this thread has left a bad taste for me; seems there is concern firstly that I have no formal education in EE.
Including the odd inquiries "what is the purpose / intent?".
Thanks to those who sincerely tried to provide answer, one post.
Including the odd inquiries "what is the purpose / intent?".
Thanks to those who sincerely tried to provide answer, one post.
More people tried to help than you think, or at least acknowledge. I, and I am sure others, downloaded the service manual, analysed the amplifier circuitry and spent some time looking for possible failure modes. I suggest you sincerely listen to those who posted, rather than demonstrating how far you can spit a dummy.
Your post 15.
The two circuits are equivalent. The drawing might not be, but those are just lines on paper, in fact the lines don't even have to be drawn straight. But if you need the confirmation, then physically wire it up yourself and see. Take two 8 ohm resistors and twist the ends together or dead bug connect the resistors as you did in your provided diagram.
Parallel resistors calculation first.
(R1xR2)/(R1+R2) = R3 all in ohm's.
Each top and bottom part (treat it as there are two of them) of your diagram of a single channel will give:
(8x8)/(8+8) = 64/16 = 4 ohms
So this is for the top two resistors, the same calculation will give the same answer for the bottom two resistors -- so 4 ohms again. 2 banks of paralleled resistors each giving 4 ohms.
Each of these banks are in series to each other.
Series resistors calculation next.
R1 (top set) +R2 (bottom set) = R3 all in ohm's
4+4 = 8 ohms
You can confirm the math and the formulii I used if you'd like.
You can again physically confirm this by making the circuit and measuring with a multimeter.
The way it is drawn, taking your diagram at face value that all resistors are the same (type, size, wattage, material, etc.), and how electricity works, there is no path of least resistance... you are still at 8 ohms through your circuit.
How you blew up your amplifier, no one here knows for sure.
Take pictures along the way during each step next time; the community here is very helpful, very knowledgeable, and well experienced (especially when given pictures and asked questions). This is the advantage of this forum over other similar forums. The forum is also very fairly moderated and monitored so everyone here can be considered most helpful and on their best behaviour.
Good luck with fixing your amp. If not, then you have a ready made chassis, a slew of parts, a nice sized heatsink, and some devices and connectors which might find a place in another project.
The two circuits are equivalent. The drawing might not be, but those are just lines on paper, in fact the lines don't even have to be drawn straight. But if you need the confirmation, then physically wire it up yourself and see. Take two 8 ohm resistors and twist the ends together or dead bug connect the resistors as you did in your provided diagram.
Parallel resistors calculation first.
(R1xR2)/(R1+R2) = R3 all in ohm's.
Each top and bottom part (treat it as there are two of them) of your diagram of a single channel will give:
(8x8)/(8+8) = 64/16 = 4 ohms
So this is for the top two resistors, the same calculation will give the same answer for the bottom two resistors -- so 4 ohms again. 2 banks of paralleled resistors each giving 4 ohms.
Each of these banks are in series to each other.
Series resistors calculation next.
R1 (top set) +R2 (bottom set) = R3 all in ohm's
4+4 = 8 ohms
You can confirm the math and the formulii I used if you'd like.
You can again physically confirm this by making the circuit and measuring with a multimeter.
The way it is drawn, taking your diagram at face value that all resistors are the same (type, size, wattage, material, etc.), and how electricity works, there is no path of least resistance... you are still at 8 ohms through your circuit.
How you blew up your amplifier, no one here knows for sure.
Take pictures along the way during each step next time; the community here is very helpful, very knowledgeable, and well experienced (especially when given pictures and asked questions). This is the advantage of this forum over other similar forums. The forum is also very fairly moderated and monitored so everyone here can be considered most helpful and on their best behaviour.
Good luck with fixing your amp. If not, then you have a ready made chassis, a slew of parts, a nice sized heatsink, and some devices and connectors which might find a place in another project.
