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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Hard disk protection diode?
Does anyone have specific information about the protection device
at the power supply inputs of hard disks? I assume that it's a zener diode or something similar in action such as an IC that acts like a precision zener diode. It's not difficult to see how such a device would provide protection against spikes, over-voltage and reverse voltage by shorting the power rail to ground and thereby triggering PSU shutdown. Devices in the BUX C*** series seem to be widely used, but I have not been able to find a datasheet or other detailed info. Can anybody shed some light on the matter? |
#2
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Hard disk protection diode?
I know I'm not directly answering your question, but...
The socket and power cords are polarized. It would be extremely difficulty to insert the plug the wrong way. |
#3
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Hard disk protection diode?
William Sommerwerck wrote:
I know I'm not directly answering your question, but... The socket and power cords are polarized. It would be extremely difficulty to insert the plug the wrong way. Thanks for the reply. Yes, I expect that reverse voltage protection would be a secondary consideration. Its primary function would be protection against over-voltage, transient or sustained. Something like a crowbar or TVS device, but without the need for very low capacitance. A datasheet or identifying the manufacturer would be a big help. |
#4
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Hard disk protection diode?
On Jan 25, 10:51*am, "pimpom" wrote:
Does anyone have specific information about the protection device at the power supply inputs of hard disks? The most important reason a hard disk would need a protection device, is that the two power connections (motor power, 12V, and logic power, 5V) have a sequence condition requirement. So, the diode might clamp +12 to +5V so that a drop in the motor power (like, normal power turnoff) doesn't result in any short time during which the "+12" is actually at lower voltage than the "+5". Or, it might ensure that the +12 supply never goes negative (which could happen if a motor is active when power is removed). Probably this diode is NOT a Zener type, which is relatively important: high current Zeners often fail short-circuit (which would halt the computer until disconnected). |
#5
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Hard disk protection diode?
"pimpom" wrote in message ... Does anyone have specific information about the protection device at the power supply inputs of hard disks? I assume that it's a zener diode or something similar in action such as an IC that acts like a precision zener diode. It's not difficult to see how such a device would provide protection against spikes, over-voltage and reverse voltage by shorting the power rail to ground and thereby triggering PSU shutdown. Devices in the BUX C*** series seem to be widely used, but I have not been able to find a datasheet or other detailed info. Can anybody shed some light on the matter? BUX * devices are usually high voltage transistors Arfa |
#6
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Hard disk protection diode?
"Arfa Daily" wrote in
: "pimpom" wrote in message ... Does anyone have specific information about the protection device at the power supply inputs of hard disks? I assume that it's a zener diode or something similar in action such as an IC that acts like a precision zener diode. It's not difficult to see how such a device would provide protection against spikes, over-voltage and reverse voltage by shorting the power rail to ground and thereby triggering PSU shutdown. Devices in the BUX C*** series seem to be widely used, but I have not been able to find a datasheet or other detailed info. Can anybody shed some light on the matter? BUX * devices are usually high voltage transistors Arfa the PSU itself usually has overvoltage protection,where it really counts;on the +5 volt supply. The +12 is loosely regulated,and only runs the motor drive.some have "balance" nodes,that trigger SD if one or more of the supplies go too far outside a window. Then you don't need the expense of OV protection on every hard drive. -- Jim Yanik jyanik at kua.net |
#7
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Hard disk protection diode?
On Mon, 26 Jan 2009 00:21:34 +0530, "pimpom"
put finger to keyboard and composed: Does anyone have specific information about the protection device at the power supply inputs of hard disks? I assume that it's a zener diode or something similar in action such as an IC that acts like a precision zener diode. Is it a transient voltage suppression diode? http://en.wikipedia.org/wiki/Transie...pression_diode - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#8
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Hard disk protection diode?
