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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Mon 18, 2019 2:59 am 
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Joined: Jan Wed 30, 2019 3:44 am
Posts: 122
Location: Lake City, SC
Well, I got back to the project again after getting two 1900s Edison machines fired back up.

The cardboard multi-capacitor reads, on the side:

704

RED +40M. 150W.V.
BLUE +40M. 150 W.V.
YELLOW +20M. 150 W.V.
BLACK COM. NEG.
GREEN +10M. 150 W.V.
Mfg. By COSMIC COND. CO
NEW YORK N.Y.


I take it the BLACK is a ground.

Then, under the tubes, there are one white-cased thing marked brown/black/orange and then another dull-brown cased thing about the size of an AAA Battery marked pinky-brown/white/black/silver.

What would these parts read as? I take it the white one is a capacitor and the dull-brown might be a carbon resistor?

There is also a very large ceramic resistor reading 10 WATTS but that's pretty self-explanatory.

Thanks to all for any help identifying these--I am trying to figure out what that 10 M means. Microfarads is my best guess. And also, finding these capacitors is a little confusing...


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Mon 18, 2019 3:22 am 
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The white thing, ceramic about 2 inches long is a 10 watt 230 ohm voltage dropping resistor in series with the filaments. It drops the extra voltage since 50L6 and 35Z5 adds up to 85 volts. So the 35 volts drop across the resistor totals up to 120 volts. See my attached schematic earlier.
For the others, need a picture. Yours appears to a little different than mine. Mine has a long flexible 230 ohm resistor. See attached picture.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sun 24, 2019 5:38 am 
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Yes the M in this case stands for Microfarads. You will need to choose individual capacitors, and pick the closest values available. I usually get axial, but in some tight quarters, radial caps work better.
The working voltage is a minimum rating. You can always use a higher voltage rating and 450 volt caps are much more rugged, while being bigger and more costly.

For resistors, M usually means Megohms, (but in the 1930s, 1 M for example can often stand for 1000 ohms, what we now call 1 K. In those older schematics, megohms are labeled 'Meg', so that's a way to check.)

The white component marked brown, black, orange could be a 10K ohm resistor. Check it with your DMM.
Use this handy program, it will help you learn.

https://www.digikey.com/en/resources/co ... ode-4-band

For 3-band readings, just add a silver 4th band to get a result. Then check with the DMM. In circuit, the resistance may not be accurate, but gives you an idea if close. Lift one leg for an accurate reading.

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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Mon 25, 2019 4:24 am 
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Joined: Jan Wed 30, 2019 3:44 am
Posts: 122
Location: Lake City, SC
Thanks guys.

I also took the reproducer off. The coil is still good in it! It needs rebuilding, as any pickup c. 1930 would. The sound in my headset is very faint, but it still makes a noise when the needle wiggles.

I'll be shopping for caps next week & try to get this show on the road.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sat 30, 2019 1:15 pm 
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Joined: Jan Wed 30, 2019 3:44 am
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Location: Lake City, SC
Update after buying a DMM:

The resistor is good, testing almost perfectly to its listed specs. The coil in the reproducer I'm not sure about. I'm going to be making a new chassis I think, or moving the knobs from the current one, to make it a little more user-friendly.

And I got my capacitors for the amp, so that's good!


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sat 30, 2019 11:45 pm 
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Location: Lake City, SC
Another update (if anyone is actually following this wild-goose chase of a build).

I tried melting the pitchy stuff out of the cardboard multicapacitor to get more wire to work with re-capping it. The end result was me setting the lawn on fire & putting it out with a hose. Of course, there is nothing left of the capacitor.

And having that burnt up & out of the way gave me time to make my own. I took a chunk of heavy plastic stock about six inches long, drilled & wired the capacitors to it with paper clips, held them down with a wee dot of hot glue, and formed a very thick piece of antique copper phone line from the 1930s into a piece of bar stock. A quick polish with sandpaper, and now we have "Common Ground."

I lined my 4 new electrolytics up positive end first, then soldered the negatives to the ground. A quick snip with end cutters took care of the extra leads. Now, I will simply have to solder the black to the ground and the colors to their respective caps, but I need more wire because I set the old ones on fire by mistake.

Oh, and I got a bunch done on the cabinet! Now it has a motor board and knobs!


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Apr Mon 08, 2019 3:46 am 
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Joined: Jan Wed 30, 2019 3:44 am
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Location: Lake City, SC
A quick trip to the city dump yielded a 6x9 speaker, resistance of 8 ohms, permanent magnet type--and it works.

Some had suggested a vintage 8" speaker but I think those are better used on good restorations, not my homebrew. Is the 8 ohms going to work, you think, with my tiny little twin-tube amplifier on this thing?

I haven't rebuilt the phonograph pickup yet, there is a lot of work yet to be done on the case.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Apr Mon 08, 2019 4:00 am 
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Location: Warner Robins, GA
For the speaker you need one that is as efficient as possible and as large as possible.

That way you get the most output from that single tube.

The ultimate far as efficiency goes would be a horn, but I don't think it would sound good enough.

Another option is to get a Peerless 7-A reproducer, mount the driver inside the cabinet and capacitively couple it to the plate of the output tube with the other end of the speaker wire grounded.

Those tend to go quite loud with little power and sound pretty good.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Apr Mon 08, 2019 11:36 pm 
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Joined: Jan Wed 30, 2019 3:44 am
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Location: Lake City, SC
More info on horns would be nice. If I could find just the one ear cup from some old Baldwin headphones then I'd have a driver...and a 6x9 horn would be pretty easy to attach one to, or I could make a horn from veneers.

I'm trying to avoid busting up a nice vintage speaker like the Peerless Reproducer. If I had one of them I'd be looking for a 1920s superhet to use with it!

When I get enough wires to hook the new capacitors back up to the amplifier, I'll try the circuits & see what results I'm getting with the parts installed.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Apr Tue 09, 2019 2:36 am 
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Location: Warner Robins, GA
You wouldn't necessarily have to bust one up. If there's room where the original horn went you could put the cabinet there or perhaps locate the cabinet elsewheres.

Another option is to look for one where the cabinet is not in good shape or perhaps someone is selling just the driver itself.

Might put an ad in the classifieds here and see what turns up.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Apr Tue 09, 2019 4:22 pm 
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Joined: Nov Wed 27, 2013 5:59 am
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Location: Metzger Oregon
I would just try the 8 ohm speaker that you have already, it shouldn't hurt anything to try it, just make sure you have the output transformer from the old speaker, it may have been mounted to the speaker frame. If it doesn't perform, then try hunting down something else.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Apr Sun 21, 2019 3:52 pm 
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Joined: Jan Wed 30, 2019 3:44 am
Posts: 122
Location: Lake City, SC
Okay, update time. (And a very happy Easter to all my fellow tinkerers out there.)

I wired up everything, pretty neat to do.

Plugged it in, all good so far--I turned it on and the tubes lit up, big hum in the speakers, a fizzing pop and a puff of white smoke--then a great flash, another, and a very loud explosion filling it up with sparks and smoke--the sharp crack sounded like a small .22 pistol going off.

It's probably going to end up as a record cupboard, or I use the motor (which works great BTW) and an acoustic horn to make it go.

Musical enjoyment is unhampered, though, for I have a pair of windup phonographs on the lid!!


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Apr Mon 22, 2019 3:38 am 
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Location: Warner Robins, GA
That was an electrolytic capacitor.

Either it was wired backwards, too low of a voltage or was connected to the wrong terminal of the rectifier where it got AC instead of DC.

I had a similar thing happen before. Turns out I had wired the cap to the wrong terminal and it had AC across it.


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