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Thank you;
Yes that was intent, to create 400w, 8ohm resistor bank(s) with the resistors I had at hand (8ohm / 100w)
So that sight difference in wiring should not have had an impact on the circuits.
I did measure a few times before applying a load to be sure each were 8 ohms, and was confirmed.
So must have been some other cause.
Out of curiosity. if the parallel resistors have a slightly different resistance; does the current flow primarily through the resistor with lesser resistance? Am wondering if maybe that is the case for the bank the left channel was connected to. too much variance between to parallel resistors.
Yes that was intent, to create 400w, 8ohm resistor bank(s) with the resistors I had at hand (8ohm / 100w)
So that sight difference in wiring should not have had an impact on the circuits.
I did measure a few times before applying a load to be sure each were 8 ohms, and was confirmed.
So must have been some other cause.
Out of curiosity. if the parallel resistors have a slightly different resistance; does the current flow primarily through the resistor with lesser resistance? Am wondering if maybe that is the case for the bank the left channel was connected to. too much variance between to parallel resistors.
hmmm...interesting choice of research for a question about a resistor bank circuit.
what's more I had mentioned the left channel power transistors failed (pnp +npn, both a 3-way short) as well as the emitter resistor (just one side); with seemingly no other damage as per small audit of other components in the path...there was no question about the issue with the amp.
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lol and your point?
This all seems too combative / am feeling a need to defend myself.
I think the main issue is stating that I have no education in this and am new to playing with it.
With all do respect; there is plenty of info online and nothing I've seen in this area of EE is complex. It is actually remarkably straight forward.
I merely had an odd result that I could not determine the cause of, and in turn looked to more experienced folks in case there is some nuance am missing....you seem to suggest it is a formal education in EE that is missing...smh.
I am pretty sure from the university physics I took so long ago said that the sum of the current going in (before the resistors) must equal to the sum of the current going out (after the resistors). It is one of the parts of Kirchoff's Laws and no current is lost.
So I1 + I2 (these parts after the resistors) = I for the whole circuit (this part before the resistors).
See, it was not that difficult after all to answer the simple question from post #2.
None of the schematics in the various pictures you posted could cause the amp to blow except picture#2 in post#1 which is a clear short circuit.
Tolerance between resistors does not constitute a problem as a single 100W resistor (handling all the flow) across the output can take the modest 42W of this amp for some time.
The fault is due to something else. Maybe some inadvertent short while poking around with a metallic object? It happened to most of us...
I sincerely hope you succeed in fixing the blown channel.
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I think you're correct Jacques.
That there is some other reason why that channel blew.
In making the resistor bank, I did have plenty of strands of wire (I used speaker wire / multi strand) kicking around the room.
I did my best to be sure all were cleaned up but perhaps, there was some happenstance in that a strand made it's way inside the unit. Still seems like one heck of a coincidence though; almost too unlikely.
I did not at all suspect that at the time it happened, presumed it was issue with resistor bank. So did not look for a stray piece of wire when I disassembled the amp to see what blew.
Am still not confident in the resistor bank, so will put it through some testing until am confident it is fine taking low power loads up to high power loads. Lack of confidence is not from lack of understanding, but lack of experience. Emotively I still don't trust it lol So need to spend time getting to know that I can trust it lol
My understanding was those circuits shouldn't be different, but then thought about how electricity takes path of least resistance and thought of the possibility of a value imbalance with the parallel resistors. Trying to "force" an explanation that it was the resistor bank....somehow.
Those resistors can take allot! With the previous testing of this amp, when the circuit was wired and connected such only one 8ohm resistor was taking the load it reached 32.6v (left CH, 32.8v right CH) just before clipping. (amp is rated for 110w in stereo at 0.08thd) Of course, that's with the resistor mounted to an aluminum heat sink and about 10 seconds powering. Was VERY hot though; and what lead me to realize I hadn't made the circuit correctly that time.
That there is some other reason why that channel blew.
