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Well, guys, I'm up a creek it seems here. I'm an old guy, raised on Tubes, and don't really understand Mosfets and the schematics for the QMX are hard for me to follow.
Some suggestions to trace the issue here would be much appreciated.
I built this QMX about 3 1/2 months ago. It's been working FB with firmware 006 ever since. This morning I was using it and transmitted accidentally with no antenna attached. It's happened before with no consequences, but this time something shorted out big time. The power supply went into current limiting at 1 amp with the voltage dropped to 6 volts. Powered off with a BIG SIGH!
Opened it up and just a little smell of hot electronics, but not the usual burnt smell. Inspecting all the boards and nothing obviously burned.
Lowered the voltage to 7 volts and current limiting to 600 mA. Pushed the encoder to power up and nothing happens. Raised the power back to 12V and with one hand on the power off switch pushed the encoder. Current started climbing rapidly so power off quickly.
Tried to figure out the schematics and I get lost with all the plug numbers not being consistent between pages and some times I see multiple connector diagrams like JP101 and JP102 that seem identical as well as new to me symbols, etc. and Not really knowing how things work in the sequence I finally started this email.
Obviously something in the power up sequence has shorted, but how to trace it I'm totally at a loss.
Some help/ideas will be greatly appreciated.
Thanks!!!
73,
Cliff, AE5ZA
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Most likely culprits are going to be the BS170's, and possibly
IC503, from other reports.
Paul -- AI7JR
On 8/28/23 15:32, Cliff wrote:
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Show quoted text
Well, guys, I'm up a creek it seems here. I'm an old guy, raised on Tubes, and don't really understand Mosfets and the schematics for the QMX are hard for me to follow.
Some suggestions to trace the issue here would be much appreciated.
I built this QMX about 3 1/2 months ago. It's been working FB with firmware 006 ever since. This morning I was using it and transmitted accidentally with no antenna attached. It's happened before with no consequences, but this time something shorted out big time. The power supply went into current limiting at 1 amp with the voltage dropped to 6 volts. Powered off with a BIG SIGH!
Opened it up and just a little smell of hot electronics, but not the usual burnt smell. Inspecting all the boards and nothing obviously burned.
Lowered the voltage to 7 volts and current limiting to 600 mA. Pushed the encoder to power up and nothing happens. Raised the power back to 12V and with one hand on the power off switch pushed the encoder. Current started climbing rapidly so power off quickly.
Tried to figure out the schematics and I get lost with all the plug numbers not being consistent between pages and some times I see multiple connector diagrams like JP101 and JP102 that seem identical as well as new to me symbols, etc. and Not really knowing how things work in the sequence I finally started this email.
Obviously something in the power up sequence has shorted, but how to trace it I'm totally at a loss.
Some help/ideas will be greatly appreciated.
Thanks!!!
73,
Cliff, AE5ZA
|
Thanks Paul. I realize that they may be blown, but from my recollection they didn't continue shorted. Low power out was the usual symptom IIRC. This is a complete short immediately on power on.
toggle quoted message
Show quoted text
Most likely culprits are going to be the BS170's, and possibly
IC503, from other reports. Paul -- AI7JR
On 8/28/23 15:32, Cliff wrote:
Well, guys, I'm up a creek it seems here. I'm an old guy, raised on Tubes, and don't really understand Mosfets and the schematics for the QMX are hard for me to follow.
Some suggestions to trace the issue here would be much appreciated.
I built this QMX about 3 1/2 months ago. It's been working FB with firmware 006 ever since. This morning I was using it and transmitted accidentally with no antenna attached. It's happened before with no consequences, but this time something shorted out big time. The power supply went into current limiting at 1 amp with the voltage dropped to 6 volts. Powered off with a BIG SIGH!
Opened it up and just a little smell of hot electronics, but not the usual burnt smell. Inspecting all the boards and nothing obviously burned.
Lowered the voltage to 7 volts and current limiting to 600 mA. Pushed the encoder to power up and nothing happens. Raised the power back to 12V and with one hand on the power off switch pushed the encoder. Current started climbing rapidly so power off quickly.
