[TechAssist] Re: Toshibas,CF3566A,CF3572B,(TAC9190)shut down issues,fixes

  • From: "Jim Myers" <jr.myers@xxxxxxxxxxx>
  • To: <techassist@xxxxxxxxxxxxx>
  • Date: Sat, 13 Sep 2003 11:02:41 -0500

Thanks for clearing that up Phil, and Q840 IS a common failure component
just like any standby regulator. As far as knowing which pin was the
problem, right, not really important, however most techs would probably
assume that Q840 is good after reading approximately 5 volts on the VCC out
pin not knowing that one of the other pins is a reset output for the micro
which can keep the micro locked up. By the way, my wife ALWAYS knows when I
do something right, last time was......hum..............around '64 maybe!
**************************************************
Jim Myers
Since 1972
Telrad Electronic Services Co.
Fort Wayne, IN 46815
*************************************************
----- Original Message ----- 
From: "Philip Bader" <tjanphyl@xxxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Saturday, September 13, 2003 8:25 AM
Subject: [TechAssist] Re: Toshibas,CF3566A,CF3572B,(TAC9190)shut down
issues,fixes


Actually the main culprit I am sure was the cap C871 (22/50v) as C871
was open in both sets.
As for Q840, it is the L78MR05. IN the second TV the cap was open and it
is a known fault for no start up or shut down but replacing it did not
get the set up.
As for why I then went to Q840, I figured the remaining troubles was
associated with the PS as well, so I took a calculated gamble using the
tech emails I searched and saw a recurring theme with C871 and Q840
always at the center.Law of averages said check it. I went to the 5V
stby pin which was high. At +5VDC normal, it was about 20% high.And My
Fluke meter only read the average DC. Maybe the extra was hash,AC or
both on the line.Since this indicated "poor health" with the device I
didn't care which pin was the actual cause.( if your child has a fever
inder his armpit, no need to measure the forehead,sick is sick).
So, troubleshooting with a mixture of percentages of known issues plus
hands on testing and PS schemo tracing.
Ta-Daa!
Why is it our wives are NEVER there to see when you do something smart?
Only when you trip over the dog...
;-)
Phil

Jim Myers wrote:
>
> Don, go back and read the original post from Phil, he calls Q840 LM78MR05,
> I'll bet it is the 5 pin L78MR05 after all. How about it Phil?
> **************************************************
> Jim Myers
> Since 1972
> Telrad Electronic Services Co.
> Fort Wayne, IN 46815
> *************************************************
> ----- Original Message -----
> From: "Jim Myers" <jr.myers@xxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Thursday, September 11, 2003 5:12 PM
> Subject: [TechAssist] Re: Toshibas, CF3566A,CF3572B,(TAC9190)shut down
> issues,fixes
>
> Oops! The 5 pin one with reset output is L78MR05, it is used extensively
in
> Toshiba sets so I guess I just Ass-U-Me'd.
> Sorry,
> **************************************************
> Jim Myers
> Since 1972
> Telrad Electronic Services Co.
> Fort Wayne, IN 46815
> *************************************************
> ----- Original Message -----
> From: <hartstv@xxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Thursday, September 11, 2003 5:02 PM
> Subject: [TechAssist] Re: Toshibas, CF3566A,CF3572B,(TAC9190)shut down
> issues,fixes
>
> Hi Jim,Are you sure the L78M05 is a 5 pin??I checked my NTE & Partsminder
> source & they all come up as 3 pin regs,ie NTE 960 or NTE
1960..............
> Don of HARTS-TVCR-ASC
> 9 Robert St,Oromocto,NB,Canada,E2V3N2
> Tel-506-357-9785,Fax-506-357-6010
> hartstv@xxxxxxxxxxx
>
> ----- Original Message -----
> From: "Jim Myers" <jr.myers@xxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Thursday, September 11, 2003 6:38 PM
> Subject: [TechAssist] Re: Toshibas, CF3566A,CF3572B,(TAC9190)shut down
> issues,fixes
>
> > I would suspect that the L78M05 was bad but not because of the 5v VCC
> output
> > being too high, rather that something was wrong with the reset output
pin.
> > This is a 5 pin device and is used to reset the micro as well as
supplying
> > the 5 volt VCC.
> > **************************************************
> > Jim Myers
> > Since 1972
> > Telrad Electronic Services Co.
> > Fort Wayne, IN 46815
> > *************************************************
> > ----- Original Message -----
> > From: <hartstv@xxxxxxxxxxx>
> > To: <techassist@xxxxxxxxxxxxx>
> > Sent: Thursday, September 11, 2003 4:30 PM
> > Subject: [TechAssist] Re: Toshibas, CF3566A,CF3572B,(TAC9190)shut down
> > issues,fixes
> >
> >
> > Phil,Glad you got your 2 units repaired.I have a question on the Q840
reg
> > that you replaced.If it's 3/4 of a volt too hi this will cause shutdown
or
> > intermittent startup?If it was low by this amount I would have replaced
it
> > but hi by this amount I would have missed this as a fix.I know you also
> > replaced a filter;but I'm just curious as to how you knew to replace the
5
> > volt reg.I would assume with the plus & minus tolerance of my meter &
the
> 5
> > volt reg,a 3/4 volt difference high would be over looked.Not trying to
be
> > pickey,very good t/sing on your part.The B+ for the micro's on these
units
> > must be very critical........
> > Don of HARTS-TVCR-ASC
> > 9 Robert St,Oromocto,NB,Canada,E2V3N2
> > Tel-506-357-9785,Fax-506-357-6010
> > hartstv@xxxxxxxxxxx
> >
> >
> >
> > ----- Original Message -----
> > From: "Philip Bader" <tjanphyl@xxxxxxxxxxxxxxx>
> > To: <techassist@xxxxxxxxxxxxx>
> > Sent: Thursday, September 11, 2003 1:58 PM
> > Subject: [TechAssist] Toshibas, CF3566A,CF3572B,(TAC9190)shut down
> > issues,fixes
> >
> >
> > > Both 35" Toahibas in for shutting down intermittantly, getting
> > > progressively worse until one stayed dead.
> > > Both Chassis# TAC9190.
> > > One came to life replacing an open cap C871 (22mfd/50V) on the smps
> > > board.
> > > The other came up with the same C871 (22mf/50V) cap plus a regulator
> > > Q840 (LM78MR05) that was outputting about 5.75VDC on a pin that should
> > > have been a steady 5VDC Standby. Measure that output across the
> > > 100mfd@xxxx Cap C844. Near the LM78MR05 IC.
> > > Always ESR all caps,and solder good.
> > > The group helped a lot with these.Good group.
> > > Phil Bader
> > > --
> > > Philip Bader
> > > Jan Phyl TV Inc. (estab. 1976)
> > > 3420 Recker Hwy. Winter Haven, Fl. 33880
> > > Fax (863) 299-8821
> > > email: tjanphyl@xxxxxxxxxxxxxxx
> > > For Professional Technicians Only
> > >
> > >
> >
>
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-- 
Philip Bader
Jan Phyl TV Inc. (estab. 1976)
3420 Recker Hwy. Winter Haven, Fl. 33880
Fax (863) 299-8821
email: tjanphyl@xxxxxxxxxxxxxxx
For Professional Technicians Only

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