RCA TV CTC169 (BG5) F35750ST Wont come out of standby - Ticking sound when Power button is pressed

[Guest]

Hi all, especially Kip, Wizard, and TVFixer1

Thanks a ton for the help. Still no luck, same problem - good standby voltages, but won't come out of standby, and I hear a ticking sound while the power button is pressed.

I did unsolder the 4 leads into the Focus / Screen block. No change. With this off, (maybe coincidence) the voltages are slightly higher at 14.1 / 149.9. Still wont come out of standby.

Before unsoldering the Focus / Screen block, I disconnected all of the connectors coming out of the power supply to the audio board, SRS board, the board behind the CRT, etc. No change. I was trying to isolate the problem back to the main board. Seems like that is where the problem is.

With the collector of the Q4401 HOT unsoldered, the voltage on the collector lead is 0.5V, and on the circuit board pad it is 140V. Standby voltages are 12.7 / 141V, set won't come out of standby, BUT there is no ticking sound. With the collector soldered in, voltage at Q4401 collector measures 140V. Pulled the collector off of Q4101 and PS is dead (no surprise).

I am happy to unsolder the audio amps U1901 and U1902, to see if they are loading the power supply, but if I have P1903 unplugged, doesn't that rule out the audio amps? Both the -17 and 16.7V lines are through P1903.

I have now replaced all 4 caps around the SMPS, CR4118 (also re-replaced CR4118 with a different style ECG580), CR4119, and CR4120 (blown apart). I also replaced the thermistor (broken), and repaired cracked solder joints on the 1.8 ohm resistor. Because I saw a puff of smoke from the C4112 / T4101 area, I replaced both of those. I verified that the 33 ohm resistor R4119, R4001, and the diode CR4105 are all good.

FWIW, I did get it to come on for a few minutes yesterday. I had left it plugged in for 3-4 minutes, and tried the power button, and it came up (after some snaps and pops). I was able to bring up the menu, so I think that indicated weak / marginal components. I can't get it to come out of standby again.

The next step for me is freeze spray and a heat gun.

Anything else to try before hauling up the scope, based on Wizard's suggestion?? Haven't used it in a while, not sure it works….

Any ideas? Just need a few more months out of it, and besides this is really pi**ing me off now, shouldn't be this difficult.
Thanks again for the help

Mark

**********End Of Post*************

Mark,

Good progess on the SMPS. Before confirming the flyback is dud, needs
to check all diodes off the flyback isn't leaky or shorted. Need a
scope, lay the probe parallel next to the flyback ferrite core with
low volts/div on the scope and watch that scope while turning set on,
if fly is bad, the scope will show noise (arcing) in time with ticking
not the nice tall thin arches at 15.7 Khz.

Otherwise flyback is bad which is appox 60 to 100 in your area.
Focus/screen block is seperate from flyback. Solder that grey wire &
clean up all flux in focus/screen block with pure actone carefully
when you're changing the flyback.

I occassionally see this happen because the HV tripler (built into fly
itself) fry when SMPS B+ is high for too long due to capacitors in hot
side SMPS.
Same story with HV dividers in ctc169-based projectors.

Cheers,

Wizard

Hi all-

Nearly as I can tell, there is both a separate audio board and a separate SRS board (F35750ST CTC160BG5). Both boards have no power, because I disconnected connectors 1903 and 1904. .

SMPS voltages appear good, but no start-up, and still hear the ticking sound.

Really appreciate the help, just want to keep it going for a few more months……..

Mark

Reply-To: "john" <[email protected]>
From: "john" <[email protected]>
Newsgroups: sci.electronics.repair
Subject: Re: more info re:RCA TV CTC169(BG5) Wont come out of standby - Ticking sound when Power button is pressed

Correct I had a Pro Set last week had bad Audio Outs keep shutting set down.
The power is feed thru a connector very close to the Outputs.
That fault had me guessing for a while 2 TDA2052,s 216806 NOT cheap.


kip

--
"Watch the return E-Mail addy its false"

I think the 169 chassis has the audio module soldered to the main board, but I
have seen blown audio IC's cause no startup; desoldering the IC pins from their
pads should temporarily work, if that's the problem.

**********End Of Post*************
Subject: Re: more info re:RCA TV CTC169(BG5) Wont come out of standby - Ticking sound when Power button is pressed
Reply-To: [email protected]
Date: Thu, 25 Sep 2003 00:29:57 GMT

Hi all-

Nearly as I can tell, there is both a separate audio board and a separate SRS board (F35750ST CTC160BG5). Both boards have no power, because I disconnected connectors 1903 and 1904.

Really appreciate the help, just want to keep it going for a few more months……..

Mark

Mark,
```````````````````````````````````````````````````````````````
I think the 169 chassis has the audio module soldered to the main board,
but I have seen blown audio IC's cause no startup; desoldering the IC pins from
their pads should temporarily work, if that's the problem.**********End Of Post*************
--

Thanks. I neglected to mention that I tried that, with no luck. Same

problem. I had also pulled all of the other plugs

associated with the PS. I'm not giving up yet... it is pi**ing me off now...

Mark

Subject: Re: more info re:RCA TV CTC169(BG5) Wont come out of standby -

Ticking sound when Power button is pressed

Disconnect the plug in lead which goes to the sound board then try it.


kip

--
"Watch the return E-Mail addy its false"

replaced the thermistor (broken), and CR4120 (blown apart). Because I saw a
puff of smoke from the C4112 / T4101 area, I replaced both of those. No
change. 12.7 / 141 is fine, but it wont come out of standby, and it makes a
ticking sound while the power button is pressed.
collector lead is 0.5V, and on the circuit board pad it is 140V.

the diodes and caps around the smps, in addition to the misc parts above.
Still a ticking sound while the power button is pressed......Seems like the SMPS