💬 OT The (not really) official electronics workbench thread

[Lord Tin Foilhat]

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

Buy a bunch of shit for cheap from China...then you'll have a big collection of stuff for repairs.

Capacitors, resistors, connectors, etc..just buy a "Here is 10 of everything" pack. You'll order it, forget about it and a month later a package will show up and now you are your own RadioShack.

 

[Lord Tin Foilhat]

See what I mean? Shits stupid cheap

 

[sktchy]

That's actually a stupid good idea cuz you never know...

Ali have neat wiring stuff like bulk zip ties and cheap rolls of wire and loom and friction tape and all that?

 

[Lord Tin Foilhat]

That's actually a stupid good idea cuz you never know...

Ali have neat wiring stuff like bulk zip ties and cheap rolls of wire and loom and friction tape and all that?

Yup. Most of it comes from China anyway lol

 

[sktchy]

Yup. Most of it comes from China anyway lol

I'd ask if they're gonna spy on me but so does the us so whatever.

 

[Ron Vogel]

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:

View attachment 185424

And coarse print.
View attachment 185423

View attachment 185427
Hit it with the iron and peeled it back. Not consistently transferring.

View attachment 185425
Second shot. Got this one hotter, still missing a piece. Wonder if there is a flatness issue somewhere.

View attachment 185426
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.

I just used that dry transfer stuff from RS back in the day

 

[Ron Vogel]

The fix is in…these things are amazeballs

 

[Lord Tin Foilhat]

The fix is in…these things are amazeballs

View attachment 185607

Idk, coulda got a Samsung soundbar instead.

 

[Ron Vogel]

Lol, how many sound bars go to -3db at 35Hz?

 

[SpeedSpeak2me]

Idk, coulda got a Samsung soundbar instead.

 

[Ron Vogel]

Ok, I get it…however this is more of a tool than entertainment.

 

[Lord Tin Foilhat]

Ok, I get it…however this is more of a tool than entertainment.

Trying to listen to EVPs for ghost voices?

 

[Ron Vogel]

Working on a new album, way more complex soundscape

Moment

A collection of music I've been noodling on for the past several years. All of the songs are personal to me. These songs had been previously lost to a hard drive crash. These are the songs that could be recovered. I am very happy to share them

ronvogel.hearnow.com

 

[Mr_Roboto]

TinySA will track harmonics off a fundamental. That is very cool.

 

[SpeedSpeak2me]

View attachment 185643
TinySA will track harmonics off a fundamental. That is very cool.

One of the reasons I bought mine.

 

[Mr_Roboto]

Been playing around with LibrePCB. So far it's missing a few items around pad layouts for components, but otherwise it's pretty good honestly. This is one of the first boards I'm working on, its basically the amp stage above with SMT parts and a different input circuit.

I took that circuit and looked at it today vs a kit I bought. It's no worse nor better harmonics wise. If anything the one I made will take more drive before getting harmonics.

I'm about to build another stage that's push pull, supposedly that will help cancel the second harmonics.

 

[Mr_Roboto]

Did a little playing around with the NTE278 parts I've been working with lately. They're supposed to be like a 2N5219. The circuit is as the image except I have a 1.5mA meter in line in the base circuit and a 100mA meter in line with the collector. I think I'm going to play with the bias a hair and probably put it at about 65mA idle. If the ammeter on my power supply is accurate, I'm probably idling at somewhere near 30mA right now. I'll have to double check that too. I think that the bias should be considerably hotter. It is likely fine for the first stage, but if I want more power out of this part class A I need to go to a higher idle current. I stopped where I did because further increasing voltage into the base wasn't getting any additional output so I figured the part had gone as far as it would at 12V. IB and IC are in mA.

V​	IB​	IC​
1.49​	0.1​	9.5​
2.31​	0.2​	14​
3.12​	0.3​	20.5​
3.91​	0.4​	27.8​
4.7​	0.5​	34​
5.5​	0.6​	42​
6.33​	0.7​	50​
7.14​	0.8​	58​
7.92​	0.9​	66​
8.77​	1​	75​
9.62​	1.1​	84​
10.32​	1.18​	92​

 

[Mr_Roboto]

Today was a wtf. I have some ST labelled 2n2219a transistors that were acting weird in my test circuit. I stuck one in the tester and this came up. These are supposed to be NPN parts! Fuckin eBay knockoffs.

 

[SpeedSpeak2me]

 

[Mr_Roboto]

They behave electrically opposite of one another.



I need bias on this but the circuit is otherwise complete. Going to put a pot on it so I can try class B and AB.

 

[Mr_Roboto]

The final product. Man this works too! I just set the bias for best linearity and went.


After the attenuator I think this is about 25dbm. That's a lot of gain. I lose about 1dbm over 1.8-28MHz. very broad band. I did not look for -3db betting it is way up there with the ferrite limiting things.


Input through the attenuator. I had this set to 0 dbm on the Genny so I am betting it is really attenuating -35dbm or so.

I think I am going to do very small transistor push pull for the second stage as well unless I can figure out how to get single ended to clean up it's harmonics.

 

[Mr_Roboto]

This may have been a bad idea. Either I'll have an amateur radio amp or an FCC violation. Not too sure of which at the moment.

 

[Mr_Roboto]

I think I had a break through on the Ubitx. They're a radio that's had some erratic power output depending on band in the past, and people have tried to remediate the amp. There's a filter before the amp chain that I think is causing the variability. This is the curve of the filter as per a simulator, pretty crazy looking. The peak is at 14MHz, and the last bump on the right is 28MHz approximately. It's down -10DBm before even getting fed into the amp chain. It also explains why 14MHz is known for spurs and noise, the amp is way over driven.

 

[Mr_Roboto]

Bad decisions have been made! I got these guys dead from an a appliance store for 20 bucks! I pulled the transistor out of one of these and it was toast, I need to do the other one. They're about $4.50 from Digikey so I'll probably go that route. The ebay kit has bridge rectifiers in it as well for $1.40. That tells me they probably take the bridge out with the transistor.


Uhoh. Lucy got some splaining to do about why she's been sticking forks in the microwave.

 

[SpeedSpeak2me]

I wish I knew what I was looking at.