Test Equipment Anonymous (TEA) group therapy thread

[mnementh]

Seen caps like that a lot recently in power supplies. Wondering if there is a second plague.

When was there ever not a plague? Capacitors are the Devil's Footsoldiers.
But seriously... look where they are. It's like they're in a special-built capacitor oven. "Failure is not an option; it comes baked in." 

the duff ones were across the 5V, 3.3V and 12V rails. One read 2.2 pF, others were in the tens, even OOC. That's a testament to the ruggedness of the polymer caps they're running on modern motherboards, in all honesty.

mnem
*Knocks self unconscious with a clock mallet*

[bd139]

That's a fair point. They take a proper beating in situ. Really when you see 105oC caps in stuff that tends to mean "I will die after 10k hours at that temp" rather than "yeah I'm fine, getting a nice tan off the heatsink". 10k hours is just over a year.

Edit: just got me another Bliley OCXO in the post. 6 days from China is pretty damn good 

[med6753]

Here are the resultant waveforms from my post last night showing excellent compensation.

First, as a control here is the 1MHz square from the Heath IG-4244 Scope Calibrator on the 2465. The rise time of that square is approx 1ns.



As an additional control here is the same waveform on the 7603N with a 7A26 plug-in. This plug-in did NOT require any adjustments or compensation. The settings on the 7603N are the same as the 2465.



Here is the 7A15A. This had a noisy attenuator switch deck which involved removal of the attenuator blocks and partial disassembly of the switch assembly to clean it. So the compensation was way off after assembly and it came right in with the procedure I described yesterday.



Finally, the 7A16A. This one was a real PITA. No only did it have a noisy switch deck requiring disassembly but it also had a defective 2X attenuator block. So this compensation was way off too. Fixed after doing my procedure. But this plug-in had another surprise. Upon application of the 1MHz square there was approx 2 minor divisions of peaking on both top and bottom of the waveform. The spec calls for no more than 0.6 minor division peaking. This is a wide band (225MHz) plug-in and there are 8 HF adjustments (4 trim pots, 4 trim caps) on the amplifier board that have to be adjusted in a specific order. But this plug-in only had 6 HF adjustments so apparently there was a revision and the manual I have is no good. But I got lucky. I carefully tweaked each control and I found the trim cap that with just a minor adjustment eliminated the peaking. So now this plug-in is dead nuts too.

[med6753]

In other news.....I should receive a replacement DC-DC converter card in the mail today so tomorrow I'll continue working on the 500VDC reference.

Switch gears from scope-nut to volt-nut. 

[Specmaster]

Nice traces med, but I have never had any problem with the compensation on my scopes, the manuals always give precise instructions and I follow those, tweak the trimmer cap and job done in a matter of minutes. But however, I have never had a Tek CRT scope so is their compensation that much more complicated and difficult to do then say HP, Iwatsu or Hitachi for example? 

[med6753]

If the compensation is grossly out....like these plug-ins were....it can be real difficult getting it back in. The reason is two fold. First, there are typically 2 compensation adjustments, flat top and edge, and they interact with each other. Plus you typically have at least 2 ranges on the same path, such as 20mV and .2V and they interact with each other too. It's very easy to get tangled up in your panties and you have no idea where you're at. But as I found out yesterday doing the compensation as I described makes it a piece of cake.

I'm familiar with the compensation schemes on other scopes. Such as my B&K 2120. One adjustment per range. Easy.

[Specmaster]

So it seems that Tek have made it a bit more complicated than they needed to then 

[bd139]

Not really. A lot of systems have multiple interactions. It just takes time to get a feel for it.

[0culus]

So it seems that Tek have made it a bit more complicated than they needed to then 

Not really. A lot of systems have multiple interactions. It just takes time to get a feel for it.

Another example of this is the HP 8568B. The way HP designed the LOs and PLLs works extremely well for performance (spectral purity and low noise and all that) but is a devil to debug because the PLLs are not independently locked!

[med6753]

So it seems that Tek have made it a bit more complicated than they needed to then 

Not really. A lot of systems have multiple interactions. It just takes time to get a feel for it.

Another example of this is the HP 8568B. The way HP designed the LOs and PLLs works extremely well for performance (spectral purity and low noise and all that) but is a devil to debug because the PLLs are not independently locked!

And I think Tek designed the compensation circuit for the same reason. Extremely accurate waveform reproduction. One of the reasons their analog scopes are the best. Just like HP analyzers are superior. But Tek could have given a better description in the manual on how to align it. I think it relies too much on the assumption that it's being checked as a part of a yearly calibration and not much, if anything, would have changed and would just need a tweak. But if you have an attenuator switch assembly that's fubar, like these were, then you're up shit's creek without a paddle to get it back even close.     

[0culus]

So it seems that Tek have made it a bit more complicated than they needed to then 

Not really. A lot of systems have multiple interactions. It just takes time to get a feel for it.

Another example of this is the HP 8568B. The way HP designed the LOs and PLLs works extremely well for performance (spectral purity and low noise and all that) but is a devil to debug because the PLLs are not independently locked!

And I think Tek designed the compensation circuit for the same reason. Extremely accurate waveform reproduction. One of the reasons their analog scopes are the best. Just like HP analyzers are superior. But Tek could have given a better description in the manual on how to align it. I think it relies too much on the assumption that it's being checked as a part of a yearly calibration and not much, if anything, would have changed and would just need a tweak. But if you have an attenuator switch assembly that's fubar, like these were, then you're up shit's creek without a paddle to get it back even close.     

