💬 OT The (not really) official electronics workbench thread

[Mr_Roboto]

Did some tinkering and replicated an offering I saw earlier. It seemed to work decent. With the nanovna on the way, I decided to build a test amp. This should let me flex into a lot of configurations for testing things like input imp dance. This will be another xacto PCB, or I may upgrade to a Dremel. Not sure yet.




Schematic

Layout
On board ready to cut.

 

[sktchy]

Ok holddd up my early college level electronics knowledge wants to know if your gonna etch that board with acid and shit? That was always fun.

 

[Mr_Roboto]

Nope.



I will admit I need to do some testing around cutting etched pcbs but I am not there. I am wanting to do more smt so that's less drilling.

 

[Ron Vogel]

I’m just here trying to fix all my broken shit

 

[Mr_Roboto]

That broken shit looks as if it would be loud if working.



Where I left off. Needs more parts. Base circuit is done the except the coupling capacitor, the emitter circuit is done, the collector circuit needs an output transformer.

 

[Ron Vogel]

That broken shit looks as if it would be loud if working.

View attachment 185159

Where I left off. Needs more parts. Base circuit is done the except the coupling capacitor, the emitter circuit is done, the collector circuit needs an output transformer.

70w/130w bi amplifier. It kinda works, I have 3 of these with the same issue. I bought everything to replace all components and have been working on one of them to isolate the distortion in the circuit. Everything but the resistor network and about 10 resistors have been replaced. Last of the parts coming today.

Everything highlighted in green or yellow has been replaced, still has a distortion that sits on top of signal mostly in 1k range.

 

[Mr_Roboto]

Do you have an oscilloscope and a function generator? I'd feed input through it then try to isolate to a stage where the distortion starts. Shotgunning parts into something is honestly a rough way to go.

 

[Ron Vogel]

I don’t, I wanted to upgrade all the electronics…so I’m throwing money at it in stages. They are pretty nice monitors, but KRK cheaped out on some stuff. I upgraded all the film caps to mkp Wima’s. They had non-audio rated caps in the entire signal path, then I used all fg-gold for electrolytic caps, etc

 

[SpeedSpeak2me]

Be careful with that electricity. Reddy Kilowatt from 1926 knows!

 

[Ron Vogel]

I got the shirt....

 

[Mr_Roboto]

https://wiki.analog.com/university/courses/electronics/text/chapter-9

Analog devices has a wiki. This looks nice.

 

[Mr_Roboto]

Be careful with that electricity. Reddy Kilowatt from 1926 knows!

View attachment 185214

I once took a belt off a microwave oven transformer. One hand rule likely saved my ass.

 

[Mr_Roboto]

I don’t, I wanted to upgrade all the electronics…so I’m throwing money at it in stages. They are pretty nice monitors, but KRK cheaped out on some stuff. I upgraded all the film caps to mkp Wima’s. They had non-audio rated caps in the entire signal path, then I used all fg-gold for electrolytic caps, etc

Keep an eye on craigslist a hundro will get you one if you are patient. You don't need anything fancy at audio frequency. At worse you could probably use an mp3 player or sound card to drive the amp. An audio frequency oscillator is probably out there in kit form.

 

[sktchy]

I'm pretty sure my love for doing this kinda stuff died when radio shack did. It was a different world when you could just go grab parts at the mall vs waiting for a week for somethin off the internet that's probably no where close to what you wanted

 

[sktchy]

I miss having an oscope though. Probably should get a cheap one or upgrade scantools one of these days.

 

[Mr_Roboto]

I'm pretty sure my love for doing this kinda stuff died when radio shack did. It was a different world when you could just go grab parts at the mall vs waiting for a week for somethin off the internet that's probably no where close to what you wanted

AliExpress is oddly good for this stuff if you are patient.

 

[sktchy]

AliExpress is oddly good for this stuff if you are patient.

That's the problem. If it's weeks I'm already over it and it'll sit in a pile of other shit forever til I come back around. It's gotta be there while I'm still fresh or I have other priorities quick lol

 

[SpeedSpeak2me]

That's the problem. If it's weeks I'm already over it and it'll sit in a pile of other shit forever til I come back around. It's gotta be there while I'm still fresh or I have other priorities quick lol

Do you have a MicroCenter near you? They do have some off-the-shelf components. Not anything like RadioShack did. Or hell, even Fry’s had a pretty good selection before they went belly up.

 

[sktchy]

Do you have a MicroCenter near you? They do have some off-the-shelf components. Not anything like RadioShack did. Or hell, even Fry’s had a pretty good selection before they went belly up.

I don't have shit but what my local hole in the wall parts store can dig up. Could maybe try a computer place but they could probably give a shit about caps and transistors and stuff. Back when I was playin with this stuff leds were newer tech so much beyond a fairly decent knowledge of the basics I'm a dinosaur anyway.

 

[SpeedSpeak2me]

I don't have shit but what my local hole in the wall parts store can dig up. Could maybe try a computer place but they could probably give a shit about caps and transistors and stuff. Back when I was playin with this stuff leds were newer tech so much beyond a fairly decent knowledge of the basics I'm a dinosaur anyway.

If you’re a dinosaur, I’m the dirt they walked on

 

[sktchy]

If you’re a dinosaur, I’m the dirt they walked on

I'm getting up there. I just make most of my decisions like I'm 12

 

[Ron Vogel]

Well, fixed the problem by buying a new pair.

Will have to fix/sell the old ones eventually so as not to be divorced

 

[Mr_Roboto]

Well, fixed the problem by buying a new pair.

Will have to fix/sell the old ones eventually so as not to be divorced

View attachment 185393

Dayum buy a scope dude. Seriously. If you were in Wisconsin we could hit up my sty of a basement and have a poke.

Meanwhile starting to see some payoff. I upped my capacitor on the l network at the input to 400pf or so compared to 100pf. I am seeing good swr on the Antuino now. Not perfect but wide spectrum so that is good. The stage is giving about 15DBm gain so I can't gripe. Up next is a variable.








After that I optimize power on the output and then I can start working on the impedances of the transistor.

The PCB assembled. I was short some adapters they're on the way.

After the input was sorted the harmonics look way better. At about 30db down this will still need filtering but not horridly. I may nibble off some gain with a 6db attenuator. Because reflected power goes 2 directions I should get about -12db on the harmonics.

 

[Mr_Roboto]

My first attempt at transferring PCB material in probably 15+ years. I have probably had the piece of junk mail printed for a test 2ish years now. I am borrowing the house iron, my wife isn't home to know.

Fine print:



And coarse print.



Hit it with the iron and peeled it back. Not consistently transferring.


Second shot. Got this one hotter, still missing a piece. Wonder if there is a flatness issue somewhere.


Third transfer, still issues. Wanna evaluate surfaces for flatness. I am using a piece of pine under the circuit board want to get a chunk of glass or something similar. Maybe borrow a 9x13 pyrex pan for a few moments.

 

[Ron Vogel]

I’m still going to fix them, but I am so limited on time. I carve out 3-4 hours to work on music Friday nights. Haven’t had any progress because of equipment issues that I just am tired of it.