I have a GE 9" under the counter TV (Model 09GP108) which has video that
fades out after the set is on for while, then comes back, and repeats the
process periodically thereafter. There is a NPN transistor labeled TP15
which appears to get hot enough to discolor the board beneath it. This
transistor checks OK with an ohmmeter, but may be breaking down under higher
voltages. The designation on this transistor is 3214. Searching for this
number on NTE results in "NTEOBS-NLA" which as I understand it means that it
is obsolete and no longer available. Has anyone found a replacement for
this transistor?

In addition, someone several years ago said this was a "12v. standby
regulator transistor". Is there a Zener diode associated with this
transistor and if so, can anyone tell me the designation on the circuit
board. As you can tell by this point, I don't have the service information
on this set (as yet) and am hoping to get by without it.

Thanks for your time.
Dan

Dan Dubosky wrote:
I have a GE 9" under the counter TV (Model 09GP108) which has video that
fades out after the set is on for while, then comes back, and repeats the
process periodically thereafter. There is a NPN transistor labeled TP15
which appears to get hot enough to discolor the board beneath it. This
transistor checks OK with an ohmmeter, but may be breaking down under higher
voltages. The designation on this transistor is 3214. Searching for this
number on NTE results in "NTEOBS-NLA" which as I understand it means that it
is obsolete and no longer available. Has anyone found a replacement for
this transistor?

In addition, someone several years ago said this was a "12v. standby
regulator transistor". Is there a Zener diode associated with this
transistor and if so, can anyone tell me the designation on the circuit
board. As you can tell by this point, I don't have the service information
on this set (as yet) and am hoping to get by without it.

Thanks for your time.
Dan



If the video fades, resolder the CRT heater pins on the neck board, it's
almost certainly something in that circuit.

"James Sweet" wrote in message
news:%vJYj.1054$5H5.83@trndny02...

Dan Dubosky wrote:
I have a GE 9" under the counter TV (Model 09GP108) which has video that
fades out after the set is on for while, then comes back, and repeats the
process periodically thereafter. There is a NPN transistor labeled TP15
which appears to get hot enough to discolor the board beneath it. This
transistor checks OK with an ohmmeter, but may be breaking down under
higher voltages. The designation on this transistor is 3214. Searching
for this number on NTE results in "NTEOBS-NLA" which as I understand it
means that it is obsolete and no longer available. Has anyone found a
replacement for this transistor?

In addition, someone several years ago said this was a "12v. standby
regulator transistor". Is there a Zener diode associated with this
transistor and if so, can anyone tell me the designation on the circuit
board. As you can tell by this point, I don't have the service
information on this set (as yet) and am hoping to get by without it.

Thanks for your time.
Dan

If the video fades, resolder the CRT heater pins on the neck board, it's
almost certainly something in that circuit.

Sounds like a good suggestion. None of the solder joints appeared to be
bad, but I know how that goes. I've resoldered all of the points on the
neck board, and the set stayed on longer than it had in the past. I'll know
tomorrow for sure.

Thanks.
Dan

"James Sweet" wrote in message
news:%vJYj.1054$5H5.83@trndny02...

Dan Dubosky wrote:
I have a GE 9" under the counter TV (Model 09GP108) which has video that
fades out after the set is on for while, then comes back, and repeats the
process periodically thereafter. There is a NPN transistor labeled TP15
which appears to get hot enough to discolor the board beneath it. This
transistor checks OK with an ohmmeter, but may be breaking down under
higher voltages. The designation on this transistor is 3214. Searching
for this number on NTE results in "NTEOBS-NLA" which as I understand it
means that it is obsolete and no longer available. Has anyone found a
replacement for this transistor?

In addition, someone several years ago said this was a "12v. standby
regulator transistor". Is there a Zener diode associated with this
transistor and if so, can anyone tell me the designation on the circuit
board. As you can tell by this point, I don't have the service
information on this set (as yet) and am hoping to get by without it.

Thanks for your time.
Dan

If the video fades, resolder the CRT heater pins on the neck board, it's
almost certainly something in that circuit.

I spoke too soon. After soldering all of the points, the problem is still
there.

Dan

Dan Dubosky wrote:
"James Sweet" wrote in message
news:%vJYj.1054$5H5.83@trndny02...
Dan Dubosky wrote:
I have a GE 9" under the counter TV (Model 09GP108) which has video that
fades out after the set is on for while, then comes back, and repeats the
process periodically thereafter. There is a NPN transistor labeled TP15
which appears to get hot enough to discolor the board beneath it. This
transistor checks OK with an ohmmeter, but may be breaking down under
higher voltages. The designation on this transistor is 3214. Searching
for this number on NTE results in "NTEOBS-NLA" which as I understand it
means that it is obsolete and no longer available. Has anyone found a
replacement for this transistor?

