[TechAssist] Re: RCA G35772AT CTC187CL FIX
- From: Larry E <videotech@xxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 13 Oct 2004 20:00:07 -0400
THANKS for all the replies I got on this, boiled down, the problem was a dead
set
with zero volts on pin 6 of eprom, fix was Q4105 located behind switch mode
transformer T4101 (marked T101). I don`t have the schematic so I don`t know
the part number, I swiped one out of a junker set. THANKS Guys I really
appreciate all your efforts, Larry E
Larry Eastman
American TV & Electronics
Crystal River, Fl. 34428
Jim Myers wrote:
> Pins 5 and 6 of the eeprom are the data and clock lines and you should
> see activity on them anytime a button is pressed in both standby and
> when the set is on. Also you should see activity on pins 5 and 6 when AC
> power is applied. You must have a short or a load on the pin 6 line
> keeping it low, check it with a scope. Here are a couple of tips to
> check, there are many more dead set tips but these are the only two that
> mention U3201 pin 6 being zero volts.
>
> Dead set. Found clock line on pin 6 of u3201 at 0vdc. Reset line pin 2
> of u3101 also low
> (0vdc). Collector of q3101 read 3.8kohms to gnd. Removed q3101 and
> voltage was still low.
> Removed c3113 and voltage returned to pin 2 u3101 and collector of
> q3101. C3113 leaky to
> ground. Replacement fixed unit
>
> Dead set. Replaced the eeprom twice and the microprocessor once.
> Checking the clock and
> data lines at pins 15 & 16 of u3101 saw no activity. The oscillator was
> running on pins 41 &
> 42. Measured dc voltage at pins 5 & 6 of the micro, found pin 6 down to
> 1.7v. Unplugging the
> front panel assembly did not bring the voltage back. Removing c3109 in
> the circuit off pin 6 of
> u3101 brought the voltage up to 4.7v and allowed the set to turn on.
> Replace c3109
> *******************************************************************************************************************
> Since 1972
> Jim Myers
> Telrad Electronics
> Fort Wayne, Indiana
>
> Larry E wrote:
> > Bob, removed and replaced, no difference, problem must be with the fact
> > I don`t have 5v on pin 6 of eprom, THANKS for the call and the tip
> > on the resistor, I`m sure it will come in handy in the future, Larry E
> >
> > Larry Eastman
> > American TV & Electronics
> > Crystal River, Fl. 34428
> >
> > "Bob@Bobs tv" wrote:
> >
> >
> >>Larry,
> >> See my second post..... If I suspect that resistor I just jump a
> >>1.5m below the chassis if that's the problem, the set will start up..That
> >>resistor is the start up bias for the regulator....I have seen a few on the
> >>RCA's and also on Panasonic's using same regulator...You can remove the
> >>output transistor while you service the power supply..on the bench... in
> >>standby at collector pad when in standby if power supply is working you will
> >>get like 140/145Volts... Also 12V and 5V will be there...Normally if you
> >>have problem in sweep the (-voltages) won't even be close or 0
> >>Volts....Remember no bias to the IC no start....RCA calls that the "start"
> >>resistor..No guaranty, but don't waste a lot of time like I did on THE FIRST
> >>ONE...
> >>
> >>Bob
> >>
> >>Bobs TV Worcester, ma
> >>
> >>woodman1@xxxxxxxx
> >>
> >>Main 508-853-1482
> >>Fax 508-853-1480
> >>----- Original Message -----
> >>From: "Larry E" <videotech@xxxxxxxxxxxx>
> >>To: <techassist@xxxxxxxxxxxxx>
> >>Sent: Thursday, September 30, 2004 2:31 PM
> >>Subject: [TechAssist] Re: RCA G35772AT CTC187CL DEAD/More info
> >>
> >>
> >>>Bob, not sure what your saying, you want me to bridge R4104 with a 1.5
> >>
> >>meg
> >>
> >>>resistor?
> >>>because pin 4 of the regulator is 0 volts? What is pin 4`s voltage
> >>
> >>supposed to
> >>
> >>>be? Larry E
> >>>
> >>>Larry Eastman
> >>>American TV & Electronics
> >>>Crystal River, Fl. 34428
> >>>
> >>>"Bob@Bobs tv" wrote:
> >>>
> >>>
> >>>>Larry,
> >>>> Bridge a 1.5m resistor (R4104) so you know for sure...Pin 4
> >>
> >>needs a
> >>
> >>>>+ voltage to get the regulator going...
> >>>>Bob,
> >>>>
> >>>>Bobs TV Worcester, ma
> >>>>
> >>>>woodman1@xxxxxxxx
> >>>>
> >>>>Main 508-853-1482
> >>>>Fax 508-853-1480
> >>>>----- Original Message -----
> >>>>From: "Larry E" <videotech@xxxxxxxxxxxx>
> >>>>To: <techassist@xxxxxxxxxxxxx>
> >>>>Sent: Thursday, September 30, 2004 1:21 PM
> >>>>Subject: [TechAssist] Re: RCA G35772AT CTC187CL DEAD/More info
> >>>>
> >>>>
> >>>>>Hi Guys, replaced the eprom and still have the same problem, zero
> >>
> >>volts on
> >>
> >>>>pin 6,
> >>>>
> >>>>>4.32 on pin 8&5. Unsoldered pin 54 of U1001 thinking it might have
> >>
> >>been
> >>
> >>>>pulling
> >>>>
> >>>>>it down, no change, Q4105 is supposed to be the 5v standby source? (no
> >>>>
> >>>>schematic)
> >>>>
> >>>>>I have ( measured to cold ground) E= 4.77 B= 5.1 C= 11.7 volts.
> >>
> >>Could
> >>
> >>>>the 4.32
> >>>>
> >>>>>be too low on pins 8 & 5 ? I was told pins 5&6 get the 5 volts from
> >>
> >>pin 8
> >>
> >>>>of
> >>>>
> >>>>>U3201
> >>>>>so I`m still confused how pin 5 can have 4.32 but pin 6 would be zero
> >>
> >>if
> >>
> >>>>the
> >>>>
> >>>>>source
> >>>>>is internally from pin 8 even with a new eprom installed, HELP!!!
> >>
> >>Larry
> >>
> >>>>E
> >>>>
> >>>>>Larry Eastman
> >>>>>American TV & Electronics
> >>>>>Crystal River, Fl. 34428
> >>>>>
> >>>>>Larry E wrote:
> >>>>>
> >>>>>
> >>>>>>Hi Guys, this 187CL is stone dead, no click from relay, HOT is good,
> >>>>>>have 160 v on collector
> >>>>>>in standby, resoldered H- driver transformer and the coil, C4107 is
> >>>>>>good, found a bad
> >>>>>>C4105 10uf @ 200 replaced it with no change, I need to know if the
> >>>>>>voltages are correct
> >>>>>>on U4101 as I don`t have the schematic, they are
> >>>>>>Pin 1= -40
> >>>>>>2= -33
> >>>>>>4= 0
> >>>>>>5= .9
> >>>>>>6= .9
> >>>>>>7= .4
> >>>>>>8&9 = 0
> >>>>>>11&12 = 165 thanks in advance, Larry E
> >>>>>>Larry Eastman
> >>>>>>American TV & Electronics
> >>>>>>Crystal River, Fl. 34428
> >>>>>>
> >>>>>
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