RCA 46" TV P46725SK won't turn on
 

I have an RCA rear projection TV P46725SK - set is plugged in and was
working fine until today when I tried to turn it on. I can hear a
faint "click click click" from the vicinity of the flyback transformer
when the power button is pressed. The power light blinks in unison
with the clicking sound. I'd like to fix this puppy since I don't have
the cash for a new TV right now and it's so heavy I dread getting it
out of the house. Help!

Possible HV Block or Convergence power Supply. Post what actual diagnostics
you have done.
"pink" wrote in message
ups.com...
I have an RCA rear projection TV P46725SK - set is plugged in and was
working fine until today when I tried to turn it on. I can hear a
faint "click click click" from the vicinity of the flyback transformer
when the power button is pressed. The power light blinks in unison
with the clicking sound. I'd like to fix this puppy since I don't have
the cash for a new TV right now and it's so heavy I dread getting it
out of the house. Help!

You are going to have to do basic tv troubleshooting and post the
results for any help. There are not easy answers. So far we know the
set does not turn on and needs repaired.

If you do not have the proper training and equipment, it is better to
pay for a quality estimate on the set so you can make an intelligent
decision on whether to have it repaired or not. Most RPTV repairs fall
under $300 total in home in most US markets.

Whats the ctc number on it ??

kip
"pink" wrote in message
ups.com...
I have an RCA rear projection TV P46725SK - set is plugged in and was
working fine until today when I tried to turn it on. I can hear a
faint "click click click" from the vicinity of the flyback transformer
when the power button is pressed. The power light blinks in unison
with the clicking sound. I'd like to fix this puppy since I don't have
the cash for a new TV right now and it's so heavy I dread getting it
out of the house. Help!

Does ctc number = chassis number? If so, the chassis number is
PTK169PFA.

I have some troubleshooting skills - I once fixed my Defender arcade
game monitor (bad flyback transformer). I have no schematics or tech
info other than a parts list and board ID sheet I found under the back
panel of the set. I have a DVM. It's not clear how to discharge the
flyback transformer... it's not like a regular TV where you'd slip a
grounded screwdriver under the rubber cap. Here the HV lead disappears
under the three projection tubes. Not sure how to get to those w/o
zapping myself in the process.

What else to check?

kip wrote:
Whats the ctc number on it ??

kip
"pink" wrote in message
ups.com...
I have an RCA rear projection TV P46725SK - set is plugged in and was
working fine until today when I tried to turn it on. I can hear a
faint "click click click" from the vicinity of the flyback transformer
when the power button is pressed. The power light blinks in unison
with the clicking sound. I'd like to fix this puppy since I don't have
the cash for a new TV right now and it's so heavy I dread getting it
out of the house. Help!

On 4 Jul 2005 10:01:24 -0700, "pink" wrote:

I have an RCA rear projection TV P46725SK - set is plugged in and was
working fine until today when I tried to turn it on. I can hear a
faint "click click click" from the vicinity of the flyback transformer
when the power button is pressed. The power light blinks in unison
with the clicking sound. I'd like to fix this puppy since I don't have
the cash for a new TV right now and it's so heavy I dread getting it
out of the house. Help!

That's a CTC-169. It is a good chassis, a bit old now. Was the picture
good, and did everything else work well before it developed the
problem? The good news is...you don't have to remove the entire set.
The internal light box, 70 pounds or so, is removeable, so a
technician can simply come to your house and remove the chassis, take
it to the shop, repair it, and return it. This chassis can be a bear
to troubleshoot if you don't have the pertinent service information
available, though.

Tom

On 4 Jul 2005 10:01:24 -0700, "pink" wrote:

I have an RCA rear projection TV P46725SK - set is plugged in and was
working fine until today when I tried to turn it on. I can hear a
faint "click click click" from the vicinity of the flyback transformer
when the power button is pressed. The power light blinks in unison
with the clicking sound. I'd like to fix this puppy since I don't have
the cash for a new TV right now and it's so heavy I dread getting it
out of the house. Help!

I remember a few CTC 169's with the sound output IC shorted.
That could cause it to go into the shutdown mode. Suggestion,
remove the power for the audio IC and see if the TV will start.

