Found this USB game controller at the thriftstore with some fun functions like actual analog feeling triggers and built in TURBO mode. When plugging it in and going to any keypad tester website, I stumbled upon a problem: The right trigger was not responsive (https://gamepadtest.com/):
I reckoned something was wrong with a solder pad or even worse, mechanical issues with the physical button. So let’s screw it open and see!
There are 6 screws to deal with, of which one hidden under the sticker.
Disgusting! Anyway, not a lot of stuff to see here without screwing it open even further. As I am not interested in a full teardown and just fixing the trigger, this is as far as we’ll go.
They were quite ambitious with this one in design, yet didn’t fully take advantage of its potential. For example, where the USB cable comes in is a footprint laid out for a USB input so you could use any external USB cable with it. This controller has a fixed cable.
Another interesting thing is how to the left and right are big pads laid out, possibly to connect 2 DC rumble motors to. Even in the plastic enclosure in the lower left and right of the picture, is visible how there are compartments which would fit these motors.
With two red arrows I indicated problematic spots. To the right a ground pad that shorts towards the CS or chip select pin of this controller. I rather have this CS pin being taken care of by design than an actual short by solder mistake. I will remove this short and assume it will not break anything.
The second and more important arrow points towards the wires that lead from the controller PCB to the right shoulder and trigger button PCB. Let’s zoom in!
We are greeted with a wire that is floating in the breeze, no wonder it doesn’t work! To make sure this cheapo flatcable won’t ruin my day in the future, I decided to replace the whole thing with a fresh flatcable.
The cable didn’t like to get soldered and got its insulation a bit molten at the controller PCB side, but electrically it is all fine… I promise!
A quick view of the other side of the pad. Pretty basic setup. Two carbon pads that get shorted when pressing a button by a rubber dome switch which I removed.
Dutch thriftstores have these now and then for nearly no money because they lack the microphones, power supply etc. etc. but they house one very particular part which I’m interested in.
But what is it? Just a main module for basic karaoke parties. Plug in 2 microphones, set the tone (variable low pass filter) and individual mic volume. And as a bonus you can add in an echo/delay at a fixed delay time and feedback level. The module is meant to sit between a game console or DVD player (just anything that can play shitty karaoke songs) and then have its audio fed to a tv or whatever as it also has a video in pass-through.
Teardown
Removing the top (by removing 4 philips head screws from the bottom) reveals all the through-hole parts including a particular DIP IC. This is a CD2399GP which is similar to a PT2399 but from another manufacturer. As all the PT2399s I bought from China gave me various issues, desoldering these becomes very worthwhile.
Note how there has been a patch at D1 in the top right corner. Has someone been in here before or did someone had to make sure it passed quality control?
Not a lot else to see here, some filtering caps and the pots. More interesting is the little cutout in the PCB and the shape of what might’ve been a battery holder in the bottom of the module. These enclosures are probably used for many different devices.
On the bottom a lot of SMD of which mostly opamps do the necessary audio trickery. Really not anything worthy to look into further.
The backside reveals how the audio and video pass-through works. Unit runs on 9V center positive adapters. This might raise questions as to why there is a 78L09 on board.
The thriftstore I often visit received a big load of 00s electronics. Some more useless than others. A 7.1 external USB sound card grabbed my attention as it used to be a much used device and cost nearly nothing. So I grabbed it.
Sadly, this device is so outdated (2009) that I had a hard time getting drivers to work under Windows 10 so I just gave up on it as I didn’t even have a usecase for it. So I decided to open it up and see what makes it tick.
Features
Two microphone inputs
Headphones output
Line-in
Front, surround, center/bass and back outputs
S/PDIF
Knobs for volume + and -, mic mute and mic volume.
Teardown
Overview
Torn down it actually looks like a sleek design and a funny small device.
I’ve seen this piece of crap lying around at the thriftstore for months. Even the employees started to notice it and decided to slap a sticker on it: 50 eurocents. Well, yellowed buddy, you can come with me.
