Restoration of a Magnavox Concert Grand

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Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Fri Jun 06, 2014 12:40 pm

You guys rooted for me to find a Concert Grand, so I want to share this with you.  

I had always read how complicated, huge and heavy a Concert Grand is.  How electrically complex they are.  How ultimately awesome, over-the-top, exclusive, elusive they are.  How everybody with a pulse was busting a gut to own one.  How they are going to be the "holy Grail" of stereos someday.  Right up there with the Zenith Stratoshere, complete with the ceramic cat.  How they cost as much as a new Chevrolet Bel-Air when they were new.  How they were the latest and greatest when they were built.  Let's hold up just a bit and examine some interesting facts that I have discovered tinkering with mine.

First off, and right up front, let me say that I am absolutely THRILLED to own mine.  I worked long and hard to find it, and even longer and harder to run it to ground and to get it home.  Like my Buick, they are going to have to pry my five Magnavox stereos from my cold dead fingers if someone wants to own them.  I rescued it from a haunted house, owned by a "twanger and banger", for pity's sake.  My comments are not intended to be negative or critical, rather just informative and to reveal what I have discovered while tinkering with mine.

My Concert Grand, with French Provincial cabinet measures 58" long, 32" high and 19" deep.  My Imperial measures 54" long, 32" high and 19" deep.  My Symphony measures 48" long, 30" high and 18" deep.  My Concerto measures 46" long, 30" high, and 18" deep.  So, from smallest to the largest, there is only 12" in length and 2" in height difference.  No Magnavox console stereo is light.  They are well-constructed of hardwood.  Even the plywood used in the bottom and structure is hardwood.  No particle board.  They utilize metal chassis.  PCB's are used for the IF strip in the tuner.  Two guys can lift even the Concert Grand to unload or load one, but you wouldn't want to stand and have a chat while holding one up!  A forklift is not required, contrary to popular legend.  My wife refers to my beloved Concert Grand as "the buffet with speakers."  Ha ha.  Very funny, hon.   Rolling Eyes 


The electronics in Magnavox stereos is "modularized" if you will.  In the Concert Grand, there are five seperate, yet inter-connected chassis.  There are six rectifiers.  There are four power transformers.  25 audio tubes.  Everything is controlled by the vital, hardworking tuner chassis.  Service I found surprisingly easy.  Disconnect two plugs, the power cord and four screws, and the amp chassis are out.  The power chassis for the tuner is held in with two screws and one plug to the tuner.  The remote chassis is held in by four screws and three plugs.  The tuner is a different story.  Several cables need to be disconnected.  The turntable needs to be removed or raised to provide clearance for the dial.  The search tuner button is above the dial, so that wire is in the way.  It is connected to a huge bundle of wires with no easy way to remove them.  Unless I am overlooking something, I don't see anything there that I cant' handle.  I will need more service information to test out the remote control and program it, as necessary, after I get done recapping it and the tuner.  The thing will need a five-gallon bucketful of capacitors and resistors, so I need to start stocking up now.  I will likely not tear into this with the exception of restringing the tuner until next summer.  All I plan to do right now is to service it really well, check tubes, and satisfy myself that it is safe to operate for short periods until I can go thru it thoroughly.  It will be nearly impossible for me to let this thing just sit until I get it gone through.  I do not intend to let the magic smoke out, nor do I intend to let it just be a lamp stand, either.  The tuner in the Concert Grand has as many tubes (13) as the entire Concerto model, less multiplex adapter.

It took me nearly a year of looking, for at least two hours EACH evening and twice on Sunday, 32 cities on Craigslist (those within a 500 mile radius of Springfield, MO) ebay, etsy, Iland, auction websites to find this thing.  Three radio websites.  So it did prove elusive.  I missed buying four other Concert Grands from the first of February to now.  

