Restoration of a Magnavox Concert Grand model 1ST800F

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Do you want to share my restoration of a Concert Grand?

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Re: Restoration of a Magnavox Concert Grand model 1ST800F

Post by Wildcat445 on Wed Aug 26, 2015 5:01 pm

I have the MPX adapter installed. I have pictures that I will get on as soon as I get them processed. The factory-recommended location for the Multiplex adapter (MPX) is to mount it on the cabinet back. I judged this to be a tenuous situation, at best. Whenever the cabinet back was removed for service the MPX adapter would have to be removed from the back. It is connected in the wiring harness from the rectifier chassis for the tuner to the tuner. There is one downside to this position. There is NO place else in the cabinet to mount the MPX adapter. So I decided to compromise a bit. I put the MPX adapter in the factory recommended location, but mounted it solidly to the cabinet instead of onto the back. This actually worked out pretty slick. I got a couple 4"X3/4" "L" brackets, or corner braces at the hardware store. I had to dodge the external speaker connection panel, so the MPX adapter is set slightly to one side. One bracket is 3 1/2" from the screw, the other side is 2 1/2" from the screw. I did not drill any additional holes in the cabinet, and I used the original screws from the speaker enclosures to mount the MPX adapter. The adapter is sitting above the rectifier chassis, behind the tuner and slightly under and behind the changer. There are electronics jammed almost solidly in the compartment containing the tuner. Repair will still be fairly manageable. I will simply unbolt the MPX adapter from the cabinet, then remove it along with the tuner and power supply chassis.

The upside to installing a MPX adapter in this old Concert Grand is two-fold. First, I get stereo FM. Drifting is somewhat more controlled with MPX, but antenna condition and placement is more critical. Secondly, and maybe more impressive, bass response and fidelity is improved with the MPX adapter. There is an output control for each channel. Advancing these controls until the output with MPX on is slightly elevated above mono FM makes a big difference in fidelity. This is a victory.

A word of caution. There are now two Molex connectors to deal with on the tuner/power supply/MPX adapter assembly. Failure to have either fully and correctly seated can result in a dead instrument.

I will get some pictures up shortly. Next step is the Phantom Control. We'll see if it actually works.

WC

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Re: Restoration of a Magnavox Concert Grand model 1ST800F

Post by 75X11 on Wed Aug 26, 2015 6:34 pm

Good work!
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Re: Restoration of a Magnavox Concert Grand model 1ST800F

Post by Wildcat445 on Wed Aug 26, 2015 6:40 pm

Thanks, 75. I can better illustrate with pictures, but how I mounted the MPX adapter was actually your idea. Had we not been discussing it one day, I would never have thought to do it like I did.

WC

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Re: Restoration of a Magnavox Concert Grand model 1ST800F

Post by Wildcat445 on Sat Sep 05, 2015 9:45 pm

Here is a picture of the MPX installation.



Another picture.



In the first picture, the corner brackets are clearly visible.  I drilled holes in the brackets to put the bolts for the MPX.  I did not change the holes in the MPX adapter, nor did I drill any additional holes in the cabinet.  I even re-used the original screws that went in the speaker compartment lids.  The MPX adapter is laying on its side, "business" side down.  Factory documentation places the wires on top of the adapter.  I found this arrangement rather clumsy and looking "really breakdownable", so I mounted it with the wiring on the bottom side.  This allows easy connections for the MPX to tuner cables and for the big Molex connector.  You will notice in the second picture the big clump of wiring.  This has since been stashed neatly out of the way, wire tied to the MPX adapter mounting brackets.  Should this adapter have to be removed for any reason, it can be removed as an assembly with the tuner and power supply chassis.  The back fits perfectly, just as it always did.  The mounting brackets and MPX adapter are lined up with the speaker connector plate, so the back still fits.  The tubes are sticking forward toward the changer.  The filter cap can on the MPX adapter is only about an inch away from the changer mechanism.  I polished the bottom of the MPX adapter in an effort to make it look better.  This arrangement is quite sturdy and poses no threat of malfunction.  I'm happy with how this turned out.

