs, and try to start with the 20w bulb, or the lowest you can find.
Normally in a situation like this, I use a variac to ramp up the ac voltage slowly, watching an inline current meter for current drain that does not drop as I crank the thing up, plus you sort of need to get a feel for how something that is working behaves, as opposed to a current that just rises, and stays that way or increases.
There are some tricks we can do around the fuses, to try to avoid cutting wires if there is a fault.
A dim bulb tester is a incandescent lamp in series with the power cord, in the same way a fuse is. If there is too much current capable of being drawn (by a short) the balance between it and the bulb will cause the bulb to glow brightly, limiting the current available to do damage in the receiver.
Normally the bulb will glow brightly as the filter caps charge, then almost completely dim out as the receiver drops back to it's low idling current.
The lower the wattage of the bulb, the less energy there is to do damage, but the longer it takes to charge the main caps.
Considering the situation, I would try to find 20,40,60 and 100 watt bulbs, and try to start with the 20w bulb, or the lowest you can find.
Normally in a situation like this, I use a variac to ramp up the ac voltage slowly, watching an inline current meter for current drain that does not drop as I crank the thing up, plus you sort of need to get a feel for how something that is working behaves, as opposed to a current that just rises, and stays that way or increases.
There are some tricks we can do around the fuses, to try to avoid cutting wires if there is a fault.
Steve 1050
Active Member
I'm still working on getting the replacement resistors, hopefully tomorrow.
Steve 1050
Active Member
Replaced resistors, locateda variac. (friend has one) slowly applied power and
poofed Q7. All the smoke escaped.
poofed Q7. All the smoke escaped.
Q7 popped?? The control amplifier on the negative supply?? Hmmmmm.....
Just to be sure, you replaced the transistors, capacitors, diodes and the two 10 ohm resistors?
Did you get extras? And the board looks clean (no residue shorting anything?).
I'll take it for granted that all the caps went in with the correct polarity connections.
We'll need to test the transistors to see what else died that didn't smoke.
When it goes back together, the output leads from the +/- 60v regulators (pins 8, 16 (& 17??))will need to be disconnected first (removing the loads), so we can get the power supply working, then find where the current drain is. Looking at the schematic, it appears that the only path for that much power drain is through the pre-drivers, drivers and output transistors in the power amp section.
Just to be sure, you replaced the transistors, capacitors, diodes and the two 10 ohm resistors?
Did you get extras? And the board looks clean (no residue shorting anything?).
I'll take it for granted that all the caps went in with the correct polarity connections.
We'll need to test the transistors to see what else died that didn't smoke.
When it goes back together, the output leads from the +/- 60v regulators (pins 8, 16 (& 17??))will need to be disconnected first (removing the loads), so we can get the power supply working, then find where the current drain is. Looking at the schematic, it appears that the only path for that much power drain is through the pre-drivers, drivers and output transistors in the power amp section.