Test Equipment Anonymous (TEA) group therapy thread

[beanflying]

Today's Pondering - How Long before the already Foreign Language of Valves becomes a Dead Language in Electronics

[med6753]

6U5 "Magic Eye" tubes are rare and hard to find. The more common version was the 6E5. They are pin for pin equivalent but have sightly different characteristics. In some instances a 6E5 can be subbed for a 6U5 but not always.

My old RCA valve book has 6U5 and 6G5 listed as equivalents and can be used to replace 6H5 and 6T5.
6E5 is listed as a sharp cut-off triode while 6U5 is remote cut-off.....whatever that means. 

It's been many years and I can't recall the difference between a sharp cut-off triode vs a remote cut-off triode. I'd have to dig out my RCA Receiving Tube Manual and check. Back in 1980's I had a Stromberg-Carlson multi-band receiver that used a 6U5 but the tube was dead. I searched a long time and couldn't find one. But I had a tube substitution manual that stated in some cases a 6E5 would work. That tube was still available NOS from GE. It did work but so-so. The shadow wasn't as sensitive as I figured it should have been.   

[med6753]

Today's Pondering - How Long before the already Foreign Language of Valves becomes a Dead Language in Electronics

It's getting there real quick even among us old farts that grew up with vacuum tubes. 

[med6753]

LifeHack # 1723...

   med, this butt-ugly hack is just for you. I figure it's at least 25% Doc Brown.    Short version: The BluRay player I got for the kids' bedroom doesn't have a rear USB; I wasn't willing to put up with the cable to the HDD sticking out the front just waiting to get broken off, so I added a port. Or three.  (SNIP)

I guess I'm a bad influence aren't I? Welcome to the dark side. 

Dude... I grew up on a farm.  "Ugly but it works" was a way of life; there were days I made 3 impossible cobbles before breakfast.

mnem

Then how come you jumped in my shit about the 2465 fan hack???  Hypocrite!!! 

[bitseeker]

'Cuz it was bigger?

Probably because it was a 2465.

[mnementh]

Then how come you jumped in my shit about the 2465 fan hack???  Hypocrite!!! 

Yes... guilty as charged. One does hope to learn the error of his ways. 

'Cuz it was bigger?

Probably because it was a 2465.

and HELLS YES! Orders of magnitude difference!

A dwagon has to draw the line SOMEWHERE, dammit! 

mnem
 

[tautech]

After reading about the magic eye tubes I had to go out to storage to plug in my old ESI 250-DA RLC bridge that I haven't powered up in years. It still works and the 6E5 tube is strong and doesn't exhibit fading as well used weaker tubes do.

I also have an RCA Chanalyst like the one shown in the photo that used 4 of the magic eye tubes.

Very cool Arthur. 

I can still just remember valve receivers with them.
Interestingly my RCA book also mentions a dual magic eye valve, a 6AF6-G, never seen one of those. 

6U5 "Magic Eye" tubes are rare and hard to find. The more common version was the 6E5. They are pin for pin equivalent but have sightly different characteristics. In some instances a 6E5 can be subbed for a 6U5 but not always.

My old RCA valve book has 6U5 and 6G5 listed as equivalents and can be used to replace 6H5 and 6T5.
6E5 is listed as a sharp cut-off triode while 6U5 is remote cut-off.....whatever that means. 

It's been many years and I can't recall the difference between a sharp cut-off triode vs a remote cut-off triode. I'd have to dig out my RCA Receiving Tube Manual and check. Back in 1980's I had a Stromberg-Carlson multi-band receiver that used a 6U5 but the tube was dead. I searched a long time and couldn't find one. But I had a tube substitution manual that stated in some cases a 6E5 would work. That tube was still available NOS from GE. It did work but so-so. The shadow wasn't as sensitive as I figured it should have been.   

Maybe the same as yours
My RCA book was dads when he fiddled with Short Wave in the 40's and 50's, so old it's now dog eared and missing covers and I now only have pages 7-242 left. All author credits and print dates long gone. 
Still it's one I've dug out numerous times since I joined the forum.

[Kosmic]

The parts touched by the retrofit are listed in the retrofit kit manual: https://www.keysight.com/upload/cmc_upload/All/08566-90151.pdf

It's not quite as simple as I said; the retrofit also replaced the front panel keyboard and a handful of passive components. I believe it also replaced the rear panel of the RF unit.

Will not be easy finding all the missing parts. Probably better reusing a broken 8566B.

[0culus]

The parts touched by the retrofit are listed in the retrofit kit manual: https://www.keysight.com/upload/cmc_upload/All/08566-90151.pdf

It's not quite as simple as I said; the retrofit also replaced the front panel keyboard and a handful of passive components. I believe it also replaced the rear panel of the RF unit.

Will not be easy finding all the missing parts. Probably better reusing a broken 8566B.

That's my plan. Unless I magically managed to find one of these retrofit kits. It really doesn't affect anything for standalone operation. However, I eventually want to take advantage of HP-IB stuff. National Instruments makes a GPIB adapter that works with HP gear.

[med6753]

I've never seen a 6AF6 either. Can't imagine what it would look like.

My RCA Receiving Tube Manual is dated 1970 so it pretty near the end of the vacuum tube era. But the nice thing is that it covers tubes from the late 1920's right up to the 10 and 12 pin "compactron" tubes which were very common before the end of production.

[med6753]

After reading about the magic eye tubes I had to go out to storage to plug in my old ESI 250-DA RLC bridge that I haven't powered up in years. It still works and the 6E5 tube is strong and doesn't exhibit fading as well used weaker tubes do.

I also have an RCA Chanalyst like the one shown in the photo that used 4 of the magic eye tubes.

Very cool! 

[neo]

Ero-Shan's got a magic eye watching us, now.

Sorting through a box of old tubes and stumbled on one I have.
Anyone want it for a project ?

Ordinarily i'd be tempted to say "ME!" but i'm too busy working on my novel or working myself half to death for profit.

Magic eyes are so cool, but I had to resist as well. Too much in the queue! *sigh*

Just for neo, an RCA 6U5 plus base and ~300mm leads

-snip-

Pulled from a then very old valve receiver.....decades ago.
Glass envelope slightly loose in base.
Filament checks OK @ 5.7 ohms

Consider me tempted. No really, i've given everyone else a chance and i got a project in mind (that may or may not take 6 months to get around to).

[tautech]

I've never seen a 6AF6 either. Can't imagine what it would look like.

My RCA Receiving Tube Manual is dated 1970 so it pretty near the end of the vacuum tube era. But the nice thing is that it covers tubes from the late 1920's right up to the 10 and 12 pin "compactron" tubes which were very common before the end of production.

'bout the time I got a bit interested in valves and by then my copy was already looking pretty second hand.

Yeah the stuff in mine goes waaaay back too.

A much later Telefunken pocket book I was given in the 80's doesn't compare to the old RCA one.

Ya want this 6U5 before neo changes his mind ?

[med6753]

I've never seen a 6AF6 either. Can't imagine what it would look like.

My RCA Receiving Tube Manual is dated 1970 so it pretty near the end of the vacuum tube era. But the nice thing is that it covers tubes from the late 1920's right up to the 10 and 12 pin "compactron" tubes which were very common before the end of production.

'bout the time I got a bit interested in valves and by then my copy was already looking pretty second hand.

Yeah the stuff in mine goes waaaay back too.

A much later Telefunken pocket book I was given in the 80's doesn't compare to the old RCA one.

Ya want this 6U5 before neo changes his mind ?

No....let Neo have it.  I got no use for it. That Stromberg-Carlson receiver is long gone.

[ArthurDent]

"6E5 is listed as a sharp cut-off triode while 6U5 is remote cut-off.....whatever that means."

Sharp vs remote is kind of like gain in that the sharp cutoff happens more abrupt with grid voltage change and remote happens more slowly (not an exact definition).

The 6AF6 was a later version used for AM/FM receivers where 2 tuning eyes were needed.

[tautech]

"6E5 is listed as a sharp cut-off triode while 6U5 is remote cut-off.....whatever that means."

Sharp vs remote is kind of like gain in that the sharp cutoff happens more abrupt with grid voltage change and remote happens more slowly (not an exact definition).

Thanks.
That's sorta what I figured. 

[med6753]

Found some pictures. 6AF6 dual magic eye.

[neo]

Found some pictures. 6AF6 dual magic eye.

I too found some pictures of the 6AF6

https://www.radiomuseum.org/forum/the_optimal_use_of_the_6af6g.html

an entire article actually. Definitely an interesting device.

[Kosmic]

That's my plan. Unless I magically managed to find one of these retrofit kits. It really doesn't affect anything for standalone operation. However, I eventually want to take advantage of HP-IB stuff. National Instruments makes a GPIB adapter that works with HP gear.

