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Topics - mjg

Open Discussion / Vintage Lego electronics content
June 07, 2023, 03:41:30 AM
Figure this might interest some people here - some 30 year old Lego Technic, with electronics in need of some TLC.

My partner works at a charity, and they have a big 2nd hand Lego sale to raise funds.  I'm helping out by checking some of the kits before they are ready to sell, and came across this one:

It's got connections and controls for 3 motors, and you can program in a sequence of movements to be replayed later.   Pretty neat for its age. 

The heart always falls when you pick it up and can feel the weight of 30 year old batteries still inside. Sure enough, the batteries had leaked and corroded, all over the place. This is usually not something we can sell, especially when they have leaked this badly. This will usually have ruined circuits underneath.

One of the 'C' size culprits:

Some of the damage:

However, I have to admire the design of this controller - the battery bay was almost completely sealed from the other circuitry, with only a tiny amount of leakage getting through to the back of the PCB. The front of the PCB has no damage at all.  There's a little Motorola chip doing the work. 

Hot wiring the controller to a 9v supply shows that everything still functions.  Success!  (Yes, that's my pedal tester doing the heavy lifting, lol)

I managed to pull the battery contacts out and cleaned them off with a small flat screwdriver, and some vinegar. Once I got the corrosion off, it became obvious that the metal has been eaten almost through. You can see daylight through some bits. This isn't going to be useable with these contacts. 

I've ordered some new battery contacts and will put them into place once they arrive. The kit will then go to some lucky person at the sale (it should sell for $200 or so we hope).

Usually we don't have to go to these lengths for a kit, but it was worth it for the potential value vs the fix (and my time, but whatever, I'm having fun).

Open Discussion / Midnight Oil concert (attempt 2)
October 01, 2022, 11:11:58 PM
A few months back I went to a Midnight Oil concert, but it got cancelled before the band started due to extreme weather.

Last night they were back in town to make up for it.  It has been raining all week here, and was up til about an hour before the band came on, but then we had a lovely clear night for the gig.

It was a good show!  They can still rock.  Peter Garrett dancing moves never fail to impress, even if he's almost 70.

I reckon the average age of the audience was about 45.  There was an elderly lady on a walker frame that set up in front of me, I kid you not.  She knew all the songs and had a great time. 

Some interesting moments where the lead guitarist sat down and did a jazz piano solo for about 3 minutes in the middle of a song...and they had a saxophone accompany on some songs.  Pete had some good rants between songs about Putin, King Charles, and politics in general. 

Anyway, it was a good night out and I'm glad I got to see them one last time.

We caught the support band "King Stingray" as well, they were good too.
Open Discussion / Midnight Oil concert tonight
April 19, 2022, 10:46:25 AM
Spending this evening at a Midnight Oil concert.  It's open air, and tonight we're getting about a month worth of rain dumped on us.  The lightning started up during the support band, so they have just sent us all back to our cars for safety and delayed the main band for half an hour, hoping the weather clears.  Very rock and roll.

Here's hoping I get to see the Oils tonight...  :D
Open Discussion / Good electronics resource on YouTube
December 23, 2021, 12:33:35 AM
I've been watching a fair few of Moritz Klein videos on YouTube - he goes into detail about how components work, explaining things from the basics and working up to full circuits. 

It's biased towards synth stuff, but I think it's still relevant to pedals. 

Anyway, here's one I just watched about sample and hold circuits.  Hoping someone might find it useful or interesting!
Build Reports / The Dad Joke
July 15, 2021, 10:51:38 AM
It's a well known fact that the best pedal concepts are based on Dad Jokes.  This is a drive pedal, inside a hard drive. Get it? A Hard Drive. Drive. Ah ha ha ha.   Sorry. 

This one has been a long time on the bench, but finally finished it this week.  The effect is a Klon into a Blues Breaker, but to be honest, any drive would have worked for the joke.  Those two were selected as I had not built either yet. 

