Phillips TV, chassis 25B800-7562, no cable but plays dvd

[beezer]

Hi,

I have a Phillips 25" model 25TS54 C122, chassis 25B800-7562 that
now plays DVD fine but it will not see cable or antenna signals at
all.

When I first got the unit, The power would not stay on. I found the
following parts shorted:

D409
IC 500 (TDA 9302H)
Q290 (2SC2383)

After replacing the above parts, the television stays powered up and
plays dvd video fine via the digital input jack (yellow)

The unit will not play regular antenna or cable and offers no auto
signal detection nor manual channel detection. So, I then decided to
replace the tuner but that did not help.

Q290 is rated at .9 watt but gets extremely warm that you can feel the
heat rise off it.

I would certainly appreciate any clues as to where to look. I looked
at the board quite hard for dry joints and touched up a few that was
in need but no luck. Obviously I have no service manual.

Thanks

 

[beezer]

Hi, there may be more parts damaged by the vertical IC blown. Check
around in same area where you found that shorted diodes. There will
be few smoked resistors. Some shares these resistors with tuner's
power. Have the must haves? Volts for the tuner.

Oh, forgot to replace few caps, many are 100uF. This is also major
cause of vertical IC frying.

Cheers,

Wizard

Ok, will do.. Have the must haves? Not really sure as I do not have
a service manual nor schematic so im basically tracing them by eye and
trying to see where they go.

I do suspect the tuner not having proper voltage as you mentioned, so
ill keep digging in that area that would supply it.

So far the resistors that I've checked seemed to test fine. I would
have thought the 1 ohm resistors would have blown but they seem fine.

Ill keep posting my progress as i go along.

Thank you for the reply

 

[beezer]

Good,

I'm surprised that didn't know what typical voltages tuner needs.
Usually 30V for tuner, 5V, sometimes 9V. Most important is tuner
getting any 30V? There is two pins on tuner that is bus control by
micro. (clock and data) Changes voltages every time channels is
selecting. Appox 3.x to 4.9V varible. AFT changes and stays to one
value when channel locks in. There is one pin that is IF and you
can't measure it, that's ok.

Losing the tuner and vertical doesn't jibe. I have repaired many
philips sets with blown vertical and never had no tuner afterwards.
Philips is notorious for using one or two source power supply and use
the flyback for rest of different power supplies.

Go larger area, check carefully items with meter. I always find at
least two diodes blown when I have to change vertical IC. If you find
a TDA9302, TDA8472 will work and makes parts stocking easier and
cheaper.

Cheers,

Wizard

Great thanks again for the added info. I am sure thats enough to help
get this set going...

No, Im not a tv repair person so I am not familar with all the enables
a tuner would need. I know computer electronics and can signal trace
radios without a problem with schematics etc etc...

Ill dig into this in a bit and see what else I can uncover.

 

[beezer]

I do get 30v and 5v to the tuner. I can not seem to find any other
junction components that are obviously shorted or open.

I will try to find the variable line from the micro processor to the
tuner for the AFT. If I can not seem to find the AFT voltage from the
processor, I would assume it would be safe to say that the processor
may not be working properly provided the components between that and
the tuner are fine?

 

[MarkC]

I have to ask if you went into the menu to change it to tuner input mode
instead of video input? Always check the simple things first. I've done
many vertical jobs on the B8 chassis & never had one that didn't get
tuner reception after I was done working on it unless the customer had
previously been using it in the video input mode. I've got a Sams for
this one so I could copy you some pages if you need them

 

[Franc Zabkar]

ACG is automatic control gain ...

That should be AGC.


- Franc Zabkar

 

[beezer]

Thank you, sometimes fingers is lagging behind my racing mind.

Good suggestion on checking the video selection in menu. Hence I
asked about "snow". In video input mode, there's no snow or picture
if has active signal input connected.

Cheers,

Wizard

Thank you both for responding and sticking with me on this.

Firstly, I do get the variable voltage to the tuner up to 5 volts and
it changes as channels are changed. This was on pin 2 so the AGC seems
fine then...

I get absolutely no snow or white noise in any out of band channel or
video mode. I been in and out of the menu over and over trying to get
something out of it.

I also got more information on the unit when it first broke. My friend
had the tv in service in his entertainment center. He then turned it
around in order to put a different cable input from the cable tv (
from his vcr). He said after that, the set would not stay on at all.

That is when I received it and I first found the diode d409 shorted. I
replaced that and I then saw there was no vertical. I then replaced
the IC for the vertical, IC500. Afterward, I got vertical and it plays
fine with the dvd input but no cable reception.

I then replaced the tuner thinking it was that so I am at this point
still.

Never have I seen or heard noise on screen during any time of working
on it and doing autoscan and autodetect for cable or antenna.

Im just not sure what to look at as every component Ive checked seems
to be fine.

thank you again..

 

[beezer]

I have to ask if you went into the menu to change it to tuner input mode
instead of video input? Always check the simple things first. I've done
many vertical jobs on the B8 chassis & never had one that didn't get
tuner reception after I was done working on it unless the customer had
previously been using it in the video input mode. I've got a Sams for
this one so I could copy you some pages if you need them

Thank you for your reply...

I been through everything in the menu with no luck. I tried every
input mode through both the basic menu and the setup menu. I get no
noise on screen or speakers anywhere, not even out of band if that
helps. DVD plays perfect.

I would love a few pages out of the Sams, but I am just not sure what
area I could use at this point.

I really appreciate your reply

 

[Jason D.]

Hi,

I have a Phillips 25" model 25TS54 C122, chassis 25B800-7562 that
now plays DVD fine but it will not see cable or antenna signals at
all.

