Test Equipment Anonymous (TEA) group therapy thread

[bd139]

Ugh just spent an hour debugging squegging audio amplifier. The first attempt went up in smoke literally, the second one wasn't temperature stable, this one squegged like a bitch. Phase shift at around 20MHz for it appears to be 360 degrees ffs. Have hacked it by slowing the transistors down with a little bit of miller capacitance although that makes me slightly sad inside.

Maybe some damping network at the output, a few ferrite beads and a lowpass at the input ... 

There's already a zobel network on the output. Input is naturally low pass (3db rolloff at 8khz as this is speech only). It's the source transistor in the output stage is doing it. Ft is around 300MHz for this which is more than a bit high for a basic audio amp as they are just in a follower arrangement. Also this is not terribly well grounded so that is contributing to it.

[Wolfgang]

... send schematics ...

[xrunner]

Her name is/was Karen Cambria, and she was an HP employee in the same building, albeit a different division.

http://www.hp.com/hpinfo/abouthp/histnfacts/publications/measure/pdf/1972_01.pdf
http://www.codex99.com/design/the-hp35.html

Very interesting thank you for the links. 

[bd139]

... send schematics ...

Very basic LM386 sub as I have run out

Real build has a lot of supply decoupling.

Edit: I could add some more emitter degeneration to Q3...

[bitseeker]

Mum safely under a blanket in bed so I escaped for a while. 

Just what is needed for TEA cleaning a 20L Espresso making steam cleaner.  Ably supporting the 90kg lump is my hydraulic lifting table eBay auction: #143029362536

And the bling shot of some of the TEA because it was in the area

Very nice, bd. TEA on one side and coffee on the other.

[Wolfgang]

... send schematics ...

Very basic LM386 sub as I have run out

Real build has a lot of supply decoupling.

Edit: I could add some more emitter degeneration to Q3...

What I would do:

- 100nF at the 2N2222 base out
- 2N2222 gets 1K at the base
- and a 100pF cap from base to collector
- bases of 2N2219 and 2N2905 also get 100Ohms in series

have fun
  Wolfgang

[mnementh]

... same as an uncleared stack full of intermediate results ... 

Or the problem encountered by a simultaneous translator when the source is an especially verbose German professor. The translator has to stay silent, until eventually they are forced to exclaim "Professor, the verb, please!".

For those that didn't learn a little German at school, in German the verb is at the end of the sentence, not between the subject and object. Yes, German is RPN

Very true. In high literature the number of verbs that come at the end of a long German sentence is never less than 5. 

Is is any wonder my wife HATES singing Wagner...?

mnem
I might still be agitating.

[Wolfgang]

Even his music has the verbs at the end. 

[bd139]

... send schematics ...

Very basic LM386 sub as I have run out

Real build has a lot of supply decoupling.

Edit: I could add some more emitter degeneration to Q3...

What I would do:

- 100nF at the 2N2222 base out
- 2N2222 gets 1K at the base
- and a 100pF cap from emitter to collector
- bases of 2N2219 and 2N2905 also get 100Ohms in series

have fun
  Wolfgang

Thanks for that. Have actually tried all that other than the series resistors on Q1/Q2. Q1 is the one that is oscillating weirdly. I added 22pf from base to collector and the whole thing is stable. I am going to swap them with BD139 and BD140 pair (of course ) as well as they are slower and easier to mount.

[mnementh]

LMAO. These dirtbags are about 10 miles from here.....unfortunately. 

Edit, and while you guys fought your battle I had a senior moment of clarity and took a nap this afternoon.

Fixed that for ya, buddy...

mnem
Remember this conversation... muahahahaha!

[bitseeker]

Yeah that's one thing I always liked about the 50g as well. Unlimited stack and 7 levels on screen.

Wondering if I should head over to ebay 



^^ genuine HP hat.

Oh, wow. I've never seen that before. I learn so much in this thread.

[bitseeker]

swmbo just brought me lunch.

salad out of a bag, with some tuna out of a pouch sprinkled on top.

gidget jumped up, sniffed the damn thing, then turned and walked away.   because even she won't touch tuna out of an aluminized plastic pouch.

Gidget is not impressed by the knife. No match for switchblade claws.

[Wolfgang]

... send schematics ...

Very basic LM386 sub as I have run out

Real build has a lot of supply decoupling.

Edit: I could add some more emitter degeneration to Q3...

What I would do:

- 100nF at the 2N2222 base out
- 2N2222 gets 1K at the base
- and a 100pF cap from emitter to collector
- bases of 2N2219 and 2N2905 also get 100Ohms in series

have fun
  Wolfgang

Thanks for that. Have actually tried all that other than the series resistors on Q1/Q2. Q1 is the one that is oscillating weirdly. I added 22pf from base to collector and the whole thing is stable. I am going to swap them with BD139 and BD140 pair (of course ) as well as they are slower and easier to mount.

Sorry meant so say BASE to collector, but you did it right anyway.

[0culus]

hey oculus

wow.....really cool instrument.

however you accidently included some offensive material in the picture.

no need to apologize.

fixed it for you.

freqq

Accidentally? Accidentally??? Come on, you should know by now that it's 100% intentional. 

[med6753]

LMAO. These dirtbags are about 10 miles from here.....unfortunately. 

Edit, and while you guys fought your battle I had a senior moment of clarity and took a nap this afternoon.

Fixed that for ya, buddy...

mnem
Remember this conversation... muahahahaha!

So how come I don't feel any smarter and in addition I haven't accomplished jack today and I'm not going to start now. 

[tautech]

LMAO. These dirtbags are about 10 miles from here.....unfortunately. 

Edit, and while you guys fought your battle I had a senior moment of clarity and took a nap this afternoon.

Fixed that for ya, buddy...

mnem
Remember this conversation... muahahahaha!

So how come I don't feel any smarter and in addition I haven't accomplished jack today and I'm not going to start now. 

But think about how much you'll accomplish tomorrow when you arisse fresh as a daisy. 
Naps are a wonderful thing as you get older and help clear the grey matter for what's yet to come.

[beanflying]

I don't get the fascination with propping up old calculators when 98% of us carry a device with us most times that will run emulators if being in the minority and a twisted perverted RPN lover is your thing 

https://play.google.com/store/apps/details?id=org.efalk.rpncalc&hl=en_AU

[mnementh]

I have no such fascination; I just like agitatin'. 

mnem
*toddles off to ded*

[mnementh]

For those possessed of actual discernible levels of Kung-Fu: This is what it’s like for the rest of us EVERY GAWDDAMN DAY!

mnem
*scernible*

[0culus]

I don't get the fascination with propping up old calculators when 98% of us carry a device with us most times that will run emulators if being in the minority and a twisted perverted RPN lover is your thing 

https://play.google.com/store/apps/details?id=org.efalk.rpncalc&hl=en_AU

(Attachment Link)

There’s something about holding the thing in my hand that emulators don’t replace.

[jh15]

I have TI59 app but I like the button feel and tape reader on my real one, and have pc100 printer.

[Neomys Sapiens]

Started up again? It's not over until the last equals button and the button pusher is 6 feet under 

Edit: I am trying to peel an LM723. I don't have a vice so this turns out to be a hell of a lot more difficult than it looks. Trying tin opener next 

Allow me to express my doubt on this statement.

[Neomys Sapiens]

My modulation meter has arrived today. A Racal 9009 for 38.- is not bad, I think.
Although testing will have to wait - I'm swamped with work. Pictures here:



Now I saw that I have nothing to match it's form factor. So I figured that a Racal counter in this enclosure would be a good fit. We'll see.

[beanflying]

I don't get the fascination with propping up old calculators when 98% of us carry a device with us most times that will run emulators if being in the minority and a twisted perverted RPN lover is your thing 

https://play.google.com/store/apps/details?id=org.efalk.rpncalc&hl=en_AU

(Attachment Link)

There’s something about holding the thing in my hand that emulators don’t replace.

What you hold in your hand and what you do with that hand is maybe better done in private 

[worsthorse]

... same as an uncleared stack full of intermediate results ... 

Or the problem encountered by a simultaneous translator when the source is an especially verbose German professor. The translator has to stay silent, until eventually they are forced to exclaim "Professor, the verb, please!".

For those that didn't learn a little German at school, in German the verb is at the end of the sentence, not between the subject and object. Yes, German is RPN

So is Tibetan.  It actually makes it easier to learn conversational Tibetan because you generally know what is going to show up where in a sentence. It only becomes a problem when the clause gets really really long...