+15 Volt supply diode, they go leaky and cause a whole slew of aggrivations.
"Do Little2" wrote in message
...

On 4 Jul 2005 10:01:24 -0700, "pink" wrote:

I have an RCA rear projection TV P46725SK - set is plugged in and was
working fine until today when I tried to turn it on. I can hear a
faint "click click click" from the vicinity of the flyback transformer
when the power button is pressed. The power light blinks in unison
with the clicking sound. I'd like to fix this puppy since I don't have
the cash for a new TV right now and it's so heavy I dread getting it
out of the house. Help!

I remember a few CTC 169's with the sound output IC shorted.
That could cause it to go into the shutdown mode. Suggestion,
remove the power for the audio IC and see if the TV will start.

Tom MacIntyre wrote:

That's a CTC-169. It is a good chassis, a bit old now. Was the picture
good, and did everything else work well before it developed the
problem?

Yes, it was working great, no sign of any problem, then yesterday it
just didn't turn on. Come to think of it, we had a power outage the
other day and I can't remember whether the last time we used the TV was
before or after the outage. But we get power outages all the time in
my area so I don't suspect that caused the problem.

First thing remove the light box (presswood box all chassis & CRTs
Mounted. If there is acover on fromt of box (convergence controls )
remove it. the HV divider block is behind it. Locate thr red wire off
slightly by its self (goes to HV transformer) remove it Put into a dry
class bottle (for insulation purposes) Now hook up speakers & attempt
to turn on If sound returns You have a bad divider block, or a shorted
anode lead to one of CRTs If sound returns plug wire from transformer
back in & remove the red wires going to CRTs one at a time & try
turning on. This will isolate problem to individual tubes If this
checks contact me & I'll make further recomendations

How should I disconnect the main HV wire w/o zapping myself?

Just pull it out...It wont bite.

kip
"pink" wrote in message
oups.com...
How should I disconnect the main HV wire w/o zapping myself?

Okay - with the main HV lead disconnected from the HV divider block,
the sound returns.

With the HV lead reconnected, and disconnecting each individual CRT
wire in sequence, no sound again (except for the tick-tick-tick). Then
I disconnected all three CRT leads (in case two anodes were bad) and
still no sound.

So - replace the HV divider block?

And repair the main smps power supply which is the typical cause of the
hv block failure.
Do not forget the hv splitter rubber insulation boots that are on all
the wires.

Would installing Tritronic's Common Failure Repair Kit (p/n
CTC169-KIT-PTV) do the trick?

What is the problem in the power supply that causes the HV divider to fail?
I have fixed many of these and while we routinely go through the PS I have
not ben aware of the PS causing the divider to fail.

Leonard

wrote in message
oups.com...
And repair the main smps power supply which is the typical cause of the
hv block failure.
Do not forget the hv splitter rubber insulation boots that are on all
the wires.

High B+ regulation in standby.
The margin for error is very small on the hv in the splitter.
As the capacitors fail in the power supply, the standby voltage will
drift over time up to as high as 165V, versus the 140~145V that is
suppose to be there.
Since that is a 15% increase in initial B+ at start up, which is beyond
the 10% margin for the insulation in the hv block, the hv is too high
initially at start up and this starts internal arcing at start up.
Over time these carbon tracks finally cascade and the hard carbon arc
short is started. The problem arises in that the regulator kicks into
run mode in about one second after turn on. The regulator is then
running off the horizontal feedback pulses for regulation. Since this
happens so fast and is only slightly above the x-ray trip voltage, the
x-ray circuit never triggers. Each turn on with standby B+ running
high will cause an arc over. The big problem we found was that if the
smps was not repaired and was the cause of the failure, it most times
would take 6 to 9 months before we would get a call back on the set
being dead. So shop policy had to be verify the smps secondary
voltages on ALL ctc169 sets, cr4118 and cr4116 must be in proper range
and clean looking on the o'scope. Extra 5 minutes of work to guarantee
no future problems.

