Test Equipment Anonymous (TEA) group therapy thread

[mnementh]

I give up.. Wanted to post a reply with an image.. The page thinks about it for a bit and then goes to... the "create a new topic" page. 

I know. But I really don't want to. I mean, what is this.. 1999? 

That usually means you tried to post either too many pics, one or more pics in a format it didn't like (regardless of posted "acceptable" filetypes), or one pic that was so big it gagged and the exercise wheel slammed to a halt, bucking the poor hamster off into the  dingweeds. 

Or it may just be lots of other users ATM, or the phase of the moon, or sunspots...

Keep the pics down around 5-9 total, and 200-400K each in .jpg format, and that rarely happens.

mnem
At least we aren't IRC...

[TERRA Operative]

Been poking the TDS784C scope this weekend. Got a couple relays for the attenuator hybrids ordered and have been mixing and matching from my stock to put the latest revisions into this scope.
Got 2x J revision (latest) on channels 1 and 2, and 2x H revision (middle) on channels 3 and 4. the rest of the 500MHz scopes have all got G revision (earliest) which is fine for their bandwidth.

I also finished building a bench PSU to power up HP 1345A CRT's, and then discovered that the 1345A vector display from my 4145A has a busted CRT, which would explain the lingering focus issues, looks like internal damage which is basically terminal for the CRT unless you can live with the small distortion on the screen (and slight lack of focus).

Not the end of the world as the 4145A is earmarked for sale (with full disclosure of course) as I have a 4145B to get my teeth into. Just a shame that the CRT is bung, but it's not worth spending the cash for an LCD.
Maybe if I can convince myself the 4145B needs an LCD, then the display from that can go in the 4145A.....

[mnementh]

Maybe Dave needs to hire this clever little rodent to eliminate wheel-buckage-induced downtime...   

mnem
*agitating-ily*

[Ice-Tea]

Been poking the TDS784C scope this weekend. Got a couple relays for the attenuator hybrids ordered and have been mixing and matching from my stock to put the latest revisions into this scope.

What's your method or replacing them? I've had some bad luck with that...

[ch_scr]

My Wiltron 6621B is not that precise frequency wise (+- 10 MHz). I wonder if it's the way they generate the current for the coil or if those YIG are just not that linear ? I think I remember seeing a Yig based Signal Generator with way better frequency stability. My assumption was that they added a PLL somehow. Or maybe they just use the 2 Coil (main coil and FM coil) to get more precision ?

Anyway I will probably experiment a little bit with those Yig. Will see how linear they are.

In a more modern device the main coil current is controlled from a dac that has the "pretune" calibration values so linearity can be improved. The PLL locking is then done with the fm coil only.

[GreyWoolfe]

Had a Hazet 1/2" drive socket set for nigh on 40 years until it got badly annealed in a workshop fire. 
Bloody good stuff !

Stahlwille rings are good stuff too and open enders nice and slim but a little weak for heavy stuff.
Look at Dowidat too.....beautifully fine rings for tight spaces.

I'm not sure I agree with the need for power driven stuff for things like wheel nuts, though.

I've almost always found that my relatively puny "upper body strength" is enough, aided sometimes by a length of galvanised water pipe to obtain more leverage.

On the odd occasion that it wasn't, the Spaghetti Monster has endowed me (& most everybody else) with a pair of considerably stronger appendages which can be used to supply more force.

This, of course, may be one of the reasons I now have a "pretend" left knee!

Well remember having this argument with my now dear departed pop not long after we got our first truck, a 8 stud 900/20 wheeled TK Bedford. We'd just done some tire work on it and he'd tightened the 1 5/16" wheel nuts with just a 18" 3/4" drive ratchet which he insisted would be quite tight enough rather than use bodily weight on an additional 3 ft length of heavy waterpipe.
Having done nearly a year in a logging workshop bouncing on 6 ft lengths of pipe on wheel nuts I let him have his say and do it his way due to the discussion becoming heated and left next day for a day in the truck well knowing wheel nuts would need tightening again at close of day.
Pop, can you check those wheel nuts I asked come the end of the day and buggered off and left him to it. 
Needless to say when I checked the extender pipe for the ratchet was not exactly where I'd left it previously. 

The subject never was given air again. 
Still, nearly 30 years on I still miss the old bugger. 

My issue has always been with getting wheel nuts back off afterwards.
I just switched to winter wheels on the truck.  To remove the nuts, the 1/2" drive air rattler was useless.  It did not even budge the nuts.  It takes a good heave with a 4 foot 3/4" breaker bar to loosen them off.  After that, the ratter is ideal to spin the nuts off and then back on.  Final tightening is done with a proper hand torque wrench.

In previous years, I have actually broken a 32" breaker bar with 1/2" drive.  However, I have learned cold breaker bars are prone to fracturing.  To be honest, I am not sure if the larger breaker bar or keeping breaker bars in the house contribute to no further breakages.  The obvious part is that SWMBO wants to break something when she finds breaker bars in her space (ie. anywhere inside the house) ...

1/2" breaker bars just won't cut it on truck wheel nuts. Period. You'll ring the 1/2" square off or break the yoke.

There's a few schools of thought on truck wheel nuts and studs, some just ensure everything is clean and barely lubricated more to keep them from rusting and ensuring relatively easy removal.
I rather like to see a good dose of oil or antiseize on the threads and yet others insist the tapers be lubricated too so to get max tightening torsion with minimum effort.
On high loads like rear duals on heavy trucks and the need to get things really tight I believe there is some merit in lubing tapers and threads especially for off road work where everything is placed under considerably more stress than on highway work.
For years we ground over hilly country with heavy loads and it sure tested if wheel nuts were tight enough.

I have never had any issue with lugnuts seizing.  I have never used anti-seize on the threads.  I double-checked my vehicle manuals; all have a specified dry torque.

I have had issue with lugnuts loosening and backing off; more than one vehicle.  I got my torque wrench calibrated; no adjustment was necessary.  As a result, I worked out alternate torque settings with a trusted garage; they confessed that they had seen other occurrences on those particular vehicle models.

On my car I used a bit of nickel anti-seize on the threads and tapers. Mainly to help prevent them scratching and galling the mating tapers on my $4000 rims.
The McGuard/TRD nuts I used have a cool feature where they have a 'floating' taper that can rotate on the nut, to further help prevent scratching and galling.

The tapers is where I do something a bit different.  I keep a piece of very fine steel wool in my automotive toolbox.  I use that to clean off the surface of the tapers on both the nut and the rim.  that gets rid of dirt and light surface rust.  As others have said, cleanliness gets the correct friction when tightening based on torque settings.

I have had a truck that had a flat surface instead of a taper.  However, the lugnut had an integrated washer.  There was a specific instruction to lubricate the washer-nut surface, but to ensure the washer-rim surface was clean.

There are those who claim that putting anti-seize on wheel studs prevents you from properly torquing the lug nuts and they will essentially be under torqued. But I've done it for years and never had an issue. Turns out the mechanic I deal with does the same.

Around here, all the mechanics say to not use anti-seize at all.  There might be something official about it, although I could not find it at the moment.

Take that with a grain of salt.     Actually, make that a tonne.  NaCl and Calcium salts are used extensively on the roads.  Nasty practice that; it really only works for ice.  However, with a lot of snow, the salt gets overwhelmed and the situation would actually be better without the salt.  The salt is also terrible from an environmental perspective, at least in the massive quantities used around here.  I tend to keep my vehicles for a long time, because the vehicle is in good shape either from not a lot of use (the truck) or the depreciation on paper does not match the actual condition (high mileage on a new car), which leads a fight against rust.  I end up using a yearly rustproofing, which is a gooey oil & wax concoction.

Regardless, there is one place around the wheel where I do use anti-seize.  I have had the experience where the wheel rim has seized onto the disc/drum/mounting plate.
After witnessing unsavoury mechanics using prybars and 8-lb sledgehammers to dislodge the rim, my imagination goes to bent brake disks and damaged rims.
I certainly do not want that, nor do I want to be stuck on the side of the road at some time.  I have been using a silver anti-seize in a very thin layer on the disc/drum/mounting plate where it mates with the wheel rim.  Since doing that, the most force needed to remove a wheel is a swift kick of the tire or tyre (in my collection, some are marked on the sidewalls as tyres and others marked as tires).

I catch up sometimes.

There, I think I just caught up ... momentarily...

Until here, I had never heard of using anti seize for the lug nuts.  The shop where I have been taking my company vans for 17 years doesn't use anti seize either.  Thankfully, I don't live in the rust belt being in Florida.  Also never had a rim seize to the rotor.  I don't have a truck though, I have a cargo van (Dodge Grand Caravan size) and a Santa Fe.  I used to have to use breaker bars to get lug nuts off and keep a 4' piece of pipe, a big 3/4" socket wrench and an impact 3/4 to 1/2" reducer for that.  Now, I rotate my own tires and my 500 ft/lb Earthquake stubby 1/2" rattler removes my lug nuts just fine as I torque to spec.  Now, if I go for tires or road hazard warranty work, I remind them to please torque to spec.  I would love to have a big boy battery impact gun but can't really justify the price.  For flats on the road which, thankfully, hasn't happened in years, both Mrs. GreyWoolfe and I have a AAA gold membership that I have had for a couple of decades.

[TERRA Operative]

Been poking the TDS784C scope this weekend. Got a couple relays for the attenuator hybrids ordered and have been mixing and matching from my stock to put the latest revisions into this scope.

What's your method or replacing them? I've had some bad luck with that...

Desolder the BNC connection, carefully remove the hybrid, then clip off the old relays.
Clean off the remaining solder and stubs from the clipped legs.
Resolder the new relays in the correct order for ease of installation (If you hold the module with the BNC connection upwards, you install the new relays counter-clockwise from the bottom right).
Lots of isopropyl alcohol to clean all(!) flux away.
Clean off the old thermal paste from the reverse side of the module where the chip is located, and from the mating location on the metal frame, then reapply new paste ( <- This is important!) on the frame. You only need a tiny bit.
Finally, reinstall the hybrid module into the frame.

Then don't forget to solder the BNC connection back into place. You'll only forget once...

[Ice-Tea]

Resolder the new relays in the correct order for ease of installation (If you hold the module with the BNC connection upwards, you install the new relays counter-clockwise from the bottom right).

That's what I can't seem to get right. I'm never able to reach all the legs.

[capt bullshot]

Nutcracker, Saskia style:

[mansaxel]

The Chinesium BT module has been installed with a more permanent power supply than the USB power bank I bodged in. The bank and the module failed some kind of negotiation, with the bank turning itself off at random. So, there was initiative for its decommission. I have 24VDC available in the cabinet, so grabbed one of my chinesium buck modules, set it for 6V (the BT module regulates >5..<12V on-chip if fed from aux power input), gave it some extra capacitance, 10µF electrolytes front and back, and hooked things together.  Works nicely.

But.

I feel like a "maker". Stringing China modules together.

Only redeeming part is there's no Arduino involvement. And the balancing module is my own build, PCB design and up.  Finally, the web site is built using Perl, with zero Node and Python involved.

Hanging on in reality, by a thread, at most.

[TERRA Operative]

Resolder the new relays in the correct order for ease of installation (If you hold the module with the BNC connection upwards, you install the new relays counter-clockwise from the bottom right).

That's what I can't seem to get right. I'm never able to reach all the legs.

I had to use a long pointy bit for my iron. Like shown below.


