Post by thread:[PIC]: Microchip Power Bricks

> -----Original Message----- > From: Andy Stephenson [SMTP:spam_OUTandy.stephensonTakeThisOuTASAMICROS.COM] > Sent: Tuesday, January 30, 2001 10:37 AM > To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU > Subject: Re: Microchip Power Bricks > > Michael, > > Of the two that failed on me, both cases were an O/C 1W ish resistor. > > Can't remember the component ref or value, but have a look around. The > first one to fail, put a hole in the res body, the second one did not. > > Rgds... > > ...Andy > You inspired me to open them up and take a look! There is a 200 Ohm 1W resistor (R3) that on both faulty supplies are well cooked, as is the PCB underneath. However, both resistors are functional, and I can see no bad solder joints. I also checked the fuse, the surge limiting thermistor, the diode bridge, and something that looked like a low value fusible resistor as well. Nothing obvious at all I'm afraid. The last one to fail has also been getting *very* hot around the main switching transistor (MOSFET?), the PCB is noticeably brown underneath this device. What has probably not helped is the nice piece of insulating foam that the PCB sits on, helping to keep everything nice and hot. Roman suggested changing the electroylitics, of which there are several, but to be totaly honest, the value of the supply is neither worth the cost of my time or the cost of replacements. I'll chop the low voltage cable (with power plug) off and use it on a bench supply for now. I really dislike switchers. I know they have their place, but any time I've had to repair one, I hate the point at which I have to plug it in and try it. I probably just a big coward, but after witnessing a couple of "catastrophic failures" (not my own!) I usualy put it on the end of an extension lead and stand the other end of the bench to power it up! At least linear supplies generaly hum quite loudly followed by a waft of smoke if they fail. In summary it looks like it is basically a poor design that is not adequately rated for it's intended use. Cheers Mike -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

>I really dislike switchers. I know they have their place, but any time I've >had to repair one, I hate the point at which I have to plug it in and try >it. I probably just a big coward, but after witnessing a couple of >"catastrophic failures" (not my own!) I usualy put it on the end of an >extension lead and stand the other end of the bench to power it up! At >least linear supplies generaly hum quite loudly followed by a waft of smoke >if they fail. Some time ago there was a common joke in my lab: "Alexandre turned indian" and everyone around would start to "hummmmmmmmmmm" for a long time. That's because I used to fix a switcher that ALWAYS blows the +5v capacitor (when it fails, it raises the voltage to +35V!!!!!) and I get that lovely aluminium can right between my eyes, making that mark of the "third eye" in me. So they say I've got to be an indian :o) Of course I solved the problem assembling a "shield" made of clear acrylic foldable between me and the damm switcher. And now I have a good view of an exploding capacitor, he he he :o) --------------8<-------Corte aqui-------8<-------------- All the best!!! Alexandre Souza .....xandinhoKILLspam.....interlink.com.br Linux User #85093 --------------8<-------Corte aqui-------8<-------------- -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Bob Ammerman wrote: > > I could be wrong, but I think that mChip supplies a conventional linear wall > wart to those of us in 110V land. Mine are heavy and don't get all that > warm. The one I got with my original dos picstart years ago was a normal one. (I never used it!! original picstart collectors item anyone??) The one I got about two years back with the new Picstart Plus is the awful switcher one but did come with a US mains lead. Since the mains lead plugs in I just use an Aussie one. -Roman -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

At 11:52 PM 01/30/2001 +1100, you wrote: I have had a number of their PSUs go bad over the years -- 2 of the big old switchers on my Picmaster and 3 of the small PSUs on my Promate and Picstart+. I normally just call my Microchip FAE and I get a new one in a couple of days. You can also fill out the service request on their website at: http://www.microchip.com/10/tools/support/service/index.htm Bill >Bob Ammerman wrote: >> >> I could be wrong, but I think that mChip supplies a conventional linear wall {Quote hidden}>> wart to those of us in 110V land. Mine are heavy and don't get all that >> warm. > >The one I got with my original dos picstart years >ago was a normal one. (I never used it!! original >picstart collectors item anyone??) > >The one I got about two years back with the new >Picstart Plus is the awful switcher one but did >come with a US mains lead. Since the mains lead >plugs in I just use an Aussie one. >-Roman > >-- >http://www.piclist.com#nomail Going offline? Don't AutoReply us! >email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email KILLspamlistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

William Bross wrote: > > At 11:52 PM 01/30/2001 +1100, you wrote: > > I have had a number of their PSUs go bad over the years -- 2 of the big old > switchers on my Picmaster and 3 of the small PSUs on my Promate and > Picstart+. I normally just call my Microchip FAE and I get a new one in a > couple of days. You can also fill out the service request on their website > at: > http://www.microchip.com/10/tools/support/service/index.htm > Sounds like a case of "release a disfunctional product and just replace the failures"... I could never do that! It would irk me severely that my name was on a crap product that is not reliable! Just lucky they fail in a way that doesn't (usually) destroy the Picmaster... -Roman -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Roman wrote: >Sounds like a case of "release a disfunctional product >and just replace the failures"... I could never do that! >It would irk me severely that my name was on a crap >product that is not reliable! Just lucky they fail in >a way that doesn't (usually) destroy the Picmaster... Some time ago our PICMASTER started acting a little funny, in that the green power LED would sometimes light and other times not. Everything else about it seemed to work fine ... 4-6 months later I decided to investigate, and found that one of the two +5V fuses (the non-socketed one, of course) had blown. Dunno why. Anyway, replaced it with an in-line, socketed fuse and all is well again. The PS is not a brick, though -- it's a big momma made in Germany. -- ______________________________________ Andrew E. Kalman, Ph.D. spamBeGoneaekspamBeGonepumpkininc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email TakeThisOuTlistservEraseMEspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

In message <RemoveME3A776D7D.6E02TakeThisOuTezy.net.au>, Roman Black <fastvidEraseME.....EZY.NET.AU> writes >Sounds like a case of "release a disfunctional product >and just replace the failures"... I could never do that! >It would irk me severely that my name was on a crap >product that is not reliable! Just lucky they fail in >a way that doesn't (usually) destroy the Picmaster... I suspect that MicroChip just buy the PSU in - probably from the cheapest quote!. SMPSU's usually fail 'safe', it's uncommon for them to damage the product they feed - they often have a 'crowbar' circuit which kills the supply if the output gets excessive. As a TV service engineer I repair a LOT! of switch mode PSU's, incidentally, the first domestic use of a SMPSU was by Ferguson in their 3000 series colour TV's - around 1970, and was totally discrete. -- Nigel. /--------------------------------------------------------------\ | Nigel Goodwin | Internet : EraseMEnigelglpilsley.co.uk | | Lower Pilsley | Web Page : http://www.lpilsley.co.uk | | Chesterfield | Official site for Shin Ki and New Spirit | | England | Ju Jitsu | \--------------------------------------------------------------/ -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestEraseMEEraseMEmitvma.mit.edu

>At least linear supplies generaly hum quite loudly followed by a waft of >smoke if they fail. You must be one of them lucky guys who evaded being sprayed by a failing large electrolytic in a linear supply ;-) I don't know what causes asthma but THAT certainly does it, at least temporarily ! I once worked in a restricted space and had this happen and I thought I had a 50% chance to make it to fresh air in time. Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads