Test Equipment Anonymous (TEA) group therapy thread

[0culus]

If only working on this 485 were like some vehicle maintenance I performed this morning which was a piece of cake. I must admit that my knowledge and experience in working with scope trigger circuits isn't even zero. It's more like -10.  And this 485 is one complex mofo. I performed some checks that tggzzz suggested but no change. One was he thought the +5V was too low (4.977V). I checked the +50V reference that it's derived from and that was +49.98V. I tweaked it up to +50.00V and that bumped the +5V to +4.980V which is basically in spec and was prior too. And as much as I hate "tweak monkeys" who randomly play with calibration settings I did give some of trigger cal controls a twist but put them back in the exact same spot as I found them. Again, no change. I think my problem is that U780 is being continuously pulsed by +A Gate but I'm not sure. For now I'm going to put this aside until tggzzz is back where he can open up his 485 and we can do comparative analysis. 

Man, my problem seems rather pedestrian in comparison. 

Anyway, I opened the 7104 back up this morning after it started shorting out again, and I believe I located the root cause. Take a look:




I wouldn't be a bit surprised if some asshole didn't loosen that thing (it screws to the outside of the case) so it would touch the chassis and the scope wouldn't work and people wouldn't bid on it. Joke's on him if that's what happened though.  Could just as likely have been loose to begin with. Anyway, I made a small sandwich of electrical tape and insulated it from the chassis. All good now. 

[mnementh]

Not a HP 200-series oscillator...?

damn.. No more clues for you  

Yeah, I didn't dare believe it myself as I was typing it. I just remembered when the topic of conversation was "All Things HP and The HP Way" you remarking that you've been seeking such a unicorn for decade(s). 

How close to the 200A? Still the same incandescent bulb filament-regulated Wien bridge oscillator circuit? 

http://www.hp.com/hpinfo/abouthp/histnfacts/museum/earlyinstruments/0002/0002history.html   HP 200A United States patent No. 2268872

mnem
*CPS-ily*

[mnementh]

Not EASY; SIMPLE. Big. Effing. Difference. Same as the prerequisite "honest self-appraisal". Most people would rather stand in a busy intersection and drill screws through their feet.

And like any addiction, the addiction to sugar is exactly as smart, cunning and deceitful as you are. Each and every one of us has the devil inside, and we most often unleash him on ourselves rather than those around us.

mnem
The Three Laws of Thermodynamics:
1. You can't win.
2. You can't break even.
3. You can't even get out of the game.

Correction, losing weight is easy if you're not a pansy who loves to lie to himself. People are either looking for cheap fixes which allow them to continue the habits they know aren't right or cheat for the same purposes and then pretend it wasn't them who making the choice to stuff food in their faces. Decide to lose weight or don't. Most people end up choosing not to. "There is no try".

Again, NO.

Simple=ANYBODY WILL UNDERSTAND IT.
Easy=ANYBODY WILL DO IT.

The simplest things to understand are often the hardest to do. If you don't understand that vital difference, you'll NEVER inspire others to do what must be done. Or yourself.

Cheers,

mnem
*Taking the hard road since nineteen mumblety-mumble*

[med6753]

Not a HP 200-series oscillator...?

damn.. No more clues for you  

He guessed correctly? 

[med6753]

They really are nice to use, if a bit large and bulky. The difference in crt quality between either of mine and my 2465B is pretty stark as well. The 2465B has a great crt, don't get me wrong, but the much larger acceleration potentials used in the mainframes makes a huge difference.

Under bandwidth limiting conditions I would also rate the 7904 slightly better than the 2465 in trace sharpness. But you know what beats that? Again, bandwidth limiting....the 465/475's are sharper.

The ultimate in trace sharpness? If you ever get the opportunity to see a restored and properly functioning 535, 545, or 547 their traces are absolutely razor sharp and without equal. 

[worsthorse]

And now for something completely TEA related...

Today I scored six boxes of data books from the 80s and 90s. Here's a photo from one of the boxes:

(Attachment Link)

There are approximately 120 books from TI, Moto, AD, Signetics, National, Plessey, GE and RCA, including several complete series. All appear to be in good shape. The whole stash cost me 12USD plus shipping.  Being a dead tree kind o' guy, I am extremely happy with this find. 

