iiinova — where your digital self keeps evolving

Sara M @anthocyanina.bsky.social · 12/10/2026

almost done with the schematic! i tried to draw it close to the original as well. (i'll make the files available when it's done)

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Sara M @anthocyanina.bsky.social · 12/10/2026

yeah, this is what i'm thinking too. thank you!

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Sara M @anthocyanina.bsky.social · 12/10/2026

when the voltage between the cathode and anode of that zener is more than 9V, Q704 and Q703 shunt the signal from the preamp output to signal ground

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Sara M @anthocyanina.bsky.social · 12/10/2026

the more i look at it, the more it looks like a muting thing, like a slow unmuting circuit that unmutes when Q812 is switched on enough. that diode Q813 is a 9V zener. in the actual circuit there's a 10k resistor between the anode of Q813 and the bases of Q704 and Q703

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Sara M @anthocyanina.bsky.social · 12/10/2026

hmmm, so this transistor is a muting switch or something similar? anyone knows for sure what the purpose of this circuit is?

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Sara M @anthocyanina.bsky.social · 11/10/2026

i still find it interesting that this was a problem only with the phono input

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Sara M @anthocyanina.bsky.social · 11/10/2026

probing input and output at the same time with the output probe connected to the dummy load's positive terminal and not connecting the ground lead to the load also worked well. turning up the volume no longer resulted in the oscillations. probing technique really matters after all!

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Sara M @anthocyanina.bsky.social · 11/10/2026

well, it turned out to be a measuring problem and not a problem with the amplifier after all! i had connected the ground lead of both probes in different locations, and it was that ground loop that was causing trouble and causing the wild oscillations. probing just input or output alone was good

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Sara M @anthocyanina.bsky.social · 11/10/2026

with a larger input signal (0.1Vrms) i can get to max Pout, and the signal looks ok, but again, can't turn up the volume knob all the way. using the "tape 2 /aux" input, i can turn up the volume knob all the way with an input of 0.1Vrms, which becomes ~800mVrms at J705 and get max Pout

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Sara M @anthocyanina.bsky.social · 11/10/2026

well, crap! as i was measuring the gain of the original amplifier to select the components for the LM3886 i found something else wrong with this thing: youtu.be/ivrVDsyl0mY 10mVrms phono input, I can't turn the volume knob high enough to get max Pout. it begins oscillating

youtu.be

not groovy

YouTube video by Sara M

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Sara M @anthocyanina.bsky.social · 10/10/2026

oh well, but if you're not going to do the whole bare die and etched components thing, where's the fun in that?

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Sara M @anthocyanina.bsky.social · 10/10/2026

So, i want to preserve the original layout in the new P700 PCB, but, this doesn't look too good to me. i'm already redoing the amplifier and finding modern component replacements for the rest of the board, maybe a few more minor layout changes won't hurt. I really don't like that jumper. hmmm

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Sara M @anthocyanina.bsky.social · 10/10/2026

xD that would be fun, don't think too realizable at home tho

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Sara M @anthocyanina.bsky.social · 06/10/2026

going through the P700 board's BOM as i'm going to rebuild it around the LM3886, so i was marking the components surrounding the STK080Gs, and i noticed R714 is missing from the schematic! how odd. the schematic also has a few different values for some components compared to the BOM, most curious!

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Sara M @anthocyanina.bsky.social · 06/10/2026

unfortunately that turned out to just be a power pack, not the full amplifier like the STK080G is, so i'm going to copy the entire P700 board but will redesign the amplifier circuitry around the LM3886 instead

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Sara M @anthocyanina.bsky.social · 29/09/2026

hmmm, it looked really fun, but the ai bit, would you ellaborate on that? on the one hand, playing oscilloscope: the game, when i'm bored of real oscilloscopes sounds fun, on the other, paying actual money for something a robot wrote, that's a precedent i wouldn't like to set. so, how much ai in it?

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Sara M @anthocyanina.bsky.social · 24/09/2026

great. thank you! i'll check this out! :D

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Sara M @anthocyanina.bsky.social · 23/09/2026

and what if the ram on your pi dies? now you have a paperweight that can't be easily fixed. ram upgrade isn't the only reason why that lockdown sucks

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Sara M @anthocyanina.bsky.social · 22/09/2026

ooo, yeah, that would be great. thank you!

