Test Equipment Anonymous (TEA) group therapy thread

[AVGresponding]

More likely it's about spreading the load on the thin metal sheet; the more fixings, the less stress where each one goes through.

I hate soldering guns... I have one, but I never (maybe twice in 30 years) use it. Yes they have loads of power, mine's 200W, but it's not controlled in any way other than your finger on the trigger (at least on mine) and because the tip has such a low thermal mass, I found it to be worse than useless for soldering anything large if it's at all susceptible to heat damage.

[mansaxel]

Do they really think that four castors attached to a thin bit of sheet metal requires 16 x 8.8 grade bolts, or are these the special chinesium version that has 8.8% of the strength of a normal ungraded machine screw? A quick look-up says that 16 grade 8.8 M8 machine screws have a combined guaranteed load of 337.6 kN (that's 34.4 tonnes or 75,895 lbf). Hmm, bit of overkill, slightly; only by a smidgeon though.

Over here we rarely get hex screws stamped in lesser grades than 8.8 -- threaded rod being the most common exception; it usually comes in 4.6 or so. There of course are other exceptions; I've got this little assortment kit of small fasteners that's followed me for a good 20 years; never sees usage where it would matter but more in household applications. Those screws are made of prime grade Chinesium, and snap at a fleeting glance.

<peeve type=pet>
What is it with vendors concentrating on stainless hardware only? Brittle crap if you don't need the environmental part.
</peeve>

I bought a bag of 50 M8 Tee Nuts (the kind you hammer into plywood to get a metric thread) from China the other week. Also M8. I'm going to use them to fit castors to my microphone stands and cable flightcase, which gets a bit heavy if you load it to its volume capacity. Wonder how much that cheapness is going to bite back. Here, too, the castors will use 16 M8 screws and the castor boards will get something like 6 each.

[Cerebus]

More likely it's about spreading the load on the thin metal sheet; the more fixings, the less stress where each one goes through.

Oh yeah, 16 bolts is fine, perfectly sensible. It's the bit where someone decided to use 8.8 graded ones that I have the WTF moment.

[Brumby]

Do they really think that four castors attached to a thin bit of sheet metal requires 16 x 8.8 grade bolts, or are these the special chinesium version that has 8.8% of the strength of a normal ungraded machine screw? A quick look-up says that 16 grade 8.8 M8 machine screws have a combined guaranteed load of 337.6 kN (that's 34.4 tonnes or 75,895 lbf, or just under 7 male Indian elephants, or a bit over 4 1/2 London buses). Hmm, bit of overkill, slightly; only by a smidgeon though.

[Cerebus]

<peeve type=pet>
What is it with vendors concentrating on stainless hardware only? Brittle crap if you don't need the environmental part.
</peeve>

Pet peeve here too.

SS is pretty, it's corrosion resistant in some circumstances, but that's almost all it has going for it. Typical A-2 or A-4 SS fastener min yield stress  is lower than that of plain old grade 4.6 plain steel. Not a lot less I'll grant you, but add all the problems with galling and seizing if you stick SS fasteners into the wrong material and they become a very unattractive choice.

Aside from the fact that SS fasteners are, what, twice the price in small quantities, I can't believe how many people pick SS because they believe that it is somehow innately 'more betterer' than plain steel not realising that there are significant drawbacks to SS, and if you pick the wrong SS for the wrong environment you don't even get good corrosion resistance.

If you really want to hear a rant about people's blind choice of "Stainless Steel" without respect to what alloy they're using for what application you need to sit down with an old metallurgist flatmate of mine, Clive, who can happily hold forth for an hour or more, all while getting redder and redder around the ears as he does so.  He feels, with some justification, that there are a lot of people who shouldn't be allowed to use metal at all without supervision from an adult (i.e. a properly qualified metallurgist).

[med6753]

That’s quite ironic in the way as the readout chips get quite toasty from my understanding. Hmm.

