[TechAssist] Re: Power MOSFET - Huge Flash

Hi Paul,

Thanks. I checked the original resistors (one was marked 360k,
not 380k) and these 2 checked OK before the transistor blew out
again. Is there supposed to be a 380k also? (maybe I missed that
one).

Bil

PC 1000
M-Pulse 5000 magnetic pulse generator
http://magpulser.com
Mammoth Lakes, CA 
760-924-1000   

               
  
Friday, July 29, 2005, 6:20:37 AM, you wrote:

PW> Bil,
PW> Check for an open R14146 (380 k) or R14145 (270 k)
PW> If these are bad, the MOSFET will literally explode when the set is plugged
PW> in.
PW> HTH
PW> Paul Westcott
PW> Kingsway Electronics
PW> 1090 Kingsway
PW> Sudbury, Ontario
PW> Canada
PW> Phone  705 566-9290
PW> Fax       705 566-5349
PW> westcott@xxxxxxx
PW> ----- Original Message -----
PW> From: "Bil Green" <tv.vcrrepair@xxxxxxxxxxx>
PW> To: ".TECHASSIST @ freelists . org" <techassist@xxxxxxxxxxxxx>
PW> Sent: Friday, July 29, 2005 4:30 AM
PW> Subject: [TechAssist] Power MOSFET - Huge Flash


>> I replaced a shorted MOSFET (driver in SMPS) and other parts
>> (listed below) and as soon as the set was plugged in there was a
>> huge flash (arcing) observed at the MOSFET and it shorted
>> immediately.
>>
>> There is carbon between the metal clip and the plastic front (not
>> the backside, and there is no crack visible in the plastic) of
>> the MOSFET. I don't want to power it up again until I have a clue
>> as to what is likely causing this (the original one didn't do
>> this).
>>
>> I did use a TDA4605-2 (instead of -3) for U14101, and I can't
>> imagine this caused enough voltage (thousands?) to create this
>> large arc.
>>
>> With less AC voltage the set probably won't start so I rather not
>> use this method.
>>
>> RCA PTV
>> model P61929
>> chassis PTK195ST
>>
>> Q101 (MOSFET) shorted
>> U14101 melted
>> R14125 burned
>>
>> Replaced 3 other resistors as recommended (checked OK)
>>
>> Bil
>>
>> PC 1000
>> M-Pulse 5000 magnetic pulse generator
>> http://magpulser.com
>> Mammoth Lakes, CA
>> 760-924-1000
>>
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