[TechAssist] Re: RCA ctc179 F35755 tuner?
- From: "Wayne Vanaman" <Wayne@xxxxxxxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Fri, 3 Jan 2003 09:59:40 -0600
When you say it won't autoprogram do you mean that the function will not
activate or that it does not store any channels?
This chassis, as far as the tuning-troubleshooting is like the ctc17x/18x
series, just a few different parts, but the same operation.
The EEPROM could be bad, the tuner may need a solder job, that sipp chip may
be bad, or some other problem
How is the pic from the video input?
The menu has a choice accessible from the remote to lock out the front
panel. Go into the menu and turn it on.
OK, a summary for just about all RCA TVs tuning system. Same basic idea
with different implementations from about ctc130 on.
The tuner tunes the default frequency of the channel and the micro looks for
the H Sync pulse. If no H Sync pulse is found the channel is de-tuned both
high and low to see if the channel freq. has been shifted, such as HRC or
IRC tuning systems. If no H Sync pulse is found the tuner will then default
to the normal channel frequency.
During autoprograming the micro looks for the H Sync pulse. The idea is
that if H Sync is absent there is no channel, and if the H Sync has been
stripped, ala cable premium channels, you don't care if it is there because
it is not a watchable signal--same as no signal. If the autoprogram
sequence completes the Cable assignment, 14-125, it then goes to ch 2-13.
If during the 14-125 scan no channels were found the tuner switches to the
air position. Since 2-13 are the same we pick up with 2-13, and 14-69
"air". If the H Sync has not discovered any channels yet the scan list is
empty. The TV defaults to Ch 3. The ch up and ch down functions will not
work because the scan list is empty. Channels can be "dial in" with direct
entry.
Again, because the micro is looking for the H Sync, if it is not found the
tuner then shifts high and low looking for the channel, hence the tuning
operation seems slow because it is tuning above and below the nominal
channel assignment, it then defaults to the nominal frequency.
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: "larry" <schntv@xxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, January 03, 2003 9:16 AM
Subject: [TechAssist] RCA ctc179 F35755 tuner?
>
> strange pix.
> will direct access all channels, wont auto program, pix is
> poor.
> looks like severe, miss aligned IF in older sets.
> dont see anything in my tips, not familiar with this chassis.
> help please.
> PS. also menu buttons dont work , on set but ok on remote.
> Larry
>
> --
> Schneider TV & Electronic Inc.
> 5415 N. Wooster ave.
> Dover, Ohio 44622 www.geocities.com/schntv2000/
> 330-343-0768 FCC. first class & Extra class K8WLY
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