1965 Magnavox entertainment center
 

Hello folks,

I just found this resource, and so far it looks like a goldmine of information. I don't have a huge collection, but I did happen across an old Magnavox years ago, which seemed to work halfway decent, so I bought it for $5.

It had a couple of problems that I couldn't seem to fix during the time I had it, and eventually deduced that the receiver component must have some bad internal components, and I never found the guts to tear into it - so it sat for 5 years.

Last week I happened across an ad in the paper for an "antique Magnavox entertainment console" - lo and behold, it was almost the same model, manufactured one month earlier in June '65 (my original unit was July '65.)

So this past weekend I spent a couple hours pulling the stereo component out of that unit and fitting it into mine, and now the sound works great - stereo, internal, external, no humming.

But now, the next issue is that the screen will come on with a good picture, good light, and will work for 10 or 15 minutes, but will then begin to briefly flicker off and back on again. This happens with some bright white streaks followed quickly by a dark screen, followed shortly after with the picture coming back in again. Does anyone have any idea what this could be? The answer feels like it should be obvious --- but I'm not sure.

I've attached photos of the two units, the first photo is of the original one I purchased (manufactured July/65) and the second / third is the one I just picked up (already partially parted out.) The fourth is a strange device I found just lying in the cabinet on the second unit. Obviously this plugs into the back of the picture tube, but I hesitate to use it before I know what it does. Anyone have any clues on that?

Thanks in advance for any advice!
-Jim

Wow ! What a GORGEOUS roundie ! Ya done good...Welcome to AK, as well... That other doo-hickey is a picture tube brightener. They are EVIL. They were used to get a little more life out of dying CRTs-but I think they actually made 'em die faster.

I second Sandy G's comment on the brightener, they tend to turn CRTs to toast. Avoid them whenever possible. Nice Maggies, BTW.

Dumont-First with the finest in television. :yes:

Thanks! I'm a real newbie at this - but eager to learn what the heck I'm doing inside the guts of these things. Swapping out the stereo to solve the sound problem was OK, and it got the job done, but it nags at me - I wonder exactly what resistor or capacitor or whatever inside the stereo was gumming up the works. Besides, I'd like to have TWO working units instead of just one...

Ya know I had a bad feeling about that Hue-Brite device - its bright red label just looked wicked from the get-go. Glad I trusted my instincts on that one and left it disconnected.

I was wondering, does anyone on here have a line on a decent book so I can learn about this stuff? I know pretty much nothing. I tried looking for an "Idiot's Guide to 1965 Magnavox Entertainment Centers" but just didn't have any luck there... Seriously though, I've scoured Barnes & Nobles, as well as half.com, Amazon, etc., and I'm amazed at how little reading material there is out there for such a wonderful hobby as this..

There may not be a lot of reading material out there, but there is a lot of experience as close as your keyboard. We'll make your quest a success.

Well, I would start by asking if there are some typical things to check. I see a lot of mention about the two large capacitors in front of the (main?) transformer - are these usually the main culprits of various failing internal components? Further, how would I check a capacitor to see if it's good or not? I know how to check resistors, but just about everything else in there is a mystery to me. But I'm a sponge - will learn everything I can.

Is it true that I could have swapped in a good stereo, only to be ruining it by running it behind those cap's, if they are in fact bad?

Could the capacitors be contributing to the TV arbitrary blackscreen on/off problem I mentioned earlier?

Since the other unit had good sound, I'm tempted to test its capacitors and compare. But again, there's that how-do-you-check-a-capacitor thing.

Thanks again for any help...

-Jim

Welcome jim. i must say that first magnavox is probably the most beautiful color set I've seen. There is a great book written about 40 years ago entitled "The Practical Handbook of TV Repairs" written by Art Margolis. I see one occasionally in a used bookstore. This is the perfect book if you're just getting into sets. Its broken down into various sections and has a list of common problems and how to ix them. It also includes common procedures like convergence, greyscale, color adjustments, replacing parts, etc.

On to better things...
Your set has tons of capacitors that perform various jobs for each part of the set. The main large cans next to the power transformer are the input filter caps. THese take out the ripple noise in the incomming power. If these fail they can prevent voltage from getting to the rest of the set. WHen bad, they produce the nasty hum you were hearing. The rest of the caps should be replaced before you attempt to operate the set any further. If one shorts, it could damage components that would be difficult for you to find. Its really not worth taking time to pull and test each one. Most caps only have a shelf life of about 15-20 years, so using this set with 40 year old caps is not a wise choice.