In other news, I just finished making a 10MHz 5th-order Butterworth Bandpass filter (9-11MHz), made it just for fun and practice.
Shown below is the output from the Leo Bodnar GPSDO compared to the same through the filter. Makes for a nice sine wave that pleases me.
Crappy Tek TDS210 FFT there too, if it shows anyone anything interesting....

[Cerebus]

The first thing that boggled my mind is that the face plate says the output is 52 ohms ?! Yes 52 not 50 !  So you need 52ohms coaxial cables and plug that into a 52 ohm load/scope, if that even exists ?! I guess there must exist 52/50 ohms adapters ?!  Still, why not make the oput 50ohms to begin with ?! how pervert is it to make a 52 ohms output ?!    WHY ?! 

Is it a " thing " to be 52 ohms in the test and measurements arena maybe, at that time anyway ? What's so special about 52 ohms that you can't do with traditional 50 ohms ? I am genuinely curious, I am sure I will learn something...

Back in the day, the "official " impedance for coax of that type was 52 ohms.
Over time, it became "normalised" to 50 ohms, which is amusing, as 52 ohms was, itself, a "normalisation" of 51.5 ohms.
Marconi, in the UK, still used 51.5 ohms as their standard.

Oh, OK.... so manufacturers took their time in the early days, to converge all to 50ohms...
Since we are alwyas told that teh world / signal integrity will collapse if the impedance is not match throughout... output, in put, cables, connectors.... I guess back there was also, just might, partially.... some incentive for manufacturers to have their own particular value of " 50 " ohms, to motivate customers to buy not one piece of gear from them.... but all of it, and charge through the roof for it. Kinda the Apple ecosystem with proprietary everything.

So basically non-50ohms stuff is normally only Vintage gear then... so it should be kept in mind if one is being vry critical about signal shape/integrity.... that maybe the distortion of his signal is nothing to do with the vintage signal generator say, nor the scope he is looking at it with.. but simply a slight impedance mismatch ! IOW.... guy needs to know what he is doing, shocking ! 

The figure of 50 is entirely arbitrary. If you want to maximize the safe power handling of an air spaced coaxial cable it wants an impedance of around 30 . If you want to minimise the attenuation of an air spaced coaxial cable you want a characteristic impedance  of 77 . However, there is also the issue that you need to match impedance between cables, connectors and so on to maximise power transfer efficiency and minimise reflections. So if you don't want to have impedance matching networks or transformers everywhere you need a compromise 'standard' impedance  - 50 sits happily half way between maximum power handling (30 ) and minimum attenuation (77 ) and is quite close to the minimum attenuation characteristic impedance for cables with non-air dielectrics (\$\epsilon_r\$ ~ 2.25). So that's how we got 50 for general purpose equipment and 75 for RF stuff (the latter minimising losses from attenuation, which matters if you're talking about an antenna down cable). It's easy to see that on something like a big transmitter you'd use 30 hardline between the transmitter and its antenna (and matching network) to minimise the physical size of that hardline.

A few percent either side of 50 doesn't make a big difference in how effective a compromise it is, and a small mismatch between a 50 cable and a 51 connector is not going to make a whole heap of difference either in terms of power transfer efficiency or reflections.

If one encounters a situation where it's justified either by reflected power levels or by the required precision then you can either put matching transformers or get really fussy about connector/cable impedance.

[mansaxel]

Hanging on in reality, by a thread, at most.

I then had to go and play Dark Side of the Moon..

Every year is getting shorter, never seem to find the time
Plans that either come to naught or half a page of scribbled lines
Hanging on in quiet desperation is the English way
The time is gone, the song is over, thought I'd something more to say

[Ice-Tea]

Resolder the new relays in the correct order for ease of installation (If you hold the module with the BNC connection upwards, you install the new relays counter-clockwise from the bottom right).

That's what I can't seem to get right. I'm never able to reach all the legs.

I had to use a long pointy bit for my iron. Like shown below.

