Topic: Nakamichi CM 300 housing question

[SHINN]

This is the one I saw on Ebay

http://cgi.ebay.com/20mm-x-0-75-Metric-HSS-Righ-Hand-Plug-Tap-M20-x-75-/110630102966?pt=LH_DefaultDomain_0&hash=item19c21167b6

I emailed the seller to find out if it is really an m20 x .75 because everyone I talked to said it was a non standard thread.
 
Shinn

[weedwacker]

Good stuff here and thanks for the pictures Roger. I wasn't even thinking of removing the lo cut switch but would cut down on the size also.  I am not that good at reading schematics but if I am seeing it correctly you just removed the 3 wires soldered to the 3 pins for the xlr connector and hook the battery spring up directly to those points instead? I don't want to chop the original housing up since I have set of 3 all original components including caps, windscreens and stand holders along with the case and manual and if ever sell them and someone wants the set stock I can just put the original housings back on the mics then. If I remove the lo cut switches it looks like I can put them back to stock fairly easily with some soldering so that may be an option also. I can have a piece of tooling made to tap a brass or copper housing to that thread using a swiss screw machine(just cost more money then). I'll post back if I decide to make them or have a local machine shop here make the housing. Thanks for all the advice everyone has provided thus far.

[Roger Gustavsson]

Good stuff here and thanks for the pictures Roger. I wasn't even thinking of removing the lo cut switch but would cut down on the size also.  I am not that good at reading schematics but if I am seeing it correctly you just removed the 3 wires soldered to the 3 pins for the xlr connector and hook the battery spring up directly to those points instead?

Not really. Pin 1 is ground and it is connected to the body/chassis. Pin 2 is signal. Pin 3 can be used for power and/or power switching. If you use an internal battery, use a shorting link inside the female connector between Pin 1 and Pin 3 (negative pol of the battery). Pulling the connector = power off. Of course, the battery or power can be external too. +V on Pin 3 and - on Pin 1.

I don't want to chop the original housing up since I have set of 3 all original components including caps, windscreens and stand holders along with the case and manual and if ever sell them and someone wants the set stock I can just put the original housings back on the mics then. If I remove the lo cut switches it looks like I can put them back to stock fairly easily with some soldering so that may be an option also. I can have a piece of tooling made to tap a brass or copper housing to that thread using a swiss screw machine(just cost more money then). I'll post back if I decide to make them or have a local machine shop here make the housing. Thanks for all the advice everyone has provided thus far.

I have one of these pack of three too. I will keep their bodies in original shape for now as they are in mint condition. Just wished someone could make new threads in the remains of the bodies that I cut down, now 38 mm shorter. They could still be used with three stacked CR1632 lithium cells inside. I would also be interested in having some extra bodies/housings.


Roger

[SHINN]

Hi Roger,  So can I use your schematic but with the battery in the cable?  I was going to use a 2 conductor plus shield cable from each mic, into a battery box, then a 2 conductor plus shield from the battery box to the mini jack. Do I need 2 separate cables going from the battery box to the mini jack? The thing that confused me is the Rane Cable diagram.

instructionshttp://www.taperssection.com/reference/pdf/DIY_CableDiagram_Rane.pdf

 On page 6, example #5. It shows a 2conductor plus shield cable for each mic (even though the 1 and 3 pins are joined at the mic connector). Then the shield doesn't connect at the the recorder end. (?)

Also, I bought the M20 tap. Its supposed to come in 2 wks.

Shinn

[SHINN]

Here's the Rane cable diagram. I didn't copy the link right.

http://www.taperssection.com/reference/pdf/DIY_CableDiagram_Rane.pdf

[weedwacker]

Hi Roger,  So can I use your schematic but with the battery in the cable?  I was going to use a 2 conductor plus shield cable from each mic, into a battery box, then a 2 conductor plus shield from the battery box to the mini jack. Do I need 2 separate cables going from the battery box to the mini jack? The thing that confused me is the Rane Cable diagram.

instructionshttp://www.taperssection.com/reference/pdf/DIY_CableDiagram_Rane.pdf

 On page 6, example #5. It shows a 2conductor plus shield cable for each mic (even though the 1 and 3 pins are joined at the mic connector). Then the shield doesn't connect at the the recorder end. (?)

Also, I bought the M20 tap. Its supposed to come in 2 wks.

Shinn

Let us know how the tap works out when you get it. If it works I will most likely order one myself or if you want rent it from you to do my project here.Thanks for the wiring diagrams looking at those I may just make a new connector outright with cabling instead. Decisions, decisions the fun part of designing things.

[Roger Gustavsson]

Hi Roger,  So can I use your schematic but with the battery in the cable?  I was going to use a 2 conductor plus shield cable from each mic, into a battery box, then a 2 conductor plus shield from the battery box to the mini jack. Do I need 2 separate cables going from the battery box to the mini jack?

Shinn,

I think you can do like this.

http://www.twin-x.com/groupdiy/displayimage.php?album=lastup&cat=0&pos=0

As there will be DC on the outputs, make sure there are capacitors in series with pin 2. The battery box should be close to the microphones, there is a risk of pickung up RF/HF disturbancies with long runs of cable. Maybe an electrolytic capacitor between pin 3 and 1, inside the bodies or close to them?


Roger

[SHINN]

Thanks for the wiring diagram! Thats cool...I thought I was going to need 2 batteries. I haven't completely figured out the capacitors yet, but I'm starting to understand it.

If that tap works I can loan it out no problem. I'll probably use it once and then it will just sit there for 20 years, haha. It's prob only like 2 bucks to send anyway. I think if you want to tap the original bodies though the ID needs to be opened up a little. I was getting 18.8mm on the body ID and 19.2mm on the thread ID (about .008" per side difference). 

Shinn