[TechAssist] Re: Zenith flyback --FIXED

  • From: John at Main TV <maintv@xxxxxxxxxxx>
  • To: techassist@xxxxxxxxxxxxx
  • Date: Wed, 16 Jul 2003 15:17:06 -0600

I think a 2SD1881 should have a base-emitter resistance because it has a 
damper.  (I always wondered if you can have a transistor with a damper 
but without base-emitter resisor).  Note that a 2SD1882 and higher are 
in a different family without dampers.  I once measured the base-emitter 
resistance of all the outputs I had in stock and found readings from 25 
to 70 ohms.  I also found a 2 to 1 ratio of the resistances of the same 
transistor type but from different batches (or between "generic" and 
original) Does anyone know if this resistance make a difference in how 
hot the transistor will operate?  I do not have a D1881 in stock but I 
just went thru a bag of D1880 and found resistances from 32 ohms to 47 
ohms with most of them at 40 ohms.    John.



Tri-County Tv wrote:
> Jim,
>       I used a 2sd1881 and measured it before I installed it and it did not
> show any resistance from base to emitter. It was my last one and the TV is
> gone now, should a 2sd1881 have resistance from base to emitter? I know what
> you are referring to as I also have seen many HOT that have about 50 ohms
> from base to emitter. And at first I thought the original was ok , until I
> checked it against my 2sd1881 which did not show any resistance.
> Tom Berger
> Tri-County TV
> Robbinsville
> North Carolina 28771
> (tricountytv@xxxxxxxxxxxxx)
> ----- Original Message ----- 
> From: "Jim Myers" <jr.myers@xxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Wednesday, July 16, 2003 1:36 PM
> Subject: [TechAssist] Re: Zenith flyback --FIXED
> 
> 
> 
>>Tom, R-U sure? Most HO transistors have an internal base to emitter
> 
> resistor
> 
>>of about 45 ohms. This is a mistake we have all made at least once.
>>**************************************************
>>Jim Myers
>>Since 1972
>>Telrad Electronic Services Co.
>>Fort Wayne, IN 46815
>>*************************************************
>>----- Original Message ----- 
>>From: "Tri-County Tv" <tricountytv@xxxxxxxxxxxxx>
>>To: <techassist@xxxxxxxxxxxxx>
>>Sent: Wednesday, July 16, 2003 12:29 PM
>>Subject: [TechAssist] Re: Zenith flyback --FIXED
>>
>>
>>Jeff,
>>        Sorry it took a little while to get back to you, as I busy kicking
>>myself in the AXX as you were completely right, and I should have known
>>better. The H.O. Transistor has a base to emitter short of 45 ohms, when I
>>checked it in circuit it read shorted but I took for granted it was just
>>drive transformer secondary winding. But when you think about it
> 
> logically,
> 
>>it had to be the H.O.Transistor. Thanks Again , and to all who replied so
>>quickly.
>>Tom Berger
>>Tri-County TV
>>Robbinsville
>>North Carolina 28771
>>(tricountytv@xxxxxxxxxxxxx)
>>----- Original Message ----- 
>>From: "Shoreline Electronics" <jstielau@xxxxxxxx>
>>To: <techassist@xxxxxxxxxxxxx>
>>Sent: Wednesday, July 16, 2003 12:23 PM
>>Subject: [TechAssist] Re: Zenith flyback --need sub info
>>
>>
>>
>>>Remove the output transistor completely:  Fire up the set and check for
>>
>>good
>>
>>>base drive...that will confirm your H-drive question:
>>>
>>>Try another output transistor to be sure....it really sounds like it's
