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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Thu 07, 2019 4:50 am 
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TR's push/pull 50L6 amp is an excellent choice if you have the output transformer for it with a center-tapped primary winding.
But to rebuild the amp in your picture, search for a design that uses one 50L6 with a 35Z5 rectifier.
Some examples here, I used the search feature top of this page, "3 tube phono":

http://www.antiqueradios.com/forums/vie ... 6&t=192303

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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Thu 07, 2019 6:11 am 
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Location: Warner Robins, GA
As I recall the particular output transformer I used is under $20 and the isolation transformer is relatively inexpensive as well.

I was working on a version using 200Vdc B+ but that requires a 140Vrms transformer to get 200Vdc unloaded and I would have had to have one built by Edcor and their design fee isn't worth it to me for one transformer.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Thu 07, 2019 5:35 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Why not restore it to original condition and operation?

http://vrps.org/documents/Radio%20Repair%20Shops.pdf


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Thu 07, 2019 6:49 pm 
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Joined: Jan Wed 30, 2019 3:44 am
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Location: Lake City, SC
Of course that was my first choice, but the %&@($!! hack that worked on it in the eighties managed to rip out all internal workings including the horn, and move the record compartment door over a ways. If I knew the make & model I could fix it as I do accurate restorations of windup phonographs.

I am unable to find a maker's mark on this. It was what is known as an "assembled" machine, put together from generic parts and sold under whatever make the dealer wanted--private label, music store, sporting goods shop, whatever.

Restoring it would be impossible because I am unable to find what model it was. Even the hole for the crank had been "filled and drilled" because this thing has had 2 motors in it.

I am fixing it up basically 1) as a way to keep it from being junk & give it purpose again as a record player, and 2) to make a landing spot for some wonderful old electrical gear! I am trying to buy parts that weren't sourced from restorable machines. My motor came with so much barn dirt and weeds seeds in it that the spindle wouldn't turn, for example. It works now, though!


Did get some headphones today--an old Alnico Magnetic, working, and a Superior by C. Brandes, not working due to missing wires. The Superiors are super heavy!

Also, I got some headphones for it.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Thu 07, 2019 6:56 pm 
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Agreed with you.

Sometimes all you can save is the cabinet.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Fri 08, 2019 9:18 pm 
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How large is the speaker that you plan to mount in this cabinet? Sorry I didn't think of this sooner, but in my experience, anything smaller than 8" diameter doesn't really benefit from a push-pull amp (ie 2 50L6 tubes). While the tubes are cheap, if you decide on a single ended design, parts from a salvage radio should cost almost nothing. Just a thought... btw I have done the same thing - taken a cabinet that was beyond repair and used it as a starting point for a project. Beats seeing them go to the firewood pile!


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sat 09, 2019 12:44 am 
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Location: Lake City, SC
Thanks, guys, for all the comments, criticism, and compliments. Like I said, I'm an acoustic phonograph man. This electronic stuff is a new world for me but I have a tiny basic amount of knowledge--plus what I'm cramming in daily!

My amplifier came the other day. It is super cheap and came on a pressed tin chassis all wired up and ready to go...fifty years ago. I need to re-cap it before I see if it still works.

The tube compliment is a 50L6 GT by General Electric and a 35V5 by National Union Electronic Tube. (Did I spell that right? It might say 3SV5 or 35VS. Hard to tell with that grease-pencil style font.)

There is a hole in the chassis for a third tube socket never wired up. In the place of this third tube is a CER-OM brand 10-watt ceramic resistor. There is no power transformer so I think this is a "hot chassis" amplifier. Might put one of those little transformers on if y'all can tell me how to put it in. All the knobs are there but I am going to put them somewhere else in the machine and then run jump leads from them to the amplifier.


SPEAKERS! Everyone loves 'em. I don't know whether to drop in an 8" speaker and mount it up behind a grill where the old horn used to be, or to buy a new horn from tubesandmore.com and find a very sensitive driver for it. I think they're compression drivers, amiright? A phonograph collecting buddy of mine told me that radio horns back in the 1920s were basically headphones in a horn, and I know that my old Edisons, Victrolas, Victors and Columbias can produce wallpaper-peeling volume & incredible fidelity with basically a candlestick phone diaphragm.

Also, I have heard tiny amps described as "headphone amps."

Enlighten me if you get a minute. I'm still not sure what I am doing but this is kind of fun. The other day I think I found out which wires from the amp's volume pot should go to the tonearm...that's the part I almost forgot; how to get input to the machine in the first place! Ha!