In addition, someone several years ago said this was a "12v. standby
regulator transistor". Is there a Zener diode associated with this
transistor and if so, can anyone tell me the designation on the circuit
board. As you can tell by this point, I don't have the service
information on this set (as yet) and am hoping to get by without it.

Thanks for your time.
Dan
If the video fades, resolder the CRT heater pins on the neck board, it's
almost certainly something in that circuit.

Sounds like a good suggestion. None of the solder joints appeared to be
bad, but I know how that goes. I've resoldered all of the points on the
neck board, and the set stayed on longer than it had in the past. I'll know
tomorrow for sure.

Thanks.
Dan





It could be further down the line as well, just trace the heater
circuit. You can verify by running the set with the cover off in a dark
room and see if the heater glow fades.

"James Sweet" wrote in message
newsuKYj.1320$ay2.281@trndny01...

Dan Dubosky wrote:
"James Sweet" wrote in message
news:%vJYj.1054$5H5.83@trndny02...
Dan Dubosky wrote:
I have a GE 9" under the counter TV (Model 09GP108) which has video
that fades out after the set is on for while, then comes back, and
repeats the process periodically thereafter. There is a NPN transistor
labeled TP15 which appears to get hot enough to discolor the board
beneath it. This transistor checks OK with an ohmmeter, but may be
breaking down under higher voltages. The designation on this
transistor is 3214. Searching for this number on NTE results in
"NTEOBS-NLA" which as I understand it means that it is obsolete and no
longer available. Has anyone found a replacement for this transistor?

In addition, someone several years ago said this was a "12v. standby
regulator transistor". Is there a Zener diode associated with this
transistor and if so, can anyone tell me the designation on the circuit
board. As you can tell by this point, I don't have the service
information on this set (as yet) and am hoping to get by without it.

Thanks for your time.
Dan
If the video fades, resolder the CRT heater pins on the neck board, it's
almost certainly something in that circuit.

Sounds like a good suggestion. None of the solder joints appeared to be
bad, but I know how that goes. I've resoldered all of the points on the
neck board, and the set stayed on longer than it had in the past. I'll
know tomorrow for sure.

Thanks.
Dan



It could be further down the line as well, just trace the heater circuit.
You can verify by running the set with the cover off in a dark room and
see if the heater glow fades.

You're right on. The heater does fade out at the same time that the problem
occurs. I'll try to trace the rest of the heater circuit.

On May 20, 9:21*pm, "Dan Dubosky" wrote:
"James Sweet" wrote in message

newsuKYj.1320$ay2.281@trndny01...







Dan Dubosky wrote:
"James Sweet" wrote in message
news:%vJYj.1054$5H5.83@trndny02...
Dan Dubosky wrote:
I have a GE 9" under the counter TV (Model 09GP108) which has video
that fades out after the set is on for while, then comes back, and
repeats the process periodically thereafter. *There is a NPN transistor
labeled TP15 which appears to get hot enough to discolor the board
beneath it. *This transistor checks OK with an ohmmeter, but may be
breaking down under higher voltages. *The designation on this
transistor is 3214. *Searching for this number on NTE results in
"NTEOBS-NLA" which as I understand it means that it is obsolete and no
longer available. *Has anyone found a replacement for this transistor?

In addition, someone several years ago said this was a "12v. standby
regulator transistor". *Is there a Zener diode associated with this
transistor and if so, can anyone tell me the designation on the circuit
board. *As you can tell by this point, I don't have the service
information on this set (as yet) and am hoping to get by without it.

Thanks for your time.
Dan
If the video fades, resolder the CRT heater pins on the neck board, it's
almost certainly something in that circuit.

Sounds like a good suggestion. *None of the solder joints appeared to be
bad, but I know how that goes. *I've resoldered all of the points on the
neck board, and the set stayed on longer than it had in the past. *I'll
know tomorrow for sure.

Thanks.
Dan

It could be further down the line as well, just trace the heater circuit..
You can verify by running the set with the cover off in a dark room and
see if the heater glow fades.

You're right on. *The heater does fade out at the same time that the problem
occurs. *I'll try to trace the rest of the heater circuit.- Hide quoted text -

- Show quoted text -

James is almost always "right on".