>>>defective...since PS is not squealing once you unsolder the collector.
>>>
>>>==========================
>>>Jeff Stielau
>>>Shoreline Electronics Repair
>>>344 East Main Street
>>>Clinton,CT 06413
>>>860-399-1861
>>>860-664-3535 (fax)
>>>jstielau@xxxxxxxx
>>>==========================
>>>"If you push something hard enough it will fall over."
>>>Fudd's First Law of Opposition - Sir Sidney Fudd
>>>
>>>
>>>----- Original Message -----
>>>From: "Tri-County Tv" <tricountytv@xxxxxxxxxxxxx>
>>>To: <techassist@xxxxxxxxxxxxx>
>>>Sent: Wednesday, July 16, 2003 12:14 PM
>>>Subject: [TechAssist] Re: Zenith flyback --need sub info
>>>
>>>
>>>
>>>>Jeff,
>>>>       I checked that and it's good.I did notice that there is no b+
>>>
>>>getting
>>>
>>>>to the driver transformer and I'm not sure if I should have voltage
>>>
>>there
>>
>>>>when you first plug it in.
>>>>Tom Berger
>>>>Tri-County TV
>>>>Robbinsville
>>>>North Carolina 28771
>>>>(tricountytv@xxxxxxxxxxxxx)
>>>>----- Original Message -----
>>>>From: "Shoreline Electronics" <jstielau@xxxxxxxx>
>>>>To: <techassist@xxxxxxxxxxxxx>
>>>>Sent: Wednesday, July 16, 2003 12:02 PM
>>>>Subject: [TechAssist] Re: Zenith flyback --need sub info
>>>>
>>>>
>>>>
>>>>>Your Horizontal Output is probably shorted.
>>>>>
>>>>>==========================
>>>>>Jeff Stielau
>>>>>Shoreline Electronics Repair
>>>>>344 East Main Street
>>>>>Clinton,CT 06413
>>>>>860-399-1861
>>>>>860-664-3535 (fax)
>>>>>jstielau@xxxxxxxx
>>>>>==========================
>>>>>"If you push something hard enough it will fall over."
>>>>>Fudd's First Law of Opposition - Sir Sidney Fudd
>>>>>
>>>>>
>>>>>----- Original Message -----
>>>>>From: "Tri-County Tv" <tricountytv@xxxxxxxxxxxxx>
>>>>>To: <techassist@xxxxxxxxxxxxx>
>>>>>Sent: Wednesday, July 16, 2003 11:19 AM
>>>>>Subject: [TechAssist] Zenith flyback --need sub info
>>>>>
>>>>>
>>>>>
>>>>>>Hello,
>>>>>>         I got this zenith color TV model SS2761S , module 9-913
>>>>>
>>,and
>>
>>>>the
>>>>
>>>>>flyback had a slit in the side with stuff oozzing out , Flyback #
>>>>
>>>95-4203
>>>
>>>>,
>>>>
>>>>>when you look this # up on tritronics, it shows a 95-4203-REP for 17
>>>>>dollars, so I ordered it, and installed it into the module and now ,
>>>>
>>>when
>>>
>>>>>you plug it in, the ps squeals, so I replaced all the usual ps
>>>>
>>>components,
>>>
>>>>>and same problem,also checked for shorts on secondary of fly and
>>>>
>>>>everything
>>>>
>>>>>looks ok, If I disconnect the collector of the HOT it stops
>>>>
> squealing
> 
>>>and
>>>
>>>>ps
>>>>
>>>>>voltages return to normal, however I am not reading and B+ on any
>>>>
> legs
> 
>>>of
>>>
>>>>>the driver transformer, I do not have the schematic and would
>>>>
> greatly
> 
>>>>>appreciate if someone could upload one. Could this replacement fly
>>>>
> be
> 
>>>the
>>>
>>>>>trouble? Has anyone had experience with this flyback?
>>>>>
>>>>>>Tom Berger
>>>>>>Tri-County TV
>>>>>>Robbinsville
>>>>>>North Carolina 28771
>>>>>>(tricountytv@xxxxxxxxxxxxx)
>>>>>>
>>>>>
> ****************************************************************************
> 
>>>>>*
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-- 
John Mielke
Main TV
Longmont,Co 80501
303 776 6955
303 776 0792  fax
maintv@xxxxxxxxxxx


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