[TechAssist] Re: GE 27GT614JX1 Chassis CTC177BE
- From: "David Lessard" <mrfixit@xxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Thu, 2 Jan 2003 14:45:32 -0500
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 Lessard
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 Lessard" <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 Lessard
> Alexandria Electronics
> 50 Harrison Street
> Alexandria, Ontario
> K0C-1A0
> mrfixit@xxxxxxxxxxx
>
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