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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Aug Mon 15, 2016 11:30 pm 
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A few more pictures of my Zenith 410 along side the Silver Marshall.

I've looked carefully over the two cabinets. They are similar in construction, yet quite different. There is a good possibility they were made by the same company, but I cannot find ANY cabinet makers mark on the Silver Marshall.

The Zenith, however has a distinct W within a circle. I believe this is the mark of the Winnebago Radio Cabinet Co. of Rockford, Illinois who did manufacture radio cabinets for Zenith.

To quote this source...
http://www.ulib.niu.edu/reghist/rc%2057.pdf

Quote:
Winnebago Radio Cabinet Company
On July 28, 1928, C.J. Stuart, Elsie Broitzman, and Mrs. Marie Bowman incorporated the
Winnebago Radio Cabinet Company with $50,000 of stock "to manufacture, buy, and sell radio cabinets and other wooden case goods." The company changed its name to Rockford Period Furniture Company on December 10, 1932.


The only clue which indeed is distinct between the two cabinets is a 3 digit number scribbled onto the two front flanking panels on the inside. Each panel has "372" written on the Zenith, and "381" written on the Silver Marshall.
This was probably to identify parts during construction.
Unless other manufactures used the exact same method with a 3 digit number, this could be a strong clue to it being made by the Winnebago Radio Cabinet Co.

As I said, no other marks appear in any way shape or form on the SM, but the Zenith has the W within a circle in 3 locations.
So, I don't know.

Any thoughts?

-Steve


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winnebago.jpg
winnebago.jpg [ 79.71 KiB | Viewed 2077 times ]

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Sep Mon 18, 2017 1:20 am 
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I bought another one of these from Hagstar at Kutztown. His has a GOOD variable cap!
However, the speaker situation on his is quite amusing! :P

At least I can make one good original complete radio. However, I would like to see them both whole. We'll see..

The power transformer in Hagstar's has also been replaced…. by a Scott transformer? Its huge and chrome plated.

Funny how I've been eyeballing 3 gang variable caps for the past year…

-Steve


Attachments:
480variablecap.jpg
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clarion480kutz.jpg
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clarion480kutzb.jpg
clarion480kutzb.jpg [ 85.97 KiB | Viewed 1912 times ]

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Sep Sat 23, 2017 4:37 pm 
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a bit of difference.


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two-gangs.jpg
two-gangs.jpg [ 97.89 KiB | Viewed 1862 times ]
bad-gang.jpg
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good-gang.jpg
good-gang.jpg [ 122.81 KiB | Viewed 1862 times ]

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Sep Sun 24, 2017 6:19 pm 
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I guess I've lost something here, or this is an unpopular thread now…

Yeah, as I had the thing out, I went ahead and recapped it.
Other than an open audio driver transformer, all seems well (besides the distorted variable cap gang)

I powered it up, and wow does it hum! The chassis that is, not the speaker. Seems to be coming from the main filter choke.
I'll see if I can tighten the laminations, though I wonder if part of the reason is there is no filter cap off of the rectifier?

Anyhow, powers up, all voltages look good, but nothing…. nothing at all.
I poke around the audio and notice I get nice popping out of the speaker if I touch at the plate of the 1st audio amplifier, but NOTHING on the grid.
Again, voltages are close to what the schematic calls for.
I lift the grid, and yeah, I get buzz, but once hooked back to the volume control, nothing.

Puzzling puzzling...

OK, finally after a lot of trial and error, I try something off the wall. The cathode goes to a voltage divider with 42 volts through a 5K resistor. I shorted out the 1500 ohm section and WHAAAA the radio comes to life!

Yeah, the volume was up and I got an earful! This radio can really belt out the sound!

So, yeah, I look up the 56 triode and bias should be around 13 volts…. 42 volts bias will certainly put it in cutoff, but thats what it calls for. What the heck?!?!?

http://www.nostalgiaair.org/pagesbymode ... 021860.pdf

Anyhow, its a working radio if I bypass the 42 volt tap on the voltage divider. Seems to be pretty sensitive :D

I don't get it…

-Steve

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Sep Sun 24, 2017 6:46 pm 
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Nothing lost I think. But somehow I missed your update to this thread. Perhaps explainable as I was in NC last weekend and only getting about 15 minutes a day to read ARF from my phone.

That is puzzling. I concur that it does not seem to follow typical application of the 56 tube. Have you looked for any updates that might have been published? Also, you didn't find the circuit hacked, and the radio obviously did work.


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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Sep Sun 24, 2017 7:35 pm 
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Thanks Rodney! I was just puzzled that nobody commented after I updated it two different times. No worries though :wink:

Well, I just figured it out!
I didn't put the Tune-A-Lite back in!
It needs to be there as it feeds bias to the grid of the 56!