Tried to figure out the schematics and I get lost with all the plug numbers not being consistent between pages and some times I see multiple connector diagrams like JP101 and JP102 that seem identical as well as new to me symbols, etc. and Not really knowing how things work in the sequence I finally started this email.
Obviously something in the power up sequence has shorted, but how to trace it I'm totally at a loss.
Some help/ideas will be greatly appreciated.
Thanks!!!
73,
Cliff, AE5ZA
|
Yes. ?That is not unusual for blown finals. ?Try replacing all 4 BS170s. ?Chances are good that will fix it. ?If not it may be the driver IC needs replacement also.
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Jeffrey,
I'll take your word for it. I've blown the finals on the QDX and it was just low power out. I guess the QMX is different. That sure is an easier fix than some other things.
I'll just pull the finals and if it will power up then I'll know they are the issue.
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Show quoted text
Yes. ?That is not unusual for blown finals. ?Try replacing all 4 BS170s. ?Chances are good that will fix it. ?If not it may be the driver IC needs replacement also.
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Well, pulled the finals and still draws 700mA when the left encoder is pushed. It stays there until I kill the power to it. No display backlight.
Other things to check? I hate to pull the driver chip with out good evidence of a problem.
Is there a way to check things further?
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Show quoted text
Jeffrey,
I'll take your word for it. I've blown the finals on the QDX and it was just low power out. I guess the QMX is different. That sure is an easier fix than some other things.
I'll just pull the finals and if it will power up then I'll know they are the issue.
Yes. ?That is not unusual for blown finals. ?Try replacing all 4 BS170s. ?Chances are good that will fix it. ?If not it may be the driver IC needs replacement also.
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A thermal camera is hands down the best way to identify a shorted component. Turn on the power and look for the thing that glows. You can get one that attaches to your phone for about $2-300.
A multimeter in continuity mode is the second best way.
First order of business is to test for continuity from ground to each of the three voltage rails. The 2x4 and 2x3 headers that the power supply boards attach to are good places to do this.
To map the drawing of JP101-4 to the physical layout on the board, look at the board from the bottom side, i.e. the side with the microprocessor on it, with all of the through-hole components facing away from you. Turn the board until the antenna connector is pointing up, and the DC input jack is pointing down. The solder pads for the headers are now in the same orientation as they are in the schematic. But don't trust me on this, use your multimeter to verify ground (the body of the antenna connector is a convenient place to test this from) and Vin (use the center of the DC input jack) at minimum. This should be enough to make you confident.
If you are seeing a short from ground to either VCC (the +5 volt rail) or VDD (the +3.3 volt rail), try removing the associated power supply board and see if the short is still there. If the short went away when you removed the power supply board, the likely culprit is a failure of D108/9, or one of the tantalum capacitors C106/7. If the short persists with the power supplies removed, you have had a failure of one of the many ICs on your main board, and it's time to decide how you value your time, money, and energy. Be aware that even if you find and replace the failed component, the same event could have damaged other components without totally destroying them, and you could boot up your radio to find that still more work needs to be done. I had this realization after I managed to make my QMX boot again by removing IC403, and weighed the cost of buying and shipping a replacement IC in single digit quantity, and ended up just buying another QMX. Maybe I'll use the old one as a source of spare parts for the new one if I manage to fry that one too.
If the short you're finding is +12V to ground, again try to see whether the short is in the power supply board or in the main board. Luckily, not too many components are actually hooked up to +12V, at least in a way that makes them liable to short to ground.
Based on your symptoms: The board stays powered after releasing the encoder, which means the CPU is awake and putting voltage on the PWR_HOLD line, which means that the 3.3V rail is good. But no display, and the display runs on the 5V rail. So I would say the issue is somewhere on the 5V rail.
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Steven,
Thanks so much for the response. I'll get to it and respond when I know more. I've a lot to learn here.
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Show quoted text
A thermal camera is hands down the best way to identify a shorted component. Turn on the power and look for the thing that glows. You can get one that attaches to your phone for about $2-300.
A multimeter in continuity mode is the second best way.
First order of business is to test for continuity from ground to each of the three voltage rails. The 2x4 and 2x3 headers that the power supply boards attach to are good places to do this.
