Re: How picky are power transitors ?

From: jmuller (jmuller_at_gil.com.au)
Date: 12/05/04 

Date: Sun, 05 Dec 2004 21:36:24 +1000

Thanks for your reply.

The monitor in question is totally 100% dead. No HV, no LED, not even
degauss.

I have measured (very carefully) voltages on the board. I seem to have a
good B+ line but absolutely NO lower voltages. 12V and 18V points are
marked but are still dead. I feel the problem most likely lies in the
power supply. (However when the monitor died it did loose H-sync for a
second then the mains filter cap exploded, could this mean the HOT is
also dead?)

Does THIS transistor have an inductor parellel to it normally? As far as
I can see the HOT is OK (not blown up, etc).

Thanks for the link to the NTE cross reference software (downloading on
dial-up is painful).

Are you aware of any other good resources I should know about? For
instance a circuit diagram for this particular monitor would be VERY
helpful, do I have to pay the manufacturer for that (compaq)? Or are
they available elsewhere?

Thank you again =--- jmuller

James Sweet wrote:
> "jmuller" <jmuller@gil.com.au> wrote in message
> news:41b2befc$0$3077$61c65585@uq-127creek-reader-03.brisbane.pipenetworks.com.au...
>
>>jmuller wrote:
>>
>>>I have a couple of dead monitors (little 15" ones) which seem to have
>>>the same problem. :(
>>>
>>>Dead power transitor.
>>>
>>>They have both short-circuited.
>>>One is marked:
>>>
>>> T
>>>K2038
>>>'41
>>>
>>>My question is:
>>>
>>>How hard would it be to find a substitute for it? Are they pretty much
>>>generic? Would any high current (5A) transitor do?
>>>
>>>
>>>
>>>- - thanks in adavnce,
>>>
>>> -- jmuller.
>>
>>Also out of circuit there is a short between where the outer legs used
>>to be. Is this normal?
>>
>>The monitor says that these aren't often transistors but "expensive"
>>mosfets. What's the chances of replacing these and how expensive?
>
>
>
> Look up the numbers on the cross reference on www.nteinc.com and compare
> specs. I believe you're referring to the horizontal output transistor, these
> can usually be subbed, but they're special high voltage (as in 1400v or so)
> high current transistors usually. The "short" on the board is often normal,
> caused by an inductor which has a low DC resistance. Often a HOT will also
> appear shorted because of the internal damper diode or resistor but you
> should be able to test two good diode junctions.
>
>

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