Greetings Dan..

Regarding:
"There is a NPN transistor labeled TP15 which appears to get hot
enough to discolor the board beneath it. This transistor checks OK
with an ohmmeter, but may be breaking down under higher voltages."

This may be an issue where the component (transistor) is getting SO
hot as to make the solder connections and thus the electrical
connections intermittent.

Some of these multi-pin ICs and transistors can get very hot indeed.
I've had a similar situation with a vertical oscillator / amplifier IC
that resulted in the horizontal line as the IC got hot. I got into the
motherboard, sucked up the old solder (Soldapullt). And applied some
new heat sink compound and remounted the IC and re-soldered the
connection with fresh solder. Clean up the resin afterwards with
Alcohol and all has been well for several years.

Likewise, the first thing I would do is unsolder your suspect
transistor, pulling up the old solder. IF it's heat sink mounted, make
sure you have wiped off the old heat sink compound and apply some new
fresh silicon based heat sink compound and re-solder the transistor
with fresh solder. Clean up the residue and see if that doesn't
resolve the issue. IF your transistor, in this case, is electrically
sound, this may be all that is needed. Ultimately, you wan to do what
you can to cool down the operation of that transistor, especially if
its been discoloring the PC board beneath it.

Cheers,
Mr. Mentor



"Dan Dubosky" wrote in message
...
|I have a GE 9" under the counter TV (Model 09GP108) which has video
that
| fades out after the set is on for while, then comes back, and
repeats the
| process periodically thereafter. There is a NPN transistor labeled
TP15
| which appears to get hot enough to discolor the board beneath it.
This
| transistor checks OK with an ohmmeter, but may be breaking down
under higher
| voltages. The designation on this transistor is 3214. Searching
for this
| number on NTE results in "NTEOBS-NLA" which as I understand it means
that it
| is obsolete and no longer available. Has anyone found a replacement
for
| this transistor?
|
| In addition, someone several years ago said this was a "12v. standby
| regulator transistor". Is there a Zener diode associated with this
| transistor and if so, can anyone tell me the designation on the
circuit
| board. As you can tell by this point, I don't have the service
information
| on this set (as yet) and am hoping to get by without it.
|
| Thanks for your time.
| Dan
|
|

dBc wrote:
Greetings Dan..

Regarding:
"There is a NPN transistor labeled TP15 which appears to get hot
enough to discolor the board beneath it. This transistor checks OK
with an ohmmeter, but may be breaking down under higher voltages."

This may be an issue where the component (transistor) is getting SO
hot as to make the solder connections and thus the electrical
connections intermittent.

Some of these multi-pin ICs and transistors can get very hot indeed.
I've had a similar situation with a vertical oscillator / amplifier IC
that resulted in the horizontal line as the IC got hot. I got into the
motherboard, sucked up the old solder (Soldapullt). And applied some
new heat sink compound and remounted the IC and re-soldered the
connection with fresh solder. Clean up the resin afterwards with
Alcohol and all has been well for several years.

Likewise, the first thing I would do is unsolder your suspect
transistor, pulling up the old solder. IF it's heat sink mounted, make
sure you have wiped off the old heat sink compound and apply some new
fresh silicon based heat sink compound and re-solder the transistor
with fresh solder. Clean up the residue and see if that doesn't
resolve the issue. IF your transistor, in this case, is electrically
sound, this may be all that is needed. Ultimately, you wan to do what
you can to cool down the operation of that transistor, especially if
its been discoloring the PC board beneath it.

Cheers,
Mr. Mentor



The transistor is fine, it's perfectly normal for cheap phenolic circuit
boards to darken. We already determined that the problem is in the power
to the CRT heater.

James, I'm sorry that my description of the problem has been inadequate.
Yes, the video does fade in and out, but so does the sound. The set seems
to be turning itself OFF and ON periodically. So, the problem may be even
further back than the heater circuit. I am beginning to suspect something
in the remote control circuit.

Mr. Mentor, the transistor which has a discoloration in the board beneath
does not have a heat sink, and I have already removed it and resoldered it.

Thanks to all.
Dan

"James Sweet" wrote in message
news:vmPYj.4107$Zy1.1108@trndny05...

dBc wrote:
Greetings Dan..

Regarding:
"There is a NPN transistor labeled TP15 which appears to get hot enough
to discolor the board beneath it. This transistor checks OK with an
ohmmeter, but may be breaking down under higher voltages."

This may be an issue where the component (transistor) is getting SO hot
as to make the solder connections and thus the electrical connections
intermittent.

