Author Topic: My 1958 Concert Grand Restoration Project  (Read 12351 times)

Pat L

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Re: My 1958 Concert Grand Restoration Project
« Reply #30 on: October 30, 2014, 07:51:50 PM »
Ray, the AMP-150CB absolutely does have a 1000hz crossover. One of our members shared the original Magnavox AMP-150 Service Manual. It's in the Download Center and it's better than the SAMs that we also have. The manual explains the differences between the amps on the first page of specifications.

As for the AMP-179, it was made for use in external speakers or as a second amp in some consoles. The amp is also essentially a variant of the 150 and has the 1000hz crossover network. Pat
« Last Edit: October 30, 2014, 07:58:05 PM by Pat L »

Harbourmaster

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Re: My 1958 Concert Grand Restoration Project
« Reply #31 on: October 30, 2014, 07:54:21 PM »
Interesting that one of those Amps is marked 179DB instead of 150...  I need to pull the Amp out of my S-37 and see what amp is actually installed.
« Last Edit: October 30, 2014, 07:56:02 PM by Harbourmaster »
-- Aloha, Ken

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AMP82-01-00

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Re: My 1958 Concert Grand Restoration Project
« Reply #32 on: October 30, 2014, 11:22:16 PM »
I felt it was only right to get those original amps back to that cabinet. My only attachment was the 500.00 I spent on them. But in the end I feel we did a fair deal. I still have to rebuild the amps for my 58cg.

I had traded a McIntosh MX113 for my current set of 58 cg amps.
David        "If it ain't interesting, its really just boring"

Pat L

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Re: My 1958 Concert Grand Restoration Project
« Reply #33 on: November 03, 2014, 09:41:06 AM »
I recapped and changed all the resistors in one of the amps yesterday. I used all the exact same value parts as the originals. It's hard to remove the original caps and resistors without damaging any of the tabs on the tube sockets. To do so I work slowly and remove most of the original solder with copper braid solder wick. I then do my best to fit the new components in the same way the originals were. I am not a professional at this and my work isn't as pretty as some, but I bet it will sound good  :) Pat

Larry H

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Re: My 1958 Concert Grand Restoration Project
« Reply #34 on: November 03, 2014, 01:53:16 PM »
This is how I do it, and it's not quite as pretty as going right to the source, but it works quite well and is sooooooooooo much faster.  I was taught this procedure by an old time antique radio restorer in the early 90s. First, I cut the capacitor leads right close to the capacitor.  Then, I bend each lead up.  I take the capacitor and measure how long it needs to be, and make a loop on each end of the cap.  I slip the two loops over the leads, bend the leads back so it will make a good connection, solder it on both leads, and clip off any excess lead.  Maybe not the prettiest thing in the world, but it works quite well and you don't have to mess with the original solder joint at the socket or wherever it is.

--Larry

Pat L

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Re: My 1958 Concert Grand Restoration Project
« Reply #35 on: November 03, 2014, 01:58:08 PM »
Larry, your technique is sensible, I often use a variant of it myself. Because I decided to change everything in these amps I did it the harder way. I have seen criticism levied against those who use this method. In my opinion it's unwarranted because the way you suggest results in less damage to the unit and it's very obvious what is original and what isn't. Pat

Larry H

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Re: My 1958 Concert Grand Restoration Project
« Reply #36 on: November 03, 2014, 02:44:08 PM »
Whatever works best for you is the method one should use.  Some people even go to the trouble of restuffing the original old caps, but I see that as a total waste of time because who is going to see underneath the amplifier or tuner anyway? 

I have a good friend 35 miles north of me who never shortens a cap lead.  He twists each lead around a pencil and uses all of the lead, then solders that to the turned up lead like I show. 

