[TechAssist] Re: Sony CTV KV27EXR20 (Chassis ANU-2) H. O. T. Shorts after 20 Minutes.
- From: "George" <grndmstrg@xxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sat, 31 May 2003 20:01:39 -0700
Dale,
Highly recommended you use OEM parts on Sony although a quality replacement
with a better rating should work ok (no counterfeits please). You mentioned
horizontal output pulse width but not the input drive amplitude, does this
level measure normal? If low it can cause overheating due to improper
switching (too much time in the linear portion of transistor conduction
curve). If used check/replace electrolytic in drive circuit. Check driver
transformer for shorted turns.
George
Afana Electronics
Moreno Valley, CA
----- Original Message -----
From: <HarrisTV50010@xxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Saturday, May 31, 2003 2:43 PM
Subject: [TechAssist] Sony CTV KV27EXR20 (Chassis ANU-2) H. O. T. Shorts
after 20 Minutes.
> I have a Sony Model KV27EXR20 Chassis ANU-2. The first time this set was
in
> the shop it had a bad STRS6301 Regulator IC but the H. O. T. Was Ok. I
checked
> and resoldered any questionable connections. The customer had the unit
home
> about 2-weeks and it died again.
> This time the 2SD1886 H. O. T. had shorted. I checked the horizontal
circuit
> using our Sencore TVA62 and everything checked ok. I replaced the H. O. T.
and
> it ran for 20 minutes and shorted again.
>
> This time I thoroughly rechecked the regulator circuit using a resistor
load
> and everything checked perfectly. I thoroughly went over the chassis for
any
> questionable connections. I resoldered everything is the base drive &
collector
> circuits of the H. O. T. I replaced the 2SD1886 again. I monitored the
base
> drive and the collector waveform using our X100 scope probe. Everything
looked
> textbook perfect. The Collector pulse width was 14us, which is normal. I
did
> start monitoring the temperature of the H. O. T. Using an Infrared
Thermometer.
> The temperature started rising and the transistor shorted at about 165
> degrees.
>
> Does anyone have any ideas what might be causing problems? I am using RCA
SK
> 2SD1886 which I haven't had any problems in the past. I checked
RepairWorld
> and someone had used a 2SC4729 as a replacement. Do I need to try an exact
Sony
> replacement? Any thought would be greatly appreciated.
>
> TIA,
> Dale
>
> Dale A. Lubow... HarrisTV50010@xxxxxxx ..515-232-1109..(Fax)515-232-3356
> Harris TV & Appliance..........335 Lincoln
> Way.....Ames.....Iowa.....50010-3384
>
>
>
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