isolation transformer needed
in [Repair]
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From: Phil Allison on 4 Jan 2010 17:21 "GregS" Meathead Plonker "Phil Allison" > >>>** Standard procedure for servicing any unit with an unknown fault is to >>>FIRST see what happens when plugged into a normal AC outlet - ie one >>>with >>>neutral and ground linked at the service box. >> >>Funny that was never on any service literature or diagnostic procedure >>documentation I ever read. Nor would I have ever made it my own >>practice as a first step thinking back 30 through 30 years. > > > I have hooked things up with isolation and later found things like a motor > short. > Works fine with the transformer. > > I didn't always first check the customers explanation and plug something > in right away before doing anything, but I do it now. ** Its important for a tech to see any symptoms the customer is complaining about, first hand. You gotta plug it in to do that. ..... Phil
From: bob on 4 Jan 2010 19:49 Phil Allison wrote: > > ** Its important for a tech to see any symptoms the customer is complaining > about, first hand. > > You gotta plug it in to do that. > > > > .... Phil > > Customer says his unit was emitting smoke and smells. You look at the unit and it smells crisp on first inspection. Are you really going to tell me your going to plug it in first??? Customer says there is sparks from the AC cord where there pet rabbit might have chewed it. You look at it and see bare copper. Your going to plug that in first? Customer brings in unit that has had liquid poured into it. Are your going to plug that in without tearing it down first? Most of the time you will plug it in to verify faults. But there are times a visual and smell no power inspection will tell you a lot. bob
From: Phil Allison on 4 Jan 2010 20:06 "bob" ( snip smartarse drivel ) ** This above utter fool does not bother to read more than one post in a thread before jerking himself off in public. Examples he missed from ME in this thread: " There are a host of other checks and inspections a service tech needs to do on and around the AC wiring, fusing devices and any AC power leads and plugs attached to a unit. Any parts that are damaged, worn out or otherwise seem unsafe must be repaired or replaced. I go through a LOT of AC plugs, fuses and fuse holders in my work. " And: " My post does NOT say that it is the very first step. It does say that with an unknown but possible PSU fault - connection to a normal RCD protected AC outlet should be done FIRST - before using an isolation tranny. Obviously, visual inspection comes very first, including carefully checking of the AC plug, lead and fuse if accessible. If the AC fuse is missing or blown, then a major fault is likely. In the latter case, MY procedure is to install a suitable new AC fuse and gradually bring up the item using a variac - all the time monitoring the current draw from the AC supply with meter specially built for that purpose. If the AC current becomes unusually large ( or the RCD trips) as the AC voltage rises - game over. ..... Phil
From: bz on 4 Jan 2010 21:43 Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_(a)charter.net> wrote in news:E0b_m.43810$_b5.35961(a)newsfe22.iad: > Nice vanity call you have there Mr. N5BZ.. Thanks! Former call was WA5DQP. My 'sine' has been 'bz' (my initials) since my first contacts as WN5DQP/0. > For some reason I have a vision of seeing you on slow scan? Sorry, no. Played with tty many years ago. A bit of playing with packet stuff. Occasional FM and SSB. CW is my favorite mode. 73 -- bz 73 de N5BZ k please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set.
From: GregS on 5 Jan 2010 09:53
In article <Xns9CF6D2D6E73C4WQAHBGMXSZHVspammote(a)130.39.198.139>, bz <bz+ser(a)ch100-5.chem.lsu.edu> wrote: >Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_(a)charter.net> wrote in >news:E0b_m.43810$_b5.35961(a)newsfe22.iad: > >> Nice vanity call you have there Mr. N5BZ.. > >Thanks! Former call was WA5DQP. >My 'sine' has been 'bz' (my initials) since my first contacts as WN5DQP/0. > >> For some reason I have a vision of seeing you on slow scan? > >Sorry, no. Played with tty many years ago. A bit of playing with packet >stuff. Occasional FM and SSB. > >CW is my favorite mode. > >73 I was just tapping out you call sign. Its been a while since I did that. A really long while for the straight key. I remembering trying to tap code while I was in the Army barracks with a temporary setup. I was using two pieces of wire ! That was 40 years ago. Seems my hand goes balistic on your letters. I need some practice though. It was a lot easier doing mine. N6GS. greg |