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sat 09, 2019 4:38 pm 
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Your amp is basically this circuit.
The 10 watt resistor is the filament voltage dropping resistor. 50(L6GT) + 35(Z5) = 85 volts, so the resistor drops an additional 35 volts for a total of 125 volts.

Quote:
The other day I think I found out which wires from the amp's volume pot should go to the tonearm...that's the part I almost forgot; how to get input to the machine in the first place! Ha!
The schematic shows you how the tone arm is wired.


Attachments:
rsz_recordplayer.jpg
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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sat 09, 2019 4:55 pm 
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In addition to the schematic I posted here is a hand drawn schematic showing a tone control, which yours may or may not have. Otherwise the same.


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RecordPlayerTone2.JPG
RecordPlayerTone2.JPG [ 95.91 KiB | Viewed 382 times ]

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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sat 09, 2019 6:27 pm 
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Location: Lake City, SC
Thanks, Paul. Mine does have a tone control, I think--two knobs, one on/off/volume and the other doesn't really do anything. Of course I have not fired up the amp.

This should go okay but I need to build a motorboard to hang the tone arm & turntable from, then rebuild the 1929-1930 horseshoe coil pickup, then re-cap the amp & wire the thing up and find a speaker...lots to do but I'm going to do it.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sun 10, 2019 1:23 am 
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Joined: Jan Wed 30, 2019 3:44 am
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Location: Lake City, SC
Good news!

Today I hooked up the amp, the motor, and a set of jumpers, plugged the mess in, and turned on power from a surge protector.

The motor kicked over instantly running smooth and quiet. The tops of the tubes glowed and, once they got good and warm, the speaker began buzzing loudly. I had not hooked up input, but think I was hearing the bad capacitors not filtering out AC current--it was a deep 60Hz buzzing. I have heard it before from fluorescent lamps.

Good stuff! I gotta recap this thing, fix up that old reproducer, and find a bigger speaker. Might be onto something.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sun 10, 2019 5:52 am 
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Congrats so far, nothing burned. :lol:
Whether one stage of amplification is enough will depend on your phono cartridge. A crystal or ceramic cartridge might work. If you are using a magnetic cartridge, you will need another stage, a triode tube, ahead of the 50L6.

Somebody correct me if I'm wrong. :lol:

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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sun 10, 2019 6:19 am 
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Yes, I was glad nothing got toasted. Watching those tubes wake up was magical. :D

EDIT: Did some digging...I have a magnetic pickup (not a cartridge, not removable & takes singleuse Victrola needles) and they can, supposedly, be almost as potent as crystal pickups regarding output voltage.

I think once I get a motorboard in her, then I can start rebuilding the pickup and recapping the amplifier.

Any recommendations on a nice speaker? I'm still not sure on the horn vs conical speaker question and am needing to know so I can plan the internal arrangements of my new-vintage guts. Anything cheap, old, efficent, and big sounds ok to me. I have room for an 8" at least and could squeeze a horn in there.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Mon 11, 2019 1:24 pm 
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My suggestion is a vintage 8" speaker.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Mon 11, 2019 4:52 pm 
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Stick with the speaker that came on your amp until you get it working. You need at lest 1V PP output from your cartridge to work with that single stage amp.

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Last edited by pauls.ironhorse on Mar Mon 11, 2019 6:02 pm, edited 1 time in total.

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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Mon 11, 2019 6:01 pm 
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Here is a shot of my vintage 50's record player under side, looks the same as what you bought. Also is a scope shot showing the cartridge output playing a 45 RPM record, you can see it takes a really high output cartridge, scope at 1V per division. (Directly on cartridge output befor amp)
Quote:
(not a cartridge, not removable & takes singleuse Victrola needles)

My cartridge was not removable or replaceable, had to fit in one from V-M Audio.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Tue 12, 2019 4:40 am 
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Thanks, Paul. I thought the note is interesting, too, about a "spring tension adjustment" "which wasn't handy" in 1962.
Or was he saying "I wish I wasn't handy!" :lol:


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Paul Irnhrs phono amp note.jpg
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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Tue 12, 2019 12:19 pm 
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Neat to see it set up the way it should have been originally.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Tue 12, 2019 4:56 pm 
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Quote:
Neat to see it set up the way it should have been originally.

Here is the restored (but no refinishing) record player for my granddaughter. She wanted one like her teenage mom used.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Wed 13, 2019 1:42 am 
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I like the slim design. The speaker blasts upward, not the greatest acoustically. But .That's a cool gift!. 8)

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Burl Ives, RIP, oldtimer.
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