Some of these multi-pin ICs and transistors can get very hot indeed. I've
had a similar situation with a vertical oscillator / amplifier IC that
resulted in the horizontal line as the IC got hot. I got into the
motherboard, sucked up the old solder (Soldapullt). And applied some new
heat sink compound and remounted the IC and re-soldered the connection
with fresh solder. Clean up the resin afterwards with Alcohol and all has
been well for several years.

Likewise, the first thing I would do is unsolder your suspect transistor,
pulling up the old solder. IF it's heat sink mounted, make sure you have
wiped off the old heat sink compound and apply some new fresh silicon
based heat sink compound and re-solder the transistor with fresh solder.
Clean up the residue and see if that doesn't resolve the issue. IF your
transistor, in this case, is electrically sound, this may be all that is
needed. Ultimately, you wan to do what you can to cool down the operation
of that transistor, especially if its been discoloring the PC board
beneath it.

Cheers,
Mr. Mentor



The transistor is fine, it's perfectly normal for cheap phenolic circuit
boards to darken. We already determined that the problem is in the power
to the CRT heater.

Dan Dubosky wrote:
James, I'm sorry that my description of the problem has been inadequate.
Yes, the video does fade in and out, but so does the sound. The set seems
to be turning itself OFF and ON periodically. So, the problem may be even
further back than the heater circuit. I am beginning to suspect something
in the remote control circuit.

Mr. Mentor, the transistor which has a discoloration in the board beneath
does not have a heat sink, and I have already removed it and resoldered it.

Thanks to all.
Dan



Oh, yes that changes things. I would look at the power supply and the
pins around the flyback transformer. If the remote circuit was the
issue, the power relay would be clicking in and out.

"James Sweet" wrote in message
news:AFYYj.2280$aJ1.293@trndny03...

Dan Dubosky wrote:
James, I'm sorry that my description of the problem has been inadequate.
Yes, the video does fade in and out, but so does the sound. The set
seems to be turning itself OFF and ON periodically. So, the problem may
be even further back than the heater circuit. I am beginning to suspect
something in the remote control circuit.

Mr. Mentor, the transistor which has a discoloration in the board beneath
does not have a heat sink, and I have already removed it and resoldered
it.

Thanks to all.
Dan


Oh, yes that changes things. I would look at the power supply and the pins
around the flyback transformer. If the remote circuit was the issue, the
power relay would be clicking in and out.

As James says, you've gotta be looking in the power supply. I think that
personally, I would feel inclined to just replace that transistor that gets
hot, even if it appears to read ok on static ohms testing. If it is one of
those large format D-line packages, just replace it with a general purpose
flatpak - whatever comes to hand in the right NPN or PNP flavour. Chances
are that transistor is either a regulator, or a standby switch, and it may
well fail when it gets hot. I have had this with transistors in that sort of
position, many times. You could just stick your voltmeter on (probably) the
emitter pin (possibly the collector pin) and just see if the voltage goes
away when the set goes off. If it does, check the other pin (collector or
emitter) and see if the input volts are still there. If they are, and the
base volts have not changed significantly, then the transistor is faulty. If
that's all too much trouble, buy a can of freezer, and give the transistor a
good squirt when the display goes off, and see if that restores it for a
while. I also agree with James that the remote circuit is most unlikely to
have anything to do with this problem.

Arfa

On May 21, 10:17*am, "Dan Dubosky" wrote:
James, I'm sorry that my description of the problem has been inadequate.
Yes, the video does fade in and out, but so does the sound. *The set seems
to be turning itself OFF and ON periodically. *So, the problem may be even
further back than the heater circuit. *I am beginning to suspect something
in the remote control circuit.

Mr. Mentor, the transistor which has a discoloration in the board beneath
does not have a heat sink, and I have already removed it and resoldered it..


Does it really "fade" out? Or do you really just abruptly lose video?

Given the problem cycles, it really does sound thermal.
Given that you lose the audio, too, it sounds like power supply.
Does this happen with the cover(s) off? If so, got any freeze spray?
If so, run it w/covers off, then when problem occurs, gently spray a
few drops of freeze liquid onto suspect components, see if you can
make it stop that way.

...or have you already tried this approach?

Thanks to all! You have been a great deal of help. I was away for the day
so I couldn't get back to the set until this evening. It did appear to be a
problem which was thermal in nature since it played without difficulty for
the longest period of time when it was first turned on. I acquired a can of
freeze spay tonight from my local Radio Shack and started to try and locate
the problem component. Spraying the transistor with the discolored board
beneath didn't do a thing, but spraying the HOT cures the problem at least
until it heats up again. As soon as I get a replacement, I'll post the
results.

Thanks again.
Dan

"Mr. Land" wrote in message
...
On May 21, 10:17 am, "Dan Dubosky" wrote:
James, I'm sorry that my description of the problem has been inadequate.
Yes, the video does fade in and out, but so does the sound. The set seems
to be turning itself OFF and ON periodically. So, the problem may be even
further back than the heater circuit. I am beginning to suspect something
in the remote control circuit.

Mr. Mentor, the transistor which has a discoloration in the board beneath
does not have a heat sink, and I have already removed it and resoldered
it.


Does it really "fade" out? Or do you really just abruptly lose video?

Given the problem cycles, it really does sound thermal.
Given that you lose the audio, too, it sounds like power supply.
Does this happen with the cover(s) off? If so, got any freeze spray?
If so, run it w/covers off, then when problem occurs, gently spray a
few drops of freeze liquid onto suspect components, see if you can
make it stop that way.

....or have you already tried this approach?

Dan Dubosky wrote:
Thanks to all! You have been a great deal of help. I was away for the day
so I couldn't get back to the set until this evening. It did appear to be a
problem which was thermal in nature since it played without difficulty for
the longest period of time when it was first turned on. I acquired a can of
freeze spay tonight from my local Radio Shack and started to try and locate
the problem component. Spraying the transistor with the discolored board
beneath didn't do a thing, but spraying the HOT cures the problem at least
until it heats up again. As soon as I get a replacement, I'll post the
results.

Thanks again.
Dan


Try resoldering the existing HOT first, they don't usually fail that way.

Greetings Dan..

Regarding:
"| Try resoldering the existing HOT first, they don't usually fail
that way."

Funny, I seem to have heard about such recommendations before..

Dan, I've also heard of a similar situation on a larger 19" set that
had a resettable fuse issue on the AC input. Ends up it was not
working correctly and was intermittent with heat. The symptoms were
the set would work for the longest time and just shut off by itself.
Usually worked when cold until which time it warmed up. But even that
wasn't a sure thing since this anomaly was truly intermittent. Many an
individual thought it was the power supply or the HOT shutting down -
ends up both were fine. This is merely an FYI..

Cheers,
Mr. Mentor



"James Sweet" wrote in message
news:YnnZj.26679$_g.989@trnddc07...
|
| Dan Dubosky wrote:
| Thanks to all! You have been a great deal of help. I was away
for the day
| so I couldn't get back to the set until this evening. It did
appear to be a
| problem which was thermal in nature since it played without
difficulty for
| the longest period of time when it was first turned on. I
acquired a can of
| freeze spay tonight from my local Radio Shack and started to try
and locate
| the problem component. Spraying the transistor with the
discolored board
| beneath didn't do a thing, but spraying the HOT cures the problem
at least
| until it heats up again. As soon as I get a replacement, I'll
post the
| results.
|
| Thanks again.
| Dan
|
|
| Try resoldering the existing HOT first, they don't usually fail that
way.

James, I know what you mean about not usually failing that way. As I
recall, every previous HOT that I have changed failed completely with a
short between emitter and collector. In this case, resoldering does not
change anything. Maybe this will be in the category of first time for
everything.

Thanks again.
Dan

"James Sweet" wrote in message
news:YnnZj.26679$_g.989@trnddc07...

Dan Dubosky wrote:
Thanks to all! You have been a great deal of help. I was away for the
day so I couldn't get back to the set until this evening. It did appear
to be a problem which was thermal in nature since it played without
difficulty for the longest period of time when it was first turned on. I
acquired a can of freeze spay tonight from my local Radio Shack and
started to try and locate the problem component. Spraying the transistor
with the discolored board beneath didn't do a thing, but spraying the HOT
cures the problem at least until it heats up again. As soon as I get a
replacement, I'll post the results.

Thanks again.
Dan


Try resoldering the existing HOT first, they don't usually fail that way.

Mr. Mentor,
In this set, there is simply an old type fuse, but thanks for the input.
I've ordered the HOT and am going to change it. I'll let all of you know
whether that solved the problem or not.

Dan

"dBc" wrote in message
...
Greetings Dan..

Regarding:
"| Try resoldering the existing HOT first, they don't usually fail
that way."

Funny, I seem to have heard about such recommendations before..

Dan, I've also heard of a similar situation on a larger 19" set that
had a resettable fuse issue on the AC input. Ends up it was not
working correctly and was intermittent with heat. The symptoms were
the set would work for the longest time and just shut off by itself.
Usually worked when cold until which time it warmed up. But even that
wasn't a sure thing since this anomaly was truly intermittent. Many an
individual thought it was the power supply or the HOT shutting down -
ends up both were fine. This is merely an FYI..

Cheers,
Mr. Mentor



"James Sweet" wrote in message
news:YnnZj.26679$_g.989@trnddc07...
|
| Dan Dubosky wrote:
| Thanks to all! You have been a great deal of help. I was away
for the day
| so I couldn't get back to the set until this evening. It did
appear to be a
| problem which was thermal in nature since it played without
difficulty for
| the longest period of time when it was first turned on. I
acquired a can of
| freeze spay tonight from my local Radio Shack and started to try
and locate
| the problem component. Spraying the transistor with the
discolored board
| beneath didn't do a thing, but spraying the HOT cures the problem
at least
| until it heats up again. As soon as I get a replacement, I'll
post the
| results.
|
| Thanks again.
| Dan
|
|
| Try resoldering the existing HOT first, they don't usually fail that
way.

Dan Dubosky wrote:
James, I know what you mean about not usually failing that way. As I
recall, every previous HOT that I have changed failed completely with a
short between emitter and collector. In this case, resoldering does not
change anything. Maybe this will be in the category of first time for
everything.

Thanks again.
Dan



Well anything can happen, I just haven't seen this with a HOT, not
saying it's not possible. I'm curious to hear the results of changing it
out, hopefully that fixes it.

Well, you were correct James, although for a while I thought that the new
HOT had corrected the problem. After I installed the new HOT, the set
continued to operate for about 1/2 hour. Since it had previously started
its cycling of off and on after about 5 minutes, I initially thought that it
was fixed. I left the set ON just to be sure and left the room. I came
back in about an hour to find the set completely off. The fuse had blown,
and the new HOT now has the classic fault of a short between the emitter and
collector.

Dan

"James Sweet" wrote in message
news:9ACZj.7$tF1.3@trnddc01...

Dan Dubosky wrote:
James, I know what you mean about not usually failing that way. As I
recall, every previous HOT that I have changed failed completely with a
short between emitter and collector. In this case, resoldering does not
change anything. Maybe this will be in the category of first time for
everything.

Thanks again.
Dan



Well anything can happen, I just haven't seen this with a HOT, not saying
it's not possible. I'm curious to hear the results of changing it out,
hopefully that fixes it.

"Dan Dubosky" wrote in message
...
Well, you were correct James, although for a while I
thought that the new HOT had corrected the problem. After
I installed the new HOT, the set continued to operate for
about 1/2 hour. Since it had previously started its
cycling of off and on after about 5 minutes, I initially
thought that it was fixed. I left the set ON just to be
sure and left the room. I came back in about an hour to
find the set completely off. The fuse had blown, and the
new HOT now has the classic fault of a short between the
emitter and collector.

Dan
This sounds like the classic problem of lack of drive to the
HOT due to bad solder connections on the driver transformer
or its related circuitry, or a bad capacitor that bypasses
the H. drive dropping resistor.. If the drive falls too low,
the HOT goes into linear mode and the dissipation goes
through the roof blowing the transistor.

David

Dan Dubosky wrote:
Well, you were correct James, although for a while I thought that the new
HOT had corrected the problem. After I installed the new HOT, the set
continued to operate for about 1/2 hour. Since it had previously started
its cycling of off and on after about 5 minutes, I initially thought that it
was fixed. I left the set ON just to be sure and left the room. I came
back in about an hour to find the set completely off. The fuse had blown,
and the new HOT now has the classic fault of a short between the emitter and
collector.

Dan



Still might have been the HOT, you may now have just exposed a further
fault. Bad capacitors can cause a HOT to blow, so can bad solder joints
in the horizontal section.

James Sweet wrote:

Dan Dubosky wrote:

Well, you were correct James, although for a while I thought that the
new HOT had corrected the problem. After I installed the new HOT, the
set continued to operate for about 1/2 hour. Since it had previously
started its cycling of off and on after about 5 minutes, I initially
thought that it was fixed. I left the set ON just to be sure and left
the room. I came back in about an hour to find the set completely
off. The fuse had blown, and the new HOT now has the classic fault of
a short between the emitter and collector.

