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PostPosted: 24 Nov 2013, 20:46 
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Joined: 06 Apr 2009, 10:08
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Location: US Pacific Northwest
Ok guys, I need some help.

I just picked up a working (at least it was 5 years ago) Magnavox "Berkley" console. It's a model 134B chassis; dual speakers, 6L6 PP output stage, dual band receiver (AM and SW), mono phonograph (working). Overall very nice. There is just one little hitch. I don't have a schematic. I have searched the internet to no avail. So I am wondering if anyone on the forum might have knowledge of where I might find a schematic for this guy.

Any help would be greatly appreciated.
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PostPosted: 01 Dec 2013, 12:31 
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Ok, I finally got my hands on a schematic.
Attachment:
schematic Small.jpg

I now have another question. This unit uses electrodynamic speakers. The field coils are in series (250Ω + 250Ω) and are wired between the first and second power supply filter caps (30µf and 10µf). Does anyone know of a reason to not increase the secondary filtering following the field coils? I want to quiet down the power stage and both the output transformer B+ center tap and the screen supply are drawn off of this 10µf filter cap.


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PostPosted: 09 May 2014, 17:41 
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It's been a while since you posted. Did you resolve the problem. I'm a bit X-eyed looking at that little squigles on the sch but the field coils are on the secondary winds. On the primary side the dif in cap value is an offset followed backwards into the 6L6's. First thing that pops into my head is ,,,,, Is there any headroom in the HV so another R's could be inserted before increased C's? Just bouncing a thought.
A beautiful piece of work that,. true art. Thanks Suncalc


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PostPosted: 09 May 2014, 18:53 
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I finally decided that because the voice coils do not couple back into the pole pieces (due to opposed direction winding) the field coils shouldn't have any problem with resonances if I increased the second capacitor. Just took a few minutes with paper and pencil to convince myself that it was ok.

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PostPosted: 09 May 2014, 21:39 
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Good to hear. Thanks


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PostPosted: 10 Jul 2014, 08:25 
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Location: Darboy, WI, USA
So... how does it sound now?

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PostPosted: 10 Jul 2014, 19:28 
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RossD wrote:
So... how does it sound now?
Well... :blush:

About the same because I haven't even had time to touch it. I was going to restore the case first, then some other projects came up, then work... long story short, it's still on my to-do list. When I do get around to it I'll be sure to post some pics and information.

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PostPosted: 12 Jul 2014, 16:44 
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I have an old stand up radio pre WWII I am sure. I know it has one tube i have yet to see in any project or pic i have seen in memory. Large bulb like. I am in the proses of moving from 3 locations to one right now so i am in the same boat as suncalc but some time in the next month pics will come if you like. I am tossed between refurbish or mmmmmmm what can be made with this stuff. The tranny is about 6" square and the spkr is electro dynamic if think is the term. If i'm wrong please correct me. It needs it's own power supply to produce the field..I think refurbish is the right thing to do. But then what ? It does to my eye look older than your pic suncalc but mine doesn't have the record player though.


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PostPosted: 18 Jul 2014, 17:11 
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I took a pic while moving. It would be a while before i did anything with this radio in any event and i am still not sure whether to re-furbish or leave alone.


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PostPosted: 19 Jul 2014, 11:14 
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She's Beautiful! The only thing I'd do to the cabinet is give it a gentle washing with some Murphy's Oil Soap and water and then give it a nice light wax buffing. You don't want to harm the patina. You might also be tempted to replace the speaker cloth. I've found that if you get in contact with the folks at Radio Daze (http://www.radiodaze.com) they may have a replacement in stock, or with a high resolution photo they might be able to help find a period original replacement piece.

I would definitely do some restoration work on the radio. Personally, I'd keep the same circuit, but completely recap the chassis, replace any worn and/or frayed wire (Antique Electronics Supply http://www.tubesandmore.com and Radio Daze are both good sources for period looking cloth covered wire) and replace the electrical cord and plug with something polarized.

That old radio is in great condition. I would keep anything you do to it as minimal as possible.

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