I could not really find any information about this particular alarm clock radio, and I even feel like I am the first on the internet to give any form of unneeded attention to it. Judging from the design, the ICs I bet it is late 80s, early 90s.
Upon plugging it in the whole darn thing didn’t turn on or respond to any button or switch configurations, I would find out later why this is so…
Features
I’m not even going to go in depth on this one. It’s a simple alarm clock radio with all the functionality you would expect from one. Leave a comment if you need details.
Teardown
Opening up is a piece of cake, four or so philips screws and we’re in.
Screwed open
All the interesting stuff in the upper part and the speaker and button interface PCB on the lower part. Tranformer is center tapped with about 9.5V per tap. Lets zoom in further.
Knob PCB
As visible, a simple rubber dome interface of which the former didn’t survive long. Dried out and broken off. Junk.
The main chip
Pretty much all functionality is put into an LM8560 from some funky company. This chip is well documented and is for some still a hobbyist favourite. The display is an LED 7 segment variety.
Absolutely terrific decades old manual children labour.
Amplifier chip and some RF tuning circuitry
The amplifier chip is a KA2201. Pretty much comparable to an LM386: low voltage, low power mono amplifier in DIP8. Also visible some coils, transistors and passives of the RF tuning circuitry. This thing does both FM and AM.
Germanium diodes!
It even has 2 germanium diodes! I can now sell it for a big profit to some guitar pedal enthusiasts.
Backside
Not much to see on the backside. The tuning mechanism and the marking NL-329 AM/F. There is also a marking of some company with “KF” as logo.
Repair
As previously mentioned, the thing doesn’t start up when plugged into mains and the 9v backup battery leads were cut off for some reason. I incidentally found out it actually does turn on when holding the mains cable at a certain angle. I almost feel bad for resurrecting it.
Horay, it is alive
The radio and audio portion of the device works fine. The alarm clock portion however does not as the button pads on the PCB barely react to any for of manual shorting. I’m not motivated enough to debug and repair this.
2 euros at the thriftstore, don’t mind if I do! The Excel-O-Tone is pretty much a dumbed down Casio VL-1. It makes monophonic bleep bloop noises with a parrot button that repeats your last played x amount of notes. You can add in vibrato on the bleep bloops and that’s about it. Also I haven’t got a clue what a Yoko is besides an exquisite musician and artist from Japan.
Features
Power on/off switch
25 keys
1 oscillator (monophonic)
4 volume levels
4 tempo levels
Off-On-Off vibrato function
Note sequence repeat button
No clue what the “auto” button does, it just stops all keys from making sound
Headphone output (3.5mm)
Battery powered (4x AA @ 1.5V)
2 extra spots to store batteries for your calculator or something?
DC IN (probably 6v)
Yellowed
Why it sucks
Wonky key response. Keys don’t register when playing too fast, sometimes stutter, sometimes plays an x amount of time even after letting go. Not very musician friendly so to speak.
Vibrato not very convincing, also why is that switch off-on-off?
The sequence repeat function doesn’t take rhythm in account, every note plays for the same duration.
Teardown
First thing we see are two speakers (such a luxury!) a small PCB on the bottom for the DC IN and headphones out and a big PCB on the top which has all the rest.
Zooming in on the interesting part shows us what they use for clock, microcontroller and audio output amp.
My guess is the CD4069 (Hex inverter) has some function as clock for the COP420 (datecode week 8, 1985) that happens to be a 4 bit microcontroller which also handles all the other functionality like the “keyboard” and other switches and buttons.
They chose to use an LM386 (type 1) as driver for the two speakers. Why they use two speakers is a cost-cutting mystery to me as the “synth” is mono. To make matters worse, it seemed like the speakers were connected out of phase which initially gave me acoustic headaches while playing the bleeps and bloops. I decided to swap the wires of one of the speakers to fix that.
Always interesting to see the manually routed single sided boards. If you didn’t know yet, the PCB designs were laid out with tape! This is why the tracks look so wobbly. The keys just use a membrane type-o technology. Nice and cheap. The switches are stuck on the PCB by those black plastic frames. No way to replace them if something were to happen to them!
Note the unused footprint in the top-left corner. Seems like they were also in the process of copying the calculator which could be found on the Casio VL-1.
Why do I even bother with toys you ask? Well it was cheap at the thriftstore and the keys felt very usable for other projects if the keyboard tuned out to be broken or straight up useless.
So I already featured some Bontempi on here, especially because they also made a ton of very beautiful vintage instruments but then went the cheapo children’s toy road and here we are.
The sounds are horrible, the features horrible, the thing is buggy and glitchy and indeed only children would enjoy it. It’s like a christmas card with knobs.
Features
On/Off toggle switch
3 sounds (pulse, piano(?), violin)
8 rhythms
24 songs with demo song button
Microphone input (wow!)
DC voltage input (+6VDC) or 4 AA batteries
37 keys (but there’s a catch!)
Volume control (2 stages: normal and overdrive)
Rhythm select and stop button (but there’s another catch!)
Sound effect button!
Tempo up and down buttons (more catches here…)
Why it sucks
The black keys do not work as expected. They just play the nearest white key to the right. In short, this keyboard is in C major but they even fricked that up by having the A key play a A#. Very fonky.
When you start a rhythm and want to play along, you will be disappointing. As soon as you play a note the rhythm ceases to exist.
Keyboard is monophonic but the demo songs polyphonic.
The louder volume setting quite literally overdrives the amplifier chip. Poor parents.
There are 2 tempo buttons for the rhythms but they both perform the same function: they toggle between two BPMs.
The sound effect button adds a pleasant tremolo to the pulse sound, but on the other two its for some reason 3x faster.
Keys cannot be held down, the sounds just stop playing after a second. Actually, the timing is dependable on the pitch of the note as higher notes are just the 1 second sample played faster.
Microphone input is very quiet, volume buttons have no effect on it. Obviously a poor passive mixer on the amplifier chip.
Teardown
So what makes this toy tick…
We turn the thing over and remove many many screws around the perimeter of the keyboard, and the back lifts off. Obviously, be careful as the battery terminal wires are connected to one of the PCBs.
Sooo… 1 speaker, a funny looking PCB in the top left, a loooong PCB for the keys and some flatcables going to a very specific PCB.
MQ386F-…, yeah yeah yeah, just the amplifier board. Utilizes our good friend the 386 in SMD package. Nothing else noteworthy here.
The other side, just some electrolytic and the +6VDC power and mic input. The most shocking feature of this PCB is the unused USB footprint. Did they ever plan to add USB to this? You would be surprised if I said that the enclosure actually also has an unused cutout for a USB. Would it be used for charging some lipo? to actually send midi data? to just power the thing with a phone charger? Will we ever know?
Ah the brains of the machine, SLAB-2. Yes, friends, this is just a black blob microcontroller which controls everything from button presses to sending out audio.
In closure
It is trash.
The PCB with the rubber and carbon thingies to register key presses is actually fully equipped to also register the black keys just fine, they just went cheap.
It would be fun to find out if the chip does anything with USB but as I have no clue what to connect with what, we will never know.
A two euro thriftstore find of some brandless keyboard that makes some funky noises. I can’t really put a date on it but it is probably some 90s equipment because the plastic housing is actually quite sturdy.
In the box is only the keyboard itself and a tiny paper which is supposed to function as manual, fully in German. Some genius left 4 AA batteries in there that started leaking but I won’t be using batteries anyway because this keyboard has a DC input jack for 4.5 to 6VDC. Great!
Functionality
Some specifications and stuff:
37 tiny keys, no velocity sensitivity here
4 non programmable drum pads
2 note polyphony, duophony?