Dan



Still might have been the HOT, you may now have just exposed a further
fault. Bad capacitors can cause a HOT to blow, so can bad solder joints
in the horizontal section.
and so can a bad integrated flyback!.. which is most of the time!

--
http://webpages.charter.net/jamie_5"

Since the old HOT still checked OK with an ohmmeter, that is with no emitter
to collector short, I reinstalled it and the set played for about 1/2 hour
before it again started its OFF and ON again recycling. With David's
comment in mind, I have now removed the circuit board from its normal area
and propped it up at a 90 degree angle so that I could attach an
oscilloscope probe to the base electrode of the HOT. It appears to be the
electrode which is driven whereas the emitter is at zero potential. I was
hoping to see it going into linear mode. It has now being playing perfectly
for about an hour. Since the circuit board has different mechanical
stressed on it when positioned at 90 degrees, you may be correct James that
this is a bad solder joint, but I must say I haven't found it as yet. I
would think that if it is the flyback, Jamie, it wouldn't care that it was
in a different position. But who knows?

Dan

"David" wrote in message
...

"Dan Dubosky" wrote in message
...
Well, you were correct James, although for a while I thought that the new
HOT had corrected the problem. After I installed the new HOT, the set
continued to operate for about 1/2 hour. Since it had previously started
its cycling of off and on after about 5 minutes, I initially thought that
it was fixed. I left the set ON just to be sure and left the room. I
came back in about an hour to find the set completely off. The fuse had
blown, and the new HOT now has the classic fault of a short between the
emitter and collector.

Dan
This sounds like the classic problem of lack of drive to the HOT due to
bad solder connections on the driver transformer or its related circuitry,
or a bad capacitor that bypasses the H. drive dropping resistor.. If the
drive falls too low, the HOT goes into linear mode and the dissipation
goes through the roof blowing the transistor.

David

Dan Dubosky wrote:

Since the old HOT still checked OK with an ohmmeter, that is with no emitter
to collector short, I reinstalled it and the set played for about 1/2 hour
before it again started its OFF and ON again recycling. With David's
comment in mind, I have now removed the circuit board from its normal area
and propped it up at a 90 degree angle so that I could attach an
oscilloscope probe to the base electrode of the HOT. It appears to be the
electrode which is driven whereas the emitter is at zero potential. I was
hoping to see it going into linear mode. It has now being playing perfectly
for about an hour. Since the circuit board has different mechanical
stressed on it when positioned at 90 degrees, you may be correct James that
this is a bad solder joint, but I must say I haven't found it as yet. I
would think that if it is the flyback, Jamie, it wouldn't care that it was
in a different position. But who knows?

Dan

Resolder the joints on the flyback.
the weight of it sitting sideways is most likely baring down on a bad
joint and keeping it going.
It could be a top side joint that you can't see.

http://webpages.charter.net/jamie_5"

Resolder the joints on the flyback.
the weight of it sitting sideways is most likely baring down on a bad
joint and keeping it going.
It could be a top side joint that you can't see.


I have resoldered the bottom joints on the flyback at least twice. When the
board was in the 90 degree position, I flexed the board in all directions to
no avail. With the board in its normal position, I then pushed on the
flyback in all directions so as to flex the board beneath it. The problem
fails to appear.

Thanks for the input, Jamie.
Dan

Dan Dubosky wrote:
Resolder the joints on the flyback.
the weight of it sitting sideways is most likely baring down on a bad
joint and keeping it going.
It could be a top side joint that you can't see.


I have resoldered the bottom joints on the flyback at least twice. When the
board was in the 90 degree position, I flexed the board in all directions to
no avail. With the board in its normal position, I then pushed on the
flyback in all directions so as to flex the board beneath it. The problem
fails to appear.

Thanks for the input, Jamie.
Dan




It only takes one joint to cause the problem, they can be really tough
to track down.

Dan Dubosky ha escrito:
I have a GE 9" under the counter TV (Model 09GP108) which has video that
fades out after the set is on for while, then comes back, and repeats the
pro

if it recurrs, could you post a video of this fault on youtube? that
would help.

meanwhile, that HOT you bought could have been a fake. there are vast
numbers around ,which fail quickly exactly like yours did.

b

After a short warm-up, the set still continues to perform as described. It
is now often enough so that I was able to look at the waveform of the signal
which drives the HOT. During the cycle to the OFF period, the waveform
callapses and the HOT during this period of time is not being cut OFF. The
waveform at the input of the driving transformer also collapses, but this
may not be surprising since one of the B+ volltages is derived from the
horizontal output transformer. In fact, any waveform with horizontal
periodicity at many of the test points collapses. There is a rather high B+
voltage of over 160 volts which doesn't seem to be effected at all. As I
said earlier, I do not have the schematic diagram so I don't know what
circuit is supplied with what B+ source.