I've literaly looked at mech drawings of solder iron points. Still couldn't work it out 

[Andrew_Debbie]

For those following along at home:

Racal Dana 9906 -- Seller accepted offer before end of auction.  Final price unknown (stupid eBay shouldn't hide the amount)
Racal Dana 1991 -- Sold for £95.  Not bad but somewhat above my final bid. 
Racal Dana 2102 -- Current Bid is £102.   Outbid.

Here is the 2102 again --> https://www.ebay.co.uk/itm/224710802719     

[TERRA Operative]

It never ceases to amaze me that some sellers can't seem to manage to take a decent photo.
Like, why even include that blurry photo taken by mistake in the link above?

I get it that some want to try to hide defects, but but if you can't even be bothered to turn on a light and hold the camera still, why bother at all?

[Andrew_Debbie]

Yeah. One of the reasons why I'm not bidding on the 2102.

[mnementh]

Until here, I had never heard of using anti seize for the lug nuts.  The shop where I have been taking my company vans for 17 years doesn't use anti seize either.  Thankfully, I don't live in the rust belt being in Florida.  Also never had a rim seize to the rotor.  I don't have a truck though, I have a cargo van (Dodge Grand Caravan size) and a Santa Fe.  I used to have to use breaker bars to get lug nuts off and keep a 4' piece of pipe, a big 3/4" socket wrench and an impact 3/4 to 1/2" reducer for that.  Now, I rotate my own tires and my 500 ft/lb Earthquake stubby 1/2" rattler removes my lug nuts just fine as I torque to spec.  Now, if I go for tires or road hazard warranty work, I remind them to please torque to spec.  I would love to have a big boy battery impact gun but can't really justify the price.  For flats on the road which, thankfully, hasn't happened in years, both Mrs. GreyWoolfe and I have a AAA gold membership that I have had for a couple of decades.

Yeah, not to pick on you, but with all the big zip-guns and oversized persuaders, etc, we were talking real trucks, not passenger vehicles (which your van still is). Quite honestly, for those the best tool really is a credit card and AAA.

Nevr-Sieze, etc are most often used as a substitute wherever there is exposure to the elements and a fastener spec calls for lightly oiled threads. The big diff is that it stays put, even on exposed threads, preventing rust and galling.

For most consumer automotive, a thin swipe of the stuff on the stud is more than enough, as it is almost impossible to not get a little bit on the cone, and that is all that is needed to prevent galling against the rim.

My own experience has been that if the threads are showing wear/galling, it is also likely the lug is already stretched/weak and prone to breakage. I've never broken a new or healthy-looking lug after applying Nevr-Sieze, only ones that were in questionable condition already. Adding any form of lubrication on a lugnut definitely does allow it to be tightened further than dry; sometimes as much as 1/4 turn it more. My tactic is usually to set my wrench to the lowest number of the range In the specification if I have any doubt, then check them again after a day or three of driving.

Some of the big trucks actually specify Nevr-Sieze, particularly those with captive washers under the nut seem likelier to have this.  The torque charts on the wall in the Brockway garage I worked at skinning Cats had this penciled in next to certain makes.

mnem
 

[Robert763]

I've been doing some more diagnostics on the Delta SM1540 PSU. It seems to be an Over Volt Protection circuit issue.
The OVP can be activiated by the voltage monitor, over temperature (SW600 is a thermal switch) or external shut down (via Q618/619). D701 is the OVP LED. One indication that the OVP is wrong is the external monitor is at 2.3V. It should be 0V or 5V. It comes from the junction of R697 / D613 (5V6 zener). The overtemp was easy to unplug. No difference. The Q618/619 circuit took a bit of figuring out. It goes to R50 ? nope thats RSD ( remote shutdown, a pin on the programming 15W D that is shown as not wired. I pulled Q618, no difference. All this takes time as you have to pull the assembly and then separate the PCBs. The main voltage reference, 5V1 is OK as is + and - 12V. The OVP reference D610, is a TL431. A diode check showed it different to a exemplar TL431 so that was swapped. No difference. The manual /remote switches had a contact open circuit. Jumpered - no difference. All the op-amps have been replaced previously. I changed IC603 and a bunch of tantalum beads anyway. No difference.
The control circuit is fairly complex and the operators manual on the website has no explanation. The schematics are also is in blocks with different sections for 3 different PSUs. Even worse it does not cover the exact PCBs in the PSU I have. Critically the OVP circuit is different  Not identifiying the op-amp sections doesn't help.
Time to reach out to Delta and see if they have proper service information.

