There is a high pitch noise in the set after
start up and there is no picture or raster on the screen . Upon checking the board the horizantal output transister is o.k. and the flyback transformer is also o.k.
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
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).
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.
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.
If there is no voltage, you have a low voltage power supply problem and/or you have not found all the bad/open parts.
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. Good luck...
There is a install kit 483531057673 for this model when the set is dead. The kit will contain 7404 and the Horizontal Driver Transformer 5402 along with resistors that will limit stress on 7404 and includes complete instructions.
This is usualy because there is either a high voltage regulation fault, or a main power supply regulation fault.
There are many things that can cause this. When the high voltage goes too far down, the raster will enlarge. High voltage regulation can be caused by faulty components in the feedback sensing, or in the high voltage multiplier, or in the flyback windings itself.
A quick way to sort of know if the high voltage is regulating is to wind the brightness and contrast from one extreme to another and observe the raster size. If the raster is changing size with the brightness on the screen, the regulation is not working well. In some of the low cost sets there will be about a 2 to 5% raster size shift in this case. The high end sets will have a near 0% shift in the raster size. A size change of about 2% is acceptable for most sets. If the CRT is weak, this test will not work well, because a weak CRT will not properly load.
If the main power supply is operating slightly over voltage, the raster size will increase. Usualy, the brightness will be a little on the high side when the supply is too high. Voltage regulation faults can be from warn components in the voltage regulator area, or in the feedback control.
This should be looked after by an experienced TV service tech. This type of fault can be involved.
Rarely picture tube also shows the same symptom. High pitch sound is due to through deflection area LOT power supply is loaded. Compulsary horizontal output transister short. From your statement i think Lot puncture takes place. Change LOT and horizontal output transister and check tv is now working.
The high pitched sound, probably not, unless you open this TV set and find out what is making the noise and replace the part. Most likely a coil or transformer is vibrating so fast that the frequency is very high. On the focus, possibly can be adjusted. Now when you take off the back of this TV set, i must warn you, follow my instructions to the letter as there is enough High Voltage in this set to make a grown man cry! After you take out all of the screws off the rear cover,carefully lift up the cover straight up. Oh by the way the TV should be face down. Opps! Not stand back up the TV set and there will be a Grey or black block like looking thing with a large red wire going to the top of the picture tube. on this block you will find two controls, one will say screen, and the other will say focus. DO NOT ADJUST ANYTHING ELSE WHEN YOU ARE IN THIS TV SET!!! No slowly rock the focus control back and forth till you get the sharpest picture. Put back on the back cover and enjoy!!! Good Luck
most high pitch noise comes from the anode conection on the picture tube thats connected to the flyback anode cap thats mean there is a high voltage leak,to stop the noise you can discharge the high voltage take off the cap and clean with alcohol.if the noise continue.you will have to put some red or clear silicone both the cap and tube stick together leave to dry for about 2 to 4 hrs.this will eliminate the leaking.good luck.
That high pitched noise you're hearing is the power supply telling you that it has too much of a load on it and lowered its operating frequency which in effect cuts its output way down! Normally you don't hear any thing since the power supply operates at a frequency that's beyond human hearing.
In an RCA this indicates more than likely that your horizontal output transistor is shorted and this short was caused by the flyback transformer shorting. This is a common happening with RCA's
You'd need to take to a tv shop and have it checked out.
Very common problem with these sets. The High Voltage transformer and the horizontal output transistor is most likly the problem.. If you know the saftey issues involved and know how to solder and unsolder, you can repair this set but theres a possibility you could also have a fault in the horizontal driver circuit, such as l401. if your not a tech its best to have this set fixed by a trained tech, if you wnt to spend between 175 to 225.00 Good Luck