To map the drawing of JP101-4 to the physical layout on the board, look at the board from the bottom side, i.e. the side with the microprocessor on it, with all of the through-hole components facing away from you. Turn the board until the antenna connector is pointing up, and the DC input jack is pointing down. The solder pads for the headers are now in the same orientation as they are in the schematic. But don't trust me on this, use your multimeter to verify ground (the body of the antenna connector is a convenient place to test this from) and Vin (use the center of the DC input jack) at minimum. This should be enough to make you confident.
If you are seeing a short from ground to either VCC (the +5 volt rail) or VDD (the +3.3 volt rail), try removing the associated power supply board and see if the short is still there. If the short went away when you removed the power supply board, the likely culprit is a failure of D108/9, or one of the tantalum capacitors C106/7. If the short persists with the power supplies removed, you have had a failure of one of the many ICs on your main board, and it's time to decide how you value your time, money, and energy. Be aware that even if you find and replace the failed component, the same event could have damaged other components without totally destroying them, and you could boot up your radio to find that still more work needs to be done. I had this realization after I managed to make my QMX boot again by removing IC403, and weighed the cost of buying and shipping a replacement IC in single digit quantity, and ended up just buying another QMX. Maybe I'll use the old one as a source of spare parts for the new one if I manage to fry that one too.
If the short you're finding is +12V to ground, again try to see whether the short is in the power supply board or in the main board. Luckily, not too many components are actually hooked up to +12V, at least in a way that makes them liable to short to ground.
Based on your symptoms: The board stays powered after releasing the encoder, which means the CPU is awake and putting voltage on the PWR_HOLD line, which means that the 3.3V rail is good. But no display, and the display runs on the 5V rail. So I would say the issue is somewhere on the 5V rail.
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Well, Steven I owe you on this one. You called it right to the component. The short was on the 5V rail and the component was D108. That is sure a tiny little diode. Going to be fun to put a new one in.
Now the fun of trying to find a part number for that diode. The parts list only gives the specs, not a part number.
toggle quoted message
Show quoted text
A thermal camera is hands down the best way to identify a shorted component. Turn on the power and look for the thing that glows. You can get one that attaches to your phone for about $2-300.
A multimeter in continuity mode is the second best way.
First order of business is to test for continuity from ground to each of the three voltage rails. The 2x4 and 2x3 headers that the power supply boards attach to are good places to do this.
To map the drawing of JP101-4 to the physical layout on the board, look at the board from the bottom side, i.e. the side with the microprocessor on it, with all of the through-hole components facing away from you. Turn the board until the antenna connector is pointing up, and the DC input jack is pointing down. The solder pads for the headers are now in the same orientation as they are in the schematic. But don't trust me on this, use your multimeter to verify ground (the body of the antenna connector is a convenient place to test this from) and Vin (use the center of the DC input jack) at minimum. This should be enough to make you confident.
If you are seeing a short from ground to either VCC (the +5 volt rail) or VDD (the +3.3 volt rail), try removing the associated power supply board and see if the short is still there. If the short went away when you removed the power supply board, the likely culprit is a failure of D108/9, or one of the tantalum capacitors C106/7. If the short persists with the power supplies removed, you have had a failure of one of the many ICs on your main board, and it's time to decide how you value your time, money, and energy. Be aware that even if you find and replace the failed component, the same event could have damaged other components without totally destroying them, and you could boot up your radio to find that still more work needs to be done. I had this realization after I managed to make my QMX boot again by removing IC403, and weighed the cost of buying and shipping a replacement IC in single digit quantity, and ended up just buying another QMX. Maybe I'll use the old one as a source of spare parts for the new one if I manage to fry that one too.
If the short you're finding is +12V to ground, again try to see whether the short is in the power supply board or in the main board. Luckily, not too many components are actually hooked up to +12V, at least in a way that makes them liable to short to ground.
Based on your symptoms: The board stays powered after releasing the encoder, which means the CPU is awake and putting voltage on the PWR_HOLD line, which means that the 3.3V rail is good. But no display, and the display runs on the 5V rail. So I would say the issue is somewhere on the 5V rail.
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Found the part ok. $0.23 and shipping $7. <sigh>
Have to try to guess what other parts I many need to justify the shipping.
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Show quoted text
Well, Steven I owe you on this one. You called it right to the component. The short was on the 5V rail and the component was D108. That is sure a tiny little diode. Going to be fun to put a new one in.
Now the fun of trying to find a part number for that diode. The parts list only gives the specs, not a part number.
A thermal camera is hands down the best way to identify a shorted component. Turn on the power and look for the thing that glows. You can get one that attaches to your phone for about $2-300.
A multimeter in continuity mode is the second best way.
First order of business is to test for continuity from ground to each of the three voltage rails. The 2x4 and 2x3 headers that the power supply boards attach to are good places to do this.
To map the drawing of JP101-4 to the physical layout on the board, look at the board from the bottom side, i.e. the side with the microprocessor on it, with all of the through-hole components facing away from you. Turn the board until the antenna connector is pointing up, and the DC input jack is pointing down. The solder pads for the headers are now in the same orientation as they are in the schematic. But don't trust me on this, use your multimeter to verify ground (the body of the antenna connector is a convenient place to test this from) and Vin (use the center of the DC input jack) at minimum. This should be enough to make you confident.
If you are seeing a short from ground to either VCC (the +5 volt rail) or VDD (the +3.3 volt rail), try removing the associated power supply board and see if the short is still there. If the short went away when you removed the power supply board, the likely culprit is a failure of D108/9, or one of the tantalum capacitors C106/7. If the short persists with the power supplies removed, you have had a failure of one of the many ICs on your main board, and it's time to decide how you value your time, money, and energy. Be aware that even if you find and replace the failed component, the same event could have damaged other components without totally destroying them, and you could boot up your radio to find that still more work needs to be done. I had this realization after I managed to make my QMX boot again by removing IC403, and weighed the cost of buying and shipping a replacement IC in single digit quantity, and ended up just buying another QMX. Maybe I'll use the old one as a source of spare parts for the new one if I manage to fry that one too.
If the short you're finding is +12V to ground, again try to see whether the short is in the power supply board or in the main board. Luckily, not too many components are actually hooked up to +12V, at least in a way that makes them liable to short to ground.
Based on your symptoms: The board stays powered after releasing the encoder, which means the CPU is awake and putting voltage on the PWR_HOLD line, which means that the 3.3V rail is good. But no display, and the display runs on the 5V rail. So I would say the issue is somewhere on the 5V rail.
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I suppose it depends on how they failed... I have (had) mine in
sockets, so they're relatively easy to remove for troubleshooting.
Good Luck!
73, Paul -- AI7JR
On 8/28/23 17:03, Cliff wrote:
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Thanks Paul. I realize that they may be blown, but from my
recollection they didn't continue shorted. Low power out was the
usual symptom IIRC. This is a complete short immediately on power
on.
Most likely culprits are going to be the
BS170's, and possibly IC503, from other reports.
Paul -- AI7JR
On 8/28/23 15:32, Cliff
wrote:
Well, guys, I'm up a creek it seems here. I'm an old guy, raised on Tubes, and don't really understand Mosfets and the schematics for the QMX are hard for me to follow.
Some suggestions to trace the issue here would be much appreciated.
I built this QMX about 3 1/2 months ago. It's been working FB with firmware 006 ever since. This morning I was using it and transmitted accidentally with no antenna attached. It's happened before with no consequences, but this time something shorted out big time. The power supply went into current limiting at 1 amp with the voltage dropped to 6 volts. Powered off with a BIG SIGH!
Opened it up and just a little smell of hot electronics, but not the usual burnt smell. Inspecting all the boards and nothing obviously burned.
Lowered the voltage to 7 volts and current limiting to 600 mA. Pushed the encoder to power up and nothing happens. Raised the power back to 12V and with one hand on the power off switch pushed the encoder. Current started climbing rapidly so power off quickly.
Tried to figure out the schematics and I get lost with all the plug numbers not being consistent between pages and some times I see multiple connector diagrams like JP101 and JP102 that seem identical as well as new to me symbols, etc. and Not really knowing how things work in the sequence I finally started this email.
Obviously something in the power up sequence has shorted, but how to trace it I'm totally at a loss.
Some help/ideas will be greatly appreciated.
Thanks!!!
73,
Cliff, AE5ZA
|
Paul - AI7JR