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 Post subject: 1st Magnavox Restore
PostPosted: Apr Mon 13, 2020 6:31 am 
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Joined: Apr Thu 09, 2020 6:03 am
Posts: 11
Good Day!

Brand new here, hoping for a little help and guidance. I picked up an old Magnavox console stereo/record player. The model is a ?ST677 (can't read 1st digit on sticker). I believe it's a '65 "colonial", based on googling. I was looking for an old console player and as luck would have it, someone local was getting rid of one. What's special is that this is the same exact stereo my grandmother had in her house when I was a kid. Fondest memories are all the Christmas albums played on that thing. =)

I've been reading and watching videos and I'm hoping to start soon on getting it up to snuff. Immediate things I see are:

1. FM is barely audible, if at all. I THINK it tunes ok.
2. AM works, tunes, but isn't as loud as I believe it should be. (Thinking maybe no more than 50% volume at full at moment.)
3. There is a 1/4" female jack by the tuner on top, looks like it is hooked into the speaker wiring route. Maybe for external speakers?
4. Turntable turns on, does not spin. Also, it looks like the speed selector is busted, it just spins, doesn't "select" one of the speeds.
5. Needle missing. When I tap where the needle goes, I DO get a signal.

So that's my starting point. I think this will be a fun project and will bring back some nice memories when running right.

Question: Can anyone share or point right direction to schematic for this stereo? The chassis number is: R20414 AA. I haven't pulled the turntable yet, so not sure what the model is on that.

Thanks for your all's time and help.

Cheers!

John G.


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Mon 13, 2020 2:22 pm 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 18752
Location: Mountains of Mourne. Ireland.
Hello John.

See Larry's informative links in this audiokarma thread...
https://audiokarma.org/forums/index.php ... le.628479/

Shoot me an e-mail address via PM (private message) and I will send you the 16-page service manual.
Your changer's model number should be under the mat or platter... or on the bottom.

Greg.


posting photos to a forum thread...
viewtopic.php?f=2&t=365653


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Mon 13, 2020 4:58 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 3610
Location: Dallas, TX
As far as the electronics, the electrolytic capacitors will have to be replaced. You will find more ceramic capacitors than paper capacitors probably. Any paper internal construction capacitors should be replaced also. Sometimes failing parts like capacitors can damage other parts like the transistors.
Transistors of that period were not quite as durable or as reliable as the present ones are.

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Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Mon 13, 2020 7:54 pm 
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Joined: Apr Thu 09, 2020 6:03 am
Posts: 11
Thanks, Greg! I found a sticker on the bottom of turntable, Part #523471-13, Ref # 6501, Model W.604.??.03 (sticker scratched away part of number).

I'll shoot you a PM.



Cheers!

John


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Mon 13, 2020 7:56 pm 
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Joined: Apr Thu 09, 2020 6:03 am
Posts: 11
Thanks, Tim! I've started watching the re-cap videos. Gotta get my soldering up to snuff. I've soldered a lot of guitar innards, so not too much of a noob. But it's been a while.

Cheers!

John


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Mon 13, 2020 10:35 pm 
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Joined: Jan Tue 31, 2012 1:55 am
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Location: Mountains of Mourne. Ireland.
You've got mail!

:) Greg.


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Mon 13, 2020 10:45 pm 
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Joined: Apr Thu 09, 2020 6:03 am
Posts: 11
egg wrote:
You've got mail!

:) Greg.


Thanks, brother! :D

John


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Tue 14, 2020 12:52 am 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 18752
Location: Mountains of Mourne. Ireland.
See Larry's... "MICROMATIC TEARDOWN AND REBUILD"
→ https://www.audiokarma.org/forums/index ... ld.213911/

Unfortunately Larry's thumbnail images no longer link to lager images... :shock:

Check your e-mail for "his" 29 high-resolution images, from my hard-drive.
I saved them back in 2010 lol.

also...
the 18-page factory service manual for your changer W604

Greg.


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Tue 14, 2020 1:10 am 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 18752
Location: Mountains of Mourne. Ireland.
You will need to remove and replace all the hardened grease. All rubber parts may also need replacing due to age related deterioration.

For service literature, motor mounts and other rubber parts which have deteriorated with the passage of time, Gary Stork at thevoiceofmusic.com is a good guy to deal with→ http://thevoiceofmusic.com/

When disconnecting interconnecting cables, label them with masking tape flags or directly with a sharpie.
Example: tuner chassis terminal-A to amp chassis terminal-A
B to B etc.
otherwise you'll get lost when it comes to reassembly... :shock:

Take your time and work methodically... :)
For anyone disassembling a record changer for the first time, taking photos along the way can often get you out of a jam later on,
and, Watch out for the Dammit clips!

Buckle-up...
Here are a few (Chris Cuff) video links that will give you an insight into the world of record changers.
viewtopic.php?p=2521885#p2521885


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Tue 14, 2020 1:39 am 
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Joined: Apr Thu 09, 2020 6:03 am
Posts: 11
Thanks so much, Greg! Slow and steady indeed. I'll tackle the receiver first, and then do the turntable phase 2. I'm actually less daunted by the turntable as a mostly mechanical thing versus the electronics in the receiver, lol. And I definitely will be snapping LOTS of pics. =)

I will try and post as I go along. I'll take all the encouragement and tips from folks I can get. ;)

Cheers!