Got a prologix and keysight gpib adapter and both are working fine with older HP gear (HP-IB)

[Cubdriver]

6U5 "Magic Eye" tubes are rare and hard to find. The more common version was the 6E5. They are pin for pin equivalent but have sightly different characteristics. In some instances a 6E5 can be subbed for a 6U5 but not always.

My old RCA valve book has 6U5 and 6G5 listed as equivalents and can be used to replace 6H5 and 6T5.
6E5 is listed as a sharp cut-off triode while 6U5 is remote cut-off.....whatever that means. 

Sharp vs remote cutoff has to do with the linearity of the tube's response, due to the way the grid is wound.  In a 'normal' tube, the grid wire spacing is even, and thus as the grid bias becomes more negative, all the "slots" close pretty much in unison.  The grid in a remote cutoff tube has uneven spacing - perhaps the turns grow more widely spaced in the center.  At first it's more or less linear, but as you bias it more negatively towards cutoff, the narrower spaced turns begin to completely block the electron flow, but the wider spaced areas still let them through.  This causes the curve to flatten out as you get closer to cutoff, causing the "off" point to be more remote.  IIRC such tubes were typically used in AGC circuits where their nonlinear response was desired.

-Pat

[0culus]

That's my plan. Unless I magically managed to find one of these retrofit kits. It really doesn't affect anything for standalone operation. However, I eventually want to take advantage of HP-IB stuff. National Instruments makes a GPIB adapter that works with HP gear.

Got a prologix and keysight gpib adapter and both are working fine with older HP gear (HP-IB)

Nice. I'll definitely be looking at them once I get my permanent lab set up.

[beanflying]

Still working on a final idea for the Knob and Feet thread. But Chalk up another fix for 3D printing and TEA unobtanium. Went with a single piece instead of two which would have been an injection moulded limitation with the original. Removed the second shearweb to save on support material and it doesn't seem to be an issue. V2 of the design will do away with the need for a spacer washer and a slightly wider PCB gap.

[mnementh]

In Other News... T-38s In the News. Again.

   https://www.nasa.gov/centers/armstrong/features/supersonic-shockwave-interaction.html

The T-38 is another of those iconic birds like the B-52; and like the Stratofortress, 60 years later she has outlived every plane meant to replace her. She was designed in a different age; when pilots were meant to fall in love with their aircraft, and she is certainly a comely creature, even if intended as a trainer. It is entirely possible her feminine curves were deliberate; to excite the male libido and ego as one, driving enlistment.

I know I was smitten after sitting in one for just a few minutes when I was eight years old; the Thunderbirds flew them back then and I went to a show. They had one of the second string aircraft (or maybe it was being transported) set up on the tarmac by the bleachers, and every kid lined up for their chance to actually lay hands on her.

In retrospect, she was a little old and tired even then; I can close my eyes to this day and see the shiny patches under and around the castle button on the stick, and paint worn through almost to white aluminum where gloved hands had flipped the same dozen or so toggles on the dash uncountable times. But to me she gleamed and shone as new. I can still remember the smell of smoked rubber and canvas and kerosene.

After that I pestered my grandparents and then my mom for weeks to get me the model kit I saw at the local Woolworth's Five & Dime. It was my first model ever; I was so careful with the glue (the real kind with toluene, that gave me a terrible headache) and I used my penknife to cut the pieces apart. The decals... oh my gawd, they drove me mad. But eventually I pieced them together in some semblance of that beloved paint scheme, as good as the real thing to my youngling eyes.

I flew so many sorties with that model... against pigeons and haybales and even my models of the NCC-1701 Enterprise, and Luke's X-Wing... but I couldn't make the cut to fly the real thing. *sigh*

*mnemories*

[bitseeker]

Still working on a final idea for the Knob and Feet thread. But Chalk up another fix for 3D printing and TEA unobtanium. Went with a single piece instead of two which would have been an injection moulded limitation with the original. Removed the second shearweb to save on support material and it doesn't seem to be an issue. V2 of the design will do away with the need for a spacer washer and a slightly wider PCB gap.

Those brackets turned out really well, bean. Bravo!

[beanflying]

Those brackets turned out really well, bean. Bravo!

The only hard part was guesstimating the 3⁰ angles on the verticals where I got lucky first time around. That and I metricated the hell out of HP's decimal inches  

30 minute print at 0.1 layer and $0.25 of filament. Value $ plenty