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 Post subject: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Feb Thu 28, 2019 5:12 am 
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Location: Lake City, SC
I've been in touch with some great guys over at the Talking Machine Forum about this...but need to know more. I also don't want to fill up the TMF inboxes with electronic stuff, considering electric starters are about as advanced as it gets over there.

Anyway, I have a 1924-1925 windup phonograph cabinet, gutted back in the 1980s and shipped over from England. It's absolutely gorgeous--big wood grain, carvings, twist legs, I mean it's lovely. The top opens up and there's a bin for records on the left and a spot for a turntable on the right.

I also have a Majestic Grigsby-Grunow phonograph motor, the big heavy kind 20 watts and 0.2 amps. It came from what I think was a Model 106 (I didn't junk it, someone did many years ago by the looks of things,) and the original tonearm for said Majestic phonograph with a horseshoe coil pickup. All this is original. I am aware that it will need to be rebuilt.

What do I need to do to rig this thing up and make it play? The aim here is to run the whole thing on vacuum tubes but if I must go solid-state I will. I'm fabricating a new motorboard and cutting some vents in the back for air, and have room for maybe a 10" speaker.

The TMF gang says I need a power supply, an amplifier (they suggested either Radiola parts or do a homebrew) and a fieldcoil speaker.

Also, if I can wire up a jack for a set of Baldwin headphones (in keeping with the 1920s theme) that would be great


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Feb Thu 28, 2019 5:22 am 
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Picture please.

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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Feb Thu 28, 2019 5:28 am 
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Location: Lake City, SC
I would if I could, but it's pretty late and there's an early-model Victor Talking Machine sitting on top of the thing.

I was just curious about the general circuit layout of the old phonographs. There are about two cubic feet of room for me to stuff wiring and chassis bits in there, and the motor is a dandy big one with a speed governor on it. It actually runs off of wall current.

Sorry about the lack of photos. I haven't any right now, and I haven't any electric goods installed to bother with it.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Feb Thu 28, 2019 6:07 am 
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Well, since you are not trying to restore to original. With the magnetic pickup something like this should work, and it is very low cost so you can mess around to see if will fit your needs without destroying the bank.
https://www.ebay.com/itm/TDA2030A-Audio ... SwweRbOFfH


Attachments:
rsz_audioamp001.jpg
rsz_audioamp001.jpg [ 23.5 KiB | Viewed 1246 times ]

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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Feb Thu 28, 2019 5:05 pm 
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Location: Metzger Oregon
Sounds like you want to keep a period look to this project, right? Using 1920s globe type vacuum tubes would be possible, but honestly I think using newer types from the 30s or 40s would be much easier. I'm not very familar with early horseshoe pickups, is the output similar to a more modern magnetic cartridge? Are you okay with doing some sheetmetal work and building your own amplifier chassis? If so, maybe a clone of a GE 6SC7 based phono preamp tied to a 6SQ7 first audio tube and 6V6 output tube would work, or something similar. I would think someone here could come up with a schematic for you, but that all depends on your comfort level building and wiring something from scratch.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Feb Thu 28, 2019 6:39 pm 
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Location: Lake City, SC
Thanks for the tip. I like the look of globe-type tubes but they are better used on original historic radios.

Yes, I would love to build it as a closer copy of an original-style set. Cloth wiring, Baldwin headphones, the whole nine yards--I was going to carve a grill to hide the speaker.

The machine was gutted in the 1980s and the sides of the motor compartment extended about five or six inches into the record bin. I am actually glad I can use this extra space.

The side door was blocked off by this same "restorer" and I will be using the recess behind it to cover the control panel. It will be made to look suitably 1930s.

Let me figure out how to post pics the right size and you've got them.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Fri 01, 2019 4:34 am 
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I would use Two 50L6 power tubes and a 12AX7 duo-triode tube for the preamp and phase inverter.
Those tubes can be powered with a line cord, preferably isolated by a 1:1 transformer.

If you have a couple of power transformers from old stereo tuners or tape players, they can be wired back to back for a 120 vac isolated power supply.

The schematic is simple, and you can add another preamp stage with a 6 volt triode tube for a total filament voltage of 120 vac.

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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Fri 01, 2019 1:43 pm 
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Thanks for the tips.

As you might guess from my Victrola hobby I'm about useless when it comes to inventing electronics, but if you have or know of a pretty good schematic to build the parts from I should be fine putting it together/restoring older amplifiers.

The tonearm has 200 ohm impedance by specifications but I haven't checked mine to see if the coil is open or not. Hope not.

I have been told that it doesn't need a pre-amp but I don't know...maybe for power switches I can put a pre-on and a post-off, like the old cartoonist drew up when he was ragging on audiophiles...


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sat 02, 2019 3:49 am 
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Location: Lake City, SC
OK: thanks to all who responded. I'm still hunting round and have decided on simply finding a vintage mono amp, a decent speaker, and some power switches--then rebuilding the horseshoe pickup and having a go at it.

The Victor amps of the late 1920s are enticing but I hate seeing them yanked out of original machines...some 1940s amps are showing up on eBay, designed for the old phonographs (which means 78s, yay!) I think one of them might work. They also are not as massive as the early hardware.

Speakers? I think an old radio speaker would do...

THANKS MUCHLY to them who brought up the types of tubes to use. I am hunting about for amps carrying those tubes and having a little luck.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sat 02, 2019 5:52 am 
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I suggested above a push-pull arrangement with two 50L6 power tubes because I know this works well and sounds good with an 8" speaker. But for that circuit, your output transformer needs to have a center-tapped primary, not that common in the low watt ratings.