As to the random picture cutting in and out, do you hear any snaping, hissing, or smell ozone? The flashes of streaks sounds as thoug you have an arcing problem in the high voltage supply. It could also be a screen or focus control that is burned. Don't use the set until the problem is isolated. Take the back off and blow all the dust out throughly. YOu may be able to see traces of arcing around the screen controls under the chassis and or inside the HV cage.

But above all please remember that these sets have anywhere from 200 to 25,000 volts lurking around inside. THe CRT stores energy like a large capacitor, so be sure to discharge the CRT before working around hazardous parts.

Welcome to AK! Theres no reason they couldnt both work if you wanted. Good advice here so far :yes: Those are very nice looking sets, both of them. :thmbsp:

John

Found one for sale online, am ordering today. I can't wait to get into it!

Any recommendations on a place to special order these capacitors from? Can I give them a laundry list and have them build all I need?

I think I hear a faint snap when the pic goes out. Then a high-pitched noise as the tube comes back in, and then it seems fairly normal. Traces of arcing would be black, burned marks? is that right? I will look for those. Do you have any images showing an example of arc damage?

Any clue how to discharge the CRT? I had been warned about this before. Don't know how to discharge it though. There's what appears to be a loose wire dangling from the back of both of these CRT's - is this some sort of grounding cable to discharge it?

Actually, there's a story about that. These units have holes in the bottom, probably for ventilation, and one of the screens was off of mine. Well I had two kittens when I first bought the set, and while I was enjoying it (before the snap-out problem began) way back then, one of those kittens climbed into the set. I had a panicky 5 minutes where I shut the set off, ran around the house finding a socket that would fit the screws in back, and hurried to get the back off as fast as I could. There she was inside, sitting innocently, sniffing about 5 inches away from the tube. *whew* Put a box underneath to cover the hole after that.

The high voltage connection to the picture tube is the single, thick wire that connects to the 'bell' of the tube, about midway between the neck and the front of the tube. There is a sort of suction cup where it meets the tube. The way I discharge a tube: get a long, straight screwdriver. With a jumper wire connect one end to the shaft of the screwdriver and the other end to the metal of the chassis. Keep one hand away from the tv and with your other hand carefully slide the end of the driver under that suction cup. Be sure your hand does not touch the shaft. When the end makes contact with the wire underneath there will be a snapping sound. (if the set has not been run in awhile there may not be enough voltage to hear a snap) I will sort of jiggle the driver around to make sure it has made good enough contact with the connection underneath. Then you can undo that wire, which involves squeezing & twisting the suction cup device until the spring loaded clip under it should release. For good measure, once the connection is pulled off I would discharge it again, and then do it once again before hooking it back up.

It sounds like something is wrong in the HV or horizontal circuit. I would nose around the horizontal first. If that circuit should run at the wrong frequency then the HV will not work. Does the picture tend to tear sideways (like the horizontal hold was misadjusted) just prior to the loss of picture? This would indicate a frequency problem

I have heard that Magnavox sets had trouble with flimsy circuit boards which fall apart due to heat. You could have a bad connection caused by that. I would take a look at the horizontal oscillator tube and see if anything unusual is happening there when the picture goes out. Perhaps the filament is going out?

Best of luck! And welcome!

Thanks, that sounds like a fairly simple technique to discharge the tube. The red cable with the suction cup is obvious to me. Metal of the chassis - any metal? Being an all-wood piece, not sure what metal to ground it to.

I see the horizontal oscillator tube - the silver canister (see photo in 1st post) has a map of all the vacuum tubes and what their job is. No obvious sign of damage to it, but I have another one in this spare set that I could try.

About the whole vacuum tube thing - should they all pretty much pull straight out of their sockets, maybe with a little rocking motion to break them loose? It looks like they should, but I don't want to pull too hard and end up breaking something...

The tubes should come up fairly easliy with a gentle rocking motion. They are fairly durable, so i wouldnt worry about destroying one by pulling it out. I would not recomend trying to clean them, or you could rub the numbers right off the tube like a dry erase marker.

In no way can you see damage or a malfunctioning tube by visual sight. You will need a good tube tester. You will need one that can test 8pin, 7pin, loktal, 9pin. novar, magnovar, compactron (14 pin). I recomend a heathkit or hickok tester from the mid to late 60s The heathkit TC-1 and TC-2 are great if they come with the adapter and booklets. A good tester will run you anywhere from 50 to 200 dollars or more.

