Recently my CRT stopped displaying and I'm not sure when or why.
During powerup, I can see misaligned scanlines for a few seconds while it brightens before dimming down to just a blank black screen, OSD doesn't show but I can hear the typical high pitched sounds of the TV as usual. I can hear it respond to channel and input changes but nothing shows up on the screen at all.
What could've possible caused this!?
Sony Trinitron KV-27FS120 Stopped Displaying
Re: Sony Trinitron KV-27FS120 Stopped Displaying
I brought this TV in to be repaired today, they handed it back to me saying the video IC was defective and they had no replacements.
As far as I can tell, that means an IC on the CW board, which could be either:
IC2751 8-759-562-43 IC TDA6108JF/N1B
IC3701 8-759-803-42 IC LA6500-FA
How could I verify this myself? What options are there for a replacement? Are there other boards that could replace this one even if there's no suitable IC substitute?
As far as I can tell, that means an IC on the CW board, which could be either:
IC2751 8-759-562-43 IC TDA6108JF/N1B
IC3701 8-759-803-42 IC LA6500-FA
How could I verify this myself? What options are there for a replacement? Are there other boards that could replace this one even if there's no suitable IC substitute?
-
Goopa-Troopa
- Posts: 4
- Joined: Sun Oct 22, 2023 5:07 pm
Re: Sony Trinitron KV-27FS120 Stopped Displaying
A quick google search shows that the second IC is an op-amp which is just a signal amplifier. If they're saying the video IC was defective, it's likely the first IC that you listed that's defective. Seems like replacements are sold here, not too expensive either: https://www.shopjimmy.com/philips-tda6108jf-n1b-ic/Cormy1 wrote: ↑Tue Oct 17, 2023 10:07 pm I brought this TV in to be repaired today, they handed it back to me saying the video IC was defective and they had no replacements.
As far as I can tell, that means an IC on the CW board, which could be either:
IC2751 8-759-562-43 IC TDA6108JF/N1B
IC3701 8-759-803-42 IC LA6500-FA
How could I verify this myself? What options are there for a replacement? Are there other boards that could replace this one even if there's no suitable IC substitute?
-
Goopa-Troopa
- Posts: 4
- Joined: Sun Oct 22, 2023 5:07 pm
Re: Sony Trinitron KV-27FS120 Stopped Displaying
Although, neither of the IC's you listed would usually be considered "THE" video IC. That would be the jungle IC, which if I read the service manual correctly is the M65582AMF chip. Any way you can ask the repair shop for clarification?
Re: Sony Trinitron KV-27FS120 Stopped Displaying
How much wear did that set have?
I've yet to see a set of that generation fail like that. Hope you manage to get it up and running again.
I've yet to see a set of that generation fail like that. Hope you manage to get it up and running again.
Re: Sony Trinitron KV-27FS120 Stopped Displaying
I can ask of course. I had asked them when I picked it up initially but they weren't very clear to me and I was feeling a bit rushed at the time. I will try to get a more specific answer.Goopa-Troopa wrote: ↑Mon Oct 23, 2023 6:31 pm Although, neither of the IC's you listed would usually be considered "THE" video IC. That would be the jungle IC, which if I read the service manual correctly is the M65582AMF chip. Any way you can ask the repair shop for clarification?
Define "much wear"
I mean it's very easily over 30 years old, and it's certainly seen regular use. I unfortunately did not witness the day when it failed. It worked the last time I used it, and then it didn't.
I'm also unsure if I trust the repair guys I brought it to, but they seemed pretty confident. I actually brought them 2 CRTs, and this one was returned to me the day I brought it in, while the other took a week to fix so I assume it was an easy diagnosis for them, while the second was a bit trickier.
I copy-pasted a chunk of troubleshooting tips for problems that sounded similar from repairfaq.org but it's difficult to say whether it's the exact issue I have.
Spoiler
No picture or raster and no sound
The screen is blank with no raster at all. There are indications that the channel numbers are changing in the display. This indicates that some of the low voltages are present but these may be derived from the standby supply.
Assuming there is no deflection and no HV, you either have a low voltage power supply problem, bad startup circuit, or bad horizontal output transistor (HOT) or other bad parts in the horizontal deflection.
Check for bad fuses.
(If you have HV as indicated by static electricity on the front of the screen and you hear the high pitched whine of the horizontal deflection when it is turned on, then the following does not apply).
1. Use an ohmmeter to test the HOT for shorts. If it is bad, look for open fusable resistors or other fuses you did not catch.
2. Assuming it is good, measure the voltage on the collector-emitter of the HOT (this is safe if there is no deflection). You should see the B+ - probably between 100 and 150 V.
3. If there is no voltage, you have a low voltage power supply problem and/or you have not found all the bad/open parts.
4. If there is voltage and no deflection (no high pitched whine and no HV), you probably have a startup problem - all TVs need some kind of circuit to kick start the horizontal deflection until the auxiliary power outputs of the flyback are available. Some Zeniths use a simple multivibrator for this - a couple of transistors. Others power the horizontal osc. IC from a special line-derived voltage. The multivibrator type are sometimes designed to fail if someone keeps turning the set on and off (like kids playing) since the power rating is inadequate.
Test the transistors if it is that type with an ohmmeter. If one is shorted, you have a problem. The usual way a TV service person would test for startup problems is to inject a signal to the base of the HOT of about 15.75 kHz. If the TV then starts and runs once this signal is removed, the diagnosis is confirmed. This is risky - you can blow things up if not careful (including yourself). See the section: Bypassing the Startup Circuit for details.
If you hear the high pitched whine of the deflection and/or feel some static on the scree, confirm that the horizontal deflection and high voltage are working by adjusting the SCREEN control (probably on the flyback). If you can get a raster then your problem is probably in the video or chroma circuits, not the deflection or high voltage.
Reduced width picture and/or hum bars in picture and/or hum in sound
The most likely cause is a dried up main filter capacitor. Once the effective capacitance drops low enough, 120 Hz (or 100 Hz in countries with 50 Hz power) ripple will make its way into the regulated DC supply (assuming full wave rectification).
Another likely cause of similar symptoms is a defective low voltage regulator allowing excessive ripple. The regulator IC could be bad or filter capacitor following the IC could be dried up.
Either of these faults may cause:
1. A pair of wiggles and/or hum bars in the picture which will float up the screen. For NTSC where the power line is 60 Hz but the frame rate is 59.94 Hz, it will take about 8 seconds for each bar to pass a given point on the screen. (On some sets, a half wave recitifier is used resulting in a single wiggle or hum bar).
2. Hum in the sound. This may or may not be noticeable with the volume turned down.
3. Possible regulation problems resulting in HV or total shutdown or power cycling on and off.
The best approach to testing the capacitors is to clip a good capacitor of approximately the same uF rating and at least the same voltage rating across the suspect capacitor (with the power off). A capacitor meter can also be used but the capacitor may need to be removed from the circuit.
Once the capacitors have been confirmed to be good, voltage measurements on the regulator should be able to narrow down the problem to a bad IC or other component.
No picture/dark picture/erratic picture
If everything else works - there is sound and high voltage (static on the screen) - but there is no picture (including no on-screen menus), this limits the likely area of problems is the video output circuitry or CRT filament connections. Check to see if the CRT filaments are glowing. If they are not glowing, check for bad soldering on the CRT neck board and around the flyback transformer.
Where the picture is erratic - coming and going entirely or changing brightness suddenly, with power off, remove the picture tube socket (carefully!) and clean the pins with fine sandpaper and use contact cleaner on the socket. This source of bad connections can result in a variety of erratic symptoms. Check for bad solder connections on the CRT neck board.
Blank picture, good channel tuning and sound
Since the tuner and sound are ok, horizontal deflection which usually generates power for most of the set is also working.
Does 'blank picture' means a totally black screen with the brightness and contrast controls having no effect whatsoever? Or, is there is no picture but there is a raster - scan lines on the screen? The direction in which troubleshooting should proceed differ significantly depending the answer.
Here are some questions:
1. As above, is there any light on the screen at any settings of the brightness and contrast controls, and/or when switching channels? Can you see any raster scanning lines?
2. Can you hear the high pitched (15735 Hz) of the horizontal deflection?
3. Looking in the back of the set, can you see the glow of the CRT filament?
4. Do you get that static on the front of the tube that would indicate that there is high voltage? Any cracking or other normal or abnormal sounds or smells?
Possible causes of no raster:
• No or low high voltage (low voltage, deflection, or high voltage power supply failure).
• Fault with other voltages like G1 or screen (G2) to CRT.
• Filament to CRT not getting powered.
• Drive to CRT bad/shut off as a result of fault elsewhere. For example, failure of the vertical deflection may disable HV or blank the screem to protect the CRT from burn-in due to the very bright horizontal line that would result. With some sets, it is possible that the X-ray protection circuitry will blank the screen without affecting tuning or audio.
Possible causes of no video (but a good raster): Problem in video IF, video amplifiers, video output, cutoff due to other fault.
It could be as simple as a bad connection - try gently prodding the boards with an insulated stick while watching the screen. Check for loose connectors and reseat all internal connectors.
TV doesn't work after being in storage
So the TV you carefully stuffed in a corner of the garages is now totally dead. You swear it was working perfectly a year ago.
Assuming there was absolutely no action when you turned it on, this has all the classic symptoms of a bad connection. These could be cold/cracked solder joints at large components like transformers, power resistors, or connectors and connectors that need to be cleaned or reseated. By 'no action' I mean not even a tweet, bleep, or crackle from anything.
To narrow it down further, if careful prodding of the circuit board(s) and various large components with a well insulated stick does not induce the set to come on, even momentarily, check the following:
1. Locate the horizontal output transistor. It will be in a TO3 metal (most likely on an older set) or TOP3 plastic package on a heat sink. With the set unplugged, confirm that there is no voltage across C to E and then measure between them with an ohmmeter. In at least one direction it should be fairly high - 1K or more. This confirms that the HOT is probably good.
(There is also a slight chance that there is a low voltage regulator in addition to the horizontal output, so don't get them confused. The horizontal output transistor will be near the flyback transformer and yoke connector.)
2. Trace back from the HOT collector to the flyback and through the flyback to the B+ feed from the power supply. Clip a voltmeter between this point and the HOT emitter. Make sure the leads are well insulated and can't accidentally short to anything. (This test can be performed across C to E of the HOT but if the horizontal deflection were to start up unexpectadly, the meter could be damaged by the high voltage pulses on the HOT collector. But if you can't find the B+ source, it may be worth the risk.) Plug it in and turn it on.
◦ If the problem is in the low voltage (line) power supply, there will be no substantial voltage across C to E.
You should be able to trace from the power line forward to find the bad part though a schematic will help greatly.
◦ If the problem is in the startup circuit or horizontal oscillator/driver, then there will be something on the order of 100 to 160 V across C to E.
In this case, a schematic may be essential.
There is also a slight chance that there is a low voltage regulator in addition to the horizontal output, so don't get them confused. The horizontal output transistor will be near the flyback transformer and yoke connector.
Older TVs with multiple intermittent problems
If the set is say, a GE, with a manufacturing date around 1980, it is possible you have one of those circuit boards best described as bad solder joints held together with a little copper. In this case, prodding may get the set started. The circuit boards in these sets were double sided using what were called 'rivlets' for vias. The rivlets were relatively massive - literally little copper rivets - and they were not adequately heated during assembly so there were bucketloads of cold solder joints that showed up during middle age. I repaired one of these by literally resoldering top and bottom of every one of the darn things with a high wattage iron.
No video on late model Sony TVs
(From: David Kuhajda (dkuhajda@locl.net).)