In making the resistor bank, I did have plenty of strands of wire (I used speaker wire / multi strand) kicking around the room.
I did my best to be sure all were cleaned up but perhaps, there was some happenstance in that a strand made it's way inside the unit. Still seems like one heck of a coincidence though; almost too unlikely.
I did not at all suspect that at the time it happened, presumed it was issue with resistor bank. So did not look for a stray piece of wire when I disassembled the amp to see what blew.
Am still not confident in the resistor bank, so will put it through some testing until am confident it is fine taking low power loads up to high power loads. Lack of confidence is not from lack of understanding, but lack of experience. Emotively I still don't trust it lol So need to spend time getting to know that I can trust it lol
My understanding was those circuits shouldn't be different, but then thought about how electricity takes path of least resistance and thought of the possibility of a value imbalance with the parallel resistors. Trying to "force" an explanation that it was the resistor bank....somehow.
Those resistors can take allot! With the previous testing of this amp, when the circuit was wired and connected such only one 8ohm resistor was taking the load it reached 32.6v (left CH, 32.8v right CH) just before clipping. (amp is rated for 110w in stereo at 0.08thd) Of course, that's with the resistor mounted to an aluminum heat sink and about 10 seconds powering. Was VERY hot though; and what lead me to realize I hadn't made the circuit correctly that time.
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The resistor will get far too hot to touch, and may even need heatsinking (depending on design) to be run at their rating.
As I noted before, a domestic amplifier, and especially a multi-channel AV receiver, should not be run at full power like this. You are very likely to cause damage to it, even if your load circuit is correct. A receiver like yours is designed for amplifying music and soundtracks where the actual unclipped power delivered by the amplifier is a fraction of the rated maximum.
Running such an amplifier like yours at it rated undistorted maximum output for more than a few seconds is likely to cause permanent damage.
As I noted before, a domestic amplifier, and especially a multi-channel AV receiver, should not be run at full power like this. You are very likely to cause damage to it, even if your load circuit is correct. A receiver like yours is designed for amplifying music and soundtracks where the actual unclipped power delivered by the amplifier is a fraction of the rated maximum.
Running such an amplifier like yours at it rated undistorted maximum output for more than a few seconds is likely to cause permanent damage.
Current through a resistor will obey Ohm's Law. Resistors in parallel will all see the same voltage, so the current through each individual resistor, I, will be I = V / R. So, the smaller the resistance, the more current will flow through it.
Yes, but we are talking about the overall current as in the diagram with paralleled resistors.
Kirchhoff's junction rule states that at any junction in a circuit, the sum of the currents flowing into that junction is equal to the sum of the currents flowing out of that junction. Therefore (looking at the diagram), the amount of current on the "exit" side of the resistors will equal the amount of current on the "entry" side.
OP was wondering:
"Out of curiosity. if the parallel resistors have a slightly different resistance; does the current flow primarily through the resistor with lesser resistance? Am wondering if maybe that is the case for the bank the left channel was connected to. too much variance between to parallel resistors."
"Out of curiosity. if the parallel resistors have a slightly different resistance; does the current flow primarily through the resistor with lesser resistance? Am wondering if maybe that is the case for the bank the left channel was connected to. too much variance between to parallel resistors."
Another word to the wise, don't muck about with speaker connections (or inputs for that matter) on any amplifier when it's switched on.
It's all too easy to short something briefly, and this can easily fry your outputs before protection kicks in. This assuming the amp even has short circuit/over current protection.
You're not the first, and certainly won't be the last to fry an amp mucking about with speaker connections [emoji28]
Don't feel too badly, at least now you get to learn about troubleshooting and repairing an amplifier.
It's all too easy to short something briefly, and this can easily fry your outputs before protection kicks in. This assuming the amp even has short circuit/over current protection.
You're not the first, and certainly won't be the last to fry an amp mucking about with speaker connections [emoji28]
Don't feel too badly, at least now you get to learn about troubleshooting and repairing an amplifier.