[capt bullshot]

I've been doing some more diagnostics on the Delta SM1540 PSU. It seems to be an Over Volt Protection circuit issue.

I've got a 3kW Delta Elektronika suppy here. I've seen these schematics, too. Agree they're hard to grok, I've had an interesting "feature" with mine:
One can set the voltage and current way above the nominal values (e.g. 90V instead of 45V) - found out this is a special "lamp driver" version.
Anyway, the OVP LED apparently has a third purpose, that isn't obvious at all: It lights when the PWM circuit cannot supply any more power to the output (because a max. duty cycle limit is hit). So the lit OVP in your unit might have a non-obvious cause: the PWM controller hitting its maximum duty cycle, e.g. because a power transistor driver isn't working anymore. It's a bit of guesswork, hope it helps you finding the fault.

[Robert763]

Hi Captain,
Interesting. I think this one senses the current in the switching transformer primary and shuts down the PWM that way. Currently the output stage is getting no drive at all and the control voltages are switched off. This is done by the MOSFETs at the lower right of the circuit. The unit does not even try to start up the main power switches.
Edit: the PWM modulator is based on a CD4046 PLL chip so the operation of that is not obvious either.

[THDplusN_bad]

Good Day,

have I ever expressed how much I dislike people who use low-quality batteries for T&M equipment?!

And how about those folks who then put the equipment back into the drawer and forget about it for years!

Mmmmh, crusty! I am quite confident that it can be repaired, though...

Cheers,

THDplusN_bad

[Kosmic]

My Wiltron 6621B is not that precise frequency wise (+- 10 MHz). I wonder if it's the way they generate the current for the coil or if those YIG are just not that linear ? I think I remember seeing a Yig based Signal Generator with way better frequency stability. My assumption was that they added a PLL somehow. Or maybe they just use the 2 Coil (main coil and FM coil) to get more precision ?

Anyway I will probably experiment a little bit with those Yig. Will see how linear they are.

In a more modern device the main coil current is controlled from a dac that has the "pretune" calibration values so linearity can be improved. The PLL locking is then done with the fm coil only.

Yes exactly what I was thinking of doing. The main coil for the coarse frequency adjustment and FM coil controlled by a PLL for fine adjustment.

Now the other option is to convert my Wiltron 6621B into a 6647B. I'm missing 2 Yig driver board to do that. Seem almost easier and fun to redo everything.

[Robert763]

Be careful when driving the FM coils of a YIG oscillator. They are very easy to burn out. Make sure you observe the maximum current rating.

[mnementh]

The Chinesium BT module has been installed with a more permanent power supply than the USB power bank I bodged in. The bank and the module failed some kind of negotiation, with the bank turning itself off at random. So, there was initiative for its decommission. I have 24VDC available in the cabinet, so grabbed one of my chinesium buck modules, set it for 6V (the BT module regulates >5..<12V on-chip if fed from aux power input), gave it some extra capacitance, 10µF electrolytes front and back, and hooked things together.  Works nicely.

But.

I feel like a "maker". Stringing China modules together.

Only redeeming part is there's no Arduino involvement. And the balancing module is my own build, PCB design and up.  Finally, the web site is built using Perl, with zero Node and Python involved.

Hanging on in reality, by a thread, at most.

No, no, no... you're looking at it all wrong. What you're really doing is just playing with Adult LEGOs. 

mnem