I am one of the people with a sudden failed regulator.
I have my build running on AC only no batteries, all parts with the exception of a couple of out of stock resistors are exactly from the BOM.
The amp had been working fine for about a week. Yesterday I turned it on with my TF10's attached, there was a squeal and then silence. The U6 regulator starts to heat up a lot, U5 remains cool.
I shut down unplugged everything for an hour to allow it to cool. Started it up and with the same result, no audio and uncontrolled heat up of U6.
Someone else reported the same problem on the same day. I'm starting to think there maybe some QC issues with On Semiconductor. When I replace them I will go back to the slightly pricier TI, National, or Fairchild regs I'm familiar with.
Funny thing is a couple of weeks ago I was responding on head-fi with a suspected failed regulator, about how generally difficult it is to kill a regulator...this is karma I guess.
I have my build running on AC only no batteries, all parts with the exception of a couple of out of stock resistors are exactly from the BOM.
The amp had been working fine for about a week. Yesterday I turned it on with my TF10's attached, there was a squeal and then silence. The U6 regulator starts to heat up a lot, U5 remains cool.
I shut down unplugged everything for an hour to allow it to cool. Started it up and with the same result, no audio and uncontrolled heat up of U6.
Someone else reported the same problem on the same day. I'm starting to think there maybe some QC issues with On Semiconductor. When I replace them I will go back to the slightly pricier TI, National, or Fairchild regs I'm familiar with.
Funny thing is a couple of weeks ago I was responding on head-fi with a suspected failed regulator, about how generally difficult it is to kill a regulator...this is karma I guess.
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see, its exactly this sort of dismissive and condescending comment that will stop people (particularly new people just starting diy and not confident in describing technicalities, possibly in a second language) coming and asking for help if they are having problems, same as over at the other forum. from the stories of the identical problems, it appears to have nothing to do with being careful, not checking for bridges etc, functional amps all of a sudden become dysfunctional amps. perhaps it is something all are doing wrong, but that itself needs to be looked into and fixed as its unlikely to be coincidence
see i started to question my own comments in that thread, i found myself confronting a particular builder immediately stating that it had to be user error because the design has been built, tested and is sound. but really this still leaves quite a few variables that dont include user error and it does the project a disservice to assume it from the get go.
and btw, i assume you mean regulator, not rectifier.. get it right!! hehe
anyway i'm off to bed, hopefully you guys can get to the bottom of it; put wicked headphones rather than fingers in your ears.
btw i'm really not just trying to cause trouble or argument here, i just think the vibe in that thread has been pretty bad from both sides and theres no need to continue here
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Thanks everyone for your comments. This seems, so far, to be isolated to just a few people at head-fi (hysteria-fi?) and exactly one (out of more than 1000) who is concerned enough to even post here. To summarize what I know so far:
I'm only aware of 3 or perhaps 4 people with the problem. Deadlylover doesn't seem to have the regulator problem, he just seems to be stirring up the pot as he's done in the past (example making a big deal out of the turn-off transient and then, after I published a scope photo of the actual transient, saying it was no big deal).
Cheapskateaudio has been an O2 detractor all along and seems to have started the hysteria. Given all some have invested in "esoteric audio", it's hardly surprising a few choose to build the O2 mainly to shoot it down however they can. It's obvious when someone is more concerned with trying to justify their own highly subjective positions at all costs, keep Santa Klaus and other myths alive, has financial interests to protect, is a H-F shill, etc.
Mikeaj and Konga (same person?) seem to have a problem but it may not be the 7912 as suspected. Both said the amp was working then stopped and the 7912 got hot. That likely means there's a short (or near short) somewhere on the negative rail and it's simply in shutdown. He/they may only expect its a regulator problem because of the other hysteria created by only a couple other people.
It is difficult to kill a regulator. To whoever posted on head-fi they're not protected against sustained operation outside their specifications should know they're being operated well within their specifications in the O2. They're not even close to being run too hot, with too much current, etc. Someone should post this on H-F:
Max Input Voltage = 35V, O2 voltage with 16 volt transformer = 23V
Max Current 1A continuous, 2.2A peak, O2 peak current < 0.4 amps
Max Junction Temp = 125C, O2 junction junction temp 45C - 65C
There are implied claims BOTH regulators somehow failed. The odds of that are near zero unless there's a problem upstream of the regulators like too high of a wall transformer voltage or bad/wrong diodes (D3/D4). The correct 1N4002 diodes are bulletproof but if someone put the 1N5818 in those locations by mistake, they may well fail shorted.
Someone else pointed out the regulators touching the top of the enclosure could be a problem if they're soldered in too "high". I agree with that although it's still unlikely to kill the regulators.
Someone might point out the regulators do not have reverse bias diodes around them, but that's because they have diodes isolating them and only small 0.22 uF caps on their outputs. Reverse diodes across the regulators are not required per the manufactures.
The BOM has specified On Semi regulators since well before the group buys but there's talk of "off brand" regulators. Either someone is horribly mistaken and considers On Semi (formerly part of Motorola and one of the biggest linear/analog IC companies on the planet) "off brand" or they're using some other unspecified parts. Konga above said On Semi but there's no proof his regulator is even bad.
FOR THOSE HAVING PROBLEMS: I would suggest the following:
Hopefully your op amps are in sockets. Remove all 4 of them, and the batteries, and see if the voltages across the battery terminals return to normal and the regulators are both barely warm. If so, you have at least one bad op amp. Replace them one at a time to find the bad one, or for less than $2, just replace all of them. If not, you likely have a solder bridge, something touching the case, or (unlikely) another failed component somewhere--the most likely suspects are the 0.22 uF caps (C17, C18).
If your op amps are not socketed, heat and lift up (desolder) one end of D1 and D5 and measure the voltages across C6 and C7. If they're normal, see above about dead op amps, solder bridges, etc.
If with no load on the regulators the voltages are still not normal, measure the DC voltage across both C4 and C5. It should be around 18 - 29 volts on each cap. Set the DMM for AC voltage and measure again. Each should be under 1 volt. If you measure high AC, replace D3 and D4. If you measure more than 30 volts DC you need a different wall transformer.
IMPORTANT: If anyone has had a regulator fail and deliver over 15 volts to the entire board (it's not clear anyone has), you should replace all the op amps after verifying the power supply is working correctly per the test procedures in the O2 Details article.
REMOVING OP AMPS: For socketed op amps carefully pry them up from each end a little bit at a time with a very small flat screwdriver. For soldered in op amps (hopefully there are not any), cut the chips out with small diagonal cutters and de-solder each pin individually.
I'm only aware of 3 or perhaps 4 people with the problem. Deadlylover doesn't seem to have the regulator problem, he just seems to be stirring up the pot as he's done in the past (example making a big deal out of the turn-off transient and then, after I published a scope photo of the actual transient, saying it was no big deal).
Cheapskateaudio has been an O2 detractor all along and seems to have started the hysteria. Given all some have invested in "esoteric audio", it's hardly surprising a few choose to build the O2 mainly to shoot it down however they can. It's obvious when someone is more concerned with trying to justify their own highly subjective positions at all costs, keep Santa Klaus and other myths alive, has financial interests to protect, is a H-F shill, etc.
Mikeaj and Konga (same person?) seem to have a problem but it may not be the 7912 as suspected. Both said the amp was working then stopped and the 7912 got hot. That likely means there's a short (or near short) somewhere on the negative rail and it's simply in shutdown. He/they may only expect its a regulator problem because of the other hysteria created by only a couple other people.
It is difficult to kill a regulator. To whoever posted on head-fi they're not protected against sustained operation outside their specifications should know they're being operated well within their specifications in the O2. They're not even close to being run too hot, with too much current, etc. Someone should post this on H-F:
Max Input Voltage = 35V, O2 voltage with 16 volt transformer = 23V
Max Current 1A continuous, 2.2A peak, O2 peak current < 0.4 amps
Max Junction Temp = 125C, O2 junction junction temp 45C - 65C
There are implied claims BOTH regulators somehow failed. The odds of that are near zero unless there's a problem upstream of the regulators like too high of a wall transformer voltage or bad/wrong diodes (D3/D4). The correct 1N4002 diodes are bulletproof but if someone put the 1N5818 in those locations by mistake, they may well fail shorted.
Someone else pointed out the regulators touching the top of the enclosure could be a problem if they're soldered in too "high". I agree with that although it's still unlikely to kill the regulators.
Someone might point out the regulators do not have reverse bias diodes around them, but that's because they have diodes isolating them and only small 0.22 uF caps on their outputs. Reverse diodes across the regulators are not required per the manufactures.
The BOM has specified On Semi regulators since well before the group buys but there's talk of "off brand" regulators. Either someone is horribly mistaken and considers On Semi (formerly part of Motorola and one of the biggest linear/analog IC companies on the planet) "off brand" or they're using some other unspecified parts. Konga above said On Semi but there's no proof his regulator is even bad.
FOR THOSE HAVING PROBLEMS: I would suggest the following:
Hopefully your op amps are in sockets. Remove all 4 of them, and the batteries, and see if the voltages across the battery terminals return to normal and the regulators are both barely warm. If so, you have at least one bad op amp. Replace them one at a time to find the bad one, or for less than $2, just replace all of them. If not, you likely have a solder bridge, something touching the case, or (unlikely) another failed component somewhere--the most likely suspects are the 0.22 uF caps (C17, C18).
If your op amps are not socketed, heat and lift up (desolder) one end of D1 and D5 and measure the voltages across C6 and C7. If they're normal, see above about dead op amps, solder bridges, etc.
If with no load on the regulators the voltages are still not normal, measure the DC voltage across both C4 and C5. It should be around 18 - 29 volts on each cap. Set the DMM for AC voltage and measure again. Each should be under 1 volt. If you measure high AC, replace D3 and D4. If you measure more than 30 volts DC you need a different wall transformer.
IMPORTANT: If anyone has had a regulator fail and deliver over 15 volts to the entire board (it's not clear anyone has), you should replace all the op amps after verifying the power supply is working correctly per the test procedures in the O2 Details article.
REMOVING OP AMPS: For socketed op amps carefully pry them up from each end a little bit at a time with a very small flat screwdriver. For soldered in op amps (hopefully there are not any), cut the chips out with small diagonal cutters and de-solder each pin individually.
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Thanks for giving the folks with problems something to look for. I myself haven't had any problems at all in the 3 weeks since I built mine. The regulators touching the top of the enclosure is really hard to do since they're shorter than the caps and mosfet in to-220. Jumping to conclusions in what could be wrong leads to missing the obvious way too often.
perfect, thanks RS. i hope you know what i mean; its things like this
with this number of builders and different avenues for kits landing in peoples hands, many maybe not buying their own parts or even knowing how to identify parts past the label on the snaplock baggie. things like this need to be looked at in exactly the way that you have just done RS with the comprehensive checklist above, the BOM that lands in peoples hands may in some cases look like the right bom, but something goes amiss.
but dismissive and divisive comments do not help anyone, they only serve to scare people from bringing up issues that may be real problems, not with the design so much as the supply chain. i think the big sanctioned GBs are likely to all be perfectly fine, but there will be kits, part finished amps, pcbs with scribbled or printed BOMs that are old etc etc. the world is full of people wanting to make a few bucks and they dont all know what they are doing
with this number of builders and different avenues for kits landing in peoples hands, many maybe not buying their own parts or even knowing how to identify parts past the label on the snaplock baggie. things like this need to be looked at in exactly the way that you have just done RS with the comprehensive checklist above, the BOM that lands in peoples hands may in some cases look like the right bom, but something goes amiss.
but dismissive and divisive comments do not help anyone, they only serve to scare people from bringing up issues that may be real problems, not with the design so much as the supply chain. i think the big sanctioned GBs are likely to all be perfectly fine, but there will be kits, part finished amps, pcbs with scribbled or printed BOMs that are old etc etc. the world is full of people wanting to make a few bucks and they dont all know what they are doing
I'm no expert when it comes to these things, but I ordered this one from Amazon two years ago and have LOVED using it.
Amazon.com: Aoyue 937+ Digital Soldering Station: Home Improvement
Not sure if you can find it in Deutschland, but if so, I'd highly recommend it for electronics work.
@qusp, good point that many may not know who On Semi is--especially among the H-F crowd. I need to do better keeping that sort of thing in mind. Here on diyAudio it seems safe to assume a bit more general knowledge. The O2 was never really intended as a total novice DIY project. Those warnings have been in the documentation from the start. The idea was someone would step up and offer at least assembled boards and that's happened nicely. To my knowledge none of those boards have had any problems at all (and MrSlim just confirmed that's the case for the ones he's built).
Of the 2000+ PC boards I know were manufactured at least many hundreds should be assembled boards by now. You can count the group buys on one hand and, at least those in the North America, Europe and Australia/NZ, were done by what seem like reputable guys who followed the correct BOMs, etc.
Out of those many hundreds of assembled boards, only a couple people have reported this issue and at least one or two of them have a track record of zealously highlighting negative things--factual or otherwise--about the O2. The other few have not even demonstrated the regulators failed. Their boards may have a bent over lead shorting something out somewhere.
Of the 2000+ PC boards I know were manufactured at least many hundreds should be assembled boards by now. You can count the group buys on one hand and, at least those in the North America, Europe and Australia/NZ, were done by what seem like reputable guys who followed the correct BOMs, etc.
Out of those many hundreds of assembled boards, only a couple people have reported this issue and at least one or two of them have a track record of zealously highlighting negative things--factual or otherwise--about the O2. The other few have not even demonstrated the regulators failed. Their boards may have a bent over lead shorting something out somewhere.
Here we have the exact reason why you get so many hateful replies. I reported an issue I was having just like you requested a few posts back and I get 8 paragraphs of derisive drivel before you offer any thing remotely helpful.
Deadlylover, mikeaj, and I just so happen to have the same issue in a very same span of time. We all reported the issues just like you asked and this is how you reply. I only suggested that based on the evidence that maybe there was a bad batch of components. Is that so beyond the realm of possibility? Like that's never happened to any builders on here in the past.
Not in any way have I been a "detractor" and poo-poo your design or even blame the amplifier itself.
No, Mikeaj and I are not the same person. My sn on head-fi is FrancisDemarte. We just happen to have the same problem on the exact same day.
This was you need to say and it would have been the end of it.
The post wasn't aimed at you Konga, it was intended as a summary of everything I know so far about this issue and you're just one small part of that. I'm sorry if you're offended but put yourself in my shoes. Something seems not quite right with at least some of what's been posted. I tried to divide the issues up by what I know about them.
You and mikeaj obviously have a legit problem. But we don't know that it's the 7912 unless I missed something?
Yes, it's possible there's a bad batch of 7912's. But haven't others claimed the 7812 has also failed? What are the odds two completely different, normally bulletproof, parts suddenly start failing the same week when there have been O2's in the wild since August?
I admit I'm prone to being defensive, but it's been my experience in the past, the only way to sort the truth from the spin at H-F is to spell out the facts. That's all I'm trying to do.
You and mikeaj obviously have a legit problem. But we don't know that it's the 7912 unless I missed something?
Yes, it's possible there's a bad batch of 7912's. But haven't others claimed the 7812 has also failed? What are the odds two completely different, normally bulletproof, parts suddenly start failing the same week when there have been O2's in the wild since August?
I admit I'm prone to being defensive, but it's been my experience in the past, the only way to sort the truth from the spin at H-F is to spell out the facts. That's all I'm trying to do.
A strong caution is in place here, if a cheap multimeter is being used for this. Some of the ultra cheap meters have a problem measuring AC superimposed on DC. I have several meters, of which one is such a dinky little meter. It works fine, but when I set the meter to AC and feed it with DC, it displays the DOUBLE DC value, instead of zero. So when you measure the voltage on the input caps of the regulators in AC setting, don't be surprised that some meters from the bargain basket display alarmingly high voltages when attempting to measure ripple voltage. It's the meter's fault.
I never bothered to find out why this meter behaves like this, but I noticed several other cheapies do this as well. I always keep this in mind when I am condemned to using it. My other meters don't have this issue. So before attempting this measurement, check if it displays 0 when set to AC and connected to a 9V battery.
its because its not a true RMS meter, but rather uses averaging to display AC and the average of AC has a DC value. basically cheap meters are useless for AC power, or measuring AC riding on a DC offset unless the AC is a pure sinewave; even then i wouldnt trust it
you have to spend some pretty serious cash on a DMM to get good quality VAC RMS metering; even those that claim to do it are mostly pretty useless until you get away from the hobbiest models. thats why i have an old benchtop HP3400A voltmeter with a modified input circuit around the workshop, because even my fluke is a bit dinky with offset AC
you have to spend some pretty serious cash on a DMM to get good quality VAC RMS metering; even those that claim to do it are mostly pretty useless until you get away from the hobbiest models. thats why i have an old benchtop HP3400A voltmeter with a modified input circuit around the workshop, because even my fluke is a bit dinky with offset AC
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Good points, thanks. I've never seen that but I could certainly imagine it happening. I just checked a seriously cheesy $5 "pen style" DMM that I got free from somewhere (with one probe built into the pen shaped body of the DMM) and even it reads close to zero on the primary side of the O2 when set to AC.
If anyone does measure a high AC voltage with a questionable meter they can desolder one side of D3 and D4 and use the resistance range to test them in both polarities for hopefully a low resistance in one direction and infinite in the other (some meters may read infinite in both directions).
