Test Equipment Anonymous (TEA) group therapy thread

[Specmaster]

What do you consider a burn-in to be?

[med6753]

What do you consider a burn-in to be?

At minimum 3 to 4 hours continuous operation with no fail. And that's being generous. Industry standard tends to be 6 hours minimum.

[bd139]

24 hours on them with a full 4 hour run / stop 50% duty cycle. I’ve seen them pack in after a couple of days.

Usual failures in this cycle are the fan motor, primary filter caps, bridge rectifiers, random tants and the little wet tantalum cap near the bottom of the interface board.

[Specmaster]

24 hours on them with a full 4 hour run / stop 50% duty cycle. I’ve seen them pack in after a couple of days.

Usual failures in this cycle are the fan motor, primary filter caps, bridge rectifiers, random tants and the little wet tantalum cap near the bottom of the interface board.

Wow, thats harsh 

EDIT;
In that case I'd consider my Iwatsu well and truly burnt in then because it sits on a desk to the left and slightly behind me, many times its been switched on to do a test early in the morning and then ignored all day because it was out of my line vision until the early hours of the following morning and that has just done that relentlessly all the time I've had without any failures, man that thing is tough.

[nixiefreqq]

OK, OK. I'll wait, next time.

LOL - no worries.  Actually, in that test mode, it's SUPPOSED to read 100MHz, so that part is working correctly.  Perhaps it will come in from 99.9999 once it has cooked for a while - lord only knows when it had last been turned on.

I was initially going to us a Tek 545B that I acquired about a year ago in an old test gear haul and had never turned on.  Unfortunately I wasn't recording when I powered it up, as it IMMEDIATELY expelled a nice cloud of smoke from its starboard side, and for the last few hours the pungent scent of eau de Allen Bradley has been slowly dissipating from the house (that or I'm acclimating to it!).  I don't want to open the windows and lose all my conditioned air - it's humid as balls outside at present.  The smoke cloud would have made for an amusing opening to a video - "we'll use this old vintage Tektronix scope to check the oscillator in the " <click> (flips mains switch) -  - "...or not..."  <excavates Tek 516>  "...counter."

And yet another thing joins the repair queue...   

Yup, you can't stop now. You're already two episodes into the repair. Gotta see what's causing it to read 100 MHz, too.

   I should have known better and anticipated that was coming!   

-Pat

the 99.999 is perfectly normal in an antique direct counter.   it will eventually drift to 100.000. and then maybe to 100.001 (and back again)

its the 'ol lsd sampling error problem.  see hp app note 200-4:


For a digital instrument like a counter, output readings are discrete (quantized) even though the inputs are continuous.  Even for the case where the input quantity is perfectly stable, the counter’s readings may fluctuate.  This fluctuation is due to quantization error (±1 count error).

The value of the LSD Displayed often is the same as the quantization error which represents the smallest non-zero change which may be observed on the display.  Because of this, resolution and accuracy statements often specify quantization error as ± LSD Displayed.
Quantization error arises because the counter can’t count a fraction of a pulse —  a pulse is either present during the gate time or it isn’t.  The counter can’t detect that a pulse was present just after the gate closed. Additionally, since the opening of the counter’s main gate is not synchronized to the input signal, the quantization error may be in either direction.  Consider a 2.5 Hz signal as shown in the figure.  In case 1, the counter’s gate is open for 1 second and accumulates 2 counts — the display will show 2 Hz.  In case 2, the same length gate accumulates 3 counts for a display of 3 Hz.
Although we say ±1 count, we do not mean that a particular measurement can vary by both + and – one count.  The measurement can vary by one count at most.  The reason that you have to say ±1 count is that from a single measurement, you don’t know a priori which way the next measurement will jump or if it will jump at all.  So the specification has to include both possibilities.

[med6753]

24 hours on them with a full 4 hour run / stop 50% duty cycle. I’ve seen them pack in after a couple of days.

Usual failures in this cycle are the fan motor, primary filter caps, bridge rectifiers, random tants and the little wet tantalum cap near the bottom of the interface board.

