[TechAssist] Re: Does how a HOT shorts tell you where the problem is?
- From: "Peter oliver" <oliver_peter1@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Thu, 26 Sep 2002 14:28:21 +0000
HOT shorts generally can be caused by 2 factors componet failures or bad
connections.
Componet failures can be FBT or yoke but can also be caused by other high
loads or timming problems... timming problems can be more common
electrolitic cap in drive or less common one of the bias and return caps
'saftey' style caps in the HV. Connections either bad factory or time
temprature diffusion conroled or mechanical account for the other. Other
componet failures are due to the fact that in many TVs the FBT is the heart
of the set that provides most voltages for operation so an excessive load on
any of the lines can overwork the HOT causing overheating and failure.
Short variants. C-E and B-C shorts are typical of overload/overheat/timming
problems there are occasional B-E shorts that can be masked by the driver
trasformer and damper network, which in built in damper transitors are the
most difficult to find as resitaces in circut read nearly normal.
So to answer your question a shorted HOT means that the timming of the Horz
is off and/or there is excessive current or voltage on the transistor.
Rember if the value for the cap that times the drive decreses the frequncy
incresses and voltage rises.
Peter Oliver
Tucson Radio TV
From: walter wood <wwood_38478@xxxxxxxxx>
Reply-To: techassist@xxxxxxxxxxxxx
To: techassist@xxxxxxxxxxxxx
Subject: [TechAssist] Re: Does how a HOT shorts tell you where the problem
is?
Date: Thu, 26 Sep 2002 06:51:08 -0700 (PDT)
I've never even thought of your question. Most read
low resistance emitter to base anyway, because of
the damper diode and resistor built in.
I do believe that near 100% of hot failures are
caused by one of two things.
Of course, bad flyback.
But the main cause I see is loss of drive caused by
the poor job that the wave solder machines do on
the thermal plane around the horiz. drive
transformer.
Machines work cheap, but they can't produce a
quality product.
Walter
--- kevinstv <kevinstv@xxxxxxx> wrote:
> General question: If the horizontal output
> transistor (HOT) has all 3 leads shorted, or is
> shorted B to C, or is shorted B to E, or is
> shorted C to E--do any of these differences tell
> you where to look for the fault?
>
> I repair both TV's as well as computer monitors
> so this info would be helpful. Most HOT's tend
> to be dead shorts to all three pins, but
> sometimes they short only partially. Thankyou.
>
> Kevin Wilks
> Kevin's TV and Video Repair
> Penticton BC Canada
> kevinstv@xxxxxxx
>
>
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=====
Walter Wood
Future Tech Home Center
2786 Hwy. 43 N.
Lawrenceburg Tn. 38464
931-829-3337
Fax 931-829-4044
mailto:wwood_38478@xxxxxxxxx
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