On Sun, 25 Jan 2009 11:07:31 -0800, "William Sommerwerck"
put finger to keyboard and composed: I know I'm not directly answering your question, but... The socket and power cords are polarized. It would be extremely difficulty to insert the plug the wrong way. It would require a very heavy hand, but I *have* seen it done. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#9
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Hard disk protection diode?
whit3rd wrote:
On Jan 25, 10:51 am, "pimpom" wrote: Does anyone have specific information about the protection device at the power supply inputs of hard disks? The most important reason a hard disk would need a protection device, is that the two power connections (motor power, 12V, and logic power, 5V) have a sequence condition requirement. So, the diode might clamp +12 to +5V so that a drop in the motor power (like, normal power turnoff) doesn't result in any short time during which the "+12" is actually at lower voltage than the "+5". Or, it might ensure that the +12 supply never goes negative (which could happen if a motor is active when power is removed). Probably this diode is NOT a Zener type, which is relatively important: high current Zeners often fail short-circuit (which would halt the computer until disconnected). I rather expect that it is similar to a zener diode in action but more sophisticated than a simple discrete zener, perhaps with more precise breakdown voltage, lower dynamic resistance and more surge current capacity. And a shorted device is not uncommon. |
#10
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Hard disk protection diode?
Franc Zabkar wrote:
On Sun, 25 Jan 2009 11:07:31 -0800, "William Sommerwerck" put finger to keyboard and composed: I know I'm not directly answering your question, but... The socket and power cords are polarized. It would be extremely difficulty to insert the plug the wrong way. It would require a very heavy hand, but I *have* seen it done. In any case, reversing a 4-pin Molex connector will not reverse the polarity. It will just juxtapose the +5 and +12V lines. |
#11
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Hard disk protection diode?
Arfa Daily wrote:
"pimpom" wrote in message ... Does anyone have specific information about the protection device at the power supply inputs of hard disks? I assume that it's a zener diode or something similar in action such as an IC that acts like a precision zener diode. It's not difficult to see how such a device would provide protection against spikes, over-voltage and reverse voltage by shorting the power rail to ground and thereby triggering PSU shutdown. Devices in the BUX C*** series seem to be widely used, but I have not been able to find a datasheet or other detailed info. Can anybody shed some light on the matter? BUX * devices are usually high voltage transistors Yes. But transistors have the BUX followed by numeric characters. These devices have a "C" before numerals. |
#12
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Hard disk protection diode?
Jim Yanik wrote:
"Arfa Daily" wrote in : "pimpom" wrote in message ... Does anyone have specific information about the protection device at the power supply inputs of hard disks? I assume that it's a zener diode or something similar in action such as an IC that acts like a precision zener diode. It's not difficult to see how such a device would provide protection against spikes, over-voltage and reverse voltage by shorting the power rail to ground and thereby triggering PSU shutdown. Devices in the BUX C*** series seem to be widely used, but I have not been able to find a datasheet or other detailed info. Can anybody shed some light on the matter? BUX * devices are usually high voltage transistors Arfa the PSU itself usually has overvoltage protection,where it really counts;on the +5 volt supply. The +12 is loosely regulated,and only runs the motor drive.some have "balance" nodes,that trigger SD if one or more of the supplies go too far outside a window. Then you don't need the expense of OV protection on every hard drive. But there *are* such devices on every hard disk I've examined. At least, I can't think of any other purpose (counting inductive spikes as an OV condition). And not all PSUs are created equal. I have seen such devices burnt out on several HDDs, even to the extent of being literally blown apart. |
#13
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Hard disk protection diode?
Franc Zabkar wrote:
On Mon, 26 Jan 2009 00:21:34 +0530, "pimpom" put finger to keyboard and composed: Does anyone have specific information about the protection device at the power supply inputs of hard disks? I assume that it's a zener diode or something similar in action such as an IC that acts like a precision zener diode. Is it a transient voltage suppression diode? http://en.wikipedia.org/wiki/Transie...pression_diode Could be. In fact, I mentioned that in my second post. What I find surprising and frustrating is that I have not been able to find any data on the BUX C*** series. |
#14
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Hard disk protection diode?