Wow, thats harsh 

EDIT;
In that case I'd consider my Iwatsu well and truly burnt in then because it sits on a desk to the left and slightly behind me, many times its been switched on to do a test early in the morning and then ignored all day because it was out of my line vision until the early hours of the following morning and that has just done that relentlessly all the time I've had without any failures, man that thing is tough.

Gee, and I thought I was the tuff guy on the block. I bow to you Sir! 

[med6753]

OK, OK. I'll wait, next time.

LOL - no worries.  Actually, in that test mode, it's SUPPOSED to read 100MHz, so that part is working correctly.  Perhaps it will come in from 99.9999 once it has cooked for a while - lord only knows when it had last been turned on.

I was initially going to us a Tek 545B that I acquired about a year ago in an old test gear haul and had never turned on.  Unfortunately I wasn't recording when I powered it up, as it IMMEDIATELY expelled a nice cloud of smoke from its starboard side, and for the last few hours the pungent scent of eau de Allen Bradley has been slowly dissipating from the house (that or I'm acclimating to it!).  I don't want to open the windows and lose all my conditioned air - it's humid as balls outside at present.  The smoke cloud would have made for an amusing opening to a video - "we'll use this old vintage Tektronix scope to check the oscillator in the " <click> (flips mains switch) -  - "...or not..."  <excavates Tek 516>  "...counter."

And yet another thing joins the repair queue...   

Yup, you can't stop now. You're already two episodes into the repair. Gotta see what's causing it to read 100 MHz, too.

   I should have known better and anticipated that was coming!   

-Pat

Wanna sell the 545B? Now that it has expelled it's magic smoke I don't have to worry about it stinking up my place. 

[nixiefreqq]

ballantine?  my old man drank their beer up until they stopped brewing the swill.

I want it, BUT...…….my hp counters might revolt.


https://www.ebay.com/itm/Ballantine-Laboratories-Digital-Frequency-Counter-Model-5700A/183383140011?hash=item2ab27ca6ab:g:dEUAAOSwcWpbdfqG

[Neomys Sapiens]

The video also includes a cameo appearance by Piglet, my favorite cable chewer...

-Pat

And that yellow box is a AN-USM415 (Ballantine) safety AC voltmeter?

[neo]

ballantine?  my old man drank their beer up until they stopped brewing the swill.

I want it, BUT...…….my hp counters might revolt.


https://www.ebay.com/itm/Ballantine-Laboratories-Digital-Frequency-Counter-Model-5700A/183383140011?hash=item2ab27ca6ab:g:dEUAAOSwcWpbdfqG

Be warned, their manuals are impossible to find! I'd be tempted but i know i'll never find a manual for it.

[Specmaster]

WTF, they can't even get the nixies to line up correctly 

[med6753]

ballantine?  my old man drank their beer up until they stopped brewing the swill.

I want it, BUT...…….my hp counters might revolt.


https://www.ebay.com/itm/Ballantine-Laboratories-Digital-Frequency-Counter-Model-5700A/183383140011?hash=item2ab27ca6ab:g:dEUAAOSwcWpbdfqG

It looks like it's been dragged behind a truck. 

[Cerebus]

What wood do you guys suppose is the most stable? I need pair of 8 foot posts, either a 3x3 or a 4x4. Leaning towards either ash or maple. Ash is dead common and cheap enough though i think maple may do better, 
*note*  Though i only mentioned ash or maple i am open to suggestions of all types so long as it can be had reasonably cheaply and available in the midwest. Also considering, poplar or alder and i'd even consider longleaf pine if i had a known source for #0 (best, structural grade) pine. Defects are all too common in #2 pine, every 4x4 i got at that length sucks too bad to be fixed.

Also some numbers for you nerds out there, the top will be comprised of .5 inch mdf 1" white fir and 1.5 inch shortleaf pine for a total of 3 inches and will weigh approximately 160 pounds. The frame for the table will be made entirely of pine, either shortleaf or long, and will weigh approximately 110 pounds not counting the upper shelves which will weigh approximately 105 pounds with just one shelf. I intend to have the post come just shy of my ceiling, the ceiling being 7'11 and post being shaved down to fit.

Now back to your regularly scheduled program, table talk over (from me) for the day.