If at all possible, try to get the sams photofact for that model TV set. This will give you detailed parts lists and adjustment instructons when you need them. Its better to fly as a newbie then fly blind alltogether.

Jim,

Several easy things you can start with, among those already mentioned. When you lose the picture, check all of the tubes around the high voltage section (horiz osc, damper, horizontal output, picture tube). Are they all lit?? If so I would take a plastic handled nutdriver and tap the accessable tubes with the plastic handle. Start with a soft tap, then kinda of work your way up in intensity (3 or 4 whaps). Don't be surprised if the damper or horiz output acts like a sparkler!

Passing that stage, turn the chassis upside down and look at the printed circuit board for bad solder joints. Also check the terminal strips for loose connections. Repair as necessary. If you aren't good at soldering, get you a good gun, like a 100 watt Weller and practice, practice, practice!

Some might say "Phil, a 100 watt gun is to hot". Ain't so. You're gonna have to get on and off the joint as quickly as possible. You've gotta have the necessary heat. Period.

Get a "Sams Photofact" for your set(S). It's your roadmap.

As far as checking caps, there are digital multimeters that have this feature. Easy and accurate enough for your needs.

The main tool in repairing these sets is to THINK, THINK, THINK! Kiss it!

Don't let your mind go crazy trying to think of engineering reasons for failure. Use common sense and you'll do fine. The reason I say this is that a lot of books are written by engineers explaining how a set was designed. There are a lot of guys that have the strictly engineering knowledge, which is great. But what you need at this point is practical "check this out" advice. Look for a book that has a lot of pictures. They were written.

Keep us posted

Can't seem to find one of these on the sams photofact site for this unit - and Magnavox had a good hard laugh when I called them "on the off chance they might still have something..."

I wonder if I tried some older repair shops that are still in business, if one of them might still have a book somewhere with the schematics...

I have almost the same unit (1964)and I got the sams photofact 746 folder 3 for the tv set. nothing for the radio part. The chassis number is from C/U45-01-00 thru C/U-04-00.

I have chassis U45043-41 - does it have to be an exact match ?

Another newbie question - flyback?
 

OK, again pardoning my ignorance, what/where is this infamous flyback device? What exactly is its job? Are there early signs of one failing, so I can judge which is the better of the two out of these two cabinets?

Thanks for any replies!

I think I answered my own question. It's the big black transformer at the right hand side isn't it... this big sucker in the red circle?

They look dusty but otherwise solid on both units.

No. Thats the power transformer. The flyback is in that big can at the other end of the chassis. As to the SAMS, there is a good chance it needs to be an exact match. As I understand it, some Magnavox roundies were RCA clones, or at least pretty close. This chassis in these pictures is one I believe to be an in-house Magnavox design.

John

I would say an exact match would be better but anyhow, your set does not have a sound amplifier in it since it is using the one from the radio. The sams 746 should be close enough. I used it to recap my set and did not have a problem.
The flyback is in the tin cage on the left side (unusual). Check if it has been replaced, the original ones were known to go bad. If it has a white HV coil on it, then it was replaced. The original ones were kind of black.

I'd be careful around the flyback. Some very old TVs had what was referred to as a "doorknob" high-voltage capacitor which could and often did store a lethal charge for months or even years after the set was turned off and even unplugged. Be sure you discharge this capacitor, if your set has one, to ground (ordinarily the chassis) and unplug the TV, in reverse order, before doing anything around the flyback transformer or anywhere in the high-voltage cage. Later designs such as your '65 Magnavox, et al. used the aquadag coating of the CRT (the coating on the bell of the tube, where the HV lead with the large suction cup connects) as the HV capacitor; this also can hold a charge for a very long time, and it can be lethal as well if not discharged before work on the HV system is begun. If the HV charge doesn't kill you it can throw you across a room if you aren't careful. It is always much better to be safe than sorry.



BTW, don't try to test for the presence of high voltage by arcing the HV lead to the chassis with the set on. This was a trick often used in TV's early days to check for proper operation of the high-voltage system, but it could prove destructive in present-day or vintage sets, especially those with solid-state circuits. Much better and safer to use either an HV probe with a meter, or, lacking that, a neon bulb on a wooden stick held near the HV cage. The latter will glow if the horizontal oscillator and other sections of the HV stages in your set are working. The HV probe and meter will not only tell you if there is high voltage, but whether or not you have enough to make a bright raster (the bright light on your screen which is the basis for a good picture).

great looking unit there... maybe you could retrofit a newer tv into the cabinet...

Thanks...

