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Zenith sets, like most others now, are adjusted electronically through a service menu. You'll need your original remote control (or a Zenith-brand universal replacement with a MENU key) to access the menu. Press and hold the MENU button until the channel number and time display goes away, then press 9, 8 , 7, 6, ENTER. This puts you into service mode.
In service mode, CHANNEL UP and CHANNEL DOWN move through the different settings, and VOLUME UP and VOLUME DOWN change the values. Make sure you write down the original value of anything before you change it so you can put it back if necessary. One of the reasons the manufacturers hide the service menu is because the set can be damaged by incorrect settings to some of the parameters.
On some models, you can't get to all the parameters unless you change
one called F MODE from 00 to 01. You might need to do this on yours.
The list of parameters varies by model and features. I haven't worked on a Zenith in a long time so I don't remember exactly what yours says, but you want to find two settings for V SIZE (vertical size) and V POS (vertical position). Adjust the size first by lowering the value until the top and bottom of the screen are black. Then adjust the position so the picture is centered (black strips close to equal size). Finally, increase the size until the picture fills the screen again. It's normal to adjust for a little overscan, meaning you push the top and bottom a little bit out of view. If you stop too soon, on some channels you might see flashing lines at the top of the picture.
When you're finished adjusting, turn the TV off to exit service mode. If you needed to change the F MODE setting, put it back to 00 first. Your picture should be properly sized after all this.
You could go into the user menu and look around to see if it has an adjustment. If not you will have to access the service menu for your tv. There may be a setting to adjust vertical size there. If that still isn't possible you may have to open the tv and look for a pot or a switch that can control the vertical adjustment. It may be by the vertical output circuitry. This could also mean that you have a defective component in the vertical circuit or inadequate voltage to that circuit.
You need to adjust "vertical height" in the service program. You need to put the set in "service mode" to do this adjustment. If you google "enter service mode RCA F32665" you should find the procedure. It will be listed in abbreviated letters such as VERT SIZE or VERT HT. Follow the instructions for entering service mode and saving the data closely!! The data you change will be listed as a number between 1 and 63. The number will only need to reduced by a small amount and you can still see the picture behind the data and watch it shrink as you adjust the number down.Always burn the new number to memory (if required) before exiting service mode. Good luck
If the picture is in an hourglass shape this has nothing to do with vertical hold. Besides, on all these sets, the hold and parameters are all uPC controled through a firmware routine that is burned in to an EPROM.
It is obvious that there is a failed component somewhere because of the hour glass shape. The area of failure is most likely in the pin amp section. If the hourglass is from the sides, it would be horizontal pin. If it is top and bottom, the fault is in the vertical pin section.
A common cause is from a capacitor that has failed in the mentioned area. Sometimes it can be an IC or other type of component in the pin amp area, but not as often as failed capacitors.
You can take the set in to service the fault. I don't think you can fix this yourself unless you are trained in TV service and have the experience and setup to troubleshoot for the bad parts, and do this type of service.
If you did not save the damage that you did, or do any damage from over-adjustment, you can make a re-set to before the adjustments were made by simply unplugging the set from the AC mains for about 10 to 20 seconds. If the improper parameters were saved, or damage was done from over adjustment, then this procedure will not work for you.
Read on for more details:
There is no default actual default. Each set is individualy set up for its optimum performance. At the factory, during the manufacturing process they set the EPROM firmware parameters to a so-called reference value before they start the calibration. This is done during production on the burner that programs the EPROM.
If the paramters are too far off to have the set working, you will have to take the set for service at a factory service rep. The factory service shop will most likely have to change the complete circuit board that constains the uPC EPROM with a new one that has the reference factory set-up. They will then have to go through the complete set-up with calibration procedures using the factory recomended calibration standards instrumentation to match for best performance. To manualy do a full calibration on the test bench it can be about 2 hours of work.
Because the factory service setup was not meant for consumer use, it is possible to over adjust parameters to the point where you can lock the set out of operation, or actualy do damage by over-adjustment.
take123, problem is with vertical circuit not eprom, could be bad capacitor supporting the IC or the IC itself is bad, that type of problem needs a tech because once it`s fixed you will probably have to go into the service menu and re-adjust the vertical positioning, this of course will require the info in the service manual which you can`t easily obtain, questions? e-mail me back, BMW Rider
That's still repairable here some tips need to consider as follow:
Intermittent loss of syncronisation, both horizontal and vertical
The surface mounted power transistor on the teletext module requires
resoldering. As there is evidence of scorching on the board the use of
a more substantial component would be indicated perhaps with small
Picture displaced vertically, picture too high or low
This problem was cured by entering the service mode (menu then
4,7,2,5), then pressing the green fastext button to access geometry
settings, selecting VP1 (vertical position) and adjusting as necessary 3)
Vertical line at the left of the picture
Replace L506 on A board, replacement part number 1-407-366-00 4)
Problems with screen size
Look out for 2 x 2.2uF electrolytics (sometimes red in color) 5)
Vertical height oversize
The eprom was found to be faulty (nvm)