I also bought a relatively unusual sort of oscilloscope. Not quite a unicorn but close.  I am going to wait until I have it in hand before I post, though. Should be about ten days..

Good score. Now if you were only the one guy in a million who could be arsed to scan 'em into .pdf and upload to the Internet Archive...

mnem
"I know it ain't me, lawd..."

I am probably not that guy, in part because properly scanning them means destroying them. There's no other good way to manage 900 page paperbound books. But here's a promise, mnen... if I ever play the lottery and, subsequently win a big jackpot, I will hire someone to properly deconstruct and scan them all. 

[bd139]

Not a HP 200-series oscillator...?

damn.. No more clues for you  

Yeah, I didn't dare believe it myself as I was typing it. I just remembered when the topic of conversation was "All Things HP and The HP Way" you remarking that you've been seeking such a unicorn for decade(s). 

How close to the 200A? Still the same incandescent bulb filament-regulated Wien bridge oscillator circuit? 

http://www.hp.com/hpinfo/abouthp/histnfacts/museum/earlyinstruments/0002/0002history.html   HP 200A United States patent No. 2268872

mnem
*CPS-ily*

It's a very late model starting 1968. It's the successor design which is an all BJT/FET wein bridge and has an AGC feedback loop instead of the bulb. But 0.1% THD sine and 1% flatness is pretty good. And it doesn't bob around when tuning like the bulb networks do (unless it's in low distortion mode).

I don't do tubes in that stuff any more. Had enough of the damn things!

Need it for filters. Turns out the 3310A is a great function generator but the sine on it is jammed full of harmonics as it's a shaped triangle wave.

[mnementh]

Awesome score!!! Even more so because you're getting it to use it, not just for sentiment! 

Good score. Now if you were only the one guy in a million who could be arsed to scan 'em into .pdf and upload to the Internet Archive...

mnem
"I know it ain't me, lawd..."

I am probably not that guy, in part because properly scanning them means destroying them. There's no other good way to manage 900 page paperbound books. But here's a promise, mnem... if I ever play the lottery and, subsequently win a big jackpot, I will hire someone to properly deconstruct and scan them all. 

Or you could be the guy who finds an old legal-size flatbed scanner and hacks it to have zero bezel on the leading edge for book scanning. I've spent a considerable amount of time on that mental exercise; I believe the solution would revolve around moving the rollers and motor from the cogged belt far enough to have a "pocket" for the body of the book to drop down at a 90° angle. Maybe an adjustable shelf to support its weight.

mnem
An idea is the most difficult thing to kill.

[bd139]

Cut the binding off with a large guillotine and get a drum scanner. Job done! Kindling comes out the other end 

if you're really lucky you can sell hooky copies on Lulu.com 

Edit: ooh they make some really fast linear ones now

[0culus]

They really are nice to use, if a bit large and bulky. The difference in crt quality between either of mine and my 2465B is pretty stark as well. The 2465B has a great crt, don't get me wrong, but the much larger acceleration potentials used in the mainframes makes a huge difference.

Under bandwidth limiting conditions I would also rate the 7904 slightly better than the 2465 in trace sharpness. But you know what beats that? Again, bandwidth limiting....the 465/475's are sharper.

The ultimate in trace sharpness? If you ever get the opportunity to see a restored and properly functioning 535, 545, or 547 their traces are absolutely razor sharp and without equal.

I'd love to have one proper vacuum tube tek, that's for sure.  Just one though, as I'm already drawing enough electricity. 

[0culus]

Not a HP 200-series oscillator...?

damn.. No more clues for you  

Yeah, I didn't dare believe it myself as I was typing it. I just remembered when the topic of conversation was "All Things HP and The HP Way" you remarking that you've been seeking such a unicorn for decade(s). 

How close to the 200A? Still the same incandescent bulb filament-regulated Wien bridge oscillator circuit? 

http://www.hp.com/hpinfo/abouthp/histnfacts/museum/earlyinstruments/0002/0002history.html   HP 200A United States patent No. 2268872

mnem
*CPS-ily*

It's a very late model starting 1968. It's the successor design which is an all BJT/FET wein bridge and has an AGC feedback loop instead of the bulb. But 0.1% THD sine and 1% flatness is pretty good. And it doesn't bob around when tuning like the bulb networks do (unless it's in low distortion mode).

