[TechAssist] Re: Sanyo DS31650
- From: Dennis Viereck <wa6ati@xxxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Sun, 20 Jan 2002 04:48:06 -0800
Jack:
Easy man.... This set will need two things for it to lock in on a TV channel.
First and foremost is the AFT crossover voltage. This is the voltage that the
IF circuitry generates when a properly tuned video carried is phased matched
to the internal 45 mhz VCO inside the demodulator chip.
Secondly you need Horizontal sync, stripped from the received video, sent to
the the Microprocessor. This H sync tells the Microprocessor that the
television is receiving and NTSC broadcast and not a scrambled picture as it
would be if the set was trying to receive a pay channel that has been
scrambled. This Sync info is typically useful to the CPU when executing auto
program. It discriminates the normal channels from unmodulated carriers, and
scrambled & vacant channels and will not allow them to be automatically stored
in memory.
Do you have any service data that will give you the pin out of the IF section
this television? It has been years since I worked on a Sanyo, but I have a
feeling if this set has an external IF circuit (meaning Tuner IF, MTS
circuitry are NOT integrated inside the tuner housing) Then what I listed
above is how the AFT and Sync detection works. I have tons of schematics over
here, what type of IF demodulator chip is this set using?
Dennis Viereck
Jack wrote:
> I have no idea how I can convince anyone that this is
> not the cure to the problem. I have changed this
> resistor and it did not fix the problem. I'm not a
> "tech-tip" tech and will troubleshoot this when I
> recieve the service data.
>
> Jack
>
> --- Gonzalo Arrivas <gna2000@xxxxxxx> wrote:
> >
> > Jack,
> >
> > There a resistor R106 27K 1/2 watt near the
> > regulator that will cause
> > identical problem.
> >
> > G.N.Arrivas CET Pittsburg, CA
> > http://www.etechhelponline.com
> > Tel/Fax 925-432-2057
> >
> >
> > >From: Jack <lightwizard_2000@xxxxxxxxx>
> > >Reply-To: techassist@xxxxxxxxxxxxx
> > >To: techassist@xxxxxxxxxxxxx
> > >Subject: [TechAssist] Re: Sanyo DS31650
> > >Date: Fri, 18 Jan 2002 15:05:56 -0800 (PST)
> > >
> > >
> > >Hey guys, any ideas on this dog?
> > >
> > >Unit: Sanyo DS 31650 CTV - Chassis # 31650-04
> > >
> > >Problem: AFT will not lock station and drifts on
> > and
> > >off carrier.
> > >
> > >Service manual is on B/O from Fox, customer is
> > irate,
> > >tried rocking aft coil. Replaced tuner and T-chip
> > to
> > >no avail. Swapping parts is not my bag.
> > >
> > >Please do not give me that missing 33 volt open
> > >resistor cure as most do. If your 33 volt is
> > missing,
> > >you get no varactor action in the tuner and no
> > >stations will pull in. That is not my problem.
> > >
> > >Help!!
> > >
> > >Jack
> > >
> > >
> > >=====
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> =====
> Electronic Wizards
> 535 North Woodlawn Suite 350
> Wichita, Kansas 67208
> 316-686-8324 316-686-4815 fax
> Authorized on: Sony, TCE, Pioneer, Denon, NAD
>
> __________________________________________________
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