Over a year ago, I posted the first efforts at fitting jacks into the space.  What followed over 12 months was a lot more excavation of the metal, to give me enough room to fit the electronics. This was done with a drill press, angle grinder and rotary tool.

The vertical space was just enough to fit the pots, PCB and a bit of 1mm foam underneath to prevent shorting.

Crazy shaped PCB was done to fit around the screw mount points in the enclosure:

Switching had to be soft touch switches, as 3PDT switches were too big to fit in the height. I've used an ATTiny chip to control a bank of optical switches to do true bypass for the Blues Breaker, and buffered bypass for the Klon. I did find a low profile relay that would have done the job, but I had the optical chips already so went with that. Two colour LED to show status of each side.

Dip switches sit in a recess at the bottom, to control two clipping options for each effect. 

Test fit.  I was super happy that it all fit in without too much crowbar needed: 

I tried metal stamping the lettering, but that didn't work out very well - the top is two layers of steel, and it didn't stamp well unfortunately. To save it, I went over things with the rotary tool, then some paint to finish. Pretty happy with how it came out - the dints around the letters I could have done without though. 

And the final photo shoot: 

Open Discussion / Marshall key holder
May 28, 2021, 07:43:47 AM
This is kinda cool.  Might have to make one. 

Open Discussion / Gardening time
March 08, 2021, 07:46:15 AM
It's harvest time here (Australia), so here's a few photos of today's pickings. 

I always do a variety of tomatoes.  They've ripened later this year (it's been a wet summer for a change), but damn, some of them are huge. 

This guy is the largest so far... not sure I can top this.  That's 1.6 pounds for those who use non-Metric:

Also... jerk birds, eating my sunflowers.  Was saving the seeds for our chickens, but the cockies like to bite off the stalks half way down and then eat the pulp out of the stems.  Jerks.

Build Reports / Honey Dripper and Glitchee
November 17, 2020, 08:18:16 AM
A couple of finished pedals this month.  These sat on the "Wall of missing potentiometers" for a long time, but they're finally done. 

The Honey Dripper first:

And then the Glitchee.  For this one I must have put the holes too high, because the pots didn't fit into the enclosure.  Some 'adjustments' with the belt sander on the pots were required to get things to fit. 

For the enclosures, I found that the wife of a work friend does acrylic paint pouring, so commissioned a few from her.  They came out pretty awesome.  Put some waterslide decals over the top, and I'm really happy with how these look.  I'll probably get her to do a few more in future, it saves me having to think up artwork, and it looks great.

General Questions / Klon into a Blues Breaker...?
November 06, 2020, 11:22:42 PM
I'm currently working on a dual pedal enclosure, and thought I'd do a Klon into a Blues Breaker, as I haven't built either before.

I've got everything on breadboard, and the two pedals sound fine when used by themselves.  But if I run the Klon into the Blues Breaker, there is so much oscillation noise that I've got dolphins knocking on the front door, and that's with me living about 300km from the ocean. 

So anyway, this combination should work shouldn't it?  Thought I'd ask before I spend hours debugging the breadboard.  First thing I want to try is modifying the gain section of the Blue Breaker to be more low gain, or maybe an audio probe to just confirm where the oscillation is coming from.

And of course, the breadboard looks a complete hot mess, so that's likely to be causing all sorts of noise that will go away once it's on a PCB:

I've been trying to do a bit of surface mount stuff yesterday.  I had 4 x SOT-23 chips to solder on, and that was about 30 minutes of frustration.  Tested the finished circuit today, and 3 of the 4 are working.  The other is not happy. 

So, some photos for people to laugh at, and then I'd like some advice for the best way to:

1) remove the one I've buggered, without damaging the board, and
2) how to not bugger future chips when I try again

Any good tutorials on soldering these things that people can recommend?   I'm using a tiny tip on the iron, and putting flux on with a pen before hand, but damn, it's hit and miss.