John


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Tue 21, 2020 6:38 am 
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Joined: Apr Thu 09, 2020 6:03 am
Posts: 11
Hi Friends:

So, building my cap list for receiver recap. Cross-checking/double-checking/hip-checking everything. Using the Sams file, the pictures all look to match EXCEPT for what I think is called the stereo decoder board (based on a youtube video I watched). See below:

Image

Image

I can see the values on the 6 black caps. Not sure what the white cap, if it's a cap, is (the one with Sprague on it).


John G.


Last edited by JGonzo on Apr Tue 21, 2020 7:00 pm, edited 1 time in total.

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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Tue 21, 2020 3:47 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 3610
Location: Dallas, TX
Wow, I thought they did something about the photos on this forum. At one time they cautioned a poster to limit the
picture size to no more than 800 pixels by 800 pixels. Not too long ago the forum rules changed to allow larger because
the forum software would re-size it. This doesn't seem to work here.
When someone posts a picture that is too big it widens the size of the thread and people have to scroll sideways to
see it all.
JGonzo, I hope you can edit your last post and change the size of the photo.
There are ways to re-size your photo before posting. I think there are threads about it.

Yes, the Sprague part is a capacitor and probably a paper internal construction. Do not change the small silver caps
with the clear cases. They are polystyrene and very stable, almost like mica. There may be some caps you are missing.
The board looks like it may be a production change. With the picture this big I loose count while I scroll.

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Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Tue 21, 2020 3:51 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 3610
Location: Dallas, TX
Read this thread.
viewtopic.php?f=2&t=365653

_________________
Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Tue 21, 2020 7:01 pm 
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Joined: Apr Thu 09, 2020 6:03 am
Posts: 11
Sorry for pic size, friends. I have shrunk and re-tagged.

Cheers!

John G.


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Tue 21, 2020 10:17 pm 
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Joined: Apr Thu 09, 2020 6:03 am
Posts: 11
Is the paper capacitor something I should swap out, along with the electros?

If so, would that be .033 micro? (It doesn't have any farad symbols next to it)

And if so, it states 100 DC under the farads. So would it be a simple little ceramic cap like this one (assuming microfarads):

https://www.mouser.com/ProductDetail/AVX/SA101E333ZAR?qs=sGAEpiMZZMsh%252B1woXyUXjzLY3xaecTVtzzcy9SxCqrc%3D


John G.


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Tue 21, 2020 10:34 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 3610
Location: Dallas, TX
Much better!
I didn't even realize the board was as long and narrow.
I count six black capacitors alright. Some of those are electrolytic. That would make seven
capacitors to replace. I wonder which board design was earlier. It is possible the circuit
is the same, just a different layout. I didn't compare them. Anytime you see a circuit with
a lot of adjustments be careful, re-adjustment may require test equipment you don't have.
Many times an adjustable coil is connected to a capacitor, if you replace the capacitor the
values probably will not be exactly the same. That would mean you would have to adjust
the coil. Polystyrene and mica caps are sometimes used that way, electrolytics never.
That tubular cap is 0.033 uf. Capacitors are almost never any smaller than
1 pf (picofarad)=1 uuf (micro-microfarad) = 0.000001 uf (microfarad).
Paper caps are commonly between 1 uf and 0.001 uf ( or 1000 pf).
Larger than 1uf probably are electrolytic.

_________________
Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Fri 24, 2020 10:07 pm 
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Joined: Apr Thu 09, 2020 6:03 am
Posts: 11
Hi Friends!

Hope you are all safe and well. Quick non-electronic restoration question. On the the knob panel, there is discoloration of the metal. Is this a "cleaning" thing, or is it a "plating" thing. I didn't want to try and clean yet in case it was the latter and make it worse. See attached picture for what I'm talking about.

Attachment:
panel.jpg
panel.jpg [ 269.71 KiB | Viewed 3358 times ]



Thanks again!

John G.


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 Post subject: Re: 1st Magnavox Restore
PostPosted: Apr Sat 25, 2020 3:46 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 3610
Location: Dallas, TX
It is a little hard to tell just from the picture. Many times manufacturer protect metal finish by applying a clear
lacquer. This can wear off in spots. On thing to watch for is that the printing is just silk screened on, otherwise
you could remove the old lacquer and re-coat the metal. The better situation (probably more expensive for the
manufacturer) is to etch the metal and fill the etched printing with paint, that can be redone much easier.
See how the plate looks after a careful cleaning with a detergent water solution. Best to keep alcohol and similar
solvents away, they could remove or damage the finish.

_________________
Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: 1st Magnavox Restore
PostPosted: May Fri 15, 2020 10:45 pm 
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Joined: Apr Thu 09, 2020 6:03 am
Posts: 11
Happy to report I finished up doing my cap replacement and switch cleaning on the receiver. WOW! What a difference! Started with one dead channel and about 30% out of the other and now have lots of loud and lovely sound coming out of it, and just through the pair of old car speakers I was using for testing. The FM signal seems a bit weak across most of the range except for one local station. I'm thinking I'm going to replace the one FM amp transistor just to see if that helps. Worst case I'm out $10 if it doesn't.

Now, on to the turntable. Here's a question:

The first thing I noticed was the turntable is missing the retaining clip for the platter. Fortunately, I see that all of the washers and bearings are present. The part number for the missing clip in the schematics is different than all the other c-clips, so I have no idea what I need to get to replace it. Can anyone point me in the right direction to obtain one?

Thanks always for the time and help.

Cheers!

John G.


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 Post subject: Re: 1st Magnavox Restore
PostPosted: May Sun 17, 2020 10:07 pm 
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Joined: Apr Thu 09, 2020 6:03 am
Posts: 11
Good news! I took off the turntable mat to clean and lo and behold: the retaining clip was under it!

John G.


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