On Mon, 26 Jan 2009 15:45:37 +0530, "pimpom"
put finger to keyboard and composed: Franc Zabkar wrote: On Mon, 26 Jan 2009 00:21:34 +0530, "pimpom" put finger to keyboard and composed: Does anyone have specific information about the protection device at the power supply inputs of hard disks? I assume that it's a zener diode or something similar in action such as an IC that acts like a precision zener diode. Is it a transient voltage suppression diode? http://en.wikipedia.org/wiki/Transie...pression_diode Could be. In fact, I mentioned that in my second post. What I find surprising and frustrating is that I have not been able to find any data on the BUX C*** series. This forum discussion is about TVS devices in hard drives: http://forum.hddguru.com/seagate-bar...ide-t9356.html The above discussion refers to this photo of a Seagate HDD with two TVS devices made by ON Semiconductor: http://forum.hddguru.com/download/file.php?id=562 The parts have the following markings: ON logo QE R617 ON logo 620 LEM . I can't find exactly the same parts in ON's datasheets, but here are a few similar looking devices: Unidirectional Zener TVS 13V 600W (marking = LEN): http://www.onsemi.com/pub/Collateral/NSB13AN-D.PDF Zener Transient Voltage Suppressor 12V 600W (marking = LEK): http://www.onsemi.com/pub/Collateral/NSB12A-D.PDF 400W Peak Power Zener Transient Voltage Suppressor 5V (marking = QA): http://www.onsemi.com/pub/Collateral/NSA5.0A-D.PDF 600 Watt Peak Power Zener Transient Voltage Suppressor 5V (marking = 6QE): http://www.onsemi.com/pub/Collateral/NS6A5.0A-D.PDF Here is a Vishay patent that discusses TVS devices with particular reference to their application in hard drives: http://www.freepatentsonline.com/WO2008002421.html - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#15
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Hard disk protection diode?
On Tue, 27 Jan 2009 06:13:23 +1100, Franc Zabkar
put finger to keyboard and composed: The above discussion refers to this photo of a Seagate HDD with two TVS devices made by ON Semiconductor: http://forum.hddguru.com/download/file.php?id=562 The parts have the following markings: ON logo QE R617 ON logo 620 LEM . 600 Watt Peak Power Zener Transient Voltage Suppressor, 12V, Unidirectional, p/n SMBJ12AON (marking = LEM): http://www.icbase.com/English/ic_sea...NS26380605.pdf The "QE" marking belongs to a 1SMA5.0AT3, 400 Watt Peak Power Zener Transient Voltage Suppressor: http://www.datasheetarchive.com/pdf-...SA-454313.html ON TVS/Zener Device Data Book: http://www.mosaico-eng.com.br/arquiv...et%20Zener.pdf - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#16
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Hard disk protection diode?
On Mon, 26 Jan 2009 15:19:08 +0530, "pimpom"
put finger to keyboard and composed: Arfa Daily wrote: "pimpom" wrote in message ... Does anyone have specific information about the protection device at the power supply inputs of hard disks? I assume that it's a zener diode or something similar in action such as an IC that acts like a precision zener diode. It's not difficult to see how such a device would provide protection against spikes, over-voltage and reverse voltage by shorting the power rail to ground and thereby triggering PSU shutdown. Devices in the BUX C*** series seem to be widely used, but I have not been able to find a datasheet or other detailed info. Can anybody shed some light on the matter? BUX * devices are usually high voltage transistors Yes. But transistors have the BUX followed by numeric characters. These devices have a "C" before numerals. The BU? marking code appears to be used by ST Microelectronics in their SMBJ series 600W Transil (TVS) range. See page 2 of the datasheet: http://www.st.com/stonline/products/...re/ds/5616.pdf The BUX marking isn't listed, but it would appear that the "U" designates a unidirectional device. The "C" appears to be the manufacturing location, followed by a numeric YWW date code. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#17
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Hard disk protection diode?
On Jan 25, 7:07*pm, "William Sommerwerck"
wrote: I know I'm not directly answering your question, but... The socket and power cords are polarized. It would be extremely difficulty to insert the plug the wrong way. I have come across these shorted protection diodes on 2 occasions now, both on Digital Audio Recorders powered by external wall warts. If the wrong polarity wall wart is used, you can get the wrong polarity 12Volts to the Hard Drive. This is shorted out by the diode, which eventually burns to a dead short protecting the drive. On both occasions replacing the diode restored the unit to fully operational. Good job they are there IMHO. Gareth. |
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