"Often admired, seldom desired" is my new motto for the Concert Grand models.  These things are huge by modern standards.  Service, unless you are very fortunate, or can work on it yourself, is non-existant.  Information on one is sketchy at best.  Wives generally oppose ownership.  They are relatively complicated.  Most people could care less.  "You bought a WHAT??!!!" is the usual remark when I tell what I just did.  My  thinking is, after collectors get their fill, these things will be curb material.  The only saving grace will be certain collectors who will have multiple instruments.  That may be their salvation.  I pray I am all wet with this.  I don't see the "Holy Grail" notation.  I have a live, purring cat to sit on mine, thank you.   

I may be proven wrong, but my initial impression of mine is that it is undoubtedly the "sexiest" electronic device I have ever laid eyes on.  It is ineffecient, pulling over 600 watts from the line, yet yielding only 100 watts output.  A Bose Wave is massively more effecient and accurate in comparison.  It would be like comparing my Buick to a new Honda.  That little four cylinder, turbocharged Honda Civic will dust my old Buick in almost every category.  Yet nothing sounds as good as a big V-8 when you stick your toe in the four-barrel carburetor.  Same thing with my Concert Grand.  The Bose wave contains a handful of Chinese electronics, while my Concert Grand has 42 glowing vacuum tubes, and was designed in the good old US of A and was put together by women on an assembly line in Indiana.  As an aside, mine is loaded with clear-top tubes.  Is this a coincidence or were these things spec'd with clear tops to look good as well as work well?

Thanks for reading and sharing these observations with me.  Your comments are invited and welcome.

WC


Last edited by Wildcat445 on Fri Jul 18, 2014 12:13 pm; edited 2 times in total

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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Mon Jun 09, 2014 12:01 am

My intent is to determine if this instrument is safe to operate, at least short term.  I have my bench loaded with projects, so did not want another one cluttering things up.  The dial string was off or broken, and I needed to repair that.  The previous owner stated that there were "a couple of bad tubes", so I wanted to investigate that.  Then I wanted to do a general cleaning to satisfy the frau and to make everything presentable.  And, last but not least, I found the little red traditional Magnavox pilot light was not burning.

The previous owner stated that he had put the dial string back on, but it just fell off again.  That is possible, I guess, if he figured out how to replace the cord with the tuner still in the cabinet, an impossible job.  And apparently he did it without disturbing any of the dust and dirt.  That was the amazing part to me.  He performed a task that was impossible without touching anything.

Replacing the dial cord on this tuner was undoubtedly the easiest one I have ever done.  Everything is in the open.  The wheel on the tuner is about 6 inches in diameter, so there is tons of room to work.  Getting the tuner out of the cabinet is the trick!

To remove the tuner, you must remove the back, remove the tuner power chassis, remove the turntable, remove the 45 adapter holder so the turntable WILL come out.  Then you unplug all the plugs on the tuner, remove the side wedges holding the shelf the tuner sets on in, then withdraw the tuner.  The switch for the search tuning is above the dial, and is in the way, so you need to hold the wire for the switch with one hand, and withdraw the tuner and its shelf, with the other.  Clumsy, but doable.  I found the dial string to be intact and in good condition.  I needed to determine what caused the string to "jump its trolley."  This particular tuner, model 61-01-00 is designed to be used with remote control.  It has two motors, built by Electro Motor and Timer Company, Chicago, that run the dial and volume controls.  The alignment of the pulley on the variable tuning cap, the pointer and the tuning cap is critical so the the automatic tuning will cycle correctly, and the dial pointer will not be forced off the end its track as well.  There are two bent tabs in the wheel on the tuning cap that contact a bi-metallic switch to return the dial to the other end.  This needs to be accurately aligned as well.  What i see that happened was, over time, the dial pointer slipped sufficiently that the tab on the tuning cap wheel would not correctly cycle the tuner.  This caused the motor to pull on the string sufficiently hard to derail the string off one of its guide pulleys.  To compound matters, two of these little guide pulleys were frozen and would not turn.  The wheel on the tuning cap had slipped and it was out of time with the tuning cap closing.  To put matters right, I loosened the wheel on the tuning cap, and turned it ever so slightly until the tab just contacted the bi-metallic switch when the tuning cap just closed.  Then I rotated the wheel until the other tab pushed the switch back the other way and made sure that the tuning cap was fully open when this occurred.  I freed up the two little guide wheels and lightly oiled them.  Then I set the dial pointer against its low-frequency stop and installed a new dial string, since I did not trust the old one.  I got it right on the first try!  The dial went its full travel, and would trigger the switch at each end of the dial, before the pointer contacted its stop. I cleaned the dry grease off the slide for the dial pointer and lubed it.  The dial pointer is right on the money with radio frequency as well.  I checked all the tubes in the tuner, cleaned everything well, and decided to re-use the eye tube, and replaced a couple dial lamps.  I have not found out how to replace the bulb in the little yellow pilot light.  I will have to jack up the cabinet and do it from the bottom.

I had everything out of the cabinet with the exception of the wiring harness for the speakers.  Everything was cleaned, tubes tested, and I checked the B+ circuits to make sure it was going to be safe to run.  I am going to operate this intrument like it is until I can get time to go thru it thoroughly.  Maybe next summer.

WC


Last edited by Wildcat445 on Fri Jul 18, 2014 12:21 pm; edited 2 times in total

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Re: Restoration of a Magnavox Concert Grand

Post by 75X11 on Mon Jun 09, 2014 5:35 pm

I'm getting the impression that next summer may be coming in June or July of 2014. Very Happy 
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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Mon Jun 09, 2014 5:55 pm

No, I really mean next summer. I have too much going on this summer to mess with going thru this thing. I have my Imperial strung all over the house that I absolutely must get done. It has taken a backseat to the CG lately. I have that Philco 38-3 almost done, waiting for a transformer. I have an RCA torn down as well. I need to repair/tune up the turntable on the CG and that is all I'm doing to it for awhile. The turntable is just a "table", at present. It does not turn.

WC

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Re: Restoration of a Magnavox Concert Grand

Post by y2kbruce on Mon Jun 09, 2014 7:38 pm

There is a thread on ARF with a CL link to 2 CG remote speakers in your cabinet style. If I read the postings there correctly, the tentative sale may have fallen through to a California buyer due to excess packing and shipping costs. Might still be available but in the Twin Cities area. Each speaker has a 15", a horn and a 12" speaker in it.
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Re: Restoration of a Magnavox Concert Grand

Post by Dr. Radio on Tue Jun 10, 2014 12:50 am

AAAARRRGGG!!

I just lost all my typing!!!

Too tired!

I'll sum up.

Congrats!!!!!!!!!!


Don't even think of using it until full restoration.

Good night.
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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Tue Jun 10, 2014 1:05 pm

Yeah, Bruce, I saw those.  Unfortunately, so did my frau.  She says not only "no", but "Hell, no!"  Way too big for our space.  I would love to have them.  A set sold on the Quad Cities Craigslist a while back for $200.  The only hope they have for getting $500 for the pair is a local sale.  Shipping would kill you.

Doc, your advice is certainly well-taken.  I have satisfied myself that I can run this thing for short periods, to play with it, until I get it gone thru completely.  I did not intend it to be a lamp stand.  I appreciate your advice and concern.  I worked too hard to get this thing and wanted one for too long, to fry it being a chump.

WC

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Re: Restoration of a Magnavox Concert Grand

Post by TubeDaddy on Sat Jun 28, 2014 8:59 pm

WC, could you post pictures of your Concert Grand?
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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Sat Jun 28, 2014 9:25 pm

I would, if I could. If you would be good enough to PM me, and give me your email address, I would be happy to send you some pictures. Do you have a Concert Grand?

WC

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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Fri Jul 18, 2014 12:44 pm

75 was right.  The decision has been made to go thru this instrument yet this summer.  Orders from "the boss."  It does "not work" and that is one of her stipulations.  EVERYTHING has to work, or out it goes.  I have a "pass" on the remote control, but I need to service everything else, or else!   Embarassed 

I finished up the Philco, have the parts I need for the little RCA, the Imperial is done and back together, so I have time to mess with the CG.  I want to apply the tidbits I learned on the Imperial to the restoration of the Concert Grand.  The difference in performance is like night and day.  I will take pictures as I go along.  If there is an item you would like to see, or want me to pay special attention to, let me know.  I have a Magnavox factory manual, a Sams Manual, a Collaro service manual for this stereo, along with other tidbits I have found along the way. We will start from here.

WC

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Re: Restoration of a Magnavox Concert Grand

Post by 75X11 on Fri Jul 18, 2014 12:53 pm

I knew it'd get you. Happy new year!
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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Fri Jul 18, 2014 2:13 pm

There is a story behind this Concert Grand that is rather unique.  I would like to share that story with you.

I found my Concert Grand on an auction site.  It was at a sale on April 18, in Ft. Worth, TX.  I made plans to attend the auction, but I missed it anyway.  I decided to call the auctioneer to see if it sold.  He was cordial enough to inform me that, yes, it had sold.  I asked would he mind giving me the name of the buyer.  Again, he complied with my request.  I asked if perhaps the buyer would be interested in selling it, and he replied that he likely would.  The buyer was a local ebay flipper and jack-of-all-trades who was into auctions to make a buck reselling.  He gave me the guy's phone number, and said he would have the buyer call me in a couple hours.  Sure enough, the guy called.  We talked a bit, he told me that the CG he had was the nicest he had ever seen, but that the record player did not work right, and that "it had a couple bad tubes."  He also told me that the "thing that moves the tuner" (dial string) was off or broken, and that he had fixed it.  He told me that he would rather trade than sell the CG for money.  I told him that I had a couple items of tube electronics he might be interested in.  I sent him pictures by email.  He replied back that he would trade those two items I had for the CG "straight up."  (A Harmon-Kardon TA 230 "Stereo Festival" and an SCA-35 Dynaco integrated amp.)  He sent me seveal pictures of the CG, and, he was right.  It was the nicest one I had ever seen as well.  I asked if it would be okay to go down Saturday to get it.  He said he would call back in a couple hours and make sure it was okay with his wife.  He called back and said his wife would not let him trade, that "she needs the rent money."  He asked me to make a cash offer.  I lowballed him, figuring I could always go up.  He accepted my offer!  I again asked if I could get it on Saturday.  We made arrangements for me to drive to Ft.Worth to get it.  He called a couple hours later and said his brother would not let him sell if for "that little amount."  "If we can't at least get "X" for it, we'd just as well sell it for parts."  "X" was over double what he had agreed to sell for.  I was thoroughly disgusted with this guy.  He seldom returned phone calls, and had bumped me at least twice after we had a deal.  He was playing me, and I knew it.  I told him to stick his 1959 Cherrywood Concert Grand, complete with remote control, where the sun did not shine, and hung up on him, thoroughly disgusted and disappointed.  

A week or so later, I was having breakfast with a friend of mine.  He told the story of how he finally got the steam colliope that he had been trying to buy "forever."  The seller had bumped him a couple times on price, and had been a real PITA to deal with.  I told him the story of the Concert Grand deal and how the guy was a real pain for me as well.  He asked me to "let me make a run at that old boy.  I'm on a roll."  This friend of mine has the gift of gab and a way to pursuade anybody of anything.  I half-heartedly gave him the CG seller's name and number and figured that was that.  Two hours later, my friend called and said "pack your grip, bring crisp $100 bills and meet me in the Walmart parking lot at midnight Monday night.  I just bought a Concert Grand, whatever the hell that is."  And for less than "X" as well.  "The guy is a putz.  He needs the money.  I have the money.  We have a deal."  Simple as that.

