Re: AE7EU Top Level PCB Mod

Diver Martin <diver.martin@...>

I used a lot of 0603's and such.  Those are a large percent of the assembly cost.  I could go to 1206's pretty easily I think....  A lot of people don't like assembling 0603's.  The other option then might be change a bunch of the resistors to through hole, same for the caps.

A coworker who's used the same assembly house got $0.40 a part for 25 PCB's, at about 180 parts per PCB he said.  That would make the assembly cost about $60.

There are a few places where resistor/capacitor arrays might be applicable in this design, which can significantly reduce costs.

On Fri, Jan 12, 2018 at 2:09 PM, chris gress <Chrisg0wfh@...> wrote:
Could you just get the ic,s fitted make the rest home assembly would that help cut the costs chris

On 12 Jan 2018 21:57, "Diver Martin" <diver.martin@...> wrote:
So, good news, bad news.

Good news: I got a BoM together, defined all the parts, etc.
Bad news:  The BoM (majority single unit pricing from Digikey, but I took out gross single-part costs like 0603 capacitors/resistors/etc) is $112.  This might vary from half to 3/4 depending on the volume, so $60 to $90 or something.  Without knowing the volumes I'd do, it's hard to define.
Good news:  I have a vendor in town that will assemble the boards.
Bad news:  It's about $1 a part to place it on the PCB in a prototype run.  There are 147 SMT parts, assuming the person buying the board installs all TH components, toroids, etc.  That's $150 a PCB for assembly worst case.  In prototype quantities, I was told $1 per part (RoHS $1.20) (qty 1-10 boards).  Past assemblies I've heard down from $0.1 per part to $0.25 per part, so I'm not quite sure where to go on that front, as it's also volume dependant I believe.  I've put out a few pings to those I know who've gotten things built up for a better guestimate, but for now, I'll go with the pessimistic $1/part.

So... Assuming a good case of $75 for the BoM, $10 for the PCB, $15-$150 for assembly, $10 shipping, not including the $500 NRE or my initial builds (so tack on $10 there too assuming a run of 100 PCB's).  Soooo... $110 to $250 is the current price bracket that I've got, the major uncertainty in the cost of per-part placement / assembly.

#1 cost item:  Relays for the tuner and other things ($35)
#2 cost item:  Teensy3.2 ($20)
#3 cost item:  Minicircuits mixer ($3.15)
#4 cost item:  20-turn precision pots ($3 total, eliminate final design)

For those who wish to peruse...  A BoM is attached.

On Wed, Jan 10, 2018 at 10:39 PM, Martin Held <diver.martin@...> wrote:
So, I've finally got a rough draft of what I'm thinking for my uBitx top PCB mod.  Features at this point are:

No modifications required to uBitx board itself (not to say a 470uF anti-pop mod might be bad, or other things couldn't be done)
ATU: 7-inductor, 8-capacitor with Hi-Z/Lo-Z switch.
Selectable Power output (two power input connectors)
Brain transplant:  Teensy3.2 96MHz ARM processor
All connections on side edges - no wiring to enclosure
Front panel with pushbutton switches
DSP Audio (Via Teensy32, would require headphones or amplified speakers)
Solderless AGC modification (Attenuator at the front end switched in during RX)
Realtime clock (via Teensy32)
Linear amplifier control (just a reed relay on a 3.5mm header, sorry, not an RCA, but you could easily change it...)
Top side only construction (would make assembly cost lower)

BoM cost:  Probably way higher than it should be.  Needs optimization, and I still need to enter in costs.
Complexity:  Probably way more than it should be.
Layout:  An ugly mess of routing.  I can't say I like it, but the constraints I put on myself made it really hard to route.  There's lots of open areas to cross with lots of signals going all different directions.

Picture of the layout and schematic PDF attached, along with a 3D view.

I think the one modification that I still need to consider is a microphone preamp.  But, I have no flippin' clue where on the PCB I'd put the gain control knob!  Might have to be an internal potentiometer....

Martin Held - AE7EU
If there aren't any questions, then what is there to learn?

Martin Held - AE7EU
If there aren't any questions, then what is there to learn?

Martin Held - AE7EU
If there aren't any questions, then what is there to learn?

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