The cr4118 failure can also cause the B+ to run high as it starts to go
leaky and fail. However I have never seen it fail to the point that
the B+ will run over 150V before the 15V line was too low for the set
to attempt to start up.

It is mainly the 2.2uF capacitor on the standby feedback line of the
smps that goes open that causes this problem. It is a simple matter to
measure the standby B+ voltage on the cathode of cr4116 with the tv
turned off to verify that there is not a problem.

Interesting. I never noticed the standby B+ going that high. I'll have to
check more closely. We have several routine checks on the 169 chassis on
any set that comes in that includes the caps in the power supply so the get
changed if they are bad. I often don't check the standby B+ until after the
repair is done so I had not noticed that. We do, however, change lots of HV
dividers in sets where the PS caps are fine. In those cases the B+ is
checked and I have not seen it out of range. I guess the small margin of
safety on the divider is the problem. I have also changed quite a few that
were dne by other shops previously and the grommets were missing or the lead
was not inserted correctly. So the OP should be careful to install it
correctly or be prepared to change it again before long.

You wold think that they would not start the horizontal osc. until B+ is
regulated. But then, you would think a critical part like a high voltage
splitter would be built with a greater safety factor.

Thanks, David.

Leonard

wrote in message
ups.com...
High B+ regulation in standby.
The margin for error is very small on the hv in the splitter.
As the capacitors fail in the power supply, the standby voltage will
drift over time up to as high as 165V, versus the 140~145V that is
suppose to be there.
Since that is a 15% increase in initial B+ at start up, which is beyond
the 10% margin for the insulation in the hv block, the hv is too high
initially at start up and this starts internal arcing at start up.
Over time these carbon tracks finally cascade and the hard carbon arc
short is started. The problem arises in that the regulator kicks into
run mode in about one second after turn on. The regulator is then
running off the horizontal feedback pulses for regulation. Since this
happens so fast and is only slightly above the x-ray trip voltage, the
x-ray circuit never triggers. Each turn on with standby B+ running
high will cause an arc over. The big problem we found was that if the
smps was not repaired and was the cause of the failure, it most times
would take 6 to 9 months before we would get a call back on the set
being dead. So shop policy had to be verify the smps secondary
voltages on ALL ctc169 sets, cr4118 and cr4116 must be in proper range
and clean looking on the o'scope. Extra 5 minutes of work to guarantee
no future problems.

The cr4118 failure can also cause the B+ to run high as it starts to go
leaky and fail. However I have never seen it fail to the point that
the B+ will run over 150V before the 15V line was too low for the set
to attempt to start up.

It is mainly the 2.2uF capacitor on the standby feedback line of the
smps that goes open that causes this problem. It is a simple matter to
measure the standby B+ voltage on the cathode of cr4116 with the tv
turned off to verify that there is not a problem.

I have noticed a few of these chassis having the increased standy B+ and
have serviced the chopper, regulator circuit before returning then to
service. It is an interesting question tho, did the HV block fail because of
the increased B+ or is it just co-incidence? Due to the age of these sets
the caps are going bad anyway and need replacing. Good point David!
"Leonard Caillouet" wrote in message
news:BR6Ae.31654$up5.29048@lakeread02...
Interesting. I never noticed the standby B+ going that high. I'll have
to check more closely. We have several routine checks on the 169 chassis
on any set that comes in that includes the caps in the power supply so the
get changed if they are bad. I often don't check the standby B+ until
after the repair is done so I had not noticed that. We do, however,
change lots of HV dividers in sets where the PS caps are fine. In those
cases the B+ is checked and I have not seen it out of range. I guess the
small margin of safety on the divider is the problem. I have also changed
quite a few that were dne by other shops previously and the grommets were
missing or the lead was not inserted correctly. So the OP should be
careful to install it correctly or be prepared to change it again before
long.

You wold think that they would not start the horizontal osc. until B+ is
regulated. But then, you would think a critical part like a high voltage
splitter would be built with a greater safety factor.

Thanks, David.