I don't do tubes in that stuff any more. Had enough of the damn things!

Need it for filters. Turns out the 3310A is a great function generator but the sine on it is jammed full of harmonics as it's a shaped triangle wave.

If you haven't read it, Jim Williams wrote a fun piece that is in his Analog Circuit Design: Art, Science, and Personalities book called "Max Wien, Mr. Hewlett, and a Rainy Sunday Afternoon" In it he discusses his quest to try to beat the distortion characteristics of the light bulb Wien bridge with modern components. Very good read. 

[med6753]

They really are nice to use, if a bit large and bulky. The difference in crt quality between either of mine and my 2465B is pretty stark as well. The 2465B has a great crt, don't get me wrong, but the much larger acceleration potentials used in the mainframes makes a huge difference.

Under bandwidth limiting conditions I would also rate the 7904 slightly better than the 2465 in trace sharpness. But you know what beats that? Again, bandwidth limiting....the 465/475's are sharper.

The ultimate in trace sharpness? If you ever get the opportunity to see a restored and properly functioning 535, 545, or 547 their traces are absolutely razor sharp and without equal.

I'd love to have one proper vacuum tube tek, that's for sure.  Just one though, as I'm already drawing enough electricity. 

So would I. But they tend to be stupid price unless it's one that's been left in a damp garage for 30 years.

Electricity? Think of the heating bills you'll save in the winter. 

[bd139]

If you haven't read it, Jim Williams wrote a fun piece that is in his Analog Circuit Design: Art, Science, and Personalities book called "Max Wien, Mr. Hewlett, and a Rainy Sunday Afternoon" In it he discusses his quest to try to beat the distortion characteristics of the light bulb Wien bridge with modern components. Very good read. 

I have indeed read that (cover to cover). Excellent book  . I'm not sure how Feynman's cargo cult text ended up in there though. Felt like padding!

[mnementh]

I'd love to have one proper vacuum tube tek, that's for sure.  Just one though, as I'm already drawing enough electricity. 

So would I. But they tend to be stupid price unless it's one that's been left in a damp garage for 30 years. Electricity? Think of the heating bills you'll save in the winter. 

Once I get to Canada. In the meantime, "heat" will remain a 4-letter word.

mnem
*opens garage door and wilts*

[0culus]

They really are nice to use, if a bit large and bulky. The difference in crt quality between either of mine and my 2465B is pretty stark as well. The 2465B has a great crt, don't get me wrong, but the much larger acceleration potentials used in the mainframes makes a huge difference.

Under bandwidth limiting conditions I would also rate the 7904 slightly better than the 2465 in trace sharpness. But you know what beats that? Again, bandwidth limiting....the 465/475's are sharper.

The ultimate in trace sharpness? If you ever get the opportunity to see a restored and properly functioning 535, 545, or 547 their traces are absolutely razor sharp and without equal.

I'd love to have one proper vacuum tube tek, that's for sure.  Just one though, as I'm already drawing enough electricity. 

So would I. But they tend to be stupid price unless it's one that's been left in a damp garage for 30 years.

Electricity? Think of the heating bills you'll save in the winter. 

I know right? It'll be my lab heater.  I need to have one fall into my lap that that 555 Mr. Carlson showed on his channel a few years back.

If you haven't read it, Jim Williams wrote a fun piece that is in his Analog Circuit Design: Art, Science, and Personalities book called "Max Wien, Mr. Hewlett, and a Rainy Sunday Afternoon" In it he discusses his quest to try to beat the distortion characteristics of the light bulb Wien bridge with modern components. Very good read. 

I have indeed read that (cover to cover). Excellent book  . I'm not sure how Feynman's cargo cult text ended up in there though. Felt like padding!

Still a great book! I enjoy reading Jim's writing, and listening to him speak. He has a way with words and a sand dune sense of humor. 

[bd139]

Still a great book! I enjoy reading Jim's writing, and listening to him speak. He has a way with words and a sand dune sense of humor. 

