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intermittent tsjirping sound Neufunk TV model 2180
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berre
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PostPosted: Sun Jun 19, 2005 6:25 am    Post subject: intermittent tsjirping sound Neufunk TV model 2180 Reply with quote

Hi,

I have a Neufunk TV model 2180 which suddenly died.

Screen and sound gone, the only thing I hear is an intermittent tsjirping sound... sounds a bit like a capacitor just before blowing up but it is intermittent...

anybody encountered this before?

cheers

berre
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Morrowrj



Joined: 14 Apr 2005
Posts: 29
Location: Pittsburgh, PA

PostPosted: Sun Jun 19, 2005 11:05 am    Post subject: intermittent tsjirping sound Neufunk TV model 2180 Reply with quote

The intermittent chirping from my tv turned out to be the result of a shorted horizontal output transistor. same thing , no picture/sound. Hope this helps.
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PostPosted: Mon Jun 20, 2005 5:40 am    Post subject: Re: intermittent tsjirping sound Neufunk TV model 2180 Reply with quote

Morrowrj wrote:
The intermittent chirping from my tv turned out to be the result of a shorted horizontal output transistor. same thing , no picture/sound. Hope this helps.


Helps a lot, thx!!

Did you just replace the transistor to solve the problem?

How can you find this horizontal output transistor? I'm sorry if this is a stupid question, I know a bit of electronics but it's the first time I'm dealing with a TV...

Thank you

Berre
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berre
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PostPosted: Tue Jun 21, 2005 9:36 am    Post subject: Reply with quote

Hi,

I've checked the printboard (unfortunatly I don't have the schematics) and I've found the word "horizontal" printed on it... very nearby I found a transistor type BU808DF... could this be the HOT?

Thx

Berre
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Morrowrj



Joined: 14 Apr 2005
Posts: 29
Location: Pittsburgh, PA

PostPosted: Tue Jun 21, 2005 6:04 pm    Post subject: intermittent tsjirping sound Neufunk TV Reply with quote

Yes, i just replaced thr transistor to fix. As to how to locate it, i had the benefit of a similiar schematic. Perhaps someone else could offer insight on how to be certain. I would say you are definitley in the right area however. Did you try checking the trans with a meter ?

also you can check this out http://www.highlandelectrix.fsnet.co.uk/repair/safety.html

perhaps it will help
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berre
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PostPosted: Wed Jun 22, 2005 8:10 pm    Post subject: Reply with quote

thx for the info, I did some more research: the BU808DF seems to be a Line Output Transistor (LOPTR ) so my question: is a HOT a type of LOPTR or is it just a synonym?

(I googled but found only a few times an association between BU808DF and HOT)

Unfortunatly nobody seems to have the schematics of my model so I'm not 100% sure but I think I have the right one....

I've tested it with my multimeter on diode test and BC, BE and CE (while it was still on the board) were beeping all over the place so I assume it's shorted (or should I take it out of the board to make sure?).

PS I've also read that the reason for a shorted HOT can be a broken flyback transformer, anybody any idea how I can test this one?

Cheers

Berre
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Morrowrj



Joined: 14 Apr 2005
Posts: 29
Location: Pittsburgh, PA

PostPosted: Wed Jun 22, 2005 9:03 pm    Post subject: Neufunk TV Reply with quote

Well first of all, yes; HOT , line output transistor(LOPTR), flyback transistor are all names for the same part. I would say if you got a passing continuity test in all configurations then it is defeinitely shorted. As for Flyback testing, i personally skipped it, but if you are ambitious, you can check out this : http://repairfaq.ece.drexel.edu/sam/flytest.htm

Good luck
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berre
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PostPosted: Sat Jun 25, 2005 8:57 pm    Post subject: Reply with quote

Just bought a BU808DFI for 3€... I'll replace it hopefully tomorrow...

Let's hope it solves the problem!

Cheers

Berre
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berre
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PostPosted: Tue Jun 28, 2005 7:16 am    Post subject: Reply with quote

Hi,

I've replaced the HOT and the problem is solved... let's hope it stays that way...

My guess is that the transistor died because it isn't cooled enough. All other transistors on the board have a metal back that's connected to the cooling-plate but this one has a plastic back which doesn't conduct the heat as well as metal.

Anyway, thank you very much for the help!! If you ever come to Belgium I'll buy you a beer Wink

Cheers

Berre
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Al_Dodge_Bundy



Joined: 05 Apr 2005
Posts: 93
Location: Netherlands

PostPosted: Tue Jun 28, 2005 8:30 am    Post subject: Reply with quote

Hello Berre,

You might wanto consider to ad some "therminal conductive grease" ("koel-pasta" in Dutch) between the TOR and the cooling-plate!!

This way the heat is tranfered, from the TOR to the cooling plate, much better!

Grtz Mark
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