hitachi tv vertical hold problem

adrenaln · Joined: 13 Feb 2006 Posts: 3 Location: nanaimo bc canada

have a hitachi ct-7899b tv that every 10-15 min the vert hold goes for a min , no vert adjustment on the menus, etc. it doesnt change if I bump it so I assume it isnt a loose solder joint, any ideas? or is it a throw away( I love the tv as it has built in surround sound and even a subwoofer on the top! sounds amazing ) HELP ME PLEASE Smile

thanks mucho

Guest · Posted: Fri Feb 17, 2006 10:11 pm Post subject:

How fast does the picture roll? Does it roll up or down?
Maybe you could try replacing the electrolytics around the sync separator or look for dry joints. Can you measure it's frequency?

adrenaln · Joined: 13 Feb 2006 Posts: 3 Location: nanaimo bc canada

it rolls from top to bottom, some channels it doesnt at all, some it is continuous , some channels every 4 -6 min it will roll 2 times

Guest · Posted: Sat Feb 18, 2006 11:40 am Post subject:

It sounds like the free running frequency of the verticle oscillator is too high. It should be a little below the video signal of your format.
When you change chanels the error from the free running to the actual video frequency is calculated and adjusted accordingly. If the error is too great it takes time to lock onto the video frequency.
If it happens while on a chanel it sounds like it is losing the synchronization from the sync separator or the verticle oscillator is not working correctly.
Can you solder new electrolytics in yourself?

adrenaln · Joined: 13 Feb 2006 Posts: 3 Location: nanaimo bc canada

I can solder anything if I have a diagram or a direction as to where they may be and what it is I am replacing

Guest · Posted: Sat Feb 18, 2006 12:45 pm Post subject:

If you get a diagram you can see what you are soldering:)
If not, replace the electrolytics around anything that looks like a verticle IC and resolder the IC's pins carefully. (don't short them)
If you have access to an ESR meter, test all of the electrolytics and replace the bad ones. Most are low ESR capacitors. Use high temperature capacitors (105 Deg. Celcius) Smile

Guest · Posted: Sun Feb 19, 2006 3:47 pm Post subject:

You already have checked your antenna plug and cables for loose/broken connections, I am sure. Smile

Check the connections on the antenna, continuity of the cable and any plugs you are using. Check inside the T.V. aswell. Maybe your tuner contacts need cleaning. A weak signal will roll.