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Sara M @anthocyanina.bsky.social · 22/09/2026

the base of QE03 in orange as reference, with the same input signal on both channels, and in yellow, the base of QE04. it's different but it doesn't look different enough for the input transistors to be dead? i'm going to have to take the entire thing out and remove the output transistors to test

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Sara M @anthocyanina.bsky.social · 22/09/2026

i traced the input signal all the way to the input of the tone control board. the green highlight is the last place where i checked the signal was good. in red is the source of the farting noises, and in orange, where i suspect the fault lies. I poked at both input chs, and saw something interesting

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Sara M @anthocyanina.bsky.social · 22/09/2026

after disconnecting the wires at J706 and J708, i connected a generator to the input of the LM391, and fortunately the entire output stage is working perfectly. the farting noises remained at those wires:

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Sara M @anthocyanina.bsky.social · 22/09/2026

another marantz receiver to fix from the same owner as the SR 2000. this one, an MR 235, has a farting channel. i opened it up and thought the problem lied in the LM391N-80, but it turned out to be somewhere else...

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Sara M @anthocyanina.bsky.social · 11/09/2026

omg, what is it with bot accounts begging for money/help insta-reposting everything?

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Sara M @anthocyanina.bsky.social · 11/09/2026

the evolution of flower's computer desk/electronics bench in a single photo! (cleaned it yesterday so it was a rare opportunity to record it 😬)

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Sara M @anthocyanina.bsky.social · 09/09/2026

just give them a good dip in some milk! (do avoid the cream on their backs)

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Sara M @anthocyanina.bsky.social · 09/09/2026

the left channel does have the original amplifier on it, so that's good, too bad these chips are so hard to find. i think i'm going to have to make another amplifier for the right channel and try to match it to the left. maybe an lm3886 based amplifier will do.

a photo of the original STK080G on the left channel of the receiver. it's all dusty. you can see some wire wrapped connections to the left. the thing looks like a big black cookie with 10 legs

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Sara M @anthocyanina.bsky.social · 09/09/2026

oh no! a bodgey channel replacement! this is going to complicate the "as close as new as possible" part, hmmm! i wonder if those long leads to the bodged board are at least partly responsible for the loud hum. those transistors should be much closer to the board, not driving down inductance lane!

an initial look inside. seen slightly to the left of the image is a green aftermarket amplifier driver board with hot glue and wires soldered directly to the input and output pins. near the middle of the image the heatsink can be seen, and a top view of an original STK080G module for one channel at the top, and two transistors that connect to the bodged board at the bottom. the dead STK 080G was removed from the board. on the right side of the image the radio tuner board can be seen

I flipped the green PCB which was just floating there, not screwed or fastened to anything at all, and we can see the components. the output transistors are connected to this board using long wires, and a lot of sketchy solder joints can be seen on the green PCB.

a closer look at the transistors on the heatsink. there's a lot of thermal paste. the markings on the transistors can't be seen from this angle. everything is super dusty

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Sara M @anthocyanina.bsky.social · 09/09/2026

today on my table, an old timey marantz SR 2000. it's humming loudly. we'll see what's hiding inside. the owner wants it to be restored to as close as new as possible, but i was told someone's been in there before

a photo of a marantz sr 2000 stereo receiver. it has a bit if a dent on the top cover, and some scratches

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Sara M @anthocyanina.bsky.social · 04/09/2026

there's *something* going on there, but i'm thinking the oxide layer is so thin that the breakdown behaviour i'm seeing there could be related to capacitive leakage? maybe it's really breakdown? hmmm

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Sara M @anthocyanina.bsky.social · 26/08/2026

hmm, i couldn't get any of these to work. the layer of oxide is too thin and when a good contact is made, the probe breaks through and shorts to the metal

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Sara M @anthocyanina.bsky.social · 26/08/2026

i grew better cuprous oxide layers on my latest attempt at semiconductors. i also got zinc oxide powder because i want to have a go at a transistor. i'll have to measure these. more updates eventually :tm:

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Sara M @anthocyanina.bsky.social · 23/08/2026

i'm trying to make a new tinning solution for PCBs, my old solution has stopped working after years, i have dubious tin chloride, and a silver cleaner with thiourea, and pure tin metal. can i make this more acidic to prevent tin hydrolysis using sodium bisulfate? will it still plate on copper?

