[TechAssist] Re: RCA G35772AT CTC187CL DEAD/More info

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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