[TechAssist] Re: GE 27GT614JX1 Chassis CTC177BE

  • From: "Wayne Vanaman" <Wayne@xxxxxxxxxxxxxxxxxxxxx>
  • To: <techassist@xxxxxxxxxxxxx>
  • Date: Thu, 2 Jan 2003 14:39:49 -0600

David:

I was wrong about Q3305.  The path for your specific TV is

U1001p63 to smd r2721 47 ohms, smd Q2705b location b18 pn 215496
Q2705e to  r2711 2k, smd c3301 .01uf, smd r43344 smd Q3301b about micro pin
39 pn 215496
Q3301c to smd r3331 2200 ohms, to u3101p39

You are looking for a horizontal pulse about 4.5v in amplitude at u3101p39.
smd transistor 215495 npn and its compliment 215496 pnp are relatively high
failure items and are in high usage in RCA sets.

Wayne Vanaman
Omega Electronics
6904 W Fairfield Dr
Pensacola, Fl.  32506-3310

Wayne@xxxxxxxxxxxxxxxxxxxxx
WWW.PensacolaTVRepair.Com

850-456-5995 voice
850-458-6369 fax
----- Original Message -----
From: "David Lesser" <mrfixit@xxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Thursday, January 02, 2003 1:45 PM
Subject: [TechAssist] Re: GE 27GT614JX1 Chassis CTC177BE


>
> Wayne:
>
> Thanks, your reply was very thorough, I love learning new stuff! You
> described exactly what is going on with this TV, in that it searches cable
> channels (14 - 125), finds nothing, then searches air channels (14 - 69),
> finds nothing, then sits there at channel 3. Either the tuner is not
working
> or the values aren't being stored. The scan time per channel is about
500ms,
> so I would assume the problem is not with the tuner. The horizontal sync
> pulses start from where? The tuner, sync seperation circuit, to which pin
on
> the micro? I will look at Q3305 buffer, what voltage values should I
expect
> to see here? Any other thoughts on this?
>
> Thanks.
>
> David Lesser
> Alexandria Electronics
> mrfixit@xxxxxxxxxxx
> (613)525-4502
>
> -----Original Message-----
> From: techassist-bounce@xxxxxxxxxxxxx
> [mailto:techassist-bounce@xxxxxxxxxxxxx]On Behalf Of Wayne Vanaman
> Sent: Thursday, January 02, 2003 2:28 PM
> To: techassist@xxxxxxxxxxxxx
> Subject: [TechAssist] Re: GE 27GT614JX1 Chassis CTC177BE
>
>
>
> David:
>
> The Thomson/RCA products in general start autoprograming at channel 14 to
> determine if they are connected to cable.  Although some will go all the
way
> to 125 some will only go into the 30s or so.  (They have been doing this
> since about the ctc13x line)  If no channels have been found by then they
go
> back to ch2 and in the Air position.  Normal operation would be, then,
> 14-125, 2-13, retune the last channel the set was on.  In the "air" mode,
> 14-something, then 2-69, retune the last channel.
>
> This way they don't need to be told Air or Cable.
>
> The channel is determined to be there if the horizontal sync pulse reaches
> the microprocessor.  Unlike many other brands that look for the 3.58Mhz
> burst.  This way if the Horizontal sync pulse has been suppressed, as in
> cable company premium channels, the channel is determined to not be there,
> and is not stored in the scan list.  Who wants to watch that anyway?
>
> A key here is that the sync pulse must reach the micro.  If the product is
> autoprogramed and the sync pulse does not reach the micro, or the micro is
> defective, the set will default to the Air position with NO channels
stored
> in memory.  The set will tune the channels if entered from a remote
control.
> The set can be put into the cable mode and the cable channels then direct
> entered.  Here is another clue:  If the tuning is Slow (most Thomson
> products will tune in the  200-400mS time frame), that is, it takes a
second
> or so to tune, then the sync pulse is not reaching the micro.  The most
> common cause of this is the failure of SMD Q3305.
>
> In your specific case, what is the problem.
>
>
> Wayne Vanaman
> Omega Electronics
> 6904 W Fairfield Dr
> Pensacola, Fl.  32506-3310
>
> Wayne@xxxxxxxxxxxxxxxxxxxxx
> WWW.PensacolaTVRepair.Com
>
> 850-456-5995 voice
> 850-458-6369 fax
> ----- Original Message -----
> From: "David Lesser" <mrfixit@xxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Thursday, January 02, 2003 1:02 PM
> Subject: [TechAssist] GE 27GT614JX1 Chassis CTC177BE
>
>
> >
> > Hi Techs,
> >
> > Haven't worked on a lot of these, tuner doesn't seem to function
properly.
> > When autoprogramming, channels 2 - 13 are skipped, it starts scanning at
> > channel 14 up to 125. Audio is good. I can see the tuner was reworked
> > (famous tuner shield problem). Is the problem likely the tuner control
> IC?.
> > I have no information on this chassis. Any information would be greatly
> > appreciated, schematic or tips.
> >
> > Thanks Gentlemen.
> >
> > "Share what you know, Learn what you don't"
> >
> > David Lesser
> > Alexandria Electronics
> > 50 Harrison Street
> > Alexandria, Ontario
> > K0C-1A0
> > mrfixit@xxxxxxxxxxx
> >
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