WC


Last edited by Wildcat445 on Sat Sep 05, 2015 9:58 pm; edited 2 times in total

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Re: Restoration of a Magnavox Concert Grand model 1ST800F

Post by 75X11 on Sat Sep 05, 2015 9:47 pm

Bet Magnavox didn't do a better install. Very Happy
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Re: Restoration of a Magnavox Concert Grand model 1ST800F

Post by Wildcat445 on Sat Sep 05, 2015 10:10 pm

Since you, 75, get the credit for "engineering" this install, I thank you for those encouraging words. Magnavox actually had lots worse ideas than this, since their idea was to hang the MPX adapter on the cabinet back. I don't see how it was possible to put the back on with all that stuff hanging off it.

Now this instrument has seven chassis, six rectifiers, four power transformers, four audio output transformers, three power cords, four motors, thirteen electrolytic power supply capacitors, and forty-four vacuum tubes from four different OEM suppliers.

The next project is tinkering with loudspeakers.

WC

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Re: Restoration of a Magnavox Concert Grand model 1ST800F

Post by Wildcat445 on Sun Sep 06, 2015 3:04 pm

In conjunction with tinkering with loudspeakers, my NEXT next job is the Phantom Control.  Allow my digression for a moment.

There has been some discussion in this thread about weak bass response in Concert Grand instruments in specific and the divided-frequency Magnavox amplifiers in general.  I have caused concern among Magnavox collectors for daring to suggest that such a condition exists.  Apparently, "somebody" has seen the light, as this topic is no longer taboo.  Thankfully.  There has been a spirited and enlightening discussion about this topic on other forums.  

There have been several theories offered for this phenomenon, so I'll try to synopsize the subject for brevity.  First, these instruments were built to accept the first of several accessories offered by the manufacturer.  Stereo FM Multiplex adapters and tape decks were the two chief examples offered.  Currently, owners of these instruments attempt to run more modern audio equipment thru these amplifiers, with varying results.  I-pads/pods/docks/doodads and CD players are the ones most often mentioned.  Bass response with these devices can sometimes be lacking.  This is due to the pre-amplification both of the Magnavox instrument and the device being used with it.  I have found that my RCA CD changer sounds better with my CG than the JVC one does.  And that using a seven-band graphic equalizer with the JVC helps even things up somewhat.  Other suggestions were to check the original speakers for proper operation.  Suggestions were offered on current production speakers that would best work with these amplifiers, mostly with longer excursion and at least 200 watts RMS power ratings.  Mulitplex adapters increase the signal input to the amplifier, thus increasing bass response with the tuner.  And, of course, a thorough component-level electronic restoration was recognized as being a must for proper performance.  In spite of iconic standing in the electronic collecting world, Magnavox Concert Grands were built using what may be considered rather sub-standard quality components.  Mine had Good_All coupling caps, wildly drifted resistors and wonky tubes, particularly the 12AX7's.  These factors, and the requisite learning curve when operating one for the first time, all conspire to give a CG weak bass performance in some cases.  I can testify that, once restored correctly and thoroughly and set up properly, these instruments earn their moniker "Magnificent Magnavox."  Mine is growing on me.  I will admit to being rather disappointed when I first got it.  I have long maintained that my Symphony is my hands down favorite.  It still is, but the Concert Grand is sneaking up on it.  No doubt these are impressive instruments, but are not for everybody.  If you can't do the restoration work yourself, let somebody else own them.  It is difficult, if not impossible, to get them worked on.  They are huge and heavy.  And expensive to restore.  I don't see any practical way to obtain a professional, competent restoration for less than $2000.  The opinion has been offered that any Concert Grand, unrestored, is worth between $1500 and $2000.  I personally feel that is high.  Too limited appeal at this point.  The guys who like them might give that amount if one was wanted badly.  Nobody else cares.  I would pay from "free" to about $500 for one, considering that the cabinet was in nearly perfect condition.  At this price, it would have to be complete with the correct changer and with the Phantom Control transmitter. It appears that the 1961 models had tuning indicators to replace the eye tube, and many instruments were built without Phantom Control and Signal-seeking tuner. These factors would lower their value to my way of thinking.  Many collectors prefer the Danish Moderne cabinet style, while the Provincial and Traditional styles were more popular when they were new, and are more plentiful today.  The cabinet finish would be difficult to duplicate exactly using today's techniques and materials.  Multiple coats of hand-rubbed oil finish would be expensive if you could find someone competent and willing to do it.