When I first got the unit, The power would not stay on. I found the
following parts shorted:

D409
IC 500 (TDA 9302H)
Q290 (2SC2383)

After replacing the above parts, the television stays powered up and
plays dvd video fine via the digital input jack (yellow)

Hi, there may be more parts damaged by the vertical IC blown. Check
around in same area where you found that shorted diodes. There will
be few smoked resistors. Some shares these resistors with tuner's
power. Have the must haves? Volts for the tuner.

Oh, forgot to replace few caps, many are 100uF. This is also major
cause of vertical IC frying.

Cheers,

Wizard

 

[Chuck]

Hi,

I have a Phillips 25" model 25TS54 C122, chassis 25B800-7562 that
now plays DVD fine but it will not see cable or antenna signals at
all.

When I first got the unit, The power would not stay on. I found the
following parts shorted:

D409
IC 500 (TDA 9302H)
Q290 (2SC2383)

After replacing the above parts, the television stays powered up and
plays dvd video fine via the digital input jack (yellow)

The unit will not play regular antenna or cable and offers no auto
signal detection nor manual channel detection. So, I then decided to
replace the tuner but that did not help.

Q290 is rated at .9 watt but gets extremely warm that you can feel the
heat rise off it.

I would certainly appreciate any clues as to where to look. I looked
at the board quite hard for dry joints and touched up a few that was
in need but no luck. Obviously I have no service manual.

Thanks

Try removing the eeprom. If reception returns, that is your problem.
Chuck

 

[Jason D.]

On Sun, 15 Aug 2004 19:01:46 GMT, [email protected] (Jason D.) wrote:

Ok, will do.. Have the must haves? Not really sure as I do not have
a service manual nor schematic so im basically tracing them by eye and
trying to see where they go.

I do suspect the tuner not having proper voltage as you mentioned, so
ill keep digging in that area that would supply it.

So far the resistors that I've checked seemed to test fine. I would
have thought the 1 ohm resistors would have blown but they seem fine.

Ill keep posting my progress as i go along.

Thank you for the reply

Good,

I'm surprised that didn't know what typical voltages tuner needs.
Usually 30V for tuner, 5V, sometimes 9V. Most important is tuner
getting any 30V? There is two pins on tuner that is bus control by
micro. (clock and data) Changes voltages every time channels is
selecting. Appox 3.x to 4.9V varible. AFT changes and stays to one
value when channel locks in. There is one pin that is IF and you
can't measure it, that's ok.

Losing the tuner and vertical doesn't jibe. I have repaired many
philips sets with blown vertical and never had no tuner afterwards.
Philips is notorious for using one or two source power supply and use
the flyback for rest of different power supplies.

Go larger area, check carefully items with meter. I always find at
least two diodes blown when I have to change vertical IC. If you find
a TDA9302, TDA8472 will work and makes parts stocking easier and
cheaper.

Cheers,

Wizard

 

[beezer]

Try removing the eeprom. If reception returns, that is your problem.
Chuck

Thats a heck of a job to find out, lol...

Wouldnt that remove the software for the menu and controls though?

 

[Jason D.]

I do get 30v and 5v to the tuner. I can not seem to find any other
junction components that are obviously shorted or open.

I will try to find the variable line from the micro processor to the
tuner for the AFT. If I can not seem to find the AFT voltage from the
processor, I would assume it would be safe to say that the processor
may not be working properly provided the components between that and
the tuner are fine?

Whoops! SHould be ACG.

ACG is automatic control gain controlled by jungle IC to the tuner to
componse for differing RF singal strength levels to one fixed signal
level for rest of the tuner so it won't swamp rest of it, not micro
itself.

Are you getting SNOW and white noise from speakers on out of band
channels? This confirms most of stuff are working but maybe either
jungle IC or tuner failed. Seen this sometimes not just philips.

But I still wondered why tuner would fail at same time with the
vertical circuit. Scratching head in puzzlement.

Cheers,

Wizard

 

[MarkC]

To simplify things why don't you forget about fixing the 'tuner' problem
& just use it as a monitor? You could patch a VCR (doesn't even have to
play) into the video & audio inputs & then use the VCR's tuner for
reception. Otherwise you are most likely going to spend alot of time & $
trying to restore it to 100%. If you have a digital cable box or
satellite receiver then use their direct line outs in the back. Also, in
trying to figure out what is causing the 'tuner' problem you may make
things worse & cause other problems.

 

[Jason D.]

That should be AGC.


- Franc Zabkar

Thank you, sometimes fingers is lagging behind my racing mind.

Good suggestion on checking the video selection in menu. Hence I
asked about "snow". In video input mode, there's no snow or picture
if has active signal input connected.

Cheers,

Wizard

 

[Chuck]

Thats a heck of a job to find out, lol...

Wouldnt that remove the software for the menu and controls though?

The eeprom is an 8 pin chip so removing it takes less than 5 minutes.
With the eeprom removed, the vertical deflection shrinks slightly but
all other functions work. Eeprom corruption is the second most common
fault on this chassis. Chuck.

 

[beezer]

The eeprom is an 8 pin chip so removing it takes less than 5 minutes.
With the eeprom removed, the vertical deflection shrinks slightly but
all other functions work. Eeprom corruption is the second most common
fault on this chassis. Chuck.

Sorry, I thought you may have ment the processor.. I will give that a
try.. However, I did fine and replace a 1 ohm resisitor in the
vertical area and a popped (literally) smt diode. The diode was
labeled as 9V, Im not sure if thats a part or its rating but thats the
only marking on it.

I will look for and remove the eeprom as you suggest and post an
update later.. thanks again