Any AA5 radio chassis could provide parts for a single ended phono amp. The phono input goes to the volume control. The output transformer will be the single-end type for a single power tube, so you would use the 35Z5 rectifier with the 50L6, and two 12 volt tubes.

Since you're looking to buy a unit already built, you could look for a portable record player from late 40s to late 1950s. You will need to add a resistor where the phono motor is sometimes used to drop some of the line voltage.

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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sun 03, 2019 4:41 am 
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And here's a pic of the amp I think I will go with.

The price is right--the seller on eBay wants $15 and I think that's reasonable. Also, it has that most wonderfully vintage-y of knobs--the "Tone Control" and what is the point of vacuum tubes on this nostalgia-themed build without a little bit of tube tone?

While it isn't driving a big speaker--remember I work on Victrola and Edison machines most of the time and know the power of a well-made HORN for adding a bit of boost! :D

It needs a power transformer but I think I'll get it here, re-cap it and rebuild my pickup first. A transformer shouldn't be too hard to get.


Attachments:
File comment: Here's the amp--I've been reading on here about adding another tube to these, which is kind of neat.
Tube amplifier.jpg
Tube amplifier.jpg [ 174.2 KiB | Viewed 1134 times ]
File comment: The c. 1929-1930 Majestic turntable and tone arm I will be using for this project. I will be making a new motorboard.
Turntable deck from electric gramophone.jpg
Turntable deck from electric gramophone.jpg [ 27.66 KiB | Viewed 1134 times ]
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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Sun 03, 2019 7:29 pm 
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Yes, that little amp is a good start. You will need to replace that big old multi-capacitor with new individual capacitors. But the new ones are much smaller and can be mounted on a terminal strip.

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Burl Ives, RIP, oldtimer.
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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Tue 05, 2019 5:04 am 
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Your best bet is to build an amplifier using two 50L6 tubes a 12SL7 and a 12SQ7.

If you don't need that much gain just replace the 12SQ7 with an 84 ohm 3 watt resistor.

You can then use a Triad N-68X isolation transformer as that puts out 126Vac for an input of 120Vac for a B+ of around 150V.

A P-T291 output transformer will work.

Best to use a vintage speaker as they are more efficient.

I think that I have a schematic using the 50L6 tubes. Will look when I get to work tomorrow.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Tue 05, 2019 6:58 am 
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A picture of the cabinet would be nice to see.
It was never mentioned whether the cabinet still has the original horn in it or not.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Tue 05, 2019 12:38 pm 
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Here's the amp schematic I have that should work good with this.

Attachment:
50L6 push pull amp no lamp.png
50L6 push pull amp no lamp.png [ 68.15 KiB | Viewed 1070 times ]


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Tue 05, 2019 6:45 pm 
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Location: Lake City, SC
Thanks for all the tips, guys...

I'm probably restoring the little Dynavox amplifier just because.

BUT! I am going to be building this one here for my project. More power is better and four tubes is better than two.

Reading the schematic is a little interesting. I borrowed a library book on electronics and should be building my knowledge (and a shopping list.)

The cabinet has no horn left. It was entirely gutted and a 1929 Columbia 153a Viva-Tonal Grafonola was cut up and installed...the Columbia's original bifurcated horn was sawed in pieces and one side closed off with Duct Tape. It was quite sad--two really nice 1920s consoles destroyed to make one..."Thing" for to fish for suckers with.

At least I paid nothing for it. The Columbia motor and reproducer have since been sent to other collectors to repair original machines!


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DSCN5675.JPG [ 165.39 KiB | Viewed 1055 times ]
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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Tue 05, 2019 7:19 pm 
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Before building the amp I suggest you get the cartridge rebuilt then play a record and measure how much output voltage the cartridge puts out.

If the output is at least around 1 volt you won't need a 12SQ7. If it is less than a volt then maybe a 12SQ7 will be needed.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Tue 05, 2019 9:28 pm 
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Agreed, as far as I know, magnetic pickups will require additional amplification, as well as some EQ adjustment. Most of the schematics as well as the eBay auction amp will be intended for a ceramic or crystal cartridge with is basically a line level, and actually the one shown in the auction will likely need something more like 3V because it looks to only have 2 tubes, which typically would be a rectifier and an a 50L6 driven directly from the cartridge. You may want to look at the "AA4" guitar amp schematic which is similar to a simple 3 tube phono amp, but with an additional gain stage added. The schematic would be useful as a starting point for you either way. See what your magnetic pickup outputs and we can go from there.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Tue 05, 2019 11:41 pm 
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Location: Lake City, SC
Quick question: I'm playing 78s recorded from about 1904 to 1948. What kind of EQ would I actually be adjusting for? I mean, the scroll-label Victor Orthophonics were designed to be played on a windup Orthophonic Victrola...pardon my ignorance but I don't see how the RIAA Curve has anything to do with playing records from before the RIAA existed.


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 Post subject: Re: Homebrew 1920s-'30s record player...I'm clueless. Ideas?
PostPosted: Mar Wed 06, 2019 5:07 am 
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You would need to find out what curves each manufacturer used once electric amplification came out.

Then again I've played 78s with a regular ceramic cartridge without the proper eq for the records I've played and they all sounded ok to me.

I suggest trying the amp I posted as is first to see if there is enough gain.

If not then add a 12SQ7. I can update the schematic showing a 12SQ7 added tomorrow.

Either that or you could use a transformer to step up the voltage from the pickup like what was often done with the early electric pickups. That would of course be more authentic.


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