Re: Pocket Tutor - hardware update

Bruce Hall


Excellent!  I hope you enjoy your build as much as I did.

One last thing:  I've been using headphones a lot with my Pocket Tutor.   If you intend to use headphones too, you will notice that output from the external speaker jack can be overwhelming.  (It creates room-filling sound with a 2W speaker.)   Will you get to the audio circuit, there are a few options to consider:

a) Use the circuit as is, and keep the volume control near zero.   It works, but you can do better.  

b)  Increase R13 to a larger value  (Easy fix, but reduces the range of the on-board speaker); or

c)  Add a series resistor between the amplifier circuit and the S-pin (sleeve) of the speaker jack.  This is mechanically trickier to do, but will be more satisfying.  I suggest a value of around 150-330 ohms.  With my headphones, 150 ohms is about right.

d) Make a short adapter cable with a series resistor in it.   Easy but clunky.


On Sat, Jul 18, 2020 at 5:28 PM Ken Kaplan <wb2art@...> wrote:
Yes, I just printed the shared cart.
Will take some time and see if I need to adjust anything.
Ordered the boards from jclpcb. 

On Sat, Jul 18, 2020, 5:18 PM Bruce Hall <bhall66@...> wrote:

I put a shared cart on the builder's guide, which will create a single DigiKey order for most of the parts.   
When I order I get lots of extras, so please review and adjust the quantities of each item you want.  Of course, if you prefer Mouser or another distributor, you will need to order them separately.


On Sat, Jul 18, 2020 at 5:04 PM Ken Kaplan <wb2art@...> wrote:
Thanks for the hints.
I'm going to get boards and parts ordered, probably tomorrow.

On Sat, Jul 18, 2020, 4:59 PM Bruce Hall <bhall66@...> wrote:
I have a few tips for anyone building the Pocket Tutor:

1.  The power supply needs a decoupling capacitor across the battery.  You should solder an additional 10uF cap across the pins of the battery jack J1.

2.  The audio and key jacks are recessed by about a millimeter.  Normally this isn't a problem, but one my plugs fails to make good contact.   So, when soldering these jacks, please situate them as close as possible to the board edge.  The extra-large soldering pads give you some leeway.

I updated the builder's guide to reflect these two changes.


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