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Sara M @anthocyanina.bsky.social · 19/08/2026

years later this still annoys me about this scope, the trigger point on the screen is offset by about 500ps, and it becomes extremely noticeable at higher frequencies. keysight never bothered to fix this, i wonder if the 1200x series also have this annoying problem

a screenshot of a 240MHz sine wave on a keysight 1102g with the trigger point set at 0v and 0s, but the waveform being displayed about 500ps earlier than the trigger point

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Sara M @anthocyanina.bsky.social · 08/08/2026

that's an option too! just that since i need to buy the internal usb c cable, and 19 pin usb 3 cable, i first want to see if what i'm looking for is already bundled together with mounting hardware and all, but it looks like the best i can find is the original image i posted, and add audio myself

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Sara M @anthocyanina.bsky.social · 07/08/2026

thank you! yeah, i saw that one, but it has no usb c :c it looks like i'll have to modify whichever one i get to either add usb c or a headphones jack

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Sara M @anthocyanina.bsky.social · 07/08/2026

my computer is a wooden plank on the wall, and i want to put something like this with the ports facing down for easy access instead of dangling cables 🙈

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Sara M @anthocyanina.bsky.social · 07/08/2026

anyone knows of a thing like this but that also passes internal audio straight from the motherboard? i've found some that have audio, but they do it with a usb hub and usb audio codec. i want a front panel thing that just passes things straight through, like this one, but also with audio

a pc front panel "module" for like a floppy bay that exposes usb A and usb C

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Sara M @anthocyanina.bsky.social · 31/07/2026

a tiny baby gecko literally jumped at the opportunity to learn about attenuators

a zoomed in photo of a baby gecko walking on a computer display that is displaying the wiki page for T pad attenuators

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Sara M @anthocyanina.bsky.social · 30/07/2026

new addition to the lab! it gets unexpectedly warm tho, is that normal? hmm!

a tinysa ultra 406 on a wire stand on a black piece of paper showing max hold and live trace of a 5GHz wifi network during heavy load. the live trace only showing brief spikes and the max hold trace tracing the entire channel width

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Sara M @anthocyanina.bsky.social · 17/07/2026

is it just me, or ia the electronics feed mostly ai bullshit ads now? hmmm

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Sara M @anthocyanina.bsky.social · 03/06/2026

found the solution: uncheck those things. they shouldn't be checked by default, but whatever!

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Sara M @anthocyanina.bsky.social · 30/05/2026

they have reversed their decision! adaptivesupport.amd.com/s/question/0...

adaptivesupport.amd.com

AMD Customer Community

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Sara M @anthocyanina.bsky.social · 21/05/2026

people on the AMD FPGA forum have complained about their shitty abusive behaviour of removing linux support in the new version, and AMD has replied with censorship: you can't call them out for being shitty or they'll ban you! but their abuse against the community with those changes?cool and normal

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Sara M @anthocyanina.bsky.social · 21/05/2026

damn, just got an email about AMD's new vivado licensing plans. the basic plan doesn't have linux support, that's quite shitty of them. AMD just keeps getting shittier and shittier, limiting rocm on older radeon and stuff, and now that shittiness is also coming to the FPGA world? damn!

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Sara M @anthocyanina.bsky.social · 19/05/2026

alright, so, how do people actually trace signals in FPGA designs? this chonkin' mess of wires seems humanly unreadable even after zooming in

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Sara M @anthocyanina.bsky.social · 06/05/2026

why the fuck does libreoffice writer untab my manual tabs when i press enter? i haven't been able to figure this out and it's making me crazy. i just want to type stuff with tabulation and have it keep the tabulation. this is so infuriating. this is a fresh install. everything default

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