OpAmp in ZyXEL Wireless Access Point POE
in [Repair]
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From: AC Me on 13 Jul 2010 09:03 Hi all. The Power-Over-Ethernet (POE) injector for a ZyXEL wireless network link has just failed. New, or replacement, POEs are not easy to locate nor is information on these devices. There is not any label or other markings indicating model numbers or other information. I opened the POE unit and discovered that it contains an AP34063 switching regulator, as would be expected, but also an LM358D (dual OpAmp). Does anyone have any idea why a POE unit would contain an OpAmp? Regards. Mike
From: Stefan Huebner on 13 Jul 2010 12:59 Am 13.07.2010 15:03, schrieb AC Me: > Hi all. > > The Power-Over-Ethernet (POE) injector for a ZyXEL wireless network > link has just failed. New, or replacement, POEs are not easy to locate > nor is information on these devices. There is not any label or other > markings indicating model numbers or other information. > I opened the POE unit and discovered that it contains an AP34063 > switching regulator, as would be expected, but also an LM358D (dual > OpAmp). > Does anyone have any idea why a POE unit would contain an OpAmp? To prevent injecting 40somewhat volts into an ISDN link or something else not aware of PoE? Reverse engineer the circuit, and you will not only see how it's done but also be able to repair this thing. Interesting enough that it uses a 34064, I also use lots of them :)
From: AC Me on 14 Jul 2010 07:42 On Jul 13, 5:59 pm, Stefan Huebner <ste...(a)huebner- informationselektronik.de> wrote: > Am 13.07.2010 15:03, schrieb AC Me: > > > Hi all. > > > The Power-Over-Ethernet (POE) injector for a ZyXEL wireless network > > link has just failed. New, or replacement, POEs are not easy to locate > > nor is information on these devices. There is not any label or other > > markings indicating model numbers or other information. > > I opened the POE unit and discovered that it contains an AP34063 > > switching regulator, as would be expected, but also an LM358D (dual > > OpAmp). > > Does anyone have any idea why a POE unit would contain an OpAmp? > > To prevent injecting 40somewhat volts into an ISDN link or something > else not aware of PoE? > Reverse engineer the circuit, and you will not only see how it's done > but also be able to repair this thing. Interesting enough that it uses a > 34064, I also use lots of them :) Thank you Stefan. That is interesting. I have examined the unit more closely with a view to reverse engineering it. There seem to be a lot of components on the board and the board seems to have more that two layers (there are few track on the top and fewer still on the bottom both of which are mostly copper). This looks daunting - but let's proceed. First steps: How many components and what type? I hope I haven't missed anything. There are 2 x RJ45 through-hole sockets, 1 x DC power jack through- hole, 2 x Electrolytics through-hole and 1 x through-hole inductor. The surface-mount contingent consists of 4 x Zener, 2 x LED, 1 x NPN SOT-23, 1 x NPN TO-252, 1 x Inductor, 1 x Diode, 18 x Resistor, 5 x Capacitor, 1 x Transient Voltage Suppressor and 1 x Fuse. .. That last component is tucked up neatly beside the 'output' (if I may describe it as such) RJ45 connector and is almost completely transparent. It would appear to be a Littlefuse 375mA device (marking of FE). It would also appear to be blown. And so this blown fuse might well be the problem. Now to track down a replacement. Thank you Stefan for your help. By the way, are there any 'design guides', 'thoughts for a long Winter's evening', etc, on POEs available that would help explain these types of devices to an idiot like me? I'm sure they would make interesting reading the next time I am bored. Take care. Mike
From: AC Me on 14 Jul 2010 08:13
On Jul 14, 12:42 pm, AC Me <mmal...(a)gofree.indigo.ie> wrote: > On Jul 13, 5:59 pm, Stefan Huebner <ste...(a)huebner- > > > > informationselektronik.de> wrote: > > Am 13.07.2010 15:03, schrieb AC Me: > > > > Hi all. > > > > The Power-Over-Ethernet (POE) injector for a ZyXEL wireless network > > > link has just failed. New, or replacement, POEs are not easy to locate > > > nor is information on these devices. There is not any label or other > > > markings indicating model numbers or other information. > > > I opened the POE unit and discovered that it contains an AP34063 > > > switching regulator, as would be expected, but also an LM358D (dual > > > OpAmp). > > > Does anyone have any idea why a POE unit would contain an OpAmp? > > > To prevent injecting 40somewhat volts into an ISDN link or something > > else not aware of PoE? > > Reverse engineer the circuit, and you will not only see how it's done > > but also be able to repair this thing. Interesting enough that it uses a > > 34064, I also use lots of them :) > > Thank you Stefan. That is interesting. > I have examined the unit more closely with a view to reverse > engineering it. > There seem to be a lot of components on the board and the board seems > to have more that two layers (there are few track on the top and fewer > still > on the bottom both of which are mostly copper). This looks daunting - > but > let's proceed. > First steps: How many components and what type? > I hope I haven't missed anything. > There are 2 x RJ45 through-hole sockets, 1 x DC power jack through- > hole, > 2 x Electrolytics through-hole and 1 x through-hole inductor. > The surface-mount contingent consists of 4 x Zener, 2 x LED, 1 x NPN > SOT-23, > 1 x NPN TO-252, 1 x Inductor, 1 x Diode, 18 x Resistor, 5 x Capacitor, > 1 x > Transient Voltage Suppressor and 1 x Fuse. > . > That last component is tucked up neatly beside the 'output' (if I may > describe > it as such) RJ45 connector and is almost completely transparent. It > would > appear to be a Littlefuse 375mA device (marking of FE). > It would also appear to be blown. > And so this blown fuse might well be the problem. Now to track down a > replacement. > > Thank you Stefan for your help. > By the way, are there any 'design guides', 'thoughts for a long > Winter's evening', > etc, on POEs available that would help explain these types of devices > to > an idiot like me? > I'm sure they would make interesting reading the next time I am bored. > > Take care. > > Mike Actually, when I write POE I really mean POE Injector. Sorry if this has caused any confusion. Mike |