Test Equipment Anonymous (TEA) group therapy thread

[beanflying]

Bet yours was just a bit faster to make too

Continuing on with Passive Projects, getting back to my CapKilla. 3D Printed Case, Trashy evilbay 250 50W Resistors, junk meter leads I had in a box, DPDT Switch to throw the bank from 250 - 1k at the outputs.

Not shown is the leftovers of a $10 Clampmeter I am going to drop across the leads so I know when it is dead.

There is no such thing as overkill 

edit: Labels fitted before Mnementh has a SOOK 

[med6753]

Since when do you need multiple 50 watt resistors to discharge capacitors?    You planning on going to the local power substation and play with HV? 

[beanflying]

There is NO SUCH THING AS OVERKILL 

If you do the numbers the instantaneous inrush current is heaps. Throw some numbers here http://mustcalculate.com/electronics/capacitorchargeanddischarge.php?vfrom=600&vto=2&vs=0&c=.001&r=1000&time=30 It doesn't take much of a Cap at a few hundred volts to peak 500W+ depending on the resistor used. The 250 setting for dropping Fat low voltage Caps will speed it up. So an all in one.

The main reason to do it is the LCR Tweezers I own will smoke above a few volts.

[neo]

Well i blew up my 895A, and without the service manual it ain't looking good. But, to be fair, who ever heard of progress without sacrifice? I am learning vacuum tubes after all, like just then i learned what NOT to do. 

[med6753]

Well i blew up my 895A, and without the service manual it ain't looking good. But, to be fair, who ever heard of progress without sacrifice? I am learning vacuum tubes after all, like just then i learned what NOT to do. 

Unlike solid state stuff vacuum tubes are pretty robust and you really have to try hard to fatally blow them up. What did you do? 

[neo]

Unlike solid state stuff vacuum tubes are pretty robust and you really have to try hard to fatally blow them up. What did you do? 

The tube is fine, the power supply is solid state and shit itself when presented a momentary short.

[bd139]

Tubes are quite easy to blow up from experience, at least when in my hands 

[med6753]

Tubes are quite easy to blow up from experience, at least when in my hands 

Anything in your hands blows up. 

[med6753]

2430 Digital (Top) vs 2465 Analog (Bottom). Both in the 1986 Tek catalog. 2430 b/w 150MHz. 2465 b/w 300MHz. One must have really wanted a DSO in 1986. Why? 2430 cost $8900 USD. 2465 cost $5350 USD. Quite a difference. 

[bd139]

Looking good! 

[malagas_on_fire]

Nice scopes a little cleaning and they look like new

[mnementh]

   Labels 4 Mnementh including the point at which smoke may begin  .

Mooning shot for Specmaster.   Short riser block/mount for the pair of fans to be made when they arrive.

That's a good mooning shot, good air flow assured [emoji16]

In all honesty, bean... looking at your stack over my morning cuppa... 

With the airtight box it's attached to, that single fan you have in this pic, mounted airtight against half of the stack, would be about PERFECT for max cooling capacity from that heatsink. Something PC weenies often overlook in their quest for crazy thermal solutions, is that it takes TIME for air to collect heat from a heat exchanger, no matter which way it is exchanging heat. They always try to make things with more fans, faster fans, less obstruction... but in terms of consistently pulling heat away from a metal mass, slow and steady wins the race. 

You want good volume of air, but slow velocity with finned aluminum. One fan, pulling down half of that stack and then forced to exit out the other half, would be VERY effective in this application. With that stack, it will be VERY hard to get venturi-effect cooling, and you cannot get the velocity needed forcing the air to shift direction 90° like you're talking. I would use the fan you have there, cut a divider sheet out of aluminum flashing or even cardboard, then slip it between the fins at the middle of the stack to divide it in half. Then make your adapter plate out of 3DP (I know you're already thinking about how to do it ) so it fits airtight against one half of the stack pretty much like seen here in your photo.

If you make it from AL flashing, just extend the divider high enough to come up the side of the fan and you'll be 98% there; a little silicone RTV sealer  around the few corners & cracks and presto; all done, ready to enjoy! 

Bear in mind that good cooling doesn't necessarily meant your heatsink never gets warm; quite the opposite. You want to place the point where conductive heat exchange from the covalent area turns into convective cooling from the fins somewhere in the center of the metal mass. This is done primarily by adjusting the air velocity rather than air volume.

Worst case, you can always go dual fans in a push/pull later or, if you must, cut the crap out of that casting for a dual pusher arrangement... if you must. But, speaking from considerable experience hand-fabbing such stuff for kicks, I really think what you've got in that picture is already a kickass solution that you should at least try out before fucking up what you already have.

Okay, I've made my suggestions... have fun. 

mnem
Also, remember the monkey puzzle. 

