My grandma has an old Magnavox Astro Sonic Stereo and the tuning knob broke on it. I think it is from the 1960's. I know that a string was attached to the knob and the tuning box, but I can figure out how it worked because every time I put a tighter string on there, the knob will just slips and won't grip. I cant seem to figure out what could work
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Hello, This will require you opening the back cover of the television to test some component with the use of an ohmmeter. This may be a slight drift - like someone is messing with the fine tuning or such a substantial change in tuning frequency that the channels go by as though you are surfing.
Possible causes depend on tuner type:
1. Quartz tuner (10 button direct access digital synthesizer) - For a slight drift, a component is probably changing value, possibly the crystal in the reference oscillator. For gross changes - flipping through channels - it is more likely to be a digital control problem - the microcontroller is misdirecting the synthesizer to change frequency.
2. Varactor tuner (buttons but not direct channel access) - If only a single pushbutton selection is the problem, the the varactor tuning diode for that button is probably changing capacitance. If all channels in a band (Vl, Vh, U) are having a problem, it is more likely to be a drifting D/A or faulty AFT (Automatic Fine Tuning) circuit or power supply.
3. Turret or switch tuner (Knobs) - A component like a capacitor is changing value.
You will have to get in there with a heat gun or cold spray and track it down the old fashioned way. At least, the problem is almost certainly localized to the tuner box (and possibly the controller if applicable).
As noted, gradual slight changes in tuning are likely due to frequency determining components drifting.
Uncontrolled channel surfing is probably a logic problem. For the quartz tuner, this could still be marginal connections causing the microprocessor to misdirect the synthesizer to change channels.
For the latter case, particularly, the cause may still be bad connections resulting in loss of channel memory and/or erratic behavior. Take care...
U want to tune in free air tv?,not analoge signal anymore.All digital now,must have a good antena like digital antena,and a digital converter box.Or must have cable or setalite signal.Than can watch without a converter box.
Yes common problem it seems with these. I can help you get the set working but this fix only prolongs the inevitable so I'm told. (more about that at the bottom) Please read entire posting before starting. You will need to take off the front panel, there are 2 screws towards the bottom on each side behind little pop out plugs. Once those are out take off the panel (pull from bottom, sometimes the round clips at the top come off, either glue them back on the panel or leave them out). There are wires attached to the panel, you can either unhook them or just take them out of the "twist tie" holders and move the panel out of the way to the left. You will now see a thin panel. Remove this one also. Once that is off you will see the bottoms of the 3 glass tubes and on the "floor" of the set there is a group of 6 small knobs. This is called the focus block. Each row of 3 knobs are labeled either screen or focus, also, there should be 3 letters R G B (Red Green Blue). (We won't be adjusting the focus knobs).You will need to adjust the Blue screen knob (on my set it was the bottom left knob). If the set will stay on for a little bit you can adjust it with it on. Once you have found the correct knob (don't worry about the white paint) turn the set on, once you see the picture slowly turn the blue screen knob counter clockwise until the blue diagonal disappear. Be careful not to turn this knob too fast while the set is on. Keep in mind, it may take a little bit to break off the paint. You will see the screen turn back to normal as you turn the knob. Adjust it just until the lines disappear This should solve your problem. If the set won't stay on, with it off turn the knob about 1/8 turn counter clockwise then turn the set on. Once it is on you can fine tune it. Adjust it just until the lines fade out of sight. (You may have to adjust back the other way until the lines show up and then back it off again). Remember to turn the knob slowly. I have heard people getting charged a lot of money for this. I was also told that this is compensating for a dying component(s) all I know it has bought me at least a year. I also read that someone has gotten several years out of there set w/o repair just by doing this adjustment whenever its needed. (once the lines start presenting themselves). I can't see spending big money on these sets when you could put it towards a new set so I will keep it going for free as long as I can. I hope this works out for you. I'm tired of typing so good luck and post if you need any more help. BTW this adjustment works if this symptom presents itself in green or red also. Just substitute the blue knob to the applicable color. Now go put your TV back together :)
On projections, there isn't much you can do as they age accept replace the CRTs. In that case you might as well buy a new one. One thing you can do is open the front speaker grill to where you can see inside the set. Depending on the brand, find the "Screen" controls, one for each tube. Some sets have all 3 on the "focus/screen" block (small black box mounted in front) and some have the knob on each individual CRT board (mounted to the bottom of the CRT). What this does is increases the current to each tube, thus making that colr brighter. Do each equally as to keep the color balanced. Only do this if you feel comfortable with working on electronics.
You can use a spliter that turns one output into two so you could connect two sets of headphones into the tv, I don't know if two headphones can be used with the same base, which company where you trying to reach`?