Likewise. Example here, fixing a Tek 465 tant (of course!) 




This afternoon's experiment... How robust is a (genuine) MRF237 VHF RF PA transistor at 14MHz on a decent heatsink?

Well it turns out I built a 180MHz power oscillator, not a power amplifier and it promptly blew the first two up before I had a chance to kill the source 

[med6753]

This afternoon's experiment... How robust is a (genuine) MRF237 VHF RF PA transistor at 14MHz on a decent heatsink?

Well it turns out I built a 180MHz power oscillator, not a power amplifier and it promptly blew the first two up before I had a chance to kill the source 

[0culus]

Still a great book! I enjoy reading Jim's writing, and listening to him speak. He has a way with words and a sand dune sense of humor. 

Likewise. Example here, fixing a Tek 465 tant (of course!) 




This afternoon's experiment... How robust is a (genuine) MRF237 VHF RF PA transistor at 14MHz on a decent heatsink?

Well it turns out I built a 180MHz power oscillator, not a power amplifier and it promptly blew the first two up before I had a chance to kill the source 

I've watched that video before, but it never really gets old. Thanks! 

Bet that smelled good. 

[Mr. Scram]

Again, NO.

Simple=ANYBODY WILL UNDERSTAND IT.
Easy=ANYBODY WILL DO IT.

The simplest things to understand are often the hardest to do. If you don't understand that vital difference, you'll NEVER inspire others to do what must be done. Or yourself.

Cheers,

mnem
*Taking the hard road since nineteen mumblety-mumble*

It's thermodynamics, so the results will come if you put in the work. If the results don't come you didn't put in the work. Feel you're putting in the work but not seeing the desired results? You're lying to yourself. It's that easy. I know as I lied to myself for years. It turns out I preferred to be comfortable.

[0culus]

So now that the 7104 is squared, I'm moving on to the other thing I snagged. 436A digital power meter. I already had a sensor cable and an 8484A sensor.  The meter seems to be in good nick.

[mnementh]

Again, NO.

Simple=ANYBODY WILL UNDERSTAND IT.
Easy=ANYBODY WILL DO IT.

The simplest things to understand are often the hardest to do. If you don't understand that vital difference, you'll NEVER inspire others to do what must be done. Or yourself.

Cheers,

mnem
*Taking the hard road since nineteen mumblety-mumble*

It's thermodynamics, so the results will come if you put in the work. If the results don't come you didn't put in the work. Feel you're putting in the work but not seeing the desired results? You're lying to yourself. It's that easy. I know as I lied to myself for years. It turns out I preferred to be comfortable.

Now you're just being deliberately obtuse and parroting back the same wrong statement in different form. You you know the difference and you know I'm right. Suck it up and move forward.

Cheers,

mnem
We're done here.

[bd139]

Sooooo, dunce hat on. Why do my MRF237’s keep exploding? Well last time I used the scope I was measuring rise time and guess which idiot forgot to put the channel vertical fine control back into the cal detent (because the knob cap isn’t aligned properly).

 

Thus the power out was about 25% more than measured which is what resulted in the destruction, not the oscillation which was tamed with a ferrite. Ffs

[0culus]

Gotta love PEBKAC...my favorite type of error. 

[med6753]

Sooooo, dunce hat on. Why do my MRF237’s keep exploding? Well last time I used the scope I was measuring rise time and guess which idiot forgot to put the channel vertical fine control back into the cal detent (because the knob cap isn’t aligned properly).

 

Thus the power out was about 25% more than measured which is what resulted in the destruction, not the oscillation which was tamed with a ferrite. Ffs

[Neomys Sapiens]

Sooooo, dunce hat on. Why do my MRF237’s keep exploding? Well last time I used the scope I was measuring rise time and guess which idiot forgot to put the channel vertical fine control back into the cal detent (because the knob cap isn’t aligned properly).

 

Thus the power out was about 25% more than measured which is what resulted in the destruction, not the oscillation which was tamed with a ferrite. Ffs

You have my sympathy on this. I ended work on friday (fry-day?) with a *ccrrricckk* of doom of a somewhat larger, higher frequency specimen. It wasn't loud. It just did not belong there.