[TechAssist] Re: RCA-CTC169AM,chass-f31221wn-32''

  • From: <hartstv@xxxxxxxxxxx>
  • To: <techassist@xxxxxxxxxxxxx>
  • Date: Thu, 24 Jul 2003 21:59:53 -0300

Tks for your reply,Larry.Here are the values of the orginal caps removed
from the smps;
C4102=2.2ufd/100v
C4104=15ufd/50v
C4108=47ufd/50v
The voltage at Q4101 is varying from 159vdc to 164vdc.
The voltage on the collector pad of the HOT Q4401 is varying from 13vdc to
40vdc;NOTE this is without the collector of HOT connected to pad & yes I'm
using the correct grounds.
Pin 3 of U4101 is varying from 0vdc to .013vdc.
I know there are hot & cold grounds for these measurements.The HOT collector
voltage is low because the chopper is not in it's proper duty cycle.This is
the same voltage measured at the cathode of CR4116,the 145vdc source.
I did replace C4104 with a 4.7/100v cap,as per your email but have same
voltage readings.What I don't understand is the orginal cap was
15ufd/50v.Man this is wierd?? Tks again for your help...regards...
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: "Larry E." <videotech@xxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Thursday, July 24, 2003 8:56 PM
Subject: [TechAssist] Re: RCA-CTC169AM,chass-f31221wn-32''


> Hi Don, you need to be carefull changing parts in a 169 chassis with a pa=
> rts list from a 27" proscan, there are 4 different families of 169 chassi=
> s`s and some of the parts
> are very different, for example C4108 in your set (family 1) is supposed =
> to be a
> 47uf @ 50 volts but in a family 4 169 it`s a 39uf @ 100v,  BIG difference=
> =2E
> The usual cause of pin 16 on U4101 fluctuating up and down is the 3 caps =
> you changed, or U4101 is bad check the values, C4102=3D 2.2 @ 100v   C410=
> 4=3D 4.7 @ 100v(not 47uf)  C4108=3D 47uf @ 50v. If those are good then th=
> e set is either in ovp or ocp You should have the following in standby (s=
> et plugged in but not turned on), Raw B+ on C of Q4101 =3D approx. 165 vo=
> lts, Regulated B+ on C of HOT=3D approx.144 volts, 5v standby on E of Q46=
> 01. If the above are correct, check voltage on pin 3 of U4101, it shouldn=
> `t be above .6v (point 6 volts) if it is the
> set is going into ocp shutdown. Let me know the results of these measurem=
> ents,
> I don`t have a scanner but I do have the schematics and 169 troubleshooti=
> ng guide.
> Remember that a lot of the capacitor values are different for the various=
>  169 models
> so be careful to replace what you pull out with the same value, Larry E
> Larry Eastman
> American TV & Electronics
> Crystal River, Fl. 34428
> 352-795-0124
> pulling out
> hartstv@xxxxxxxxxxx wrote:
>
> > This direct view 32'' unit has me baffeled.Orginally came in with the H=
> OT shorted.Replaced with an OEM 2SD1885.Everything else was ok so fired i=
> t up.The HV was 38.5KV,too hi,so took the chass out to bench test.Turned =
> it on without a yoke plugged in & I think that's when my problems started=
> =2EQ4802 smoked in the pin cct.Replaced it & plugged a yoke to the set.No=
> w my smps won't start.Pin 16 reads 8.5vdc then slowly goes up to 10.5vdc =
> & then starts going back down to 8.5v.So changed all the normal parts for=
>  this smps,ie,the U4101,C4102,4,8,Q4101.Did not help.Replaced the infamou=
> s CR4118.Checked or replaced both LM311 in the vert & pin cct;also C4403,=
> CR4401,CR4402.Again no go.Checked or replaced all trans in the PWM cct,Q4=
> 405,6,7,8,9.Same results;the regulator is trying to start but keeps going=
>  up/down from 8.5v to 10.5v.Raw B+ is solid at 165vdc,no ripple.All these=
>  tests were done with HOT collector lifted.I have checked all my tips for=
>  this unit,& I know there's a ton of them but
> >   can't find the problem.I have changed so many parts too numereous to =
> mention,ie caps,diodes,transistors but I'm stumped.Any assistance would b=
> e greatly appreciated or if someone would be so kind to email a pdf for t=
> his brute.The only print I have is a profax for the 27'' set.BTY i also c=
> hecked all transistors in the Q4300 & Q4700 series.........TIA...........=
> =2E
> > Don of HARTS-TVCR-ASC
> > 9 Robert St,Oromocto,NB,Canada,E2V3N2
> > Tel-506-357-9785,Fax-506-357-6010
> > hartstv@xxxxxxxxxxx
> >
> > ***********************************************************************=
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