The most stable wood is Mahogany, the real thing not 'African Mahogany', Sapelle or any of the other pretenders to the throne. There's a reason it was traditionally used for pattern making in the foundry industry - if a wood can survive a foundry and keep its dimensional stability it's good. However as Swietenia macrophylla is on  CITEs appendix II you aren't going to see any at a sane price anytime soon. It's close cousin Cuban Mahogany (Swietenia mahagoni) is a fair substitute but will also leave your wallet limping.

For a white hardwood little beats Baltic Birch for stability. For jigs and other things that must be dimensionally stable Baltic Birch plywood is the material of choice and is cheap to boot - commonly used in luthiery for bending formes where it gets exposed to steam and heat and still keeps its shape. In solid timber form it is only slightly less good than in plywood form. Hard Maple (Sugar Maple) probably comes second of the common timbers, but is tough on tools and tooling. Ash is only fair to good in stability and is better used in situations where its strength and elasticity are the properties you're looking for. That said, it would be fine for your application if you can't get some good Maple at a good price.

There are some oddities and rarities that might score better (e.g. Hornbeam) but that have never been commercially available in any quantity.

[tggzzz]

What wood do you guys suppose is the most stable? I need pair of 8 foot posts, either a 3x3 or a 4x4. Leaning towards either ash or maple. Ash is dead common and cheap enough though i think maple may do better, 
*note*  Though i only mentioned ash or maple i am open to suggestions of all types so long as it can be had reasonably cheaply and available in the midwest. Also considering, poplar or alder and i'd even consider longleaf pine if i had a known source for #0 (best, structural grade) pine. Defects are all too common in #2 pine, every 4x4 i got at that length sucks too bad to be fixed.

Also some numbers for you nerds out there, the top will be comprised of .5 inch mdf 1" white fir and 1.5 inch shortleaf pine for a total of 3 inches and will weigh approximately 160 pounds. The frame for the table will be made entirely of pine, either shortleaf or long, and will weigh approximately 110 pounds not counting the upper shelves which will weigh approximately 105 pounds with just one shelf. I intend to have the post come just shy of my ceiling, the ceiling being 7'11 and post being shaved down to fit.

Now back to your regularly scheduled program, table talk over (from me) for the day.

The most stable wood is Mahogany, the real thing not 'African Mahogany', Sapelle or any of the other pretenders to the throne. There's a reason it was traditionally used for pattern making in the foundry industry - if a wood can survive a foundry and keep its dimensional stability it's good. However as Swietenia macrophylla is on  CITEs appendix II you aren't going to see any at a sane price anytime soon. It's close cousin Cuban Mahogany (Swietenia mahagoni) is a fair substitute but will also leave your wallet limping.

For a white hardwood little beats Baltic Birch for stability. For jigs and other things that must be dimensionally stable Baltic Birch plywood is the material of choice and is cheap to boot - commonly used in luthiery for bending formes where it gets exposed to steam and heat and still keeps its shape. In solid timber form it is only slightly less good than in plywood form. Hard Maple (Sugar Maple) probably comes second of the common timbers, but is tough on tools and tooling. Ash is only fair to good in stability and is better used in situations where its strength and elasticity are the properties you're looking for. That said, it would be fine for your application if you can't get some good Maple at a good price.

There are some oddities and rarities that might score better (e.g. Hornbeam) but that have never been commercially available in any quantity.

I believe aerospace grade wood is usually sitka spruce; alternatives include douglas fir and western hemlock. You don't want wings warping etc, so dimensional stability is of some interest.

[URI]

ballantine?  my old man drank their beer up until they stopped brewing the swill.

I want it, BUT...…….my hp counters might revolt.


https://www.ebay.com/itm/Ballantine-Laboratories-Digital-Frequency-Counter-Model-5700A/183383140011?hash=item2ab27ca6ab:g:dEUAAOSwcWpbdfqG

Nice one! And a serious counter in my eyes with its input for an external reference of 1Mhz. 

Go, get it! You do want it, don't you..? 

No GPIB, so nothing for me.   

[Mr. Scram]

Just wanted to pass on a smaller fleaBay find... this is apparently a fellow tinkerer who has hooked up with some local equipment scrappers to make some TEA money.