Wow… I completely missed the fact that it has a 4 pin socket and one pin goes to the 250K and 150K resistors in the low end of the volume control circuit.
This increases the grid voltage to about 26 volts!

So, the cathode voltage is about correct, but the grid should be 26 volts, NOT .1

Holy cow! That circle is a Tune-A-Lite contact, not a junction.

Well, learn something new everyday! :D

OK I can move forward now.

-Steve

EDIT:
And a 2.2 uf @ 630V between the 5Z3 end of the filter choke and the center tap of the HV winding silences the buzzing choke.
I tried a 1.0 uf but it still buzzed slightly, 2.2 uf quiets it completely.

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Sep Mon 25, 2017 12:53 am 
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Yeah, I know there are still some paper caps in there, but here is what I have now.
Its working pretty darn good!

The Tune-A-Lite is so silvered over you can't see much glow. :(

I know, I've not done any stuffing here. It takes time and I just wanted to get this one going.

-Steve


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underchassis.jpg
underchassis.jpg [ 106.24 KiB | Viewed 1833 times ]

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Sep Mon 25, 2017 2:45 pm 
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Hi Steve!
Glad to see that you are really coming along with the unit!! Quite a bit different than working on a Zenith, eh?? Certainly makes much more challenging.
Cheers!!
Joe


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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Sep Mon 25, 2017 3:40 pm 
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Thanks Joe!

Yes, definitely different than a Zenith, though it is interesting how much TCA went to make it "look" Zenith.

I believe the reason for the Tune-A-Light tuning indicator being wired into the volume control was to offer a QAVC function like Zenith did.
But, the thing is so worn out, its useless now. Just glad it lets the audio amp stage work.

I know Atwater Kent also used one of these for a QAVC function. This is my first experience with the little tube. Wish it was good. :wink:

-Steve

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Sep Mon 25, 2017 10:15 pm 
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How nice…

The power transformer just gave up. :(

-Steve

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Sep Mon 25, 2017 11:13 pm 
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Hate it when that happens. Now I power up everything on my Sencore Powerite and carefully monitor consumption. It's saved at least 1 transformer for me, though it's not fool-proof.

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Sep Mon 25, 2017 11:46 pm 
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Does the power transformer heat up when there's no rectifier tube plugged in? If it doesn't, it's saveable.

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Sep Mon 25, 2017 11:58 pm 
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It is odd, the set was playing fine, then suddenly silence.

I could smell that sickening smell of a transformer burning. Pulling the rectifier I get 10 volts on the HV winding and about 2 volts on the rectifier heater winding.
It was quite warm, but it does have the 5Z3 and two 59s next to it.

I've yet to take it apart, but I worry there is little hope.

-Steve

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Mar Wed 28, 2018 2:33 am 
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Yes, I know 6 months have passed. I go at things slowly due to life… Much to my dismay… :(

I've been trying to keep an eye out for a suitable replacement, which will fit, and supply proper voltages, but so far I've found nothing.

I've contacted Heyboer and they gave me a quote for replacing the transformer. I've decided to do it!
I await further instructions from Heyboer.

I felt this radio was playing very nicely when i had to up and going. Its worth it to me to get it finished after all I've gone through.

-Steve


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bobbina.jpg
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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Mar Fri 30, 2018 12:56 am 
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That's great you will get it going again, keep the updates coming! Will that new transformer look different or will it look similar to the original?


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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Mar Fri 30, 2018 1:14 am 
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Thank you!
I am sending the top and bottom shell as well as the bobbin to Heyboer. (The bobbin will be dissected will help them understand the ratings) The core and laminations will be new, but with the old shells, it should look like the original.
Maybe stacked a bit higher for a more cooler running transformer.
It shouldn't look out of place.

Not like that Scott transformer on the other chassis, Wow!
It just didn't have the right windings for proper operation.

-Steve

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Mar Fri 30, 2018 2:21 am 
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Maybe you'll be starting a trend. The next generation will begin to re-stuff the transformers for peace of mind, similar to how we re-stuff the capacitors today. :)


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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Mar Fri 30, 2018 6:59 pm 
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Steve,
Good luck with the transformer. This is the first time I saw the post. They are beautiful radios.
Henry


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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Jun Wed 13, 2018 4:47 pm 
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Thank you Henry!

Yes, I know this is a delayed response.

Heyboer still has the transformer. I'm not sure how long to wait on it.
My recent order from EDCOR took 11 weeks. i suspect Heyboer is much the same, perhaps longer?

I know, be patient :)

-Steve

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 Post subject: Re: Silver Marshall Mfg 4802 console
PostPosted: Jun Wed 13, 2018 7:15 pm 
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Steve, I admire your perseverance.

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