Intermittent 3 strikes symptom but "sometimes" starts up, turns on and
displays great pic and good sound but B+ seems to regulate about 10 - 15
volts too high.... about 154 vdc.
I found that if I reduce the B+ going to pin #2 of flyback by about 10 volts
with a 27 ohm resistor that it powers on just fine, every time, so I am
hoping that if I can reduce the regulated B+ to a lower correct voltage that
all will be OK and will work fine as it should without the voltage dropping
resistor.
I checked values of resistors and electrolytics ESR all around SMPS primary
(changed R14108, 0.1 ohm, 3W) and secondary without finding any significant
deviations from the norm. Resoldering around Flyback, HOT, L4401, HDr
xfmr, etc had been done and has been redone.
How do I reduce the B+ ..... adjust? component change?
TIA
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>CTC203J2 RCA Hospital Model #J20541
>
>Intermittent 3 strikes symptom but "sometimes" starts up, turns on and
>displays great pic and good sound but B+ seems to regulate about 10 - 15
>volts too high.... about 154 vdc.
>I found that if I reduce the B+ going to pin #2 of flyback by about 10 volts
>with a 27 ohm resistor that it powers on just fine, every time, so I am
>hoping that if I can reduce the regulated B+ to a lower correct voltage that
>all will be OK and will work fine as it should without the voltage dropping
>resistor.
>I checked values of resistors and electrolytics ESR all around SMPS primary
>(changed R14108, 0.1 ohm, 3W) and secondary without finding any significant
>deviations from the norm. Resoldering around Flyback, HOT, L4401, HDr
>xfmr, etc had been done and has been redone.
>
>How do I reduce the B+ ..... adjust? component change?
>
>TIA
Sofie,
Check on secondary side, these SMPS use feedback regulation full time,
TL431 is the TO-92 size via 2 1% (green bodies) resistors and
regulates SMPS circuit via optisolator.
Like mine, I had one run high, was in that secondary side feedback
circuit.
ATC113 uses same SMPS, horizontal and vertical designs as CTC203.
Cheers, Wizard
SMPS not regulating or regulating high, always check the feedback
circuit components.
Did you find a faulty component or did you adjust slightly the balance
of R1 / R2 ?
How did you get the B+ lowered? ..... what is the correct B+ voltage?
David:
.... the solder joints and the circuit traces are in perfect condition,
but I resoldered them anyway and checked the traces with a meter and
with a magnafying glass.
Thanks for your inputs.
electricitym
.
.
> How do I reduce the B+ ..... adjust? component change?
>
> TIA
> --
Dan, make sure the flyback wasn't replaced with a generic one at some
point. Excessive hv is normal for this. I usually add a 472 2KV disc
across the timing cap to reduce the HV when a generic is used.
John