Here's one of the good ones under a microscope (next to the world's largest resistor):

And here's the not working one.  I think I had about 5 goes at it, probably cooked it?

Build Reports / Flabulanche and boost
August 11, 2020, 08:43:44 AM
Finally got some boards finished and boxed.  This is the Flabulanche from MBP, with a Paperclip boost from Nucleon. 

Custom enclosure, which came out of an external hard drive box.  It's steel, so quite strong, and can take stomping no trouble.  (I still plan on doing another pedal inside an actual hard drive... that's a project for another month though).

So... the guts are a mess.  Lots of off-board wiring so that I could put the knobs where I wanted.

Also for fun, I had an old bike light LED strip, which I've hot glued in with some red perspex, so the whole enclosure inside glows red when the effect is on. 

On the outside, a big knob for the gain, and little ones for volume, tone, and the boost level.  The toggle is the compression switch. 

Did the lettering with the dremel, which worked out kinda neat for a change, so I was happy with that.  Usually attempting this kind of lettering will result in me scratching the crap out of things and having letters that look like a 4 year old writing in crayon.  Used a much smaller dremel bit this time, which seemed to make it more controllable. 

Open Discussion / Music theory recommendations?
May 26, 2020, 08:28:19 AM
My partner is learning some music theory stuff at the moment, and she's not enjoying the whole "it's the circle of fifths, just memorise it, yo" type approach.  Her background was maths and theoretical physics years ago, so she needs more of an explanation of why these things are so, and how to arrive there at first principles, not just something to follow blindly.

So, can anyone recommend any good resources along those lines?  Youtubes or real books, either is good.  The more maths the better. 
Open Discussion / Happy Star Wars day
May 04, 2020, 03:04:06 AM
Hope you all enjoy May the 4th.  I'm wearing my X wing pilot outfit today.  Have to say, it's the first time I've ever worn a suit to work. 
Open Discussion / Science time! (contains Dad brag)
February 26, 2020, 09:46:10 AM
Some of you might remember my kid's science project from a few years back, when he made a tremolo from some cleaning liquid, a motor and some copper wires.  Here was the build report:

Anyway, fast forward to this year's science project.  He broke his arm at around the time he was thinking of what to do, and this got him thinking about building a robotic arm to play half of the guitar for him.  (He was in the plaster for 6 weeks - it was an impressive break)

The project won the school science fair, and the State science fair, and a few weeks ago we found out it won the National science fair for primary school kids.  So, yeah, Dad brag. 

Here's the video that he submitted as part of the entry:

Open Discussion / Reverb tank ideas...?
October 16, 2019, 07:28:02 AM
I've had a reverb tank circuit sitting on my breadboard for way too long now (like, most of the year), and I'm struggling to call it finished. 

I suspect that this is my usual problem of trying to put too many knobs and features onto a board. 

For now I've got a driver/recovery circuit, with variable drive, tone, and volume for the tank signal, and a separate volume for the dry signal.  Switchable between mixing the wet+dry on one output jack, or splitting it to two output jacks so you can have dry to one amp, and reverb to another. 

Also have added dry kill and wet kill switches, with tails, soft touch switching on the panel and a remote foot switch. 

I tried adding a third channel for a digital reverb, but that was a bit underwhelming really.  Reverb mixed with reverb sounds just like reverb.  Who knew?  So I scrapped that idea.

Now wondering if I should put an optional delay circuit into the mix somewhere.  But I've already got delay+reverb pedals so probably don't need that.

Anyway, any ideas for a reverb tank that I should try?  Or should I just stop procrastinating and make the board already?  :)

I had a few hours with the rest of the family out of the house today, so decided to build a spring reverb tank recovery on breadboard.  It was going pretty well, but after a while I could smell burning.  Not good.

I figured it was the wacky 15v circuit I'd built, so tried to work out what I'd done wrong.  None of the parts seemed hot.  Burning smell getting worse.