I never change any resistors unless there is an open one.  These tube amps are generally forgiving enough that resistor variances don't matter too much.  Sometimes, on a serious set like the Concert Grand, I would check ohm readings on each resistor and replace those way out of tolerance.  I don't do that on run of the mill sets.
--Larry

AMP82-01-00

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Re: My 1958 Concert Grand Restoration Project
« Reply #37 on: November 03, 2014, 03:07:52 PM »
i think that is a great way in tuners or chassis that look like a rats nest.
David        "If it ain't interesting, its really just boring"

AstroSonic100

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Re: My 1958 Concert Grand Restoration Project
« Reply #38 on: November 03, 2014, 03:37:44 PM »
I've also used the "J" hook method myself with no problems.  It was necessary when I restored my 1950 Philco radio-phono console.  Philco layered all the capacitors and resistors and there was no way I was going to unsolder the leads on tube sockets and terminal strips. 

The most interesting capacitor this set had was a three lead .01 rf capacitor going from the main chassis to a sub-chassis for the FM section.  One lead went straight through the capacitor with a tap for one side of the .01 cap and the other side of the cap was a lead that went to ground.  Philco was also famous for winding coils around paper caps. 

I have eight Philco table sets and one console.  They are very good performers for picking up distant AM stations.  The only downside is sometimes they are a pain to recap.
Ray

Larry H

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Re: My 1958 Concert Grand Restoration Project
« Reply #39 on: November 03, 2014, 05:47:53 PM »
The important thing is that you make a good connection with each cap installed.  I always take a small screwdriver and pry around on soldered leads to be sure there's not a cold solder joint.  I also check the original manufactuer's solder joints as well, and believe it or not, I've found cold solder joints from the factory!
--Larry

Harbourmaster

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Re: My 1958 Concert Grand Restoration Project
« Reply #40 on: November 03, 2014, 08:45:19 PM »
lead dress can be an important issue in some parts of the circuit. By using the method that Larry describes you have far less chance of upsetting things than if you completely remove the old components.

Personally I fee that all of the attention paid to making things look as close as possible to the original under the chassis is nothing but a waste of time unless you are working on a museum piece that is going to be on display where people could actually see your handiwork.

Same goes for covering up under chassis leads with spaghetti tubing when replacing caps. I mean who the hell is ever going to touch them when the unit is operating? Or how might they ever cause a short circuit as long as you have reasonable clearance between leads?  Are you going to have some Go-Go girl dancing on top of your amplifier or something???   :o
-- Aloha, Ken

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Larry H

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Re: My 1958 Concert Grand Restoration Project
« Reply #41 on: November 03, 2014, 11:30:14 PM »
If a capacitor is running right next to the bottom of the chassis, I install the new one exactly the same way.  You don't want the capacitor body touching the chassis, but just close to it.

I agree about not putting spaghetti tubing on the leads.  I see some restorers do this and frankly I can't understand why they do it.  Some will say it's "pride of workmanship" that causes them to do this.

RCA and Magnavox didn't put spaghetti on capacitor leads unless they were really close to another component, so there's no need for any of us to do it either.
--Larry

Pat L

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Re: My 1958 Concert Grand Restoration Project
« Reply #42 on: November 13, 2014, 07:01:15 PM »
Hi all,
I have brought the Concert Grand to the stage of being operational. It's not completely finished yet as the record changer still needs to be gone through. Here is a video of me and my chiuahua Princess testing it out. Pat

https://www.youtube.com/watch?v=h05-V1a7bLE

Pat L

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Re: My 1958 Concert Grand Restoration Project
« Reply #43 on: November 13, 2014, 07:17:21 PM »
Here are some pics of the chassis and speakers installed and powered up. You will notice everything is original except the heavy magnet woofer. I have substituted a Jensen P15LL until I find an original Magnavox heavy driver. The speaker is equivalent in all respects with the original and is highly regarded itself, It's often found in high end systems and Leslie cabinets.

Also, I have not yet wired in the external speaker selector switch as it is not the exact switch that would've came in this console. The switch and speaker plugs in this console are unique to this year of Concert Grand. In fact the amps in this unit do not use the same sockets for the sound output as regular Amp-150's. That was a big surprise to me and really made me think :) Pat

Harbourmaster

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Re: My 1958 Concert Grand Restoration Project
« Reply #44 on: November 13, 2014, 07:17:30 PM »
Nice to hear it singing again Pat!!

I really need to buckle down and get going on my Imperial!
-- Aloha, Ken

No Console Left Behind!