Leonard

wrote in message
ups.com...
High B+ regulation in standby.
The margin for error is very small on the hv in the splitter.
As the capacitors fail in the power supply, the standby voltage will
drift over time up to as high as 165V, versus the 140~145V that is
suppose to be there.
Since that is a 15% increase in initial B+ at start up, which is beyond
the 10% margin for the insulation in the hv block, the hv is too high
initially at start up and this starts internal arcing at start up.
Over time these carbon tracks finally cascade and the hard carbon arc
short is started. The problem arises in that the regulator kicks into
run mode in about one second after turn on. The regulator is then
running off the horizontal feedback pulses for regulation. Since this
happens so fast and is only slightly above the x-ray trip voltage, the
x-ray circuit never triggers. Each turn on with standby B+ running
high will cause an arc over. The big problem we found was that if the
smps was not repaired and was the cause of the failure, it most times
would take 6 to 9 months before we would get a call back on the set
being dead. So shop policy had to be verify the smps secondary
voltages on ALL ctc169 sets, cr4118 and cr4116 must be in proper range
and clean looking on the o'scope. Extra 5 minutes of work to guarantee
no future problems.

The cr4118 failure can also cause the B+ to run high as it starts to go
leaky and fail. However I have never seen it fail to the point that
the B+ will run over 150V before the 15V line was too low for the set
to attempt to start up.

It is mainly the 2.2uF capacitor on the standby feedback line of the
smps that goes open that causes this problem. It is a simple matter to
measure the standby B+ voltage on the cathode of cr4116 with the tv
turned off to verify that there is not a problem.

Coincidence due to age? Maybe. What I find mostly is the cap will be
marginal. After the set is plugged in a while it all warms up and the
B+ seems to be close enough to the ideal 143V. But when the set is
cold, the B+ is higher. Typical bad capacitor problem.

A 10% increase in B+ on start up is a 10% increase in HV, 28,000 volts
is quite a lot less than 30,800 volts.

They do have the unit regulating at start up. The standby rough
regulator feedback is doing the regulating, when it fails to regulate
on the money, there is nothing that will keep the set from coming on,
until it goes so high that there is a catastophic failure.

So as always, check/replace the capacitors in the smps and cr4118
everytime.

The TV had been making an arc sound for quite some time when the set
was cold, however everything still worked fine. Which leads me to
believe that the HV splitter was having some issues? However now
while doing some test I fine that I don't even have power going to
the HV transformer. The only place I can seem to fine any juice in
the system is on main board to the right of the set (if looking in
from the rear). If anyone could make any suggestions I would
appreciate it. It is a classic case of worked one day and not the
next

Ok its a CTC169...
You will have to rebuild the SMPS section ...First 2.2mfd 22mfd 39mf
Then whilst in standby mode check voltages....+15Von cr4118
Then ...134V on HOT collector
If OK fine..
If not rebuild Horizontal Out section HOT/Blue Box caps etc..
Whilst in there replace HV Block..

kip
"fosjef67" wrote in
message .. .
The TV had been making an arc sound for quite some time when the set
was cold, however everything still worked fine. Which leads me to
believe that the HV splitter was having some issues? However now
while doing some test I fine that I don't even have power going to
the HV transformer. The only place I can seem to fine any juice in
the system is on main board to the right of the set (if looking in
from the rear). If anyone could make any suggestions I would
appreciate it. It is a classic case of worked one day and not the
next

Maybe even the pcc diode and associated cap?
"kip" wrote in message
.. .
Ok its a CTC169...
You will have to rebuild the SMPS section ...First 2.2mfd 22mfd 39mf
Then whilst in standby mode check voltages....+15Von cr4118
Then ...134V on HOT collector
If OK fine..
If not rebuild Horizontal Out section HOT/Blue Box caps etc..
Whilst in there replace HV Block..

kip
"fosjef67" wrote in
message .. .
The TV had been making an arc sound for quite some time when the set
was cold, however everything still worked fine. Which leads me to
believe that the HV splitter was having some issues? However now
while doing some test I fine that I don't even have power going to
the HV transformer. The only place I can seem to fine any juice in
the system is on main board to the right of the set (if looking in
from the rear). If anyone could make any suggestions I would
appreciate it. It is a classic case of worked one day and not the
next