Magnificent Magnavox Theatre Console Questions
 

I'm hoping some of you may be able to shed some light on whether the Magnavox console I have is a worthy candidate to restore, or if it should be parted. I'm hoping I can get it running again. I would really like to have it playing records and tv shows, and I cant wait to hear how the big woofers and horns sound.

This unit belonged to my grandparents. It was purchased new. However, I'm fuzzy on what year that was, and no manuals or documentation are available.

I came into possession of it in 2005 and has flawlessly performed the duty of Picture Frame Supporter, with additional duties depending on holiday season needs. The console has not been powered on since it was moved here. Prior to loading on the truck to bring here, the tuner worked, music played through the speakers, the turntable spun around, but I did not see the television turn on.

My best guess is that it is from 1961, Model Number 1MV355R, Run 1. I don't really know what all I'm looking at though, and hope the pictures show what all the components are.

I have had difficulty finding any similar model, and the various options available year to year are especially confusing to my novice eyes.

Any assistance in ID'ng the components, where to get service manuals and parts, and generally any tips, tricks, or cautions I should take would be greatly appreciated.

(Exterior Photos)

Here are some interior photos:

And a couple more of the interior:

The 122 on the CRT label is probably the date the tube was made, the 22nd week of 1961, the set probably followed soon after.

It's absolutely worth fixing, provided the CRT is good, most of the large screen sets I've seen from that era had weak tubes, they got watched a lot and from the dirt I'd say that one was watched a lot too!

First order of business it to get, or find someone nearby with a Picture Tube tester, if it's OK then you could proceed with the restoration, if it's not you might be able to find one but the 24 inch tubes are very hard to find.

It really wouldn't surprise me if it works at least somewhat right now, Magnavox sets were superbly built.

prob work fine, I would use a variac and monitor the B+, if the can caps are ok, I would think just a tube problem if the TV does not work. it has a 5U4 so I would look there if the B+ is not shorted.

This sounds like it should be a simple task, and hoping the tube is good. I haven't found another picture tube identical to this one yet.

Ok, I'm going to google everything you just wrote there and get back to you. :scratch2:

Can I get a Lingo Lesson from you?

B+: where and what is this?
Can caps: what determines their acceptability?

5U4? I recognize this.

Is there a Cliff Notes reference that I can purchase, or access online, that you would recommend for a crash course?

B+ is the main low voltage power for the set (by low voltage i mean 200-400volts). a digital multimeter set to DC volts will tell you if its what it should be. You will need a schematic to know what it should be.


the can caps are going to include the filter caps, prob 350v 40uf or something like that. If you have a multimeter you can get an idea if they are at least not shorted by checking the resistance from the + term to the chassis, it will start off very low resistance but should quickly rise to around 10k ohms (all this done with the the set unpluged). If it does this then its prob ok to try a power up.

Your prob not going to hurt anything if you just plug it in and see if all the tubes light up. Just a wild guess, a weak 5U4 would keep it from working. If you can get your hands on a tube tester I would check that one.

if you get sound from the speaker then there is a good chance the TV B+ is ok.

If the CRT does not light up, then you may have no high voltage. There are special probs for measuring this at the CRT anode cap, beware the CRT anode has around 20kv when working, and the CRT can store a high voltage for a while even after the set is turned off.

If you are new to electronic work remember that there are high voltages that can kill and very high voltages that can knock you senseless, so if you are a complete newb you may want to see if someone can help you check it over.

Not knowing your skill level makes it hard to say but you may want to do some more reading before tackling a TV or any line current powered devise.

The main concern is the high current that is available at the power plug, you get tangle up with that and its not good.

you may want to try checking of some you tube clips on checking out a TV, while there is a TON of garbage on you tube, there are a few informational clips as well.

B+ is the main voltage used to power the various circuits on each chassis.

"Can caps" means the tall cylindrical aluminum parts on each chassis, typically 1 to 1.25" in diameter and 1.5 to 3 inches tall. They are electrolytic capacitors ("caps" for short) and in a device of this age they will often go bad. (If they are bad, they can damage or ruin other expensive parts as soon as the TV is turned on, but they can be replaced first for only a few dollars and some work.)

5U4 (actually 5U4GB in your TV's case) is the part number for the main power supply rectifier tubes.