After 5 or 10 minutes of wondering what was causing the smell, I thought I'd check outside.  Huh.  Burning smell outside the house as well.  Maybe the neighbours have lit their fire? 

Went back inside, and kept breadboarding.  Smell is definitely stronger inside, and getting worse.  After another 5 minutes, I thought I'd check the rest of the house.

Oh.  Right.

I'd started cooking dinner.  Left some beans boiling on the stove about an hour ago. 

Grey smoke billowing out of the saucepan, smoke all through the kitchen and the rest of the house, down to about eye level. 

My lessons for the day:

- don't get distracted by the breadboard
- use a kitchen timer
- get a new smoke detector, because the one we have didn't make a peep, and it was swimming in smoke. 

Open Discussion / Pickups for a hurdy gurdy?
June 20, 2019, 10:33:37 AM
A mate of mine is building a hurdy gurdy... which is really hard to type without autocorrect getting upset.

He has asked me how he would install pickups to connect to a small amp. 

I'm thinking it will be something like a semi-acoustic?  Small microphone or piezo or whatever.  The instrument seems to have different sounds from different sets of strings, so probably needs pickups in multiple locations. 

Anyway, anyone have experience with this kind of instrument?   :o
Build Reports / Phaser build
May 08, 2019, 10:06:07 AM
This is based on the Mu-Tron Phasor II circuit, with a few more options to vary the sound.  I've put in two rotary switches, which let you vary the number of stages in the phaser from 3 to 8, and change the tone capacitors of the first four stages.  Also a 'slow' switch to really drop the speed of the phasing, and a relay bypass. 

For something different on the enclosure, I've used the drill press with a depth stop, and drilled a pattern using different drill bit sizes. It was a bit nerve racking with the larger bits, as I thought it might punch through the metal completely, but it worked out pretty nicely in the end.

Stamped lettering, which got a bit hairy near the edges, where I didn't support the enclosure underneath properly.  It ended up bending then tearing the aluminium, and I had to hammer it back into shape.  Whoops.  Doesn't show with a bit of a sand, thankfully.

Open Discussion / New (old) (free!) amp day
April 24, 2019, 12:05:49 PM
Got this for free today - my partner saw it on a local 'free stuff' website.  A 'Princeton', but not a Fender amp.  It's a Prince PG-100SA - solid state 30w amp.

As far as I can tell, it would have been produced in the 1970s by the Prince Tsushinkogyo company. They renamed in 1980 to Arion, and stopped making amps in the mid 80s. 

It's got a bit of character, and could do with some cosmetic work, but it still fires up and worked fine.

It has a small spring reverb built in, as well as tremolo. 

I'll need to replace the back panel, fix the carry handle, fix the power light, and maybe change the scratchy volume pot. One of the input jacks seems to have been glued in place at some point, and wobbles a fair bit, so I'll replace that too. I'll also have to find some knobs for it, once I work out what the original would have looked like.

Build Reports / Solar Flare
November 05, 2018, 08:00:43 AM
This is a 'Solar Flare' board from Nucleon FX.  Thanks again to Rockhorst for the build of the year prize last year.  It's taken me this long to get through them all!

The circuit is based on the Keeley Fuzz Head.  I've used an AC128K for the germanium transistor, and for the diodes I went with 1n4148, 1n270, and a cheeky D9K hanging off the side of the board. 

The enclosure was an old tobacco tin.  The previous owner died from lung cancer.  Don't smoke, kids.  Public service announcement done.   Anyway, this is a much better use for the tin.

It sounds... fuzzy.  I'm not sure that I'm a fuzz connoisseur, so probably not the best person to judge this one. :)

I used a waterslide print to do the labels on the top... but after 60 seconds under the water, the decal still didn't budge.  At this point I realised that I'd grabbed the vinyl sticker paper, not the decal paper.  Don't put sticker paper under water.  It doesn't work.