Author Topic: Newbie with Concert Grand.  (Read 353 times)

Balderdash1

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Newbie with Concert Grand.
« on: May 24, 2017, 08:33:41 PM »
Hi all,

This one has been on my radar for years but have never seen one anywhere close to where I live.

I was perusing CL yesterday and for some reason I started searching for Magnavox's. An ad came up for "retro stereo". That sound's pretty vague and cheesy, but this time it was the holy grail. When I opened up the photo, I thought it looked better than your run of the mill console stereo. I thought with luck, it could be an Imperial.

Once I opened the add it said, "Concert Grand $300 or best offer. I thought it must be a joke. I know it's not like a million people are searching for Concert Grand's, but I can't imagine the listing being up for more than several hrs without the seller being deluged with phone call's.

The number was listed and I called right away. The lady said it had been in the family for many years and that it was lovingly cared for and that it was still available. She said that her parents had passed recently, and that the family had just conducted an estate sale the this past weekend and that no one seemed interested in the Magnavox. She then told me that the company that conducted the sale told her, "you might as well take this to the dump because no one want's these old stereo's any more".

Anyway, this was a case where no one involved realized what they had. Very surprising as Google is just a click away. I offered the lady $ 200 and she almost seemed a little shocked. Frankly, as this thing weighs at least a couple of hundred pounds, I think they would have been fine if I would have just hauled it off for free.

No biggie. $200 is a small price to pay for something as cool as this. BTW, it did come with the remote.

I'll get some pictures up over the next few days.

My question though is, I don't really want to mess with it until I'm sure it's not going to blow up. I did turn it on for about 30 seconds and heard a little hum and some scratchy pots..

Not looking for a full restoration at this point, just want to be able to safely play it for a bit.

Is there a protocol for starting a job like this? Any capacitors I should look at..or maybe give it a good cleaning?
 

danrclem

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Re: Newbie with Concert Grand.
« Reply #1 on: May 24, 2017, 09:53:43 PM »
First of all welcome to Vintage HiFi.  You did good, very good in finding a CG for that price.  Congrats!  ;)\

At minimum you'll want to change the filter caps out before you play it.  If you don't you could risk damaging the transformers.

Looking forward to some pictures.

Bill

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Re: Newbie with Concert Grand.
« Reply #2 on: May 25, 2017, 01:48:51 PM »
Congrats and welcome!  And yes pictures please. 

Bill

electra225

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Re: Newbie with Concert Grand.
« Reply #3 on: May 28, 2017, 07:42:54 PM »
Congrats on your Concert Grand.  I urge you to resist the temptation of running it to any great extent without having it serviced first.  Relatively cheap and replaceable components can go bad and cause catastrophic damage that can be hard to repair.  Better safe than sorry. 
If it ain't broke, call me.  I can break it....

Larry H

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Re: Newbie with Concert Grand.
« Reply #4 on: May 28, 2017, 08:58:50 PM »
Electra 225 is right.  Don't play this thing until all capacitors, including electrolytic filter capacitors, are replaced in each power amplifier, and the AM-FM tuner.  If you do play it without fully servicing it, you stand a chance of burning up one of the power transformers, and you don't want that to happen.
--Larry

electra225

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Re: Newbie with Concert Grand.
« Reply #5 on: May 28, 2017, 10:08:55 PM »
There is a guy on another forum who recently bought one with a burned up power transformer.  He did not repair it correctly.  Now he has a hacked CG.  It is a nice instrument otherwise.   

If you are not fairly experienced with repairing electronics, I might caution that a Concert Grand is not a good first project.  They have lots of parts.  Not terribly complicated, but if you fry something important, parts can be scarce and spendy.  The battery for the remote control can cost nearly twenty bucks.  I don't know what part of the country you are in, but finding somebody to do it might prove challenging.  I don't know anybody who fixes these things except "US".  Good luck.   ;)
If it ain't broke, call me.  I can break it....

TC Chris

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Re: Newbie with Concert Grand.
« Reply #6 on: May 30, 2017, 08:53:05 PM »
OK, I'll speak out for being bold and giving things a try.  The others are right that (especially on expensive equipment) it's important to do some capacitor replacements.  On inexpensive items, you can gamble and plug it in.  Quite often all goes well.  But sometimes... not often, but enough to be notable... an electrolytic capacitor in the power supply will short out from age, and it will take a power transformer with it.  It happens quickly, usually announced by the smell of burning transformer insulation.  Oops.  There are some standard replacement transformers but maybe not for a great big amplifier.  Similarly, a coupling capacitor can go bad and leave a tube biased wrong and burn up the tube.  But replacing capacitors doesn't require an engineering degree.  There are some simple rules.

1.  Go slowly and observe markings.
2.  Know how to solder (and unsolder).
3.  Honor the voltage ratings on the component you are replacing.
4.  Honor the value on the component you are replacing, although most of them will tolerate some variation (and modern values won't match old-time values exactly anyway).
5.  Pay special attention to the polarity of electrolytic capacitors.
6.  A repeat of no. 1:  be patient and work slowly.  We make our stupid mistakes at 1:00 a.m. when we are in  hurry to get the job done.
7.  Ask lots of questions.
8.  Develop some familiarity with a schematic diagram that shows how the circuit is designed and what is connected where.

The others are right that the CG has a lot of parts.  That does make it a bigger job.  But lots of us don't have a tube-electronics repair guy down the street, so our choices are doing it ourselves, or not doing it at all.  Life is more interesting when we take some risks and stretch a bit to learn something new.  Sometimes we make mistakes, dumb mistakes, and I keep making my share.  But that is how we learn and improve and have fun. 

So I say, replace those filter capacitors right away, absolutely, don't mess around. Then maybe the coupling capacitors, although that's a little less urgent.  And then if you are ambitious and having fun, look toward checking and replacing some resistors, which also drift off-value with age and extended use.  And any time you don't know what to do or didnt record what you took out, stop, be patient, and ask questions.

Chris Campbell

Balderdash1

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Re: Newbie with Concert Grand.
« Reply #7 on: June 02, 2017, 11:46:15 AM »
Thanks everyone

I had a local audiokarma tube guy stop by and check some things out. The 6v6s all look good. The 12ax7s are low and need replacing. I haven't looked at tube prices lately and was shocked.

We turned it on for a bit and everything seemed OK. Not going to run it further until I pull the tuner and replace some caps and give it a good cleaning.

Do most of you try to replace the can cap or put caps underneath to equal can values?

danrclem

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Re: Newbie with Concert Grand.
« Reply #8 on: June 02, 2017, 05:20:01 PM »
If it were me I'd put them underneath that is if there's plenty of room.  They won't be seen and the cans won't be disturbed.  If you decided later on to go ahead and put them in the cans then it would be easy to remove the caps that were put in.  That's just me though.

I've got a Sherwood S-5000II that doesn't have the room so I'll have to put them in the cans.  Never done it before but not too many people think it's a fun job. 

Harbourmaster

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Re: Newbie with Concert Grand.
« Reply #9 on: June 02, 2017, 05:52:45 PM »
Plenty of room under the chassis on these... no reason to restuff.



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