Perhaps as someone suggested it may be the horizontal output transformer,
but if that is the problem, I cannot understand why spraying the HOT with a
component coolent would seem to get rid of the problem at least temporarily.

I've gone over the circuit board with a jeweler's loupe in order to see if
there are any suspicious solder joints. Yes, I know that is not 100%
effective. Anything that looked even the sightest bit suspicious, I
resoldered it.

As Sam Goldwasser states a problem with blowing HOTs may require
substitution of components in order to solve it. I'm not sure how much more
I am willing to invest in view of the age ot the set.

Thanks to all.
Dan

Dan Dubosky wrote:
After a short warm-up, the set still continues to perform as described. It
is now often enough so that I was able to look at the waveform of the signal
which drives the HOT. During the cycle to the OFF period, the waveform
callapses and the HOT during this period of time is not being cut OFF. The
waveform at the input of the driving transformer also collapses, but this
may not be surprising since one of the B+ volltages is derived from the
horizontal output transformer. In fact, any waveform with horizontal
periodicity at many of the test points collapses. There is a rather high B+
voltage of over 160 volts which doesn't seem to be effected at all. As I
said earlier, I do not have the schematic diagram so I don't know what
circuit is supplied with what B+ source.

Perhaps as someone suggested it may be the horizontal output transformer,
but if that is the problem, I cannot understand why spraying the HOT with a
component coolent would seem to get rid of the problem at least temporarily.

I've gone over the circuit board with a jeweler's loupe in order to see if
there are any suspicious solder joints. Yes, I know that is not 100%
effective. Anything that looked even the sightest bit suspicious, I
resoldered it.

As Sam Goldwasser states a problem with blowing HOTs may require
substitution of components in order to solve it. I'm not sure how much more
I am willing to invest in view of the age ot the set.

Thanks to all.
Dan




Well you've come this far, gotta figure out what's going on now, if only
for the curiosity.

Have you tried poking around with an insulated stick while the set is on
in order to track down a bad connection? Could be a cracked trace as
well, those can be hard to find. Is there an IC that supplies drive to
the HOT? Perhaps the voltage to that is dropping?

"James Sweet" wrote in message
news:d31%j.1379$GT5.271@trndny01...


Well you've come this far, gotta figure out what's going on now, if only
for the curiosity.

Have you tried poking around with an insulated stick while the set is on
in order to track down a bad connection? Could be a cracked trace as well,
those can be hard to find. Is there an IC that supplies drive to the HOT?
Perhaps the voltage to that is dropping?

Yes, James, I have poked and poked with an insulated stick of the type that
I used to use for adjusting IF transformers. I have never been able to find
anything that resulted in producing the problem. You are right that I am
still intensely curious as to what the defect is, and I will probably
continue to putter with the set in-between other projects.

Today, I found someone in a previous post who recommended a replacement for
TP15. If you recall, this was listed by NTE as obsolete and no longer
available. It is the transistor which has discolored the board due to heat.
I bought an NTE 287 which was recommended as the replacement and installed
it, but that has not resulted in any change. Tomorrow I will probably buy
the Sam's Photofact Folder on this set just so I don't keep wandering around
the board in the dark. I am fully aware of the fact that this may not help
all that much if the defect is somewhere in the feedback loop involving the
HOT, the output transformer, and the B+ supplied to previous stages. It
sure would be nice to know what in the world I'm looking at on the board.
Who knows ??? It might even help.

Dan

Success, at last!!! This is just to put an end to this thread of messages.

I finally bought the schematic diagram for this set and began to search for
the problem. After the set was ON for a short while, the negative voltage
spike at the base of the HOT would disappear. Sometimes it wasn't there
even from the beginning. Accordingly, the HOT was not being shut OFF as
rapidly as it should be, and the temperature of the HOT would rise to the
point where it would shut down, and in some mysterious fashion cause the
system control chip to turn the set OFF. The feedback loops in this set
are numerous. At first I thought that the 100Mfd capacitor which
differentiates the square wave to develop the spike was deffective, but
replacing it did not solve the problem. I then resoldered the joints in
this area particularly around RP21 and LP02, and this cured the disappearing
spike and the turning OFF and ON.

So, James, you were right. It was a bad solder joint all along.

Thanks to all for your help.
Dan