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  #1  
Old 04-19-2007, 07:59 AM
radotvguy radotvguy is offline
mike g
 
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magnavox , HELP!!!!

Ok guys , i am kinda new as i said once before to tvs . Basically i fooled with radios and some small b/w tvs a few times . Anyhow , i got a 1965 magnavox color roundie . Heres my question . Should the electrolytic metal can caps be changed on these ???? . It looks like someone tacked in another cap to one of the cans becuase of a problem at one time ??? . Is is advisable to remove the cans and replaced them with three electrolytics with ground side , grounded to chassis or should i have special cans ordered???

Next question is , i wasgetting buzzing lines across the screen last night , then i got a bunch of green retrace lines on the screen and a hissing noise from the crt . Can anyone shed some light on this and tell me where to start to look . All tubes are good , all controls are clean and seem to be working , all mylar caps tested ok too . Not sure where to look at this point . Replaced two bad electrotytics i found also .
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  #2  
Old 04-19-2007, 12:01 PM
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jpdylon jpdylon is offline
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Definitely replace those electrolytic filter cans. I think its tacky to add a cap across a problematic one. if it shorts, you will still kill the power supply.

As far as the retrace lines and hissing, sounds as though you have some high voltage leaking out some place. First place I would look is at the CRT socket. Gently and slowly wiggle it off, as the plastic guide key sometimes breaks. look for green corrosion or rust on the pins of the CRT and the socket. polish the pins with 1000 grit sand paper or better. a small bit of deoxit on a pipe cleaner works for the socket. MAKE SURE TO LET IT DRY OVERNIGHT BEFORE USE.

Next is the spark gaps (if this has them) on the grid wires going to the CRT socket. You may need to find a way to take them apart or replace them if they cannot be cleaned.

If the problem is still evident, check inside the HV cage for burned or melted flyback transformer coatings. Magnavox chassis seem to be notorious for killing flybacks. check all wire and dressing to make sure there are no cracks or breaks in the wires and that all the insulating gromits are in place.

Another thing I might try is to get a cheater and run the set in a dark room with the back off. Notice if you can see any blue corona and where its coming from in the chassis. However if its comming from the CRT neck and the neck is glowing blue or purple, then the tube is defective and its time to look for a CRT.

Good luck
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Old 04-19-2007, 12:34 PM
radotvguy radotvguy is offline
mike g
 
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magnavox

thanks , i am going to try that tonight . Thanks for the advice .

Question . Should i replace the three section electrolytic with just three seperate caps .
I am going to try to get some photos to post , this set has me a bit stumped, however like i said , its my first color roundie i ever tried restoring . I did notice the rubber coating on one of the flyback windings was melted or fell off and melted on high voltage regulator tube , which was a 6bk4 . I changed that tube , as well as the damper . Since i got the set , i already changed the horizontal output tube once , it just went one night while i was running the set . I did hear that from plenty of people that magnavox burns up flybacks . Lucky for me , i just aquired a NOS flyback for this set . I will give yur advice a try tonight .
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Old 04-19-2007, 12:51 PM
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bgadow bgadow is offline
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Yes, I replace the can caps with seperate caps to cover each section. You can usually find space under the chassis to place them. Try to stay close to the original location. It can be tempting to transplant them to other empty spots under there but sometimes that can cause electrical intereference to other circuits. Make sure that when you are done the old caps are completely out of the circuit. Lots of times on these sets the electrolytics still have life left in them but I would say if you are going to replace one you might as well take the time to replace them all, and get it over with.
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Old 04-19-2007, 12:52 PM
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Phil Nelson Phil Nelson is offline
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It is fine to replace a multi-section can electrolytic with separate caps. Disconnect the old caps completely, rather than wiring in parallel with them.

Some times there is enough space under the chassis to install the new caps there. You can add a little terminal strip to provide mounting points, or some times you can wire point to point and secure the new cap with a little plastic tie. Carefully insulate the new connections, in any case.

If there is not enough room under the chassis, then you can remove the can and use that space to mount the new caps. This changes the appearance, but not everyone cares about that. Again, find some way to secure the caps. Don't leave them flopping around on the ends of their leads.

If you want to preserve the original appearance, you can remove the can, remove the innards, "restuff" it with new capacitors, and reinstall it on the chassis. You can cut off the bottom of the can with a Dremel tool or hacksaw. Then screw a big wood screw into the innards, heat the can with a heat gun, and pull out the softened guts. After you make up the new caps to fit inside (make the leads long enough!), you can fill any empty space with cardboard and hot glue, then glue the can bottom back on with JB Weld or other epoxy.

Regarding ground connections, look carefully at how the originals are connected. Some can electrolytics are grounded to the chassis. In others, the negative lead of the cap is connected to something else. It makes a difference!

Phil Nelson
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  #6  
Old 04-19-2007, 01:58 PM
radotvguy radotvguy is offline
mike g
 
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magnavox

thanks , i got some new caps on the way .
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  #7  
Old 04-19-2007, 07:26 PM
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Larry Melton (oldtvman)
 
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multi-section caps

It's becoming harder to find multi-section caps, and if they've been around awhile the eletrolyte made be dried up. The newer single value caps are smaller and do a good job. On that set I have the same series and the filter cap usually 160mf@250vdc goes leaky first. I always swap that one out.
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  #8  
Old 04-20-2007, 07:32 AM
radotvguy radotvguy is offline
mike g
 
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mag

there is a guy in Kansas i think who actually makes electrolytic can capacitors to the value and voltage you request . However it isnt cheap , but i would just use individual caps myself becuase no one can see the inside of the set once the cover is on anyway .

Well i looked further into the magnavox last night . I tested the crt and it was shorted , i guess that was my problem being the set was working the other day , so i either got to have it rebuilt or find another tube . 21afj22. ooh well
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  #9  
Old 04-20-2007, 12:49 PM
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bgadow bgadow is offline
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Some shorts can be removed from a picture tube using a decent picture tube tester/rejuvanator. Sure worth a shot. Do you know what elements are shorted?
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Old 04-23-2007, 10:49 AM
radotvguy radotvguy is offline
mike g
 
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maggy console

yes i tried removing the shorts with a tester that is able to clean and remove shorts, however i was unable to remove shorts . Basically i am going to send out the tube to be rebuilt
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  #11  
Old 04-24-2007, 12:55 AM
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reeferman reeferman is offline
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I've done this before and on rare occasions have been successful.

Be carefull if you try this. Take the socket off of the CRT to expose the pins. Remove the 2nd anode, turn on the set. When you have high voltage, move the HV lead around the pins so the juice jumps to the pins. Circle around all of the pins a few times, check for results, try again if need be.

If you know between what pins the short exists, you can try grounding one side then hit the other with the high voltage. If you have a heater to cathode short, and try the grounding trick, most likely you'll ruin the heater. What have you to lose?

Don't worry if you see sparks fly. Something is happening..for better or worse

If you have a gassy tube you will have your own "Northern Lights" display in the comfort of your own home.

Have your 2nd anode clean & dry and you won't have to worry about getting zapped (assuming you use common sense).

Good luck
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  #12  
Old 04-24-2007, 08:41 AM
radotvguy radotvguy is offline
mike g
 
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maggy console

thanks for the advise , but it basically is going to need a crt . The crt is old and tiried . I gatta take it out and sent it to Hawkeye for rebuilding . Just gatta get a few bucks together . Those crts are not cheap to rebuild .
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