[TechAssist] Re: citizen model JCTV2704 chassis M3L523S
- From: Edward Gaidies <teltek3@xxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Thu, 5 Aug 2004 00:22:28 -0400
More then I wanted to know.;-)
Only Bob and I are allowed to talk dirty, as such.
Interesting..though.;-)
-Ed-
On Aug 4, 2004, at 11:50 PM, Damon wrote:
> Ooops, when you stated base waveform, I thought you meant base as in
> "baseline".....( I rarely check base waveforms), normally they look
> like a
> "raggy" square wave anyways.....
>
> However the collector waveform should be a smooth pulse, about 12uS
> wide,
> anywhere from 1000V to 1100V max on most TVs, probably 80% ride right
> around
> 1050V.
>
> The caps can induce a raggy looking collector pulse or heat up a
> transistor
> pretty fast if it's nearly open.....partly open/low value can cause it
> to
> fail like yours is. That 12uS pulse width can point to the problem
> too......more than 12us generally indicates bad IHVT/leaky cap (lowered
> voltage too), less than 11uS would show opening caps.....so the 12uS
> check
> is another tool in our toolbox...
>
> Damon Brunger
> Telrad Electronic Services
> Ft Wayne, IN 46815
> ----- Original Message -----
> From: "Alvin Rose" <ajroseca@xxxxxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Wednesday, August 04, 2004 9:18 PM
> Subject: [TechAssist] Re: citizen model JCTV2704 chassis M3L523S
>
>
> | Hi Damon
> | I will check the capacitors in the collector circuit
> | and the divider ladder in the pincusion circuit..the waveform
> | I referred to was on the output transistor Base lead
> | would this effect the input to the base lead.
> | Alvin
> |
> | Damon wrote:
> |
> | >You have open or off-value high voltage caps on the collector, you
> may
> also
> | >find bad caps in the pincushion's "divider ladder" . The spikes and
> "square
> | >wave" effect are the indicators.
> | >
> | >Damon Brunger
> | >Telrad Electronic Services
> | >Ft Wayne, IN 46815
> | >----- Original Message -----
> | >From: "Alvin Rose" <ajroseca@xxxxxxxxxxxxxxx>
> | >To: <techassist@xxxxxxxxxxxxx>
> | >Sent: Monday, August 02, 2004 9:40 PM
> | >Subject: [TechAssist] citizen model JCTV2704 chassis M3L523S
> | >
> | >
> | >| Hi Guys
> | >| we have a citizen tv which is shorting the horrizontal output
> | >| transistor..Have replaced it twice..Set will run for half an hour
> | >| and then will short the transistor..Scoped the collector and
> there is
> no
> | >| saddle in the waveform but a small amount of ringing on the
> reference
> | >line.
> | >| The base waveform looks like a modified square wave with a number
> of
> | >| high spikes at the start and finish of the waveform..I replaced
> the 22
> mfd
> | >| electrolytic in the primary of the driver transformer with no
> improvement.
> | >| Driver transister tests ok..Had anyone had this problem with this
> model
> | >| Your help is appreciated
> | >| Alvin Rose
> | >| Radio & Tv Centre
> | >| Marystown, Nl
> | >|
> | >|
> | >|
> | >|
> |
>> |
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Tel-Tek Electronics
Ontario-Canada
teltek3@xxxxxxxxxxxx
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