8 “instruments”
8 “rhythms” (rhythmical rearrangement of the 4 drum pad sounds)
Rhythm start and stop knob
Rhythm timing LED indication
Tempo up and down control (16 levels of tempo)
Vibrato function (actually quite cool and non-intrusive)
Demo knob (Plays Greensleeves melody with whatever instrument selected)
Microphone input
Headphone output
4.5-6VDC input (center positive) or 4x AA batteries
Mono speaker to the left
Master volume stepped control
Microphone volume stepped control
On/off switch with power LED inducation
Tear it down!
It takes about 8 or so philips screws to get the back lid off. Have to be careful cause there are flimsy wires connecting the battery terminals to the keyboard… board.
So yeah, batteries on the bottom lid, speaker bolted to the left, a brown single side PCB for switches, buttons and jacks. Smaller green PCB for all the digital stuff and power amp for the speaker. Connections are made with flimsy wires and those vintage ribbon cables that barely move cause they have solid core wires inside.
Now, this board is soldered by children or something (wouldn’t be surprised), there is stray solder everywhere but I guess it passed quality control. The nice part of the PCB is that if you look carefully, there are indications of components and padnames on the PCB.
Like to the right, SP for speaker, VCC, a +6v rail and a +5v rail. And to the left some designators for the throughole components. The big star of the show, the digital chip (which has all the logic and sounds on it) is the only SMD part in the whole thing.
Due to the nature of the shitty ribbon cables it was hard to peak under the PCB where all the goodies are. To the right a giant black SMD IC I mentioned before. To the left an LM386 doing its power amplifier job. Interestingly also a trimmer potentiometer. I’m not quite sure what its job is but I assume global tuning of the instrument but I haven’t tried. The fun thing is, this whole instrument is terribly voltage controlled. Modulate the power supply and you will modulate the pitch. The circuitbending community goes wild!
A close up of the speaker side of the keyboard. 1W 8 ohms, nothing special here and on the brown PCB are some more passives doing who knows what.
I didn’t bother to get the brown PCB out, it will not be exciting at all. It will probably look very similar to the board of the Bontempi BT 805.
The incredible noise killing mod
When powered by a noisy source like a phone charger, the keyboard won’t like you. The speaker starts buzzing and just won’t shut up. Using a good PSU or a linear one fixes most of the problems. To fix it even more, I invest 2 cents by soldering a random 470µF capacitor to the +5v rail to ground. Problem solved!
Sounds!
Here is a collection of various sounds the keyboard can make, enjoy!
All 8 instruments, vibrato on, MUSIC BOX – VIOLIN – FLUTE – ORGAN – GUITAR – BANJO – HORN – PIANO
It’s noticeable how most of these “instruments” sound like retro 8 bit sounds, quite fun to play with. Violin tries the hardest to actually be a real instrument. Organ is a mystery to me what it is trying to sound like. Banjo is interesting cause it has an asynchronous tremolo going on. It is possible to trigger a note right when it is silent, which is quite annoying honestly. Piano is just a horn with a shorter decay.
“Horn”, without and with vibratoAll 8 rythms, DISCO – BALLAD – MARCH – SWING – POP – WALTZ – RHUMBA – TANGORhythms at different tempos, can get quite fonky!The 4 percussive sounds, feel free to sample, KICK – SNARE – HIHAT – “COWBELL”
The kick is just a decaying note, actually interferes a lot with bass heavy instruments like the “horn”. The cowbell is just a joke.
Greensleeves demo song featuring all instruments with no vibratoThe same but with vibrato
And to finish the article, a piece of music I created in 5 minutes by layering many of the instruments and trying to keep time with the drum pads, enjoy!
Another thriftstore find for a staggering price of €1.25! This analog style (bass)guitar tuner by Korg from the 80s works on a 9V battery and uses a switch to change which string is being tuned. It also features a function to very roughly check battery health. The tuner can use a built in microphone or a 1/4″ jack basic instrument cable to let the tuner listen to the guitar.
The GT-6J with its worn down box.