This fellow, member n2cbu has high ratings, lots of interesting stuff, and is not only willing to combine shipping, he has his storefront set up to automatically do so.  This parts list has $24.49 worth of shipping by individual part; essentially a very reasonable $3.50-ish/item minimum. That all combined down to a Net shipping cost of $4.24.

His store motto is "From my basement to yours: If you don't need it, I HAVE IT!!!" I wanna support him just for THAT! 

I bought 2 of the 100ohm 0.1% resistors and one 25-ct strip of the 5315ohm 0.1% resistors. I intend to put them all on a breadboard and make a ladder strip with double rows of 0.100" pins & jumpers so by putting in series or parallel I can make a very good, very cheap scalar resistance array that should have values pretty much in the middle of every range up to 500000 ohms.

Cheers,


mnem
*Pretty good at making bad decisions*

I bought a few items from him and actually posted about it before. My items unfortunately came with issues which should have been noticeable before shipping. He also tends to remove the serial stickers from devices, which I really don't like. The response to the issues was adequate though, and communication and packaging is good. It's certainly not a scammer and he does seem to care about providing a good service.

[neo]

The most stable wood is Mahogany, the real thing not 'African Mahogany', Sapelle or any of the other pretenders to the throne. There's a reason it was traditionally used for pattern making in the foundry industry - if a wood can survive a foundry and keep its dimensional stability it's good. However as Swietenia macrophylla is on  CITEs appendix II you aren't going to see any at a sane price anytime soon. It's close cousin Cuban Mahogany (Swietenia mahagoni) is a fair substitute but will also leave your wallet limping.

For a white hardwood little beats Baltic Birch for stability. For jigs and other things that must be dimensionally stable Baltic Birch plywood is the material of choice and is cheap to boot - commonly used in luthiery for bending formes where it gets exposed to steam and heat and still keeps its shape. In solid timber form it is only slightly less good than in plywood form. Hard Maple (Sugar Maple) probably comes second of the common timbers, but is tough on tools and tooling. Ash is only fair to good in stability and is better used in situations where its strength and elasticity are the properties you're looking for. That said, it would be fine for your application if you can't get some good Maple at a good price.

There are some oddities and rarities that might score better (e.g. Hornbeam) but that have never been commercially available in any quantity.

Thank you. The problem with oddities like hornbeam or any mahogany is that i am looking for a 4" by 4" by 90" that doesn't cost me a fortune.  So then hard maple is at the top of my list followed by sweet birch (which is a baltic birch).

Also, i may have overstated the need for perfect stability all i require is a post that will behave better than construction lumber.

[URI]

What wood do you guys suppose is the most stable? I need pair of 8 foot posts, either a 3x3 or a 4x4. Leaning towards either ash or maple. Ash is dead common and cheap enough though i think maple may do better, 

Why not using Aluminium T-slotted extrusion profiles? You have to decide once which system you want to use (in Germany you have to choose Bosch or Item, for example) as those slightly differ and are not compatible.

I built the upper part of my bench of it and if I had to build my bench from scratch I would choose to make it from Aluminium T-slotted extrusion profiles. You can find offers for custom cut profiles on the net quiet easily.

This is what I made the top of my bench of (40mm x 80mm Item compatible profile):


It's a bit like fischertechnik (a famous tech toy here in Germany, even used for training purposes) but bigger (fischertechnik: see https://en.wikipedia.org/wiki/Fischertechnik):


Depending on how strong the Profile is (I chose the strongest type), it's very strong and will carry all your boat anchors with ease.   

[bd139]

Always wanted to build something with that stuff. This is a good excuse. I need somewhere I can stash an SA on my desk and the top two shelves aren’t strong enough for more than about 15kg a shelf.

[mtdoc]

What wood do you guys suppose is the most stable? I need pair of 8 foot posts, either a 3x3 or a 4x4. Leaning towards either ash or maple. Ash is dead common and cheap enough though i think maple may do better, 
*note*  Though i only mentioned ash or maple i am open to suggestions of all types so long as it can be had reasonably cheaply and available in the midwest. Also considering, poplar or alder and i'd even consider longleaf pine if i had a known source for #0 (best, structural grade) pine. Defects are all too common in #2 pine, every 4x4 i got at that length sucks too bad to be fixed.

Also some numbers for you nerds out there, the top will be comprised of .5 inch mdf 1" white fir and 1.5 inch shortleaf pine for a total of 3 inches and will weigh approximately 160 pounds. The frame for the table will be made entirely of pine, either shortleaf or long, and will weigh approximately 110 pounds not counting the upper shelves which will weigh approximately 105 pounds with just one shelf. I intend to have the post come just shy of my ceiling, the ceiling being 7'11 and post being shaved down to fit.

For your application, stability will not be dependent on the type of wood. It will depend on your construction methods and joinery.

No need to spend money on exotic hardwoods (Mahogany!!) or Sitka Spruce! (used for its strength to weight ratio).

If you did need a hardwood (you don’t), Oak is The most readily available and least expensive in most parts of the US.

Pine is soft and easy to work with but also the least strong.

Just use Doug Fir which is the standard high strength construction softwood used in the US for dimensional lumber. Seal it with a polyurethane. Easy to stain first if you’d like a different wood look.

[URI]

mtdoc is right, the construction is more important than the type of wood.

Below you can see a construction detail of my bench. It's one post of my bench top with corner brackets for stiffening the joints of the profiles:


In the overall view you can see most of my Test Equipment (most of it quiet heavy) residing on my bench top that's held by two posts only (but 40mm x 80mm strongest Aluminium T-slotted extrusion profiles).
I would build that with two post on every side as part of the tables if I would build it from scratch now, but it was a refit.
My bench actually consists of two tables back to back; One is my computer/working desk, the other is my lab bench.
The two posts of the named bench top sit between those two tables: Its posts are tightly screwed to each of the tables thus holding them together.
Each of the tables is made of 30mm pine glulam with tabletops made of 30mm birch glulam.
The table legs are built L-shaped (very stiff..) and connected by a frame (also pine glulam) made of boards 30mm thick and 100mm high.
The right screws in the right angle hold all that solidly together.   
I don't fear to be crushed by my Test Equipment.   

[bd139]

On benches like that I worry about the floor. After watching a friend wheel a 46" CRT screen into the corner of his living room and it and him going straight through the floor 

[URI]

On benches like that I worry about the floor. After watching a friend wheel a 46" CRT screen into the corner of his living room and it and him going straight through the floor 

I had to compensate for some Milimeters the floor* sank after I loaded the benchtop with my boat anchors, indeed.   
But my bench has threaded feet to accomplish that.   

Edit:
*- wooden floor on the ground floor (for the Brits among us/first floor for all those speaking American English  ). Underneath is a solid floor that covers the cellar -but I don't know how this house was built. I'm very sure the wood gave way because the cellars top didn't change a bit -there must be gap between those two structures.

BTW: The load is distributed to a floor area of ~2.7 square meters through eight table legs.

[Cerebus]

I believe aerospace grade wood is usually sitka spruce; alternatives include douglas fir and western hemlock. You don't want wings warping etc, so dimensional stability is of some interest.

The defining characteristic there is the stiffness to weight ratio. Sitka is the Carbon Fibre Composite of the carbohydrate foam world. It's no accident that it forms the soundboards of many musical instruments (guitars, pianos, harps,...), but cut quartersawn to fight any tendency to instability.

Sitka has a Tangential/Radial shrinkage ratio of 1.7, Western Hemlock 1.8, Douglas Fir 1.9, Birch is 1.4, Mahogany is 1.4. A ratio of 1.0 would be ideal for stability purposes, the larger the figure the more prone to warping and twisting with changing humidity.  The individual shrinkage figures for Sitka and Mahogany are respectively (Tangential 7.5% from 'green' to 'dry', Radial 4.3%) and (Tangential 5.1%, Radial 3.7%) indicating that Sitka moves more in absolute terms and twists more with changing relative humidity than Mahogany. Longitudinal change is intermediate between T and R. (Figures from p117 in "Understanding Wood" by R Bruce Hoadley.)

[Berni]

Now that's quite the heavy duty top shelf with how much boatanchory its having to hold up.

My bench uses pine for most of the supports purely due to being cheap. The actual top is i think acacia but the legs are made from beech wood because of how solid it is. The special part about my bench is that it is 3m long yet only has legs on the ends so that i can put a chair anywhere i want, yet is still plenty solid.