We headed for Ft Worth and arrived about 3 pm.  The address the seller gave was in a rundown industrial area.  There were several junkyards, biker bars, strip clubs, just a generally unsavory part of town.  The building at the address housed a "gentleman's club" and some other business, later revealed to be a "haunted house."  The owner of the CG was the "media coordinator" for the gentleman's club and run this haunted house as a tourist trap.  The Concert Grand was sitting on a bench in the haunted house.  The seller fired it up and turned it nearly full blast "to hear her thump."  We handed him the money.  He and his "brother" wrapped the CG in probably $50 worth of shrink wrap and bubble wrap, a couple blankets we had brought, wrapped all that in a plastic tarp and loaded it into our GMC pickup and strapped it down.  It would have survived a tornado.  After I got it home and unloaded into the family room, I called the auctioneer and thanked him for his consideration, and that I had gotten the CG.  He revealed that the guy I bought it from had paid "a lot less than $20" for it at the auction I had missed!

WC

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Re: Restoration of a Magnavox Concert Grand

Post by 75X11 on Fri Jul 18, 2014 2:51 pm

Those punks on A&E can't hold a candle to that saga!
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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Fri Jul 18, 2014 3:47 pm

Although my Concert Grand was in nice condition, it was also dirty.  Nasty dirty.  My guess is that this thing was purchased new, used sparingly for ten years or so, something newer and better came along, the old stereo was put in the foyer or dining room, and was generally unused for thirty years or so.  It appears to have low hours on it.  There are certain tubes I have found to be typically weak in Magnavox instruments, that were quite good in this one.  I tried cleaning the cabinet with my usual Windex method, and was unsuccessful.  I had read a thread on "that other forum" about using steel wool and GoJo on cabinets to clean them.  I was a nudge apprehensive about using steel wool on my Concert Grand cabinet, so I substituted cheesecloth.  That method worked well.  I was shocked at the amount of dirt I took off.  I followed this with a good coat of orange oil.  A few days after that, I gave the cabinet a coat of Johnson's paste wax.  

The other indication of low hours, and years of disuse, was the changer.  The Collaro Conquest F-200-C changer was nearly totally frozen solid.  Only the platter would rotate.  The "Jesus clip" that holds the platter on was gone, so this fact was not a secret.  I had heard of motors being frozen on Collaro changers, but this is the first I had actually seen.  That baby was stuck.  Tight.  I removed the motor, after removing the idler wheel, and a couple pieces of linkage.  I took careful pictures, lest I forget how things went back together.  I got the lower bearing retainer off, no problem.  The rotor was stuck in the upper bearing.  I allowed it to soak in PB Blaster for a couple days, which did nothing.  I gave it a shot of lacquer thinner.  Nothing.  More PB Blaster.  Nothing.  I finally decided to try something else I had read about, but had never tried.  I got my soldering gun out, heated the tip red hot, and applied heat to the rotor and bearing.  The rotor fell out on the bench in about 30 seconds.  I took the bearing retainers all apart and soaked the individual parts in lacquer thinner overnight.  Then I assembled everything and gave it a drink of turbine oil.  The motor now turns smoothly, coasts for a long time, and runs just fine.  Now the problem is that all the changer mechanism is stuck tight as well.  The changer is permanently in "reject" but everything is so tight, it stalls the motor.  The good news is that the wheels must be pretty soft if they grip well enough to stall the motor.  Now I get to perform a task that I detest.  I have decided to go into this project with a new attitude.  Not having a working turntable in a Concert Grand would be tacky.  I need to learn to do this.  I have armed myself with all the technical literature I could get my hands on, and have spent time reading on what I need to do.  Now I get to do it.  I will take pictures, try to get them posted somehow, and will share this adventure with you.

WC

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Re: Restoration of a Magnavox Concert Grand

Post by Dr. Radio on Fri Jul 18, 2014 8:44 pm

What a great story! How ironic that such an incredible piece of machinery brought next to nothing at the auction---sadly, I bet most thought it was on-par with the typical particle board 1970's jobbers. I'm so glad YOU got it WC. Someone who truly respects it.

What a great story! I'm glad you weren't jumped in that 'shady' part of town!


