(Feeler)AKG C-12 and 251 Vintage style piont to point boards for Apex 460

[synchroman]

I would be in for 5-10 sets

 

[OPR]

All done now  we now also have some nice turrets on acrylic at the Base of the mic to hookup the transformer too....

 

[Melodeath00]

Looks very good. Do you have any kind of ballpark price? I know you're still figuring out the exact price, but a general range would be good. This point to point board will be an added expense for me, since I will still have to purchase chunger's PCB for wiring up the PSU, so I'd like to gauge how much would be added. Thanks!

And yes, a 251 version would be fantastic as well!

 

[Winetree]

Do we still have to buy Chunger's P.S.B.
or will it just be a mod to the stock Power Supply?

 

[Melodeath00]

Do we still have to buy Chunger's P.S.B.
or will it just be a mod to the stock Power Supply?

Chunger's PCB kit comes with a PCB for the PSU and a PCB for the Mic. Even if I do point-to-point for the mic, I will need the PCB for the PSU, but maybe that's just me!

 

[OPR]

Modding the Apex psu to provide the tube bias has been discussed at the link below, also chaining the zeners  to get a 120v B+ has also been discussed somewhere so try using the search feature or google. The info is out there  or you could Use one of Matador and Chungers PSU's

http://www.groupdiy.com/index.php?topic=53304.0

Because this is not a PCB it will definitely be more expensive as it's not a 100% automated process to build a set,(which is why the world turned to the easily automated screen printed PCB in the first place! But PCB is harder(not impossible) to design well.

At the moment I'm still working out the cost can I ask what all those interested would consider a reasonable price?

 

[Gus]

Have you looked up the MSDS or searched for what happens when you heat some plastics up?

When I machine plastics I check the MSDS and also lookup possible machining issues, you need to be aware what they can outgass if they get to hot.  So what happens when you heat the plastic when you solder to the turrets?

 

[OPR]

Hi Gus
Here is the MSDS on the Material I used for the prototype(Methyl methacrylate). Basically the same as Plexiglas  ACRYLITE®, Lucite and Perspex.

http://www.australiansheettraders.com.au/uploads/Cast%20Acrylic%20MSDS%20-%20MC.pdf

The material is used in Vac forming and heat forming and bending also worked well cnc type for milling applications
The soldering thing was my  biggest concern but it is very stable and doesn't seem to melt easily at all .

What are you using Gus?

 

[OPR]

I've been looking into the material used and it seems the first C12 came out in 1953 and polycarbonate was invented in the same year but Plexiglas(acrylic-Poly(methyl methacrylate) had been around since 1928 and was released on the market in 1933 according to wiki that is .
I'd say it was most likely 3-4mm Plexiglas(acrylic-Poly(methyl methacrylate) because of the time frame and considering R&D of the mic would have been happening prior to1953....

 

[Gus]

I have not machined a plastic inside a microphone that was exposed to heat from soldering.
I found this I am not sure if it the same material, read section 7
http://www.lucitelux.com/docs/Lucite-Lux-Frost-MSDS.pdf

I sometimes machine parts. I read the the MSDS and then search for hazards of machining the materials dust, what might be released with heat, etc before starting. 

 

[maq3396]

What extent of temperature would you see in one of these microphones?

If not too high, then why not 3D print the rings out of pla or abs?

For the volumes that would be required this could be a very practial and inexpensive approach (ie almost free)

 

[OPR]

Thanks for your input Gus yes it's pretty much the same material (Acrylic) like what was used in the original mic in 1953. As Ive said it's very stable when soldering provided exercise the same precaution you would when soldering polystyrene capacitors ie nice hot iron and short exposure. I did do some tests giving the terminals more heat for longer and it was still quite stable even when a little overexposed and no nasty odors.

What extent of temperature would you see in one of these microphones?

The operating temperature isn't all that high and The heat exposure Issue is more a concern when soldering the components to the terminals which are in direct contact with the plastic.

If not too high, then why not 3D print the rings out of pla or abs?

The idea was to get as close to the original mic as possible ie circuit layout and materials.

 

[OPR]

I've been looking at the costing for the C-12 Skeleton terminals and have found them to be quite labor intensive .ie installing turrets and particularly the precision required drilling the holes for the  M2 fastening screws in the three mm Acrylic, not to mention the machining and material costs...I now fully understand why PCB has replaced PTP!! So I think for complete finished sets the price would be around $150.00-$170.00  and if people wanted to Diy Turrets and fastening screws which would require a precision drill press and a turret installation tool (and lots of practice!!). I think it would be around $100.00-$120 per set. could those interested Email, PM or both to let me know if there 100% in and I'll see if wee can get this thing rolling!!

 

[OPR]

251 Board step 1....

 

[OPR]

First prototype complete and sounding way more detailed than any Apex 460 PCB Hack!!

251 pics

 

[Woot]

Looking good APR!

Would you be happy to provide dimensions? I am looking to build 2 251's into Beesneez ELAM body later in the year, so if I could fit these, would be perfect.

Cheers,

Matt

 

[Dylan W]

How are you planning to handle pattern switching on the 251?

 

[OPR]

Looking good APR!

Would you be happy to provide dimensions? I am looking to build 2 251's into Beesneez ELAM body later in the year, so if I could fit these, would be perfect.

Cheers,

Matt

These are made to fit an apex 460 body so there unlikely to fit....But I could probably custom make you something.

How are you planning to handle pattern switching on the 251?

Matt

For now it's a hybrid of 12 and 251 ie 9 pattern but the front of capsule is directly coupled to the grid "251 style". I left a heap of room up the top of the board for later modification ie relays to get the original pattern switching as an option for those who wish to do so..

 

[Woot]

These are made to fit an apex 460 body so there unlikely to fit....But I could probably custom make you something.

Hmmmm that would be great. Do you need dimensions?

 

[OPR]

Actually I'm in Melbourne Australia too! so It would probably be best to post or drop the body off to me so I can size it up...