The Secret Society of Lathe Trolls

Hi,

Did that rotatable 3D model I posted a link to not work or was it confusing or need more clarification?

Mark

Hi, I used a gap filling CA (super)glue. But other glues might be better (e.g. JB Weld or other epoxy). I glued the stylus holder to the driver and aligned it with the driver after mounting it then finally I glued the stylus shank to the holder after everything set. Make sure you have the stylus in ...

Hi, So far, the only mod I made to the board is to increase the resistive load (R9) on the ceramic pickup from 220K to 1Meg. That gets the bass response back. I have found that my cheap USB supply has quite a bit of 60 hz ripple and it becomes audible once you open up the lows. When I ran the board ...

Hi, Great work! I never had much luck with a piezo pickup (but don't let that stop you from trying). On the plus side its very high output. But, its also very high impedance, so its hard to shield from the stray fields. On top of that, the common pickups on the market today are not very Hi-Fi, so I'...

Hi, I've attached a PDF of the schematic that I traced of the circuit board for the PO-80. It's a pretty nice design. A boost converter to bump the 5Vdc up tp 12Vdc to run the platter motor. I class D 5 W audio amp and a preamp for the ceramic pickup. One thing I noticed is that they load the pickup...

Hi, The wow and flutter should be somewhat additive if you record and playback on the same system. I expect that the wow and flutter to be worse during embossing. If I get time over the weekend, I'll measure the wow and flutter when embossing with playback on a decent turntable. I have not tried to ...

Hi Everybody,

Here is a link to the Fusion 360 Project for the head.

https://a360.co/3gvbmgg

Mark

Hi, I measured the wow and flutter with just the playback arm and its pretty bad. Here is a screen shot. Wow and Flutter.png You can see the unweighted comes in around .6% From the scope screen, you can see there is a major 25 Hz component that corresponds to 1500 RPM, which is about the motor shaft...

Hi,

Looks to me like the motor runs right off the AC mains. From the schematic, it looks like the amp and motor each have their own power switch and can be run independently.

Mark

Hi,

Here you go. I can also provide Fusion project files if you think you could use them.

Hi, Just connect right to the wires going to the cutter head. No need to get into the K8 amp at all. Any 50 watt or greater mono amp will do fine. Might want to put a in line fuse holder and start with a 1/4 amp fast blow fuse until you get the hang of how much power you can throw at the head. Mark

Hi Everybody, When the PO-80 came out a few weeks ago, I decided to grab one and see if it could be hacked to get better performance. I put the kit together and played with it for a bit and then went to work upgrading it. Rather than be stuck with buying blanks and cutting styli from Teenage Enginee...

Why do you want to decrease the torque. Is the servo unstable with the smaller platter?

Hi,

There is no need to make them round. Especially for testing. Just cut them as squares with whatever means you have and drill a hole.

Mark

Yes, monitoring the input signal.

Let us know what you find after playing with this.

If this meter was designed to connect parallel to the head, it would not cause any significant additional loading. Its really just measuring the AC voltage at the drive coil just like any analog voltmeter. Its also possible that it was designed to be located at the input to the power amp (line level...

That looks correct, but you should test carefully using a signal generator and an AC voltmeter to see if where the 0 dB reading is at. Also not sure what the other terminal is for. Perhaps one terminal is 500 ohm and the other is 8 ohm, since the meter has both scales.

In the states, its the green wire ground. This is the single round contact, not the two flat ones. There are adaptors that allow you to lift this ground. They are designed for older two prong AC outlets. Not sure the equivalent exists outside of the US. This is not a long term safe thing to do. It i...

Hi,

Any light dimmers nearby? If you float the safety ground with the inputs unplugged does the buzz go away? If you have dirty AC mains power, perhaps a good line filter would help.

Mark

Hi, I thought about using a low cost Chinese metal lathe for that purpose some time ago. I still think it would be a great idea. I don't think a wood lathe would be as good a base as I don't believe they have feed screw and half nut to move the carriage like metal lathes do (but I could be wrong her...