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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Sat Jul 19, 2014 1:37 pm

I wanted to go to that auction in the worst way.  We were driving back from Arizona, and it was right on the way.  Not even a mile off the freeway.  But, due to the usual screwing around that takes place, and getting stopped by some snarky state cop in New Mexico, we arrived in FT. Worth after the auction was over.  This was a consignment auction.  I had previously spoken with the auctioneer about my interest in the stereo.  It had been in an estate sale earlier and had not gotten a bid.  The auctioneer took the CG to his auction house and held it for the consignment sale.  It has been my experience that consignment sales are one step before going to the landfill, so I figured I could buy it cheap.  I strongly believe that the guy I bought if from paid like $3 for it.  I am well satisfied that I could have certainly bought my CG for less than $50 at that sale.  I find it incredible that, considering all the times this Concert Grand had been moved by people with no love for it, that it is in as good a shape as it is.  Everyone involved deserves credit for their carefully handling of a $3 stereo!  There is not a mark on it beyond what would be expected on something over 50 years old.  Even the back is nearly perfect, photofinish and all.

I had missed buying four other Concert Grands this Spring.  I had one in Wyoming bought, but there was a blizzard in Wyoming, and the cabinet was rough.  The guy would not budge on his price, so I passed.  I kicked myself for doing so.  These things do not grow on trees.  Two others were too far away to be practical, and the other one was blabbed about all over ARF, so the price got out of my budget and I lost it.  I decided that I would have to go a route that nobody knew about, and keep my mouth shut about any "find" until I had it setting on terra firma on my own property.  My wife was totally supportive of me having a Concert Grand, but asked me to set a budged and promise to stick to it.  And it had to be clean and it had to work before I could bring it into the house.  We compromised on both the budget and the working before I brought it into the house.  We agreed I could work on it in the family room, since I could not carry that heavy thing to my upstairs shop in the garage.  But I had to clean it and check for "critters" befire it came thru the door.  I actually beat the original budget by over $100, since my friend negotatiated a better deal, and we drove a diesel truck, which returned better fuel mileage.

I had registered on AuctionArrows.com, Auction Zip.com. etsy, ebay, iland, craigslist and three radio forums.  AuctionArrows.com was the winner.  Anytime a Magnavox "anything" was listed at auction, I would get an email.  That's how I found mine.  I figured I had to stay off popular sites and not say anything if I found one.  That was the toughest part.  I did not even tell Neali, and he was looking just as hard as I was.  I stuck to the plan, and, by the grace of God, it paid off.

WC

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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Sat Jul 19, 2014 2:42 pm

A member has asked how many Concert Grands were built, total, and when did Magnavox stop making them.

I don't have a definite number that I can swear to.  I heard at one time 300, but I have never seen any "hard" numbers.  As far as I know, they started production of mono models 300-H and 250-H in 1957.  In mid-1958, stereo models were introduced.  These had less power than the mono '57's and were allegedly not popular.  I have only seen one stereo '58 ever.  The "real" 100 watt stereo models came out in 1959 with the 1ST800F and the 1ST801 models.  My thinking is that these were availble thru the end of tube production in 1963.  I have never seen a documented 1962 or 1963 Concert Grand, although I understand they exist.  We need to remember that Magnavox sold its instruments in furniture stores frequently, so their instruments were marketed in series rather than individual year models.  Production numbers for Magnavox are hard to come by.  My personal opinion is that less than a thousand Concert Grand and Imperials were built.  These models were expensive and built to order.  

Another interesting fact, seldom recognized, is that all the stereo Concert Grand and Imperial models, starting in 1959, featured stereo-compatible FM tuners, although the FCC had not approved the final version, nor authorized FM stereo broadcast until in 1961.  These instruments were built to accomodate Multiplex adapters, also not available until 1961.  RCA did not produce a stereo-copmpatible FM tuner until 1963, with the introduction of the solid state New Vista models.  I have never personally seen a Concert Grand or Imperial tube instrument of any vintage with a factory-installed FM Multiplex adapter.