WC

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Re: Restoration of a Magnavox Concert Grand model 1ST800F

Post by Wildcat445 on Sun Sep 20, 2015 4:12 pm

Our Concert Grand is gaining stature in our affections. Its transition from sounding like a 300-pound clock radio to an instrument worthy of being considered "Magnificent" has been nothing short of amazing. I'm sure the Magnavox guys are going to grind their teeth at this comment, but that's okay.

One feature I have found amazing is how good the stereo separation is considering the speakers are only about three feet apart. Arguably, instruments with side-firing speakers may be better, but this thing sounds pretty good. We are slowly weaning ourselves of the monstrous Pioneer SX-1050 and Peavey speakers system we use with our CD changer. The Pioneer system has been restricted to use in my "laboratory" used with my processing records to digital. My wife actually likes the CG better than her little "Contemporary" that she has used for so many years. I never expected that.

We run the Concert Grand with the back removed. The thing puts out so much heat that I feel chassis cooling is better with the back off. It also keeps the heat out of the changer compartment and tuner. It has been running about four hours this morning, and there are two cats laying on the rear edge of the cabinet, enjoying all the heat rising from the electronics. It is very likely that the original back will never be put back on this cabinet. I am designing a different back that will allow better ventilation and will allow me to see all the glowing tubes. I would like to create a back made of luaun and wire mesh of some kind. If I get this task accomplished for the CG, I would like to make another back for the Imperial. It has a worse ventilation issue than the CG. Even with the back off, the poor MPX adapter gets warm enough to fry eggs on the bottom. It resides above the rectifier for the tuner chassis, so it has a rough existence. It does not appear to cause a problem. This is the location recommended by the factory.

We have been playing "Nashville Sound" country music most of the morning. Bill Anderson, Jimmy Dean, Mel Tillis, Al Martino, Del Wood, Hank Williams, Jr., Burl Ives and a couple I can't recall at the moment. This early stereo material was recorded in "hyper-stereo" and is typical of what was currently available when this stereo was new. I will admit my affection for this type music. It sure sounds good on our Concert Grand.

WC

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Re: Restoration of a Magnavox Concert Grand model 1ST800F

Post by jerryhawthorne on Sun Sep 20, 2015 4:43 pm

WC, it has been a long long journey and so glad you have that beast working well. You must have a very large workbench! Very Happy
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Re: Restoration of a Magnavox Concert Grand model 1ST800F

Post by 75X11 on Sun Sep 20, 2015 5:15 pm

Few Magnavox instruments ever had it so good. Hope you continue to reap the harvest of your labors!
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Re: Restoration of a Magnavox Concert Grand model 1ST800F

Post by Wildcat445 on Sun Sep 20, 2015 7:50 pm

Jerry, I did the restoration of the Concert Grand in our AZ room.  I put the front to the wall and covered what was left with a huge afghan the wife had made specially for the occasion.  I took out one component at a time, tested and repaired it, then put it back into the cabinet.  I did the amplifiers first then checked them in the cabinet.  Then the tuner and so on.  The afghan was made to not only hide my mess, but to serve as cushioning so I could use the top of the cabinet for a testing bench if I needed to.  Fortunately, everything worked out okay.  That was the only way I had to handle everything.  My shop is upstairs in the garage.  No way was I going to haul that thing up stairs.  And 75, I believe this low-hour Concert Grand may get some running time now.  I still want to experiment with speakers and get the Phantom Control working.  And I'm building a new back for the cabinet with the assistance of a friend who is a good woodworker.  Thanks for your interest.

My belief is that Magnavox messed up when they built this thing. It has taken me a long time to figure out what to do, and I'm still not done. I'm in no hurry, and patience has worked out well in this case.


WC

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Re: Restoration of a Magnavox Concert Grand model 1ST800F

Post by Bill Cahill on Wed Jun 15, 2016 7:41 pm

Well, at least one thing went right today. I got an e mail from the owner of the Magnavox FM tuner adapter. He said If I Still want it I could have it for my original offer of 65.00.
I expect it next week.
Sorry for stealing your thread; I couldn't find where we were talking about the Magnavox tuner.

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Re: Restoration of a Magnavox Concert Grand model 1ST800F

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