This following assumes that the more basic TV troubleshooting has already been performed and resulted in no solution - i.e., filaments are lit up, CRT voltages are all correct but the cathodes are all in cutoff, main power supply voltages are present, etc
The 3 most common causes of no video, but good audio are as follows:
1. AKB blanking due to either a fault in the AKB circuit or the CRT has one gun that is too weak and the AKB won't unblank the CRT.
2. Loss of vertical deflection. The system control must see the vertical return pulse to unblank the video.
3. Loss of data bus communication with the Jungle IC. The Jungle IC must send the all OK signal to the micro before it will unblank the video.
To troubleshoot:
1. Try changing the volume with the volume control. If it changes the data bus is not the problem. This is assuming the TV is tuned to a good TV station.
2. Mark the EXACT position of the screen/G2 control with a marker. Then turn the G2 control up.
◦ If the picture unblanks and a gray scale bar pattern is used, you can usually see which CRT gun is weak. Time to replace the CRT for a long term fix. All of the temporary fixes I have tried resulted in only a few months extra life out of the tube.
◦ If the picture does not unblank and it looks kind of like there is a halo near the top of the screen. The vertical circuit needs checked for proper operation and repaired. WARNING do not continue to operate the TV set in this mode for any length of time, it will crack the CRT from localized heating!!!! (because the guns are shooting into the extreme top of the tube and possible the neck of the tube) RETURN the G2 control to the exact position that was marked before you started.
The typical failure mode of the vertical circuit in a Sony causes only one of the vertical supply resistors to open usually. Either the +15 V or -15 V. This puts a full + or -15 V on the yoke which deflects the guns into the glass envelope of the tube.
The screen is blank with no raster at all. There are indications that the channel numbers are changing in the display. This indicates that some of the low voltages are present but these may be derived from the standby supply.
Assuming there is no deflection and no HV, you either have a low voltage power supply problem, bad startup circuit, or bad horizontal output transistor (HOT) or other bad parts in the horizontal deflection.
Check for bad fuses.
(If you have HV as indicated by static electricity on the front of the screen and you hear the high pitched whine of the horizontal deflection when it is turned on, then the following does not apply).
1. Use an ohmmeter to test the HOT for shorts. If it is bad, look for open fusable resistors or other fuses you did not catch.
2. Assuming it is good, measure the voltage on the collector-emitter of the HOT (this is safe if there is no deflection). You should see the B+ - probably between 100 and 150 V.
3. If there is no voltage, you have a low voltage power supply problem and/or you have not found all the bad/open parts.
4. If there is voltage and no deflection (no high pitched whine and no HV), you probably have a startup problem - all TVs need some kind of circuit to kick start the horizontal deflection until the auxiliary power outputs of the flyback are available. Some Zeniths use a simple multivibrator for this - a couple of transistors. Others power the horizontal osc. IC from a special line-derived voltage. The multivibrator type are sometimes designed to fail if someone keeps turning the set on and off (like kids playing) since the power rating is inadequate.
Test the transistors if it is that type with an ohmmeter. If one is shorted, you have a problem. The usual way a TV service person would test for startup problems is to inject a signal to the base of the HOT of about 15.75 kHz. If the TV then starts and runs once this signal is removed, the diagnosis is confirmed. This is risky - you can blow things up if not careful (including yourself). See the section: Bypassing the Startup Circuit for details.
If you hear the high pitched whine of the deflection and/or feel some static on the scree, confirm that the horizontal deflection and high voltage are working by adjusting the SCREEN control (probably on the flyback). If you can get a raster then your problem is probably in the video or chroma circuits, not the deflection or high voltage.
Reduced width picture and/or hum bars in picture and/or hum in sound
The most likely cause is a dried up main filter capacitor. Once the effective capacitance drops low enough, 120 Hz (or 100 Hz in countries with 50 Hz power) ripple will make its way into the regulated DC supply (assuming full wave rectification).
Another likely cause of similar symptoms is a defective low voltage regulator allowing excessive ripple. The regulator IC could be bad or filter capacitor following the IC could be dried up.