I'm understanding much better at this level of explanation. :thmbsp: I understand the electrical basics, in the general sense, and need to research more on how that translates to the older technology.

I do have a strong background in the use of lab a testing equipment. Results I can get, what they mean I may not have a clue yet.

I found a strong current about 20 years ago when working on a microwave. It wasn't a feeling I want to revisit.

I will be needing to pick up a few new tools. :banana:

Any recommendations for the variac? Or a reasonably priced tube tester?

Also, are there any other resources for the tech manuals? The one I see most referenced is SAM.

I'm sort of jelous. That set has a nicely stiled cabinet, and a really good amp chassis. The only things that would make it nicer is if it was a model a remote control chassis, and or a color TV then it would be my definition of the best combo one could find.

If you want to go a step beyond repair on the audio portion and replace all out of tolerance parts in that section and adjust the tuner for best performance, then you will probably be surprised how great it sounds.

Once you get it running the way you want it I would reccomend a modification. If you use an RF source that has audio outputs (like a DVD, VCR or cable/satelite box, etc.) to feed the TV portion a signal then I reccomend modifying the sound input to the audio portion for the TV so that you can switch between the poorer fidelity monophonic sound from the TV's sound demodulator (preserving this keeps better originality of function and aids in troubleshooting any new or relapse problems in the TV) and the better quality sound output direct from the TV signal source to feed the audio amp.

If there is excessive hum in the audio or any of the electrolytic cans get hot after(or during) powering the set up on a variac then you should replace the electrolytics, and continue from there.

The Sam's technical publishing co. is still in bussiness, and offers nearly every service manual they have written since 1947. They can be found here http://www.samswebsite.com/ , but if the copyright on your manual has expired you can legally get the manual cheaper from other vendors. Some libraries also offer sams manuals for free (though the sometimes necessary photo copying will gobble up some change).

I may take flack for this, but in a pinch on a few occaisions where my variac was in a different part of the country than me I've pluged sets into outlets ( you can get adapters for light sockets too) that were controled by a dimmer switch to do about the same thing a variac does (ie start the set at 0v and slowly work my way up to line voltage).

Regarding the TV, as the very first order of business, find somebody with a CRT tester to determine if the jug is any good or not. The Maggie 24" and 27" wide-deflection CRTs were notorious for very short service life. If the one you have still has any emission, consider it a minor miracle.
BTW, welcome to the affli.. er, addiction.:D
Bill(oc)

I may be wrong, but I suspect that this shortcut would not work well for a set with a power transformer (such as the Magnavox pictured), as these switches are not designed to work with an inductive load. Might be ok for an older transformer-less set with series string heaters.

jr

A series light bulb I think would be a better current-limiting trick to check for shorts rather than using a dimmer. One time I saw a neon beer sign hooked up to a lamp dimmer at at an antique store and it was giving off the odor of burnt transformer so I unplugged it. The transformer had gotten extremely hot.

variacs come up on ebay now and then. if you have a surplus store near by they sometimes have them.

the best ones are really a lot more than just a variac, I have one that has a meter on both the output voltage, current and its isloated from the line with an isolation transformer.

a standard variac is just a variable tapped autoformer, and provides NO isolation from the line. you can vary the output from 0-140vac (approx) but you still have to be careful since one side of the output will be hot with respect to the ground. Your set has a power transformer so this isolation takes place there, but on other sets this may or may not be the case.

Back in the day manufactures would incorporate interlocks that would prevent the set from geting power with the backs removed due to the shock hazards of lack of isolation from the mains (transformeless sets) and the metal chassis was always mounted in such a way as to prevent any metal screws from contacting the metal chassis and being exposed. this is also why its important to not replace plastic knobs with metal ones on some sets.

A reg autoformer variac isi fine as long as you are aware of the shock hazard and you have some way of monitoring the circuit being powerd up. Again the best way to do this IMHO is a voltage and current reading on the B+ right off the output of that 5U4.

Tube testers are on ebay all the time, but of course the operating status is a big gamble. If you mainly want to do TV works then I would stick with a later model emission tester, something that can test the later compacton tubes.

google tube testers, there is a good site, lizard tales or somethng like that that goes into great detail on testers.