The resistors in parallel will average out.
Eg. If one is actually 8.5 ohms and the other 7.5
Yes, a little more current will flow in the 7.5 ohm resistor. But overall, the total resistance for the parallel pair is still close enough to 4 ohms. Actually 3.98 in this hypothetical case.
Note resistance will change as a resistor heats up - usually it will increase though, putting less load on the amplifer than it would at room temperature.
Eg. If one is actually 8.5 ohms and the other 7.5
Yes, a little more current will flow in the 7.5 ohm resistor. But overall, the total resistance for the parallel pair is still close enough to 4 ohms. Actually 3.98 in this hypothetical case.
Note resistance will change as a resistor heats up - usually it will increase though, putting less load on the amplifer than it would at room temperature.
I don't understand why the resistor loads connect to terminals labelled "power+" and "power -". If connected across power supply + and -, you sure would get a bang and smoke there. So do those labels really refer to audio output and power supply ground as they probably should for any load?
FWIW, I've loaded many domestic amplifiers with 8 ohm resistive loads to ensure the owner got what he was paying for in a repair. I didn't often take them up to more than about 75% of full rating though, for the reasons mentioned here by others. On the other hand, professional, as in live performances and P.A. amplifiers, have to do what they're rated to and load tests are usually required to verify the sustained maximum rated power over some interval of seconds or minutes even. It's a scary experience and nobody wants to refit a tube of power transistors because they made a small error somewhere but pro. users and their insurers demand what the spec. says.
FWIW, I've loaded many domestic amplifiers with 8 ohm resistive loads to ensure the owner got what he was paying for in a repair. I didn't often take them up to more than about 75% of full rating though, for the reasons mentioned here by others. On the other hand, professional, as in live performances and P.A. amplifiers, have to do what they're rated to and load tests are usually required to verify the sustained maximum rated power over some interval of seconds or minutes even. It's a scary experience and nobody wants to refit a tube of power transistors because they made a small error somewhere but pro. users and their insurers demand what the spec. says.
The first picture in your first post is :
Two parallel Circuits connecting in serial so it does not actually change anything..
To calculate, use that Formula:
R1 X R2 : R1+R2 this would be for the TOP two resistors each 8 Ohms @100 Watts
8X8 = 64 : 8+8 = 16 = 4 OHMS = If resistors are of equal Value you can just add the Value and then divide through the number of the resistors. But I wrote the full formula.
The same accounts for the second Two Resistors
Since the second two Resistors are in Series with the first two, so you do not lose anything and you do not win anything..
For Serial connection Resistors the Formula will be: R1+R2 = 4+4 = 8Ohms You do not even get the wattage of these 100 Watts Resistor increased nor decreased.
That counts for the First Picture in your first Post.
The second Picture in your First Post is a TOTAL SHORT CONNECTION,
Usually Speaker Output Fuse would blow, I could not see that you mention blown fuses. I have read that there were Smoke signals, so I tend to believe that you did not connect these resistors across the OUTPUT TERMINALS of the speakers,so no need to waste time about the second picture in your first post.
For the third Picture in your first post, there you have 4 and 8 ohms in series, this would be
4x8=32 : 4+8= 12 then 32:12= 2.6 OHMS RESISTANCE of these 3 Resistors connected, but wattage would be for the upper two resistors @100X2 = 200Watts and the lower one would be 100Watt, so overall Wattage would be less than 100 Watt viewing over all three Resistors. Voltage and also current would not be divided equal in this array.
But this is not the reason that the Amplifier blows up..
if connected to Speaker output. fuse would blow..
Either you do not tell us everything or there are no fuses in the output of the Speakers terminals of the Onkyo.. I will check the circuit of that Onkyo later. just to know if there are fuses or not..
Next time before you go and connect anything, take a lecture about OHMS LAW.
Hope this helps to clear up the smoke, using this formula above you can even calculate how much power was crossing or appearing in each of these resistors.
Regards..
Chris