Hacking The Teenage Engineering PO-80

[Skwoz821]

All right, I tested it on a poly carbonate (CD) disc, instead of polystyrene.
Behaves a lot better, but there’s still a squeal, however, at much lower volume.
I’ll attach my results, I’m too afraid to damage my needle.
Just gonna wait till one of you can give me some advice.

[markrob]

HI,

Sorry about the delay responding. I was away on vacation and then came down with the flu. I'm still recovering, so give me some time to respond better.

Looks like you did a nice job getting that fabricated (the prints look a bit rougher than my resin printer, but that shouldn't matter). Are you using a screw to clamp the shank to the driver? I used an 0-80 screw on mine. You really want everything to be tightly clamped. If there is any extra play, that could cause the screeching. The angle looks pretty good. You could try a bit more of the stylus sticking out to increase the back angle. I was adding of weight (~25g) to the top of the arm. You may need to experiment. I assume you have removed the adjustable tensioning mech from the arm so there is no upward force. I don't think you can damage the stylus unless you drop it on a hard surface. Its ground to a cone shape, so the tip is pretty sturdy. Still, you are right to use caution.

I did all my testing on CDR blanks. What are you using?

I was using my home made embossing styli, but I have one of Mike's here and when I feel better I'll give it a try.

Mark

[Skwoz821]

It appears I have sorted it out.
I found that removing additional weight solved all my problems.
I have the tensioning mechanism on and set to 1.1 to 1.3 cm. Anything more and I start hearing noise.
The cut is dead silent now and appears to track perfectly fine on a real turntable.

I have everything screwed and tightened down, yes!

Perhaps my 3D printed parts weight more than yours?
They seem rather negligible in weight though.

I’m using CD-Rs as testing blanks!

[markrob]

Glad you got this sorted out. I think you did the right things to troubleshoot the issue. I've found that there is not an across the board correct downforce number that works. There are so many variables that you need to find the operating weight by trial and error. Too little weight and and you don't track. Too much and noise occurs. The window can be small sometimes.

Mark

[pennstate913]

Printed your parts out Mark and have managed some pretty good cuts using a 50w and 100w amp, many thanks for the stl's. I've started working on making a larger version to cut 7" blanks. I've attached a sample and a pic of the many iterations of gear track til I figured out the dimensions correctly

[farmersplow]

it's incredible what can be created from a toy with "hacking", love and hard work. Congratulations to all who worked on this project....
Thomas

[markrob]

Printed your parts out Mark and have managed some pretty good cuts using a 50w and 100w amp, many thanks for the stl's. I've started working on making a larger version to cut 7" blanks. I've attached a sample and a pic of the many iterations of gear track til I figured out the dimensions correctly

Hi,

Glad you are getting some good results. I love your updated rack for the overhead. If you get that sorted out, please post the stl files.

Mark

[Skwoz821]

Here is my mod to cut 7 inch.
You'll want at least a 1.5mm blank however, preferably 2mm.
All done from adapted stock parts, cuts perfectly for me.

https://www.youtube.com/watch?v=4ZfgoAuWMlQ

[markrob]

Hi,

I was Inspired by skwoz821's 7" mod and came up with my own. In this version, you do not need to make or change change the rack. Just remove the two small screws that hold the head slide and bolt my all in one head mount in its place. It seems to have plenty of clearance for a standard 7" 45 and the rack has enough range of motion to reach the label at the center. The downside is that you can't slide off the head assembly via the clip on method of the original. You can go back to the original by removing the two screws. I'm assuming once you change to a 7" system, you would not want to go back. I have not tried to emboss yet, but based on the results posted here, I'm assuming that will be no issue.

Here are a Fusion 360 render of the model, two views of the completed 3D print in place, and a zip with the 3 parts in STL format needed to make the extension. You will need to drill out the two holes that take the head pivot shaft to 2mm. The model prints with two smaller pilot holes. The head mount is clamped and glued to the base. I used CA glue. The clip might need some sanding or shimming to allow retaining bump engage properly and is attached via #4 or similar hardware. It could also be glued in place.

Mark

[kugelblitz]

Thanks for posting these parts! It almost seems to me this tread could be pinned in the newbie forum, since it's a cheap but more and more functional entry point into the world of lathes.

