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Bad P6KE150A Transient Voltage Suppressor Diode In HP Power Adapter
Normally we call our articles a repair when we add or replace a component in a device to make it work. However the device in this repair did work by just REMOVING one single component!, so I maybe better call this article a Fix instead?
But let us start from the beginning. I found a used LCD Monitor at the Dump in my neighbourhood, a FLAT PRO_ MEDION Monitor. They had removed the Screws and its Stand. So I mounted another heavy Alu Metal Stand I had saved from an old disassembled Monitor. And it had no 19V 2.5A Power Adapter either. Therefore I used an old HP Power Adapter to test it which worked great although the Adapter only was designed for 18V 1.1A, thinking it wouldn’t really matter because often the given Amperage is higher than the real Amperage. And since the Monitor worked without any problem whatsoever I put it aside for another occasion.
And yesterday I quickly needed a Monitor to test and install my friend’s 2 desktop computers. Why I used the Medion LCD Monitor and the HP Adapter (a HP AC POWER to DC C6409-60014 Adapter).
But after about less than a half hour or so the Monitor screen went blank. And after measuring the DC Adapter output it was obvious that only 2.5V DC never would work. So I continued my work on my friend’s PCs after attaching my Medion Monitor to my +30V 10A DC adjustable Wanptek KPS3010D. This little adjustable but great DC power supply unit was also mentioned in one of my previous Laptop repairs.
The Monitor needed 2.49A at 19V according to the display of the PS3010D. So my HP Power Adapter (previous for a Printer Power Supply) was working too hard and finally had quit on me! Removing the 3 screws to open the Adapter was easily possible after pinching through the bottom Sticker/Label. The now defect HP printer AC-DC Adapter would have to wait for another moment after I first had fixed my friend’s little PC problems. Below is the Monitor and the KPS3010D.
And today I opened the 18V 1.1A HP Power Adapter to investigate further. I couldn’t find anything wrong with the secondary Dual Diode, the Primary Diode Bridge, The Fuse, or the Power Transistor a Toshiba K2545 Silicon N Channel V-Mosfet . Everything was okay. Following photos show the inside of this service friendly made Adapter.
Previous photos showed the DAP 001 controller from STMicroelectronics / Heisener electronics that was not burned either. And the Toshiba K2545 Silicon N Channel V-Mosfet. And all Diodes and resistors were fine, except ZD1 that had a resistance of 24 ohm in both directions. And after I removed it from the PCB and tested it with my fast and great working PEAK DCA Pro 75 tester (that operates on a cheap and simple single AAA battery!), The Display showed ‘No Component detected’.
The ZD1 Diode with P6KE150A marking was a 600W Suppressor diode from Littlefuse. And I decided to remove it because the reason for activating this protector Diode was now disconnected (which was removing the Monitor from the adapter) and there were no other faults. I also used my Blue ESR Tester to measure the ZD1 resistance in both directions. It was 19 Ohm.
So because nothing else seemed broken, burned or short circuited I used the Light Bulb trick to see if the HP Adapter would work again after having removed this Littlefuse suppressor Diode.
And it did! Following photos show the 18.35 V output that was restored! And I have said it probably often before that the repair did cost almost nothing. But in this case I didn’t even need a new component to make the Adapter work again! (Of course I must buy a Littlefuse suppressor Diode P6KE150A for Safety reasons, but since the Power supply also has a Primary Fuse for protection and it already works again, it only protects in case of any overvoltage). Next photos show the defect ZD1 protection Diode and the PCB bottom where the diode was removed.
And the last photo shows the Fixed Power Supply.
The removed Suppressor Diode is much faster than VDRs that are also used in Power Supplies for the same prevention. It short circuits any Overvoltage momentary within 1.0 ms or even in Pico seconds to protect the Circuit on the contacts that the Diode is attached to. These Suppressor Diodes are also called TVS Diodes, Transorbs, Transient Voltage Suppressors or Thyrector Diodes.
In case of this P6KE150A the Peak Current (IPPM) is only 2.9A which is about a tenth of the value of a P6KE15A Diode which is 28A. This is related to the Breakdown Voltage that is much lower for the P6KE15A Diode. And the Maximum dissipation is for all P6KExxx components always 5W. And Power = Voltage multiplied by Current. The Breakdown Voltage of the destroyed P6KE150A in the HP Adapter is min 143V and max 158V. And the Clamping Voltage is 207V.
In the HP Adapter the Diode was destroyed which means that it is used beyond the specs that it was designed for. So it normally would survive a big (600 Watt !) short overvoltage spark. Suppressor Diodes that are destroyed can end as Shorting Diode, Open Diode, or as degraded Diode. And in all cases the TVS Diode must be replaced for safety reasons. Such a diode exists in fact out of two special diodes in antiserie (opposing positions of both avalanche Diodes) connected together and placed in a single Diode housing.
There are also TVS Diodes that rectify in one direction and overvoltage suppress in the other. This Internet Link gives more useful information about them: https://en.wikipedia.org/wiki/Transient-voltage-suppression_diode
Especially the Characterics of the TVS Diodes are here very well explained!
TVS Suppressor Diodes are still seldom used in circuits built by amateurs but could easily prevent the destroying of expensive Semiconductors. Like this article proves because all other parts including the Semiconductors are still fine after the overvoltage power surge.
And since the P6KE150A TVS Diode used in the HP Adapter of this ‘repair’ only costs $1.60 dollar when 20 pieces are ordered at Free Shipping, it would be just stupid not to replace it. Safety First at all times is the smartest thing to do!
Albert van Bemmelen, Weert, The Netherlands.
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Note: You can read his previous repair article in the below link: