Royer MXL 2001 Mod P.S. redrawn w/ PBC layout

[doorunrun]

I'm undertaking the Royer Mod project with a MXL 2001 and as a way of organizing my plan of attack I thought I'd start with building the power supply.

I redrew the schematic in Scheme-It to make it easier to read.

For laying out a PC board I wanted to try and match the original board's compact layout. To that end I came up with this visualization;

It's an enlargement of the PCB photo from Royer's original article overlaid with what I think are the proper positions of the circuit's components.
The thick darker brown area is unetched copper on the reverse side of the board. It serves as a common ground. I doubt the original used through-hole-plating; maybe short jumper wires or component leads were used to connect layers.

My plan is to use perf-board for my version with approximately the same layout and wire the underside point-to-point.

Hope this helps those who approach the project in the future.

 

[doorunrun]

Oops, I didn't label the 3-pin XLR output jack properly.
Pin 1: Ground
Pin 2: connect to pin 2 of 5-pin microphone connector
Pin3: connect ot pin 1 of 5-pin microphone connector

 

[Khron]

With perfboard, you'll want to consider peeling off unused copper in the higher-voltage areas.

 

[doorunrun]

It's nice having a project to help learn KiCAD...


PCB board layout trying to match the original board,
and a 3D view:

I did this mainly to test fit components on an old perfboard I have, but who knows where this will lead.

Cheers!

 

[Khron]

In case you'll have pcb's made with that layout, in addition to plenty of clearance in the high-voltage areas, it's worth to otherwise flood fill the bottom layer with a groundplane. Less copper to etch off, less wasteful, and there's no such thing as too-low-impedance for a ground connection.

 

[doorunrun]

....it's worth to otherwise flood fill the bottom layer with a groundplane. Less copper to etch off, less wasteful, and there's no such thing as too-low-impedance for a ground connection.

Yes, absolutely. I haven't quite figured that part out in KiCAD. It's next on my list, along with setting and locking PCB dimensions.

Thanks for your comments!

 

[doorunrun]

A minor update, I got the PCB layout done and uploaded to OSH Park and JLCPCB.

By gosh, OSH quoted something like $99 for 3 boards. Jeez, JLC had 'em beat quoting like $8, BUT $20-something in 'economy shipping.'

I'm sticking with point-to-point-perf-board for now. I think I'll tinker around KiCAD-ing a PCB for the mic and maybe bundling the two projects will offset the shipping through JLC.

The perf-board I prepped for the mic measures 60mm long with the wide top 39mm and the narrow bottom 35mm. Should be interesting to try laying out the edge-cut for it.

 

[rock soderstrom]

A minor update, I got the PCB layout done and uploaded to OSH Park and JLCPCB.

By gosh, OSH quoted something like $99 for 3 boards. Jeez, JLC had 'em beat quoting like $8, BUT $20-something in 'economy shipping.'

I'm sticking with point-to-point-perf-board for now. I think I'll tinker around KiCAD-ing a PCB for the mic and maybe bundling the two projects will offset the shipping through JLC.

The perf-board I prepped for the mic measures 60mm long with the wide top 39mm and the narrow bottom 35mm. Should be interesting to try laying out the edge-cut for it.

Why don't you etch the circuit board yourself? There are several tutorials on the subject on youtube. Of course, P2P on Perfoboard is also possible, but having your own PCB is much nicer.

 

[Khron]

... And/or score "islands" onto a blank copper-clad board - really convenient especially for one-offs.

 

[doorunrun]

Why don't you etch the circuit board yourself? There are several tutorials on the subject on youtube. Of course, P2P on Perfoboard is also possible, but having your own PCB is much nicer.

You're right. I've done it before using a Sharpie to cover the traces. I've got fresh etchant from when Radio Shack closed it's doors and some double-sided FR-4 from a '70s hamfest. Sure why not!

 

[rock soderstrom]

You're right. I've done it before using a Sharpie to cover the traces. I've got fresh etchant from when Radio Shack closed it's doors and some double-sided FR-4 from a '70s hamfest. Sure why not!

Cool!

I'm by no means an expert in PCB design, but I think your first design needs a little more love.
I am a slightly advanced beginner...

I would make the arrangement of the components look nicer, make the solder pads bigger and avoid right angles. Do not forget a fuse for the secondary side of your transformer. Just a few suggestions, here are one of my humble designs as a practical example...

Have fun!

Edit: better stay single sided, its much easier.

 

[doorunrun]

Cool!

I'm by no means an expert in PCB design, but I think your first design needs a little more love. I am a slightly advanced beginner...
Have fun!

Edit: better stay single sided, its much easier.

I've admired your work while searching power supply designs here for my "Mystery RCA Mixer-Amp" project. Your single-sided suggestion is a good one!

I would like to use stuff I have on hand, stuff that's been gathering dust around the shop.

Still, it's fun to do the scheming and consider one's options!

Thanks!

 

[rock soderstrom]

I would like to use stuff I have on hand, stuff that's been gathering dust around the shop.

+1

That is often my motivation too. If you do the etching yourself, you can make everything fit.
Big plus.

 

[Chrisfromthepast]

I recommend adding 4mA leds (and the appropriate resistors) to each rail. They also have a safety function as a bleeder resistor, so you know when your board is safe to touch because the leds are off.

 

[rock soderstrom]

I recommend adding 4mA leds (and the appropriate resistors) to each rail. They also have a safety function as a bleeder resistor, so you know when your board is safe to touch because the leds are off.

Yes, that's a good idea. As you can see, I have also implemented this. A useful safety feature and really amazing how bright today's low current LEDs shine with extremely low current flow.

 

[doorunrun]

With the HV/LV LM317-Asian power supply I put together using an EICO Multiplex adapter chassis I used one its neon bulbs as the HV indicator.

BTW, EICO used an ingenious lamp holder for the neon bulb made from folded stiff fiber paper. I HAD to use it

That's one I didn't use and I didn't want to lose track of it.
They also used the same material to insulate the inside of the slide switch covers seen at the top of the photo.

 

[FunkyTek]

You're right. I've done it before using a Sharpie to cover the traces. I've got fresh etchant from when Radio Shack closed it's doors and some double-sided FR-4 from a '70s hamfest. Sure why not!

FR-4 is good stuff. Jeez I have a bottle of that stuff still myself, unopened. It's been a long time since I etched my own board. I have a couple MXL-2001's specifically for the Royer mod. I never got off my butt to actually do them. I just didn't need any more tube mics, but this might inspire me to make them for fun. Thanks.