Either of these faults may cause:
1. A pair of wiggles and/or hum bars in the picture which will float up the screen. For NTSC where the power line is 60 Hz but the frame rate is 59.94 Hz, it will take about 8 seconds for each bar to pass a given point on the screen. (On some sets, a half wave recitifier is used resulting in a single wiggle or hum bar).
2. Hum in the sound. This may or may not be noticeable with the volume turned down.
3. Possible regulation problems resulting in HV or total shutdown or power cycling on and off.
The best approach to testing the capacitors is to clip a good capacitor of approximately the same uF rating and at least the same voltage rating across the suspect capacitor (with the power off). A capacitor meter can also be used but the capacitor may need to be removed from the circuit.
Once the capacitors have been confirmed to be good, voltage measurements on the regulator should be able to narrow down the problem to a bad IC or other component.
No picture/dark picture/erratic picture
If everything else works - there is sound and high voltage (static on the screen) - but there is no picture (including no on-screen menus), this limits the likely area of problems is the video output circuitry or CRT filament connections. Check to see if the CRT filaments are glowing. If they are not glowing, check for bad soldering on the CRT neck board and around the flyback transformer.
Where the picture is erratic - coming and going entirely or changing brightness suddenly, with power off, remove the picture tube socket (carefully!) and clean the pins with fine sandpaper and use contact cleaner on the socket. This source of bad connections can result in a variety of erratic symptoms. Check for bad solder connections on the CRT neck board.
Blank picture, good channel tuning and sound
Since the tuner and sound are ok, horizontal deflection which usually generates power for most of the set is also working.
Does 'blank picture' means a totally black screen with the brightness and contrast controls having no effect whatsoever? Or, is there is no picture but there is a raster - scan lines on the screen? The direction in which troubleshooting should proceed differ significantly depending the answer.
Here are some questions:
1. As above, is there any light on the screen at any settings of the brightness and contrast controls, and/or when switching channels? Can you see any raster scanning lines?
2. Can you hear the high pitched (15735 Hz) of the horizontal deflection?
3. Looking in the back of the set, can you see the glow of the CRT filament?
4. Do you get that static on the front of the tube that would indicate that there is high voltage? Any cracking or other normal or abnormal sounds or smells?
Possible causes of no raster:
• No or low high voltage (low voltage, deflection, or high voltage power supply failure).
• Fault with other voltages like G1 or screen (G2) to CRT.
• Filament to CRT not getting powered.
• Drive to CRT bad/shut off as a result of fault elsewhere. For example, failure of the vertical deflection may disable HV or blank the screem to protect the CRT from burn-in due to the very bright horizontal line that would result. With some sets, it is possible that the X-ray protection circuitry will blank the screen without affecting tuning or audio.
Possible causes of no video (but a good raster): Problem in video IF, video amplifiers, video output, cutoff due to other fault.
It could be as simple as a bad connection - try gently prodding the boards with an insulated stick while watching the screen. Check for loose connectors and reseat all internal connectors.
TV doesn't work after being in storage
So the TV you carefully stuffed in a corner of the garages is now totally dead. You swear it was working perfectly a year ago.
Assuming there was absolutely no action when you turned it on, this has all the classic symptoms of a bad connection. These could be cold/cracked solder joints at large components like transformers, power resistors, or connectors and connectors that need to be cleaned or reseated. By 'no action' I mean not even a tweet, bleep, or crackle from anything.
To narrow it down further, if careful prodding of the circuit board(s) and various large components with a well insulated stick does not induce the set to come on, even momentarily, check the following:
1. Locate the horizontal output transistor. It will be in a TO3 metal (most likely on an older set) or TOP3 plastic package on a heat sink. With the set unplugged, confirm that there is no voltage across C to E and then measure between them with an ohmmeter. In at least one direction it should be fairly high - 1K or more. This confirms that the HOT is probably good.
(There is also a slight chance that there is a low voltage regulator in addition to the horizontal output, so don't get them confused. The horizontal output transistor will be near the flyback transformer and yoke connector.)
