[TechAssist] Re: (TechAssist) (Sony) Transistor D2578 - need sub
- From: "Damon" <damon101@xxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Mon, 6 Sep 2004 07:36:12 -0500
Thermal runaway occurs when the base/emitter junction's gain increases due
to temperature, which then increases the current from
collector/emitter....which further increases the temp on the BE
junction....thus increasing gain....thus increasing CE current......A
Vicious cycle which can easily be broken by adding a resistor to the
emitter/ground path (usually a low resistance)......there's a formula for
that....
(blah blah x 10 = Re) (or base voltage/base current x 10 = Emitter
resistor's minimum resistance).
A horiz output does not use an emitter resistor because it is DESIGNED to
operate as a switch where base current is so large (1/10 of emitter current)
that it is incapable of going into >>>amplification<<<< ((The C/E junction
will have more than 0.1 Volt across it if it does!)
That can happen if you use a lower gain Horiz output....or a Horiz out with
a different base resistor....etc...that's why some replacement H. Outputs
get awfully hot and blow for no reason.....and sends us into a 3 hour
excursion into the Horiz output circuit looking for something bad.....the
only thing bad is the bad choice of replacement transistor.
HTH
Still vacationing.....
Damon Brunger
Telrad Electronic Services
Ft Wayne, IN 46815
----- Original Message -----
From: "Kevin" <kevintv@xxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Sunday, September 05, 2004 9:14 PM
Subject: [TechAssist] Re: (TechAssist) (Sony) Transistor D2578 - need sub
| What is thermal runaway in the H/O section?
|
| Kevin Wilks
| Kevin's TV & Video Repair
| Penticton BC Canada
| kevintv@xxxxxxx
|
|
| -----Original Message-----
| From: techassist-bounce@xxxxxxxxxxxxx
| [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of S. Pasher
| Sent: Sunday, September 05, 2004 6:48 PM
| To: techassist@xxxxxxxxxxxxx
| Subject: [TechAssist] Re: (TechAssist) (Sony) Transistor D2578 - need
| sub
|
| I use 2SD2539 as a replacement for a lot of H/O's. In the Daewoo it is
| recommended that the 2SD1880 be replaced with it. I runs a lot cooler
| then
| 1880 and the Daewoo's problem is there is thermal runaway in H/O
| section.
|
| Buck Pasher
| Buck's TV
| Gander Newfoundland
| Canada
| 709-256-7738 (Fax & Phone)
|
|
|
| ----- Original Message -----
| From: "Jorge Camboni" <geo@xxxxxxxxxxxxx>
| To: <techassist@xxxxxxxxxxxxx>
| Sent: Sunday, September 05, 2004 6:47 PM
| Subject: [TechAssist] Re: (TechAssist) (Sony) Transistor D2578 - need
| sub
|
|
| > Best sub is 2SD2580- pretty good ones are 2SD2539 and 2SD2553 (proven
| > many times, usually run almost cold).
| > The 2SD1880/81 may work, you have to try them and monitor the
| temperature,
| > they're lower gain transistors than 2578/80 series which are much
| newer.
| > All of them have an integrated damper diode.
| > There are more subs, of course, those are the most popular (and
| > unexpensive) ones.
| > Jorge
| >
| > At 07:44 p.m. 04/09/2004 -0500, you wrote:
| > >I need a sub for transistor D2578 out of a Sony TV. Thanks.
| > >
| > >Kenny Barnes
| > >Kenny Barnes tv
| > >928 South Marshall st.
| > >5154325250
| > >Boone, Iowa 50036
| > >
| > >
| >
| >-----------------------------------------------------------------------
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| >
| >
| > Jorge Camboni, GY Electronics, Richardson, TX
| >
| >
| >
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