Well yes, perhaps I wasn't clear. This military 7603 is equivalent to the civilian 7603N with the 'N' meaning no readout board. Therefore, no fan.

[factory]

Finally getting somewhere with the HP 5248M, bit tired tonight but will explain more tomorrow. 

Well I went through testing all the transistors in the 5MHz to 10MHz multiplier stage (A26) but couldn't find anything that was causing the low output voltage, I came to the conclusion that the crystal oven might be the cause.
To verify the board was OK before troubleshooting the oven, I disconnected the DIV output from the oven & used a Philips RF source in it's place (which was set it up using the oscilloscope for the correct rms level), well that made a big difference as I was now getting the correct output from the multiplier. 



Before & after at A26(6),


Oh dear not another faulty HP crystal oven I thought, the only accessible adjustments are the fine/course for the frequency & a filter for the main 5MHz output (BNC).
The manual only tells you to adjust the 5MHz filter if the output (BNC) on the back of the counter is below 2.5Vpp, which I had checked & it was well above. I had also checked the input to the A26 board was around 70mV or so I thought, turns out I should have checked the rms level not peak to peak  and this was a bit low.
After looking at the circuit I couldn't work out why the DIV output was low if the main output was fine. The 5MHz filter adjustment is in this part of circuit so I made a note of the original position before adjusting it, to my surprise the A26 board starting working as it was supposed to and I had well over the required 5Vpp at A26(6)  , I guess the original owner must have twiddled with it instead of fixing the separate oven power supply. 
 

The self check was finally useable, note the two LSD are still faulty (probably the last parts in the repair queue), still not getting anything through from either input, which I expected as the function control board still needs working on.

David

[Robert763]

This arrived yesterday 

[tggzzz]

With nothing TEA to buy lately I've been forced to resort to near-TEA acquisitions

Ramco has one auction ending on the 1st, another on the 8th; both catalogues are up.

[xrunner]

This arrived yesterday 

Good thing they used that much tape - it's on it's last legs on top! 

[med6753]

This arrived yesterday 

Tease! 

[Robert763]

Nothing Blue though, not even TE 
Five of theses 3CCD analog cameras plus a bunch of lenses, controllers and cables. Probably flip most of it. These cameras are from the mid nineties and cost about $5k without lens. They were about the pinacle of "small" analog camera technology.
lot also included a weird JVC "15 megapixel" analog still camera that uses a 2/3" video CCD  of about 440k pixels combined with a shift lens, digititizer card and specal software to take multiple exposures and get high resolution. when they say still camera they mean the subject must be still  Needless to say the digitizer card and software are unobtanium.

[Robert763]

I did get some TE this week, A Hagner S3 Photometer. This is primarally a view-thrugh 1 degree luminance meter. Basically the same as the Minolta LS100 but it has the addition of an external illuminance sensor. This not only gives illuminance but it allows you to use any diode or current output sensor for light or even just as a picoammeter.
Not bad for £25 inc postage. that's 1% of the  cost of a new one 

[AVGresponding]

Good news, bad news.


Good news: I won an auction for a Brown Box (Keithley 195A £36 shipped).

Bad news: It's coming from devon_it_recycling, which means it will be even rougher than the pictures imply...

[GreyWoolfe]

With nothing TEA to buy lately I've been forced to resort to near-TEA acquisitions. One shiny new metal arse tool cabinet.



I had to giggle when it came to fixing the castors on. These are the supplied M8 machine screws:



Do they really think that four castors attached to a thin bit of sheet metal requires 16 x 8.8 grade bolts, or are these the special chinesium version that has 8.8% of the strength of a normal ungraded machine screw? A quick look-up says that 16 grade 8.8 M8 machine screws have a combined guaranteed load of 337.6 kN (that's 34.4 tonnes or 75,895 lbf, or just under 7 male Indian elephants, or a bit over 4 1/2 London buses). Hmm, bit of overkill, slightly; only by a smidgeon though.

Enjoy the new cabinet.  I have come to prefer red instead of black. It's a much more striking color. 

[mnementh]

I still prefer SS, no matter what C sez. 

mnem

[factory]

Seeing all those rusty fasteners on some otherwise clean Farnell TE I think I prefer SS too.

David

[tonyalbus]

Good news, bad news.


Good news: I won an auction for a Brown Box (Keithley 195A £36 shipped).

Bad news: It's coming from devon_it_recycling, which means it will be even rougher than the pictures imply...

They are quite well build... it should arrive good.
i have a restore/calibration video for it on my channel, working on this DMM was a pleasure..
Nice catch

[mansaxel]

Seeing all those rusty fasteners on some otherwise clean Farnell TE I think I prefer SS too.

David

There is a Shiny! attraction in stainless, but galling..

[BravoV]

Well, not TEA related, but brought home something different. 

[bd139]

That'll be handy for close quarters engagement in the upcoming zombie apocalypse.

[Cerebus]

Seeing all those rusty fasteners on some otherwise clean Farnell TE I think I prefer SS too.

David

I like them for appearance on things like test equipment, I've got buckets of small "who cares what alloy" SS M3 and M4 fasteners for that because in most places on TE they see more no load worth mentioning. Moreover, there's nothing wrong with then in load bearing situations if someone who knows what's what has designed them in. Where they scare me is where people replace perfectly good, designed in fasteners for SS without doing the appropriate figuring out. Back in my motorcycling days there was a trend for buying complete fastener replacement kits in SS for motorbikes - there may still be, I haven't looked at a biker's mag in years. Some of them were carefully designed and some were put together by people who just looked up the sizes of the existing fasteners and made up kits of the same fasteners but in stainless. You could tell which was which, the properly designed ones didn't include SS fasteners for places that were inappropriate, the bad ones did (e.g. aluminium crankcase castings that the manufacturer had supplied properly passivated screws/bolts for so you wouldn't get galvanic corrosion).

[Robert763]

Even worse than than SS are the anodised aluminium cap-head screws. Designed for cosmetic applications but nothing to stop people replacing a HT cap-head with cheese
/www.ebay.co.uk/itm/M6-x-20-mm-Bolts-Aluminium-Red-Anodised-Bolts-25mm-Red-Screws-M6-Cap-Head-Bolt/172427228357

[mnementh]

Seeing all those rusty fasteners on some otherwise clean Farnell TE I think I prefer SS too.

David

I like them for appearance on things like test equipment, I've got buckets of small "who cares what alloy" SS M3 and M4 fasteners for that because in most places on TE they see more no load worth mentioning. Moreover, there's nothing wrong with then in load bearing situations if someone who knows what's what has designed them in. Where they scare me is where people replace perfectly good, designed in fasteners for SS without doing the appropriate figuring out. Back in my motorcycling days there was a trend for buying complete fastener replacement kits in SS for motorbikes - there may still be, I haven't looked at a biker's mag in years. Some of them were carefully designed and some were put together by people who just looked up the sizes of the existing fasteners and made up kits of the same fasteners but in stainless. You could tell which was which, the properly designed ones didn't include SS fasteners for places that were inappropriate, the bad ones did (e.g. aluminium crankcase castings that the manufacturer had supplied properly passivated screws/bolts for so you wouldn't get galvanic corrosion).

Having rebuilt more than a few such beasts... Your "properly-passivated" screws are usually as soft as case-hardened cheese. And on rice-rockets, also JIS. And a complete dicksore to get out without stripping after they've had a couple decades to trade ions with the surrounding aluminum.

There are always tradeoffs; I prefer to reassemble with  a good hard hex-head (SS or otherwise) equivalent after spending hours with hammer & impact driver and/or EZ-outs getting the fucking thing apart. I might be the poor bastard who has to take it apart next.

mnem
 

[med6753]

Ready to mount on the circuit board.