Test Equipment Anonymous (TEA) group therapy thread

[mnementh]

I liked the dio-citor, myself... 

mnem
 

Skipped your morning coffee? That's the standard symbol for a Varicap.

McBryce.

Ahem:

mnem
*agitating-ily*

[0culus]

After yesterdays Blood Bath of injuries I opted for some 'safe' woodworking by Laser. Because Lasers are safer 

Couple of woodworking tools, marking gauge, marking knife and a center finder. Trial fitted and glue up tomorrow time permitting. Marking knife blade is subbed by a ply one until I brave the hacksaw and grinder.

Fusion 360 for the modelling bit.

"Dang! Do Not Look into Laser with Remaining Eye!"

 

[mnementh]

Hey @Brumby want to raise the blood pressure of SHMBO 'some more'        Needs some love but if it was closer I would find a place for it in the toy collection  eBay auction: #193188410543

Oh, now THAT is a thing of beauty... bet those are all glass-substrate too. *sigh*   

When I was a kid, I'd spend hours collecting them from dead TVs in the dump, remove the endcaps by filing & wiggling them loose, then soak and scrape all the insulative coating off.

What for...? Because to my youthful mind, the gunmetal-iridescent coating and light-transmissive qualities were EXACTLY what a finished LightSaber power crystal should be (Remember, back then there was only scant reference from Ep IV, V, & VI and a couple books by Alan Dean Foster); I'd spend hours making little battery-powered lamps out of found materials that featured the things with light passing through. That may in fact be how I first got into electronics...

*mnemories*

[Mr. Scram]

Hardly. We are still visitors... tourists. The trailer is in storage stateside until all our paperwork is complete. We arrived here with what we could pack in the back of a Rav4 (plus 3 storage bins on a trailer-hitch fanny-pack).

So much cash outlay just getting here, then all the stuff you need to buy to "startup" a new household... Dishes, cutlery, coffeepot/nukebox/toaster, etc... the first pantry & fridge-full of food... Shit, we spent $350 yesterday to get Parkas & heavy pants for the boi & grrl. At Costco we spent that much just on 2 kids, FFS!

So yeah... there's a reason I'm shopping nonessential shit like this from the Thrift. 

I still got 4 good satellite speakers out of the thing... plus I can always seal up the sub & make it passive; run it from another amp. Maybe shell out the CAD$10 for a TPA3116D2-based 2.1 amp board upgrade. Woohoo!!! 

mnem
Dammit... now I'm thinking about how I need my printer to make the backplate... 

You moved a metal shark but not your toaster and plates?

[mnementh]

   Although not strictly test equipment - it certainly is a Boat Anchor. On the weekend it was our state's biggest buy and sell - lots (well 3)of Yaesu FRG 7s - a lovely receiver.

But a FT101B for AUD 50 with all bits minus the 'finals' was too good to pass by. Cosmetically pretty good, no final tubes but I happened to have a spare pair for my working FT 101E, The dial has the sticking issue and some idiot has burnt out one of the blades in the power connector - so a bit of sleuthing will be required - a bit of fun. My fingers remain attached at present!

*wistful sigh*

Grand-dad had a FT-101EX. Most of my positive memories with him revolve around that thing... like listening to people cheer over a Cricket match and several evenings spent listening to his stories and hand-winding a 3KV transformer on a car battery booster-charger XFMR because my fingers were little and he didn't want to grind the welds off to separate the laminations...

*more mnemories*

[mnementh]

...was going for this.   maybe a little too old and too obscure?

Oh, now yeah... it makes sense. More like the Venn diagram of that reference' obscurity and my own personal obtuseness... mixed in with hazy memories of a movie I haven't seen in decades. 

mnem

[AVGresponding]

I chose to stay out of yesterday's discussion of scars and stitches because I don't want to rehash in my mind all the nasty injuries I had as a kid with glass, rocks, and deli meat slicers. 

The stories I could tell and the scars to prove it. 

Dayum you guys are clumsy...

 Only had 2 injuries needing stitches in my 49 and counting years, both to fingers and to the bone, 3 stitches in my left index finger (trimming lego caterpiller tracks down to cam chain at age 14), self applied butterfly stitch to my right pinky (received from the chipped rim of a glass cup I was washing out to have a cup of tea  ).

Never broken a bone.

Oh wait, I remember, I've had 3 trips to hospital for my eyes, 2 to have brass swarf tweezered out, and once for a scratched cornea. That last one was probably the most uncomfortable injury I've ever had, like a burning itch that was impossible to scratch...


EDIT: OT, I been at it again, got a Robin SmartPat 5000, and have a Fluke 1953A counter on the way, pics to follow   

[mnementh]

   A few years ago I was given a THX certified sound system, I was told that it was a 5.1 system and I was expecting something small like you see in computer shops with the flat panel type of side speakers, instead I was confronted with this beast of a system that weighs over 40lb .

Getting it home and connecting it to my computer took my breathe away with its huge powerfull deep bass and sheer volume, the thing is capable of delivering continously 200W of power, not peak power but 24/7 RMS watts that shakes the doors and windows if you wind the volume up. Watch a movie and have the sound delivered via this on the PC is awesome, it beats the pants of my system for the TV and to think I got it free, even today I pinch myself, never heard anything to match it either, watching movies on it, you get that real deep rumble that makes your stomach tremble just as you get in the cinema.

   

LOL... this morning, I put the subwoofer from a Z5300 THX system on the bench to triage. (Pics scavenged from the IntardNet)

It too is one of those man-eating black boxes that makes your gonads vibrate from across the room. I don't have a LOT of hope for it; it's missing the control pod and I can see some Darwin-Award-Contender wrapped a blown fuse with speaker wire when it died due to some form of abuse. 

But it uses the same satellites as the ones I have so I figured I'd take a CAD$25 gamble, as it was a $700 system when new. 

The painful part will come IF I discover it isn't beyond salvation... acquiring the missing satellite speakers and control pod, THEN I'll need to spend real money on a DSP with remote to tie it into my TV. 

You moved a metal shark but not your toaster and plates?

Yes. ALL OF IT into a 30-foot trailer. Which is in storage for the next 2-6 months until our paperwork is complete. What CAME WITH US across the border was only the absolute necessities... winter clothes (for Texas), a campout's worth of kitchen essentials, my smallest Technician's case full of tools. Plus my just-built gaming/VR PC and of course... my son's Pokemon collection and our Lightsabers.  PRIORITIES, man!

mnem
*tzzzt* 

[bd139]

Ooooooh NanoVNA is a whole box of amazing. Got it hooked up to PC now and using NanoVNA-saver



1.8m BNC cable. Measured at exactly that length!!!!

[mnementh]

Fuck you. 

mnem
 *tzzzt-tzzt*

[Specmaster]

@bd139, thjat case you made sure looks good and quite sexy in blue to boot 

[med6753]

@bd139, thjat case you made sure looks good and quite sexy in blue to boot 

Took the words right out of my mouth.....looks good in blue.

Papa Smurf approves. 

[bd139]

Hahaha 

[med6753]

An 8810A ongoing update. It took just under 2 hours to reach yesterday's cal point. Not unreasonable but the similar 8800A's reach that point in under .5 hours. But what IS encouraging is that it's been powered up for 5 hours now and once it reached that cal point it has NOT drifted any lower. 

I think I know why the change from last week's miserable total drift from 9.9974V down to 9.9964V but I'll wait and see once it has close to 10 hours on it.

[tggzzz]

An 8810A ongoing update. It took just under 2 hours to reach yesterday's cal point. Not unreasonable but the similar 8800A's reach that point in under .5 hours. But what IS encouraging is that it's been powered up for 5 hours now and once it reached that cal point it has NOT drifted any lower. 

I think I know why the change from last week's miserable total drift from 9.9974V down to 9.9964V but I'll wait and see once it has close to 10 hours on it.

My Solartron 7081 has a procedure for when it has been in storage for a while. You wrap it in a blanket, turn it on, and let it cook at 40C for a day. Apparently that evaporates any volatiles on the PCBs.

Maybe something similar is happening here.

[med6753]

An 8810A ongoing update. It took just under 2 hours to reach yesterday's cal point. Not unreasonable but the similar 8800A's reach that point in under .5 hours. But what IS encouraging is that it's been powered up for 5 hours now and once it reached that cal point it has NOT drifted any lower. 

I think I know why the change from last week's miserable total drift from 9.9974V down to 9.9964V but I'll wait and see once it has close to 10 hours on it.

My Solartron 7081 has a procedure for when it has been in storage for a while. You wrap it in a blanket, turn it on, and let it cook at 40C for a day. Apparently that evaporates any volatiles on the PCBs.

Maybe something similar is happening here.

I suspect part of it is exactly that since it had not been used in quite a while but I don't think it explains all of it. 

[mnementh]

Hmmmmm... initial inspection shows no evidence of fire or magic smoke, and the rails are steady on at +/- 25.5V from a good old-fashioned linear power supply buried in the sub enclosure. After an hour powered up, all finals feel slightly warm but none warmer than the others.

Based on specs, I expect this should deliver right around 25W continuous per TDA7296 in AB operation, and this thing has 8 of the little bastards with two in BTL mode for the sub at probably 75W continuous or so. Fukkin-a-diddy! That's $50 worth just in the finals!!!

Now I need to figure out how to do turn-on/un-mute to inject signal & see if they're all healthy... I have an eval circuit in the datasheet, so should be able.

Hmmm... https://www.diyaudio.com/forums/chip-amps/135930-logitech-5300-remote-2.html

mnem
 

[med6753]

Hmmmmm... initial inspection shows no evidence of fire or magic smoke, and the rails are steady on at +/- 25.5V from a good old-fashioned linear power supply buried in the sub enclosure. After an hour powered up, all finals feel slightly warm but none warmer than the others.

Based on specs, I expect this should deliver right around 25W continuous per TDA7296 in AB operation, and this thing has 8 of the little bastards with two in BTL mode for the sub at probably 75W continuous or so. Fukkin-a-diddy! That's $50 worth just in the finals!!!

Now I need to figure out how to do turn-on/un-mute to inject signal & see if they're all healthy... I have an eval circuit in the datasheet, so should be able.

mnem
 

Suggest putting the Toronto FD on alert. 

[bd139]

Hahaha. Waaamp waaamp kaboom 

[mnementh]

Hmmm... https://www.diyaudio.com/forums/chip-amps/135930-logitech-5300-remote-2.html

No effing way in 'ell it can possibly be that simple.

mnem

[Carl_Smith]

So recently they shut down the plant I worked at.  I am now back in the ranks of the unemployed.  I hated that job anyway... But before I left I ended up with a bunch of junk that nobody wanted, and this item is some of that "junk."  It's a Staco Energy Products variable transformer.  Guys at work thought it was junk but I told them I wanted anything they were throwing away with copper or brass in it so they gave it to me.
 


The terminal plate was broken off and the ground wire for the shaft was unwound and hanging out the back because there's no stops on it at the ends of the coil and someone unwound it.  So I cleaned it all up, took the plate off and superglued it and reinforced the back with Horror Fraught epoxy, put it back together, wound that ground wire back inside around the shaft, and ended up with this.



OK, so I hadn't wound the ground wire back in on that pic, but I did afterwards.

So now the big question is what to do with it.  I chopped an old damaged extension cord in half and hooked it up and it seems to work fine.  But I didn't give it a hard test, just a 60W light bulb in a trouble light.  But it worked fine as the worlds most overkill light dimmer since it is rated at 3.5KVA.  Here's a picture of my suicide setup:



To really make it something useful, and safe, I'd have to find a nice enclosure to put it in, find some sort of knob, and figure out how to put stops on the knob so you can't turn the wiper off the end of the coil, add some sort of power switch and circuit breaker or fuse, add an outlet.  And I would probably want a voltmeter as well...

Might be easier to just buy a variac all ready to use if I ever actually need one.  Not that actual need matters in the TEA room.

[mnementh]

mnem
 

[bd139]

This NanoVNA thing is the nuts. Thanks again xrunner. And also TEA FTW.

Quick filter synthesis and test case.

So using normalised filter tables, I picked 0.1dB ripple Chebyshev parameters and put together a simple test (this is not going to be used!) 7 element low pass LC filter. HP35s was programmed to generate the L(n) and C(n) parameters from global variables for frequency of 7.5MHz and normalised impedance of 50 ohms. Tables are available on the Internet. Mine came from hardcopy of EMRFD. Used DaveCAD on back of an RS envelope for the design.



Much futzing later. Double sided board gouged and filter assembled. Used Peak LCR45 to check the toroids and they needed 1 turn less than toroids.info calculated.



So on to the NanoVNA it goes. Filter sweep looks promising!



So plugged it into the PC and got a segmented S21 sweep. That gives 500 points across 1-30MHz.



Pretty good!

Measurements from sweep:

Corner freq = 7.22MHz
3dB point = 7.8MHz (close enough)
40dB down = 17.22MHz
Insertion loss = 0dB
Max passband ripple = 0.2dB (close enough)

Bing-fucking-o!

[VK5RC]

... our state's biggest buy and sell ...

Is that Aussie colloquial for what's called a "bring and buy sale" here in Blighty? Something along the lines of a jumble sale but where the goods to be sold (usually for some good cause) are brought along and donated on the day by the people who have also come to buy things.

I can't speak for all situations but typically a 'buy and sell' is hosted by one organisation - they charge a few dollars entry fee for buyers, the sellers get a slightly higher 'table' fee. Also sausage sizzle and tea/coffee sales help coffers.

[xrunner]

This NanoVNA thing is the nuts. Thanks again xrunner. And also TEA FTW.

Cool. It's the real deal. Sure someone with a multi-thousand dollar Agilent VNA can pick at it's performance, but for a hobbyist it's pretty damn good.

I tried a quikie Xperiment today. I had a box of old CATV cable (75 ohm) I was going to throw out and I wanted to see if it would indicate a flaw about halfway down the line if I damaged the cable (I didn't have a piece of good 50 ohm coax I wanted to damage). I did a TDR measurement on it knowing that the impedance was a mismatch and I didn't know for sure what the velocity factor was because of no markings on the cable. I did get a reasonable length indication even if it wasn't exactly correct.

However, I gnawed a good chuck out of the middle of the cable halfway down the line with some wire cutters (almost all the braid was gone) and I didn't get much of an indication of the fault, but I did see a little blip at that halfway point. But I was not being very careful in my setup and so I must try again with a better setup and 50 ohm coax.