[markrob]

Hi Again,

Now that I have the 7" adaptor, I was finding that operating the small button on the rack was difficult. So I came up with an extension to allow me to press the button with the blank installed. I've attached some Fusion renders, a photo of the device in place and the STL files. If you print this, I would use 100% infill and you will need to tap 3 holes at 4-40 or similar metric size. 2 holes on the side of the slide and one hole on the clamp. The two side holes are used to clamp a rubber band that servers as the return spring. I used CA glue to position and attach to the case of the PO-80. I placed it so that when the actuator is fully extended the arm just sits on the orange button. I used gap filling CA glue and held in place for about 1 minute to allow the glue to set. I would wait 24 hours for a full strength cure. Note that my clamp is a bit thinner than the current STL. I used a 4-40 x1/2" flat head screw for the slide and 4-40 x 1/4" for the clamp screws. The rubber band I had here was about 1mm x 3mm IIRC. Clamp one side wit the screw, pull to desired tightness and clamp with the other screw.

[markrob]

Hi,

Now that we can do 7" cuts, I wanted to see if I could increase the LPI from what I measure as about 89 to 120. I have modeled and resin printed a replacement pulley that does that. This gives you about a 35% increase in cut time possible. For the NAB standard 45 rpm 7",the start of audio is at 6.56" diameter and the end is 4.25". That gives about 1.16" of audio. At 89 LPI, that gives you 2:18 minutes of play time. At 120 LPI, you get about 3:05. See the microscope photos and a picture of the pulley in place along with STL file below. This should be printed on a resin printer to preserve the details.

Mark

[CutR]

Fantastic work Mark, your really spoiling us with your gakken/PO-80 mods and single handedly have up the game and value if this little machine. There is no lathe that one can purchase under a $100 and with a few mods be able to cut 7"s just like that, ok you might able to get a beat up Wilcox-Gay or equivalent for a little more and be able to cut 12*s as-well but certainly not an ATOM or VANROCK which of course is a much better machine hence the prices they go for.

Once again thank you Mark and keep up the sublime work, going to get the new pulley and actuator printed up this week.

[farmersplow]

... but certainly not an ATOM or VANROCK which of course is a much better machine hence the prices they go for.

I'm not so sure about that anymore ! If Mark keeps it up, he'll soon be cutting 14" stereo in copper !
Great work Mark!

[markrob]

Hi Everybody,

Thomas, thanks for the kind words. The work you are doing is incredible. I'm following your progress. Looking forward to seeing the finished lathe.

It was brought to my attention, that I left out one of the STL files for the actuator. The zip attached here has the correct set of 3 files.

Mark

[pennstate913]

Mark what are your thoughts on using a small stereo cutting head? I've been trying to model up an arm that would work with the additional weight/load without coming up with anything "decent"

[markrob]

Hi,

I don't see why not, but if you are embossing, the stereo separation is vey low. I heard some theories on why that is so (e.g. U shaped grooves vs. V shaped), but I've never dug into it to see if that is really true or if could be improved. It would be a challenge to get the size and weight reduced so that its practical.

Mark

[pennstate913]

The one on the left is the head I made using the same sized driver from the Gakken. Both actually currently have Gakken styli fitted too. Have tested that they "function" but only crude 'tattoo' style cutting since I don't have the mounting arm or carriers made yet.

[markrob]

Hey,

That looks nicely done!

I checked and Dayton has a smaller exciter that has a 9mm voice coil vs. 13mm that I used. One drawback is that its BL product is about 1/2 of the 13mm driver. That might be made up for since you will be using 2 drivers. Also, the Gakken head design has about a 3:1 mechanical impedance reduction due to the lever design of the stylus mounting. This forces the driver to make a much larger excursion to cause the stylus tip to move. On the plus side, it makes the head very stiff against the cutting or embossing media at the expense of needing more drive current. The direct coupled stylus of the stereo head requires much less driver excursion, but will be more affected by the media. The physical OD is ~21mm vs ~26mm Check out P/N DAEX9CT-4

Mark

[Skwoz821]

Excellent work, markrob!
I'm glad my 7 inch idea was useful!
Nice to see a 3D files for groove pitch!
I had rolled a bunch of tape on my gear to increase runtime, worked better than you might think.
I found a good number was 4:05, edge to label, at 45 RPM.
If I'm correct, that's 105 LPI? So, I'm excited try your bigger gear.