Backside with 9V battery compartment.
From the front the slide selector is visible with the 6 strings on any basic guitar to choose from.
The battery check mode makes the needle jump into the green area when the 9V battery is still good to go!
Connected my phone to it with a 440Hz test tone, it is still bang on!
Tearing it down!
To get into the tuner, only one philips head screw one the back has to be removed. The enclosure consists of two shells that are clipped together. Some gentle wiggling will make them separate.
To get a view of the component side, the panelmeter has to be desoldered from the PCB as the panelmeter is glued against the front shell.
Nice handdrawn circuit layout. Apparantly this PCB is an LM-352-A.
At the component side (from left to right) we get a view of the electret microphone, the footprint where the panel meter goes and the input circuitry for the power supply. In this case the 9V is fed to a TO-92 7805 5v linear regulator.
There are two ICs on board. An LM358 DIP-8 generic dual opamp and an MSM5208RS DIP-18 from OKI. Datecode seems to be week 19 of 1981! This IC most probably handles everything needed to compare the input signals with the reference frequencies and in turn drives the panel meter. I could not find a datasheet on this IC so if anyone finds it, be sure to message me!
The PCB also has two trimmers on board. One is accessible via the battery compartment so probably used to finetune the panel to 440Hz, either by user or factory. No clue what the function is of the other pot.
When a product proudly mentions quartz, it just means that there is a quartz crystal inside. The dimensions of the quartz crystal are defined so it resonates at a certain frequency with quite a lot of precision. This one is apparently trimmed to resonate at 5.51912MHz. You would be surprised how hard it would be to find a replacement for that frequency…
Here some more beauty shots:
Side view
Electret microphone and 5V PSU circuitry
The epicenter of tuning
A fun video where I feed the tuner a frequency modulated signal from 430 to 450Hz:
Saw this unit lying around at a thriftstore (€5) thinking it had something to do with audio because it had tape written all over it. Then I googled and found something about the Hammond XC3000? Like is it some sort of rotary speaker controller? I got excited and bought it right away to find out later it’s nothing but a so called slide dissolver.
I think the big idea is that back in the day where slide projectors were still a thing, you’d set up 2 of them and used a slide dissolver to switch between the two and make some sort of interesting audiovisual spectacle.
I don’t own any slide projectors and audio intrigues me more than video, so I might reuse the fader controller as some sort of synthesizer ribbon controller.
Anyway, I opened the thing up. It was full of CMOS logic ICs so that was a nice sight. Less nice were the amount of repairs that were done to it. I guess it wasn’t very reliable but important enough for the previous owners to replace chips capacitors and resistors all over the board. Anyway here some shots:
Excuse me for the mess. So we have a hand control input for the fader controller on top there, and a tape input I assume for… audio? The rest of the LEDs and buttons are a mystery to me. The device also uses 50 shades of DIN connectors so there’s no DC input or other simple way to turn it on.
Opening up the fader controller, we see a slide potentiometer with two end switches. I assume they allow you to go to the next slide. There’s also this blue non latching switch labeled “FLASH”. Not a single clue what that’s supposed to do but induce seizures on those watching the show.
Look at that! Quite beautiful if you ask me. Nowadays we’d use a single microcontroller to handle all of this, but back then? Digitial CMOS everywhere.
As I have no clue how this device works, can’t find any schematics or am bored enough to trace the whole machine, I’ll just leave you with a load of closeups of the board!
Another cheap thriftstore find. This 1968 cassette recorder comes with a (electret) microphone and runs on 6VDC. it also has an output for “external “SR” radio”. Whatever that may be.
It works well under low volume but at higher volume it starts squealing and with a bit of artistical input you can make it sound like a formula 1 car.
If anyone has more information or is familiar with this problem and knows a cure, don’t hesitate to leave a comment or contact me!
Front viewIn- and outputsBackside with battery compartmentView when removing the back lidClose up of the PCB
Trevor's Repair Café 