If anyone does measure a high AC voltage with a questionable meter they can desolder one side of D3 and D4 and use the resistance range to test them in both polarities for hopefully a low resistance in one direction and infinite in the other (some meters may read infinite in both directions).
I have another (better) meter which is also not a true RMS meter, but it doesn't have this problem. I think that the manufacturer of the cheap meter has left out the input capacitor on the AC ranges. Instead, it just rectifies the input voltage and measures the average resulting voltage and displays it with a correction factor. However, that doesn't explain the observed factor of exactly two...
Edit: mine was even less than € 5, and it is a handheld meter with "normal" test leads. Imagine how cheesy that one must be inside.
Edit: mine was even less than € 5, and it is a handheld meter with "normal" test leads. Imagine how cheesy that one must be inside.
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@rocketscientist : Does this mean that I can use the output from a voltage output DAC chip without coupling capacitors? Could I use a source with 2-3 volts of DC without any consequences? I have a modded iPod with the output taken directly from the Wolfson chip to film capacitors to block DC. If the O2 is not effected by the DC at it's input, then I could just connect the DAC output directly to the O2. That would be very interesting for the whole DIYmod/imod crowd, since fitting great caps into the iPod case is a major issue, or for anyone using a voltage output DAC, since they usually don't have more than a few volts of DC.
If this is absurd, I apologize. I hadn't thought that putting DC into the input of an amplifier was reasonable, but since you wrote the statement above, I thought I would ask. Thank you for your consideration.
Aaron.
Keep in mind that while DC of a few volts will not damage the O2, it can still drive the input amp into clipping since it's amplified with the same gain as the signal there.
The ODA will hopefully have an extra coupling capacitor (bipolar 'lytic should do) and input pull-down resistor. I guess space was too tight in the O2.
The ODA will hopefully have an extra coupling capacitor (bipolar 'lytic should do) and input pull-down resistor. I guess space was too tight in the O2.
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@orpheus, I was talking about things that might damage the ICs in the O2. DC up to 7 volts won't hurt the O2 but if the DC is high enough it will force the first stage into clipping. At 2.5X gain, 2 volts of DC would shift the operating point of the first stage to +5 volts leaving only about 5 volts left for "swing". That would limit the max output to about 3.5 Vrms. 3 volts would severely limit the maximum undistorted output.
If you can live with 1X gain, you could easily get away with it on AC power. So it depends on what headphones you're trying to drive. There would likely be a potentially nasty turn on/off transient if you powered up/down the iPod with the O2 on and the headphones connected.
There's room to "hack" some high quality film input caps into the O2 if you want. Two more of same highly transparent 2.2 uF caps already used can probably sit behind the input jack and gain switch laying on their sides. You could desolder the "input" end of R3 and R7 and wire from those resistors and the pads they were just desoldered from. This would put the caps in series with the resistors and solve the issue with no external hardware. Just keep the wires really short (wire wrap wire works well). The caps could be secured with a dab of hot glue or similar.
If you can live with 1X gain, you could easily get away with it on AC power. So it depends on what headphones you're trying to drive. There would likely be a potentially nasty turn on/off transient if you powered up/down the iPod with the O2 on and the headphones connected.
There's room to "hack" some high quality film input caps into the O2 if you want. Two more of same highly transparent 2.2 uF caps already used can probably sit behind the input jack and gain switch laying on their sides. You could desolder the "input" end of R3 and R7 and wire from those resistors and the pads they were just desoldered from. This would put the caps in series with the resistors and solve the issue with no external hardware. Just keep the wires really short (wire wrap wire works well). The caps could be secured with a dab of hot glue or similar.
Thank you for taking the time to respond. I might try adding some input caps to my O2, or just keep the caps in the iPod as I have them now. I appreciate the consistent thoroughness of your responses. Thank you again for all of your work and for sharing this amplifier with all of us.
Aaron.
as i said it depends on the type of AC, if using it on a music signal +DC, rather than plain regular sinewave based AC power, you will have this problem on anything but a true RMS meter. for example square wave causes big issues. if you cheapie works on that its a miracle
i'm not saying it will display double, since that is just straight up weird, but the AC or DC readings you get will not be accurate (as in...you know the mV it claims to show is meaningful). without one that is true RMS to check it against you dont have a point of reference.
i dunno if the above explanation makes sense, since i only just opened my eyes after 5hrs sleep and there is no caffeine coursing through my veins yet
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