WC


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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Sun Jul 20, 2014 6:33 pm

Here are a couple pictures of my Concert Grand.



Coded 1959, Model 1ST800F.  French Provincial cabinet.  Cherrywood finish.



WC

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Re: Restoration of a Magnavox Concert Grand

Post by 75X11 on Sun Jul 20, 2014 6:45 pm

One Handsome unit!
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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Sun Jul 20, 2014 6:49 pm

Thanks, 75.  Very Happy 

WC

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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Sun Jul 20, 2014 10:11 pm

I have been working on the changer some today.  



This shows the underside.  You may notice that little chunk of linkage on the lower left hand corner with red paint on it.  This is the linkage that causes trouble when you remove the changer from the cabinet.  The instructions say to put the changer speed in the "16" position when withdrawing the changer from the cabinet.  In any other position, this linkage is on the outside of the motor board, and gets caught on the cabinet.  I took this picture after I got the motor apart, cleaned and lubed.  I was ready at this point to remove the screws from the changer mechanism and dig into it.  I took pictures mostly for documentation lest I messed up.  There are three shafts that were pretty tight.  I removed the clips, removed the shafts, cleaned everything up well, relubed, and re-assembled.  You may also notice a little spring in about the center of the changer mechanism with part of it visible, and part hidden.  That little spring is apparently stretched.  Apparently part of its job is to return the changer wheel to rest away from the motor shaft.  This only happens sometimes.  When it drags on the motor, it causes the turntable speed to go wonky.  I can "fix" it temporarily by just slightly moving the reject knob.  Also if I release the reject knob rapidly, sometimes the unit will shut off.  This linkage hits the linkage to the switch and shuts it off.  If I release the reject knob gently, it works fine.  When I started, I had a turntable that was nearly totally frozen.  Now I have one that will play on all speeds, reject on all speeds, change records from all speeds, and will shut off when the last has played.  The LP needle is broken, so I have made my tests with a 78 rpm record.  I can live with it like it is until I can find the spring I need.  I am going to replace the drive wheel and both needles.  The drive wheel is a tad noisy, and will only get worse.  Working on this thing once is enough.

WC

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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Sun Jul 20, 2014 10:37 pm

My next project is to attempt to put to rest the complaint of poor bass response in Magnavox "dual frequency" or "compound" or "bi-amps" or whatever you want to call them. In my experience, poor bass response is not a design flaw, but is a symptom.

This instrument will be my third that I have used my "improvements" on. The first two were successful. More than I could have hoped. This one should be no different. Experience has taught me that these amplifiers suffer adverse effects from aging components and those that have drifted in value. There are changes in filter capacitor values that help. There are cathode bypass capacitor value changes that help. Replacing all the rectifier, af amp, and audio output tubes with currently manufactured units help. There are tube subs in the tuner that help with drifting. 6EU7 tubes can be a problem. I have been known to replace 12AT7 tubes with 12AX7 for more gain. This is not always a possiblilty, but I mention it as an option. I commonly find several of the resistors in the amps have drifted high in value. I have found 220K grid resistors as high as 494+K in value. All these little, seemingly insignificant flaws add up to degraded amplifier performance, particularly in bass response. The phono balance, hum balance, channel balance, and treble amp adjustments all have an effect on amplifier performance, and must be carefully adjusted. Simply put, any Magnavox instrument suffering from an actual degredation of bass response is in need of a thorough servicing.

WC

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Re: Restoration of a Magnavox Concert Grand

Post by TubeDaddy on Thu Apr 23, 2015 11:01 pm

That's a beautiful Concert Grand you have Wildcat. I've seen one of these in person, but it wasn't as clean as yours is. I am impressed with how sharp your looks, even nice clean grill cloth.
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Re: Restoration of a Magnavox Concert Grand

Post by Wildcat445 on Thu Apr 23, 2015 11:47 pm

Thank you, Tube Daddy. I hope you will follow along as I go through this instrument in the coming months. Very Happy

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