[TechAssist] Re: for the record + repairing without a schematic?
- From: "Peter oliver" <oliver_peter1@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Sat, 19 Oct 2002 21:04:23 +0000
There are a lot of common problems on data bases although once your at it
for a while you don't really look up common problems. Examples of common
problems on US NTSC 3.58 sets
Zenith Horz line = vertical ic and/or connections on or near IC and possibly
a cap. (goes for most sets that use a LA7838 IC)
Zenith DEAD watch out for 25" sets between 1993-95 as bad crts killed a lot
of these.
Sony KV27TS27 no audio Replace the SBX sound mpx IC possible also fix tuner
for bad intereal grounds.
RCA/GE/proscan W/ CTC177 thru CTC187 snow or intmt may jump Repair on board
tuner grounds + a few interal connections..
The most common problems are cause by crystalized sodder that creates bad
connections and possible eventual componset failure. Electrolitic capacitors
esp ones near heat sources are a close second. But many times You find that
customers put up with intermittant problems until the set goes dead or is no
longer useable. Certain models have common problems and maufacters sometimes
interchange parts so problems can drift around. As for needing a schematic I
rarely use one except in stubbron or difficult sets for example I had a
mitubishi CS3114R that had a horzontal line (verical failure) so I redid the
caps and Vertical IC as it had corrodeded and the caps were leaking fluid
but tested ok.. After that didn't work I looked a the tech-assist data base
that said Check IC6E3 (+12v reg) it was ok so I pulled sams 2875 and trace
it back to T902 The componets were ok did replace on leaky cap but had pull
and resodder the componets from pin 18 of the transformer as some
corrosion/oxidation had occured at R915 and D907 then the set worked
perfectly.
A lot of troubble shooting is done visually though looking for bad
connection, burned parts, exploded caps, cracked transformers, etc. Then
once you have an idea where to start looking test some parts and if nothing
jumps out then locate the schematic. An example of visual troubble shooting
was today had a call on a Magnovox console This one had a manual
tuner/on-off W./ a Delta Gun CRT, It had sound but no HV or picture and the
filiments for the CRT were lit. A look At the HV section reveiled that the 4
pin saftey cap had popped (one end was loose and it was leaking fluid)
Putting new one in (after finding one since I haven't used a saftey cap for
at least 15 years) fixed it.
But Unfortualy for many tech schools Electronics therory bares little
reseblence to actual failures. But it is good that you got some hands on
exp.
Peter Oliver
Tucson Radio TV
Tucson, AZ USA
Since 1946
From: "Stefaan Van Slycken" <vanslycken@xxxxxxxxxx>
Reply-To: techassist@xxxxxxxxxxxxx
To: <techassist@xxxxxxxxxxxxx>
Subject: [TechAssist] Re: for the record + repairing without a schematic?
Date: Sat, 19 Oct 2002 17:05:27 +0200
So, these "common problems", are these the ones found in the databases you
mention, or do you mean like bad switch, blown LOT, bad contacts... are
there other things to look at first? Sorry about my question being so
general, but as i mentioned i don't have any experience on other brands of
tv's (except a daewoo with bad contacts, but a child can fix that ;-)...
thanks!
Stefaan Van Slycken
Van Slycken Elektro
----- Original Message -----
From: <gulftech@xxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Saturday, October 19, 2002 4:17 PM
Subject: [TechAssist] Re: for the record + repairing without a schematic?
>
> Stefaan,
>
> We pull a schematic on less than 20% of the sets repaired here, maybe
> less. Many sets have common problems, or hard ones that you never will
> forget. Some sets are difficult and a schematic is needed, but not on
> hand. Sometimes a schematic is unavailable, would take a long time to
> get, or simply too costly to purchase. This greatly increases repair
> time, and requires greater skill and knowledge of circuits than if one
> had the schematic.
>
> Some sets would simply require too much time to repair without a print.
> Since time is money, the set is returned as a no repair. In such a case,
> I honestly tell the customer that I am not able to repair the unit
> without a service manual. It doesn't happen very often, but customers
> understand. Some shops make up bull stories, but that is pretty
> transparent.
>
> One of the best things you can do is to purchase a good troubleshooting
> database ("Tips program"). I have used many, but use only two at
> present-Winstips (http://www.ServiceSoftware.com) and Tech Repair CD
> (http://tech-repair.net). These would be of less value to you than
> someone in the United States, since most of the sets covered are US sets.
> Also, develop your own database. Keep a record of make, model,
> complaint, and the fix for each set you do. Then, when you run into it
> again, you won't have to resort to memory. One of my techs carried a
> pocket notebook for years, recording every repair. With computers, no
> need to do that anymore.
>
> HTH,
>
>
> Ken Smith
> Gulf Technical Services
> 3034 Gulf Breeze Parkway
> Gulf Breeze, FL 32563
> 850-934-8324 (Voice) 850-932-0819 (Fax)
>
>
> On Sat, 19 Oct 2002 10:12:38 +0200 "Stefaan Van Slycken"
> <vanslycken@xxxxxxxxxx> writes:
> > hi techs...
> > some might notice i only posted a few questions and very little help
> > to other techs... i'm a starter too (like babalino, whose posts
> > cause me to post this, so nobody thinks i'm just a lurker hoping for
> > help without doing anything myself). I'm a graduate in electronics,
> > and did three months of learning at the local thomson repair center,
> > where i learned a lot more than in school...
> > So far, i only have experience on the
> > thomson/telefunken/saba/nordmende sets (which are all the same brand
> > actually), unfortunately these are not sold under that name in the
> > states... and i can't see any similarities in RCA chassis numbers,
> > so i guess these are different from the european ones...but if i can
> > be of any assistance, i'll try my best.
> > * One question though: can a tv be repaired without a schematic?
> > I'm used to working with all the right technical documentation, but
> > sometimes i get these cheapo tv's and i wonder if they're even worth
> > looking at. If you *can* get a schem, it's at least â,¬25, and then
> > you haven't even spent time looking for the error, so repair costs
> > will be way too high for the customer. Do you guys use schematics
> > for every repair? Are there any "tricks" to try?
> >
> > kind regards
> > Stefaan Van Slycken
> > Van Slycken Elektro
> > Belgium
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