As so many members have now obtained PCBs due to the kind generosity of Peter, 'Electronpusher0', hopefully quite a few are now nearing completion or even already completed. Since In Liston Smith first published the Mini-Mod in the BVWS Bulletin back in 2013, it's proved hugely popular. There have been several threads and bursts of activity on the forum - notably in 2015 and 2018, and in 2021, it still has legs!
I thought it might prove useful to create a 'Mini-Mod 2021' thread where constructors of Peter's boards can share their experiences, results, performance, and any difficulties in constructing and adjusting the project (hopefully few!). I've completed mine and it worked straight off and performs equally as well as did others that I've produced in the past, one of which I still have for comparison.
I used what components I had to hand, so in some instances I bent the legs of 5mm capacitors to find 10mm spaced holes, and I used a mixture of ceramic, Mylar and polystyrene capacitors. Ian Liston-Smith had said that 680 uF capacitors are a bit uncommon, but 470 uF should do fine instead. The only 680 uFs I had to hand had 5mm spaced pins so I used 470 uF, which seems fine.
The only small challenge I guess was soldering the Audio input but there are two options - one is three holes spaced for a 3 pin socket, or separate holes if preferred. I used the three holes to solder the wires to anyway and had no problems. Likewise, if it's desired to fit an LED, the LED holes are close together (2.5mm), but I had no problems with that either. (The LED is an option anyway - if it's not fitted, neither is R9 required). I fitted an ultrabright one which only consumes 1mA and might prevent a PP3 from being run down if inadvertently left on.
The transistor pads are close together, but again, with a fine pencil-tipped iron it's no hassle and the plated-through holes wick the solder in really well.
To box it up calls for a box with internal dimensions at least 75-80mm wide x 100mm long and maybe 50mm deep to comfortably accommodate the PCB and the PP3 Battery. I guess those on a higher pay grade than me might created a 3D printed bespoke box with a battery compartment, but I just made yet another little comb-jointed box from scrap mahogany and created a waterslide decal for the front panel.
Daft in a way - that took me longer than building the PCB, but if it was a chore, I wouldn't do it, and all it costs is my time. The most pleasurable aspect of retirement (of which I've had 26 years to date), is that you dance to no-one tune but your own. (Except loved ones of course). I screwed the PCB to the bottom of the box with 6BA C/S crews from beneath, and used wires from the PCB which were long enough to fit the sockets, switch and LED to the front panel before screwing it down.
The PCBs are superb.
How wonderful that JLPCB will produce small batches of boards of such high quality at such a low price and cater for our modest needs, and will give an instant quote online. JLCPCB is a massive outfit - 800,000 customers in 170 countries, 3,000 employees, 20,000 orders a day, Five factories totalling 450,000 sq M working 24/7. They turn orders around in 24 hours, with 0.23% fault rate. 600,000 sq metres per month capacity. They also do auto SMD assembly (35 million parts/month), and yet they'll sell us hobbyists half a dozen boards for little more than a tenner post free.
Worth watching their video here:
https://jlcpcb.com/aboutUs
I've attached a few pics of my Mini-Mod:
Pic 1: Completed PCB.
Pic 2: Unmodulated 1 MHz (300 Metres) output at the aerial.
Pic 3: Output modulated by 1kHz sine wave. (albeit at low amplitude).
Pic 4: An angled view if the little box I made.
Pic 4: The waterslide decal I made for the front panel. (If it's any help to anyone, feel free to copy it).
Hope that's of interest and that others will add their experiences to the thread.