If I run out of ideas to fix it, I will probably do that - retrofit with a newer unit - but I want to give it my best effort to be 100% original. It's pretty neat to watch the old thing crackle and come to life after half a minute, makes houseguests "Ooh!" and "Aah!" every time!

When I get the chance to crack it open again, I think I need to ground out the tube, check the flyback unit, and start changing capacitors. Anyone have any clue on what it costs to get all new caps for a project like this? Should I expect to spend $50? $100? $500? What if I just focus on the larger capacitors, starting with the power supply caps and working smaller from there?

I'm still waiting on my repair guide ordered a month ago (?! deadbeat sellers....) from Half.com. I definitely want to read that through before starting back in on this.

http://www.thisoldtoy.com/new-images...26348873-B.jpg

(An ideal record player for slow jazz.):D

I have a small record collection, including some from Miles Davis, McCoy Tyner, Gerry Mulligan, Theloneous Monk, etc., and some older stuff going back to Fats Domino on the old '78's... So anyway, I was in Best Buy about a year ago or so, looking for a new record player (which they do still sell, amazingly enough) that I could hook into my stereo receiver. But when I asked if they had any that played 78's, the clerk adamantly insisted that 78 was never a record speed, only speeds were ever 33/45/16, and that I must be confused.

Of course that doesn't beat the time my wife's nephew was hanging out at our place, had to call his mom for a ride home, and came back out of our bedroom with a confused look on his face - had no idea how to use a rotary phone! Hah!

I think that this dating process happens to all of us. Although I own a 1963 Ford Falcon with three speed standard transmission(on the column) and can drive it without any problems, I am not sure I would know how to drive a Model T Ford as my grandfather did.

I sure do not know how to handle horse teams as he did.

Yeah, doesn't the Model T have the shifter on the floor and the accelerator on the column? That would take some getting used to.

"78 was never a record speed...[you] must be confused" is pretty galling, isn't it? I'm curious about how old this guy was who thinks if he never heard if it, it couldn't have existed. Does he thinks 33 and 45 formats directly superceded cylinders? Or is anything prior to stereo archaeological?

either repair or sell it!!
 

...

I've carefully removed all components from the second unit. They're all sitting in a dry storage room in the basement. The chassis, now empty, is being used as a temporary desk for our 16-year-old son. I told him I'll probably be putting it back together in about a year or so, so he has to take care of the wood.

In the meantime, I'm going to practice on these components, as I get up to speed on electronics troubleshooting. It's really handy to have another working set to compare against, so as to minimize any bad wiring or mistakes.

These guys aren't joking about high voltages. I started playing with TV repair as a 12-year old, when I "inherited" an old TV from my brother when he went off to college. I was very confident that I could figure it out, since I had repaired radios and tape recorders successfully. I didn't know half as much as I thought I did :no: (typical for that age! :D ). I didn't know about how long those things could store a charge, or how big a charge. Unexpectedly discharging that voltage from a set that had been off FOR OVER A WEEK was one of the scariest moments of my life! Probably didn't help that it was iin very dry desert conditions. I'm lucky to still be alive after that. Do take all precautions! :yes:

Thats no BS. I started tearing into old B&W sets when I was maybe when I was 7-8 years old and remember getting nailed by a Midland 12" set... Scared the **** outta me at first but then I knew I was hooked. Im still very paranoid around HV nipples and short them down with a clip lead until Im ready to connect the HV cap.

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You guys didn't mention dielectric absorption - you can completely discharge a high voltage capacitor, and then if you disconnect the ground lead and come back some time later, it can have re-developed a partial charge, enough to be painful. Always discharge just before poking around, and leave the ground lead on if possible.

Yeah, I read about this today when I was reading up on capacitors. Nasty business, man.

I can't wait to get back into this project, but I have to finish up my Pontiac project first. I just got done installing my freshly machined crankshaft into my 400 block, and let me tell you folks, Pontiac rear main seals are a pain!

Gotta finish this before it gets too cold in the garage - then it'll be time for Magnavox restoration, much more winter-friendly than car stuff ;)

One of the long time (sponsor?) members of my ham radio club in college relates a tale of carrying a small CRT face down through his "observatory" (complete with dome). His grip slipped and he dropped the CRT between his hands, shattering it a million pieces. The screwdriver he was also carrying mysteriously evaporated. When the dome was disassembled some 20 years later, he found the screwdriver, firmly embedded in the top of the dome about 40' above the floor. It seems that the motion of the CRT between his hands created enough of a charge that when he bumped the anode connection, it caused him to launch his arm and the screwdriver!