Yeah, both companies had some of the finest engineers working in these respective areas. Lots to be learned by disassembling and troubleshooting these older boxes, especially since full documentation is available in many cases.

I have a Tek 2465B and I love it. Tek for scopes and HP for RF gear...happy TEA matchup. 

[bd139]

HP for power supplies as well.

You know my favourite thing though? The TDS210. Sure it's crap by modern standards but it just feels right, doesn't make any noise and doesn't take any room.

[med6753]

I found a service manual that shows the revisions to amplifier board in the 7A16A plug-in. Mine is the higher S/N.

[0culus]

HP for power supplies as well.

You know my favourite thing though? The TDS210. Sure it's crap by modern standards but it just feels right, doesn't make any noise and doesn't take any room.

I need to consider getting a digital scope at some point. While I strongly prefer analog instruments to use, I recognize the usefulness of features like one shot captures.

If I had the money, I'd consider getting one of these too:

https://www.tek.com/spectrum-analyzer/rsa306

Unfortunately, it's $4k to start and the options I'd want add 1k here and another 1k there.  I think I will instead get a hackrf and use the variety of open source software available for interfacing with it and providing spectrum analysis capabilities.

edit:

[bd139]

HP for power supplies as well.

You know my favourite thing though? The TDS210. Sure it's crap by modern standards but it just feels right, doesn't make any noise and doesn't take any room.

I need to consider getting a digital scope at some point. While I strongly prefer analog instruments to use, I recognize the usefulness of features like one shot captures.

If I had the money, I'd consider getting one of these too:

https://www.tek.com/spectrum-analyzer/rsa306

Unfortunately, it's $4k to start and the options I'd want add 1k here and another 1k there.  I think I will instead get a hackrf and use the variety of open source software available for interfacing with it and providing spectrum analysis capabilities.

edit:

Yeah I have one of those SA's on the "will buy once they have been obsolete for 20 years" list 

Digital scope benefits are quite wide for me to the point I regularly crank up an analogue scope. I use mine as a frequency domain instrument with a power meter and AWG for example. Poor man's bode plotter:

[0culus]

Nice!

Yeah, it's kind of unfortunate for the hobbyist that modern RF instrumentation is so insanely expensive. The old boat anchor HP stuff is great for narrowband work, but if you want to work with modern wideband protocols, real time capabilities are very nice to have.

[bd139]

Yes exactly that. It's insanely expensive or it's relatively old and tends to like to drop dead regularly. As this isn't being used in a professional capacity, I think that's why I've been motivated to build stuff rather than buy. I have nearly put the money down a couple of times for a DSA815-TG but just can't bring myself to pull the trigger. Instead I have a few Toko helical filters sitting here and am collecting bits to build my own SA

[0culus]

Yes exactly that. It's insanely expensive or it's relatively old and tends to like to drop dead regularly. As this isn't being used in a professional capacity, I think that's why I've been motivated to build stuff rather than buy. I have nearly put the money down a couple of times for a DSA815-TG but just can't bring myself to pull the trigger. Instead I have a few Toko helical filters sitting here and am collecting bits to build my own SA

Nice! I feel comfortable with the HP 85xx series SAs because full service documentation is available. I can work on them. That Tek thing in 20 years? Who the heck knows? It's probably totally unrepairable and who knows if the software that runs it will even be available.

Another thing that hobbyists are priced out of is VNAs. Almost necessary for serious RF design, but even old systems can end up costing as much as a decent car. 

[bd139]

Good point about repairability. That Tek SA is probably trash if it goes wrong.

On VNA front, as I'm sure tautech will pop up and say, Siglent do a reasonably affordable option. For me, I'm not sure I'd extract the full value from it so I went with the slightly crappy option. I only care about simple cases of VSWR / return loss, power gain and some classes of input matching problems up to VHF so I built a simple power meter and use an MFJ-259B impedance analyser (second hand). Seems to do enough and allows me to produce sound designs which is the main thing. That cost 12% of Siglent's offering 

[med6753]

That's why I stay away from all things RF. Too much voodoo and too damn expensive. 

[Martin.M]

puh. the 3th evening now, searching the shortet C in the Wandel+Goltermann SPM11.

I am busy 

[bd139]

That's why I stay away from all things RF. Too much voodoo and too damn expensive. 

I've found that the more you read and understand, the less money it costs.

I was reading some old articles from the early 1970s a while ago about 10GHz band. The people doing it were using basically a selection of trash, 20k voltmeter, slide rule and some balls to solve all the problems they had. I figure that if they can do it with less than I've got, I only need to bridge the knowledge gap.

Also this is why I have one metric ton of varactors on my watch list 

[Martin.M]

here is a date for friends who are at august in germany:

Maker Faire Hannover,   17+18 august, Hannover Congress Centrum,
Eilenriede-Halle, look for "Wellenkino" and "PTB"   

[med6753]

That's why I stay away from all things RF. Too much voodoo and too damn expensive. 

I've found that the more you read and understand, the less money it costs.

I was reading some old articles from the early 1970s a while ago about 10GHz band. The people doing it were using basically a selection of trash, 20k voltmeter, slide rule and some balls to solve all the problems they had. I figure that if they can do it with less than I've got, I only need to bridge the knowledge gap.

Also this is why I have one metric ton of varactors on my watch list 

Gee, I'm already a scope-nut and volt-nut. You want me to become RF-nut too? I may lose all my marbles, and my money. 

It's been 1 month retired and I'm loving it.  Not bored and keeping busy on my own terms. