Old phonograph needle wiring

[dscottguitars]

Hi,  I have an old tube record player I am trying to 'rebuild' for my nephew who is really into vinyl these days.  I have put together a single ended 6aq5 amp for the unit and now I'm ready to 'figure' out the needle wiring.


The needle has four wires:


yellow: not hooked to anything, just a terminal
blue: not hooked to anything, just a terminal
red: hooked up to volume pot
black: hooked up to pin 2 of a 35w4 rectifier, going through a 0.05uF cap to pin 3 of a 50eh5 tube and that has a 0.05 cap going to ground


That black wire is my main confusion.  What are the connections to the heater of the 50eh5 tube and the two caps for?  Are the caps necessary?  I'm inclined to believe the black wire is a ground wire, but would like to know more.


I can't find a schematic anywhere.  It's a Steelman Model 2-1232-1. 


Is it just as simple as any pickup with a one lead to the volume and the other to ground?


Included is the schematic of my amp.

[sluckey]

Is it just as simple as any pickup with a one lead to the volume and the other to ground?

Yes it is. Don't let the wiring of your old amp confuse you.

However, 4 wires from a needle (actually cartridge) kinda suggests a stereo cartridge. Are there actually 4 wires connected to the cartridge? If so, you will need to tie the two pairs of stereo wires together to feed into your mono amp. Otherwise, you will lose one of the stereo channels.

There are other ways to convert stereo to mono, but a pic of your actual unit would help decide the best way. I assume since you mentioned 35W4 and 50EH5 that this is a low end portable record player?

[dscottguitars]

I think it's too old to be a stereo record player.  The blue and yellow wires have connectors on the ends by the needle but are not connected to anything and they go to a terminal strip and not connected to anything there either.  Only the black and red wires are connected to the needle.


I'm sure it is a low end player, probably for a kid's bedroom.  That's why I'm putting in the amp. I am putting a guitar input jack and extension speaker jack for my nephew to use it as a practice amp too and play along with records if wants.


Thanks for your help!

[sluckey]

Only the black and red wires are connected to the needle.

In that case it's a very simple hookup.

BTW, why are you using a 4 watt resistor between the input jack and preamp grid?

[dscottguitars]

I got a hundred of them really cheap, for $15.  I get asked that question often...LOL

[PRR]

> It's a Steelman Model 2-1232-1.

That is a very basic HOT-CHASSIS mono player.

The original did NOT have a power transformer, and no preamp(!).

I ass-ume you plan to abandon the onboard amplifier and play through your 12AX7/6AQ5 amplifier?

The original needle was Ceramic, and most likely Sapphire, and by now most likely a groove-gouge. I would not put a record under it.

The original needle is probably a so-called "High Output" (to avoid needing a preamp); a very strong signal.

For more fun, the 2-1232-1 fed the motor and the 25EH5 heater in *series*. So the motor is wound nominal 92V 60Hz AC.

A 50EH5 may be a mistake or an alternate design. Really hard to guess at this point.

Yes, the needle should be just 2 wires. Maybe a ground too, though the hot-chassis design makes this less likely. 4 wires suggests some post-1960 retro-fit.

The original had the needle "common" returned to an R-C network to "B-" for less fatal shock (and better EH5 drive). In a true isolated-power amplifier, this would be your common ground.

[dscottguitars]

That schematic does not look like what I have.  As you can see in the picture the brown AC wires go to the rectifier tube and continue to a phonograph switch and then to a transformer on the phono chassis.  Per your description I think the voltage issue (92v) is not relevant here.  Your schematic shows a diode I am assuming is the rectifier.  You can see I've already cut out much of this amp.  The copper colored amp is the one I'm using and the schematic I posted. 


I guess I should get a new needle?

[PRR]

> does not look like what I have.

Steelman made at least 101 models, more than half of them in 1957-1960. The listing is confusing and may be wrong.

I assume you know the motor works without a tube. Then your only issue is needle wiring.

The only "needle wiring" I see in your pix is maybe the shielded(?) lead coming in lower-right of picture 100_5413 going right to a tube pin.

Personally, if I was going to play any records on this, I would get a new stylus. (I have some potentially valuable disks ruined by playing with over-worn stylus, typical of low-price players. Every time Desmond hits a high note it sounds like a boiler split open.)

Sometimes a whole new ceramic cartridge is about the same price as a stylus. Exact model is not critical, since you can cobble a mounting, and your new amp has way-ample gain for any of them.

That new cartridge may come with connection diagram. I suggest you get stereo (even for mono playback). Wire L and R together. Some were 3-wire L G R. Some were 4-wire L LG R RG.

Some clip-lead experimentation will tell what pairs-of-pins are live. Some listening to known-stereo recordings will suggest if you are getting both channels, just one, or both but no middle (out of phase). This will be hard because $1.99 cartridges had poor stereo separation and balance.

--- They aren't $1.99 no more!! Of the low-price end of that list, I'd think about "RCA 115050 115059 type Electro Voice 264" or "Astatic 51-1 51-2". If he will be putting more than 50 hours play on this thing, he really should get the Diamond (a $10 option on the 51-1) or spare sapphire needles.
____________________________________________


> I think it's too old to be a stereo record player.

Both were available at the time.

Evidence is that this is mono (just one power tube).

However, it comes to me..... the 60FZ5 and 50EH5 were *designed* to reduce the cost of a stereo record-player from three audio tubes to two audio tubes. They have high gain, and combined with high-output needle (developed FOR this application), you avoid a preamp bottle, a major savings in this market.

OK, you are making 30 models a year, stereo from $59.95 to $24.95. How do you make a $19.95 product? You make a mono, but using the in-hand parts from the low-cost stereo machines. So it is oddly possible that the original needle was a (hi-output) stereo cart with a mono amplifier.

The machine I mistakenly cited had two speakers and probably touted that fact loudly (not mentioning there was only one amplifier channel).

[PRR]

Just found this:

http://www.amazon.com/FEO-Turntable-Ceramic-Cartridge-Diamond/dp/B00R6DBKZ8

A no-name copy of an Audio-Technica, "with diamond Noodle", $13 shipped from China.

Pins seem to be marked R+ R- L+ L-, you can figure it out.

Mounting not clear. (One 3-star review notes "not universal", duh.) I suspect it is in two parts, the gut and a snap-bracket. If not, be clever, or use Shoe Goo. If the noodle is really diamond, it is permanent enough. If the user becomes a 19-hour/day record hound for more than a few months, he will want a much better turntable anyway.

Also this:
http://www.amazon.com/Crosley-Magnavox-Phillips-Ceramic-Cartridge/dp/B002W2EH12/ref=pd_sim_sbs_267_19
$21 shipped. 4.4 stars from customers. Does not say what kind of gem the noodle is. 4.4 stars. Whole store behind it which I did not explore.

_______________________________
The better type of cartridge is "magnetic". Less stress on the record, and potentially flatter response (though this has been debated for over 60 years). Easier to find needles for today. Not so very hard to find whole good turntables in attics with magnetic carts in them; and new mag-cart turntables are not more expensive than many vintage ceramic cartridges alone. BUT a mag-cart needs a RIAA Preamp (not a guitar preamp). While preamp hacking can be fun, many-many-many hours of fun, this will set you up fast:
http://www.amazon.com/PYLE-PRO-PP444-Compact-Turntable-Preamp/dp/B004HJ1TTQ/ref=pd_sim_sbs_267_47
$13 plus shipping.

[dscottguitars]

Thank you!