[beanflying]

I was going to roll a 3DP mount for the fans so it would be easy to make them separately baffled. While I wait for the others to arrive I can have a go at in and out with the one I have and load it up without the speed holes in the case.

[mnementh]

Bet yours was just a bit faster to make too

Continuing on with Passive Projects, getting back to my CapKilla. 3D Printed Case, Trashy evilbay 250 50W Resistors, junk meter leads I had in a box, DPDT Switch to throw the bank from 250 - 1k at the outputs. Not shown is the leftovers of a $10 Clampmeter I am going to drop across the leads so I know when it is dead. There is no such thing as overkill 

edit: Labels fitted before Mnementh has a SOOK 

Ummm... okay, I'll bite. I know a sook is a crab (female, I think); but the only acronym I know for that is Scope Outside Of Knowledge, but even when I was in school that one was "archaic" usage at best.

Since when do you need multiple 50 watt resistors to discharge capacitors?    You planning on going to the local power substation and play with HV? 

There is NO SUCH THING AS OVERKILL 

If you do the numbers the instantaneous inrush current is heaps. Throw some numbers here http://mustcalculate.com/electronics/capacitorchargeanddischarge.php?vfrom=600&vto=2&vs=0&c=.001&r=1000&time=30 It doesn't take much of a Cap at a few hundred volts to peak 500W+ depending on the resistor used. The 250 setting for dropping Fat low voltage Caps will speed it up. So an all in one.

The main reason to do it is the LCR Tweezers I own will smoke above a few volts.

Yeah, I know, med.  I discharge 1-10F stiffening caps with a 10Ω/5W resistor on alligators; you CAN do the same with Line voltage caps but it gets sparky so I have another 100Ω one for those. Or literally any 1/2-5W resistor I have lying around. 

RMS vs τ=RC applies; unless you have something like a 1F/450V cap to deal with, the time spent dissipating those wattages is literally milliseconds and all you have to worry about is surge current capacity or MDP, which is the amount of current capacity before a resistor acts as a fuse and blows off the board.  This is usually 100-1000x TDP.

Well i blew up my 895A, and without the service manual it ain't looking good. But, to be fair, who ever heard of progress without sacrifice? I am learning vacuum tubes after all, like just then i learned what NOT to do. 

This is real-life application of "The Role of Failure in Design". Well-done!   

Tubes are quite easy to blow up from experience, at least when in my hands 

Anything in your hands blows up. 

Better keep him away from the pr0n closet then!!!      

mnem
*tubular bells*

[mnementh]

I was going to roll a 3DP mount for the fans so it would be easy to make them separately baffled. While I wait for the others to arrive I can have a go at in and out with the one I have and load it up without the speed holes in the case.

 

mnem
This post approved by:

[mnementh]

   2430 Digital (Top) vs 2465 Analog (Bottom). Both in the 1986 Tek catalog. 2430 b/w 150MHz. 2465 b/w 300MHz. One must have really wanted a DSO in 1986. Why? 2430 cost $8900 USD. 2465 cost $5350 USD. Quite a difference. 

Well yeah... the ability to capture nonrepetitive events was a game-changer back then; one of the Holy Grails of scope design. Along with ever-shorter risetimes, which was one of the 24xx series strong points. 

Looks beautiful to me... empirical proof that DSO and CRO can not only peacefully coexist, but will in many cases happily cohabitate as well. 

mnem
"No electron gun, no sale." ~ old man Kirsch

[med6753]

Well yeah... the ability to capture nonrepetitive events was a game-changer back then; one of the Holy Grails of scope design. Along with ever-shorter risetimes, which was one of the 24xx series strong points. 

Very true even though it's memory capacity is laughable by today's standards.

Looks beautiful to me... empirical proof that DSO and CRO can not only peacefully coexist, but will in many cases happily cohabitate as well. 

mnem
"No electron gun, no sale." ~ old man Kirsch

So far they are getting along. No fights have broken out. 

[mnementh]

Well yeah... the ability to capture nonrepetitive events was a game-changer back then; one of the Holy Grails of scope design. Along with ever-shorter risetimes, which was one of the 24xx series strong points. 

Very true even though it's memory capacity is laughable by today's standards.

Yeah... looking at the developments in RAM technology over the decades, it boggles my mind that they were able to make RAM fast enough with ANY usable depth to do this. AT ALL. Just shows what the "bleeding edge" of the time was capable of. That kind of inspired genius is sorely lacking in pretty much everything designed nowadays; the art of designing stuff that's "never been before" has suffered from the race to the bottom vs bean-counter attrition just as has every other facet of modern life.

If you can't produce it, package it, and sell it before next quarter it just isn't important. Fuck ever even bothering to understand what it is you've got in the first place. 

mnem
Fuck Ayn Rand.

[tggzzz]

   2430 Digital (Top) vs 2465 Analog (Bottom). Both in the 1986 Tek catalog. 2430 b/w 150MHz. 2465 b/w 300MHz. One must have really wanted a DSO in 1986. Why? 2430 cost $8900 USD. 2465 cost $5350 USD. Quite a difference. 

Well yeah... the ability to capture nonrepetitive events was a game-changer back then; one of the Holy Grails of scope design.

Storage scopes were available well before the 24xx series. I used one in the 70s, and they weren't a new concept then.

Of course they were a pain to use, but it took a surprisingly long time for analogue storage scopes to be completely supplanted by digitising storage scopes.

[bd139]

I think that's because most of the early digital storage ones were crap! Case in point, this horrid thing which passed through my hands very quickly:



Edit: found another picture:



That was CCD based.

[tggzzz]

Well yeah... the ability to capture nonrepetitive events was a game-changer back then; one of the Holy Grails of scope design. Along with ever-shorter risetimes, which was one of the 24xx series strong points. 

Very true even though it's memory capacity is laughable by today's standards.

Yeah... looking at the developments in RAM technology over the decades, it boggles my mind that they were able to make RAM fast enough with ANY usable depth to do this.

RAM wasn't a problem, in the sense that you could spend money and solve the problem. The problems were:

• with a conventional ADC as we know it today in digitising sampling scopes, the samples/s and bits/sample. Stunning improvements have been made since the 90s
• where such ADCs were inadequate, one technique was to have an analogue sampling front end, in the form of a CCD. The captured signal was read out of the CCD at a slow rate that could be digitised by the available ADCs. The CCDs had a limited length, for various reasons

I suspect you are noticing the limitations of the CCDs, not the limitations of RAM.

[kj7e]

Been playing with 10MHz OCXO's and wanted another dedicated power supply I could run for some long term testing.  Found what looked to be a clean, late version HP 6227B (0-25v, 0-2A, dual channel) on eBay not to far from me.  This was the only test equipment item in the sellers store, so I made an offer for $75 from the $135 asking and they accepted.  Shipped fast, and very well packaged which was a pleasant surprise.  Its in better shape than I had hoped for, appears 100% original and no signs of any work.  I am seeing some ripple at max load, more so from the main channel.  The main filter bank caps do appear week, and C10 on the master regulator board needs to be replaced, but this is to be expected.  The hunt is on for some caps, but well worth it for such a nice piece of gear, they don't make things like they use to.

[tggzzz]

I think that's because most of the early digital storage ones were crap! Case in point, this horrid thing which passed through my hands very quickly:

Yes indeed. Stunning ADC (and DAC) improvements have been made since the early/mid 90s. That was one of the disappointingly few major differences when I returned to electronics a few years ago. (Nanopower is the other).

[bd139]

Been playing with 10MHz OCXO's and wanted another dedicated power supply I could run for some long term testing.  Found what looked to be a clean, late version HP 6227B (0-25v, 0-2A, dual channel) on eBay not to far from me.  This was the only test equipment item in the sellers store, so I made an offer for $75 from the $135 asking and they accepted.  Shipped fast, and very well packaged which was a pleasant surprise.  Its in better shape than I had hopped for, appears 100% original and no signs of any work.  I am seeing some ripple at max load, more so from the main channel.  The main filter bank caps do appear week, and C10 on the master regulator board needs to be replaced, but this is to be expected.  The hunt is on for some caps, but well worth it for such a nice peace of gear, they don't make things like they use to.

nice bit of kit and very nice photos. Thanks for posting!

I think that's because most of the early digital storage ones were crap! Case in point, this horrid thing which passed through my hands very quickly:

Yes indeed. Stunning ADC (and DAC) improvements have been made since the early/mid 90s. That was one of the disappointingly few major differences when I returned to electronics a few years ago. (Nanopower is the other).

At the same time it has led to "commidity integration" where every device is the same digital ARM black blob with some light weight analogue interfaces around the edge. As always I'm too late to the party to enjoy the good bits.

[tggzzz]

I think that's because most of the early digital storage ones were crap! Case in point, this horrid thing which passed through my hands very quickly:

Yes indeed. Stunning ADC (and DAC) improvements have been made since the early/mid 90s. That was one of the disappointingly few major differences when I returned to electronics a few years ago. (Nanopower is the other).

At the same time it has led to "commidity integration" where every device is the same digital ARM black blob with some light weight analogue interfaces around the edge. As always I'm too late to the party to enjoy the good bits.

That's always been the case.

I have a Tek instrument where dividing a 5us pulse train down to 10us (and 10us to 50us, all the way down to 5s) is done by three transistors, a couple of diodes, a few resistors and capacitors.

TTL? Bugger that, even RTL and DTL were in the future!

Here's the schematic of three such stages...