2. Trace back from the HOT collector to the flyback and through the flyback to the B+ feed from the power supply. Clip a voltmeter between this point and the HOT emitter. Make sure the leads are well insulated and can't accidentally short to anything. (This test can be performed across C to E of the HOT but if the horizontal deflection were to start up unexpectadly, the meter could be damaged by the high voltage pulses on the HOT collector. But if you can't find the B+ source, it may be worth the risk.) Plug it in and turn it on.
◦ If the problem is in the low voltage (line) power supply, there will be no substantial voltage across C to E.
You should be able to trace from the power line forward to find the bad part though a schematic will help greatly.
◦ If the problem is in the startup circuit or horizontal oscillator/driver, then there will be something on the order of 100 to 160 V across C to E.
In this case, a schematic may be essential.
There is also a slight chance that there is a low voltage regulator in addition to the horizontal output, so don't get them confused. The horizontal output transistor will be near the flyback transformer and yoke connector.
Older TVs with multiple intermittent problems
If the set is say, a GE, with a manufacturing date around 1980, it is possible you have one of those circuit boards best described as bad solder joints held together with a little copper. In this case, prodding may get the set started. The circuit boards in these sets were double sided using what were called 'rivlets' for vias. The rivlets were relatively massive - literally little copper rivets - and they were not adequately heated during assembly so there were bucketloads of cold solder joints that showed up during middle age. I repaired one of these by literally resoldering top and bottom of every one of the darn things with a high wattage iron.
No video on late model Sony TVs
(From: David Kuhajda (dkuhajda@locl.net).)
This following assumes that the more basic TV troubleshooting has already been performed and resulted in no solution - i.e., filaments are lit up, CRT voltages are all correct but the cathodes are all in cutoff, main power supply voltages are present, etc
The 3 most common causes of no video, but good audio are as follows:
1. AKB blanking due to either a fault in the AKB circuit or the CRT has one gun that is too weak and the AKB won't unblank the CRT.
2. Loss of vertical deflection. The system control must see the vertical return pulse to unblank the video.
3. Loss of data bus communication with the Jungle IC. The Jungle IC must send the all OK signal to the micro before it will unblank the video.
To troubleshoot:
1. Try changing the volume with the volume control. If it changes the data bus is not the problem. This is assuming the TV is tuned to a good TV station.
2. Mark the EXACT position of the screen/G2 control with a marker. Then turn the G2 control up.
◦ If the picture unblanks and a gray scale bar pattern is used, you can usually see which CRT gun is weak. Time to replace the CRT for a long term fix. All of the temporary fixes I have tried resulted in only a few months extra life out of the tube.
◦ If the picture does not unblank and it looks kind of like there is a halo near the top of the screen. The vertical circuit needs checked for proper operation and repaired. WARNING do not continue to operate the TV set in this mode for any length of time, it will crack the CRT from localized heating!!!! (because the guns are shooting into the extreme top of the tube and possible the neck of the tube) RETURN the G2 control to the exact position that was marked before you started.
The typical failure mode of the vertical circuit in a Sony causes only one of the vertical supply resistors to open usually. Either the +15 V or -15 V. This puts a full + or -15 V on the yoke which deflects the guns into the glass envelope of the tube.
Re: Sony Trinitron KV-27FS120 Stopped Displaying
It can't be over 30 years old, I think you probably meant 20 years. The FS120 model mostly dates from the years between 2002 and 2004.
What I meant by wear was mainly how many hours it had (estimate of course). I understand it can be pretty hard to judge if you took it in second hand, but one indication might be whether as an owner you were giving it 50h a week, 15h a week, or 5h a week, and for how many years were you using it that way. Of course even if it had been out of box and had little use, it's always possible that by now something needs fixing, but generally I've found these very late Trinitron's to be incredibly sturdy.
What I meant by wear was mainly how many hours it had (estimate of course). I understand it can be pretty hard to judge if you took it in second hand, but one indication might be whether as an owner you were giving it 50h a week, 15h a week, or 5h a week, and for how many years were you using it that way. Of course even if it had been out of box and had little use, it's always possible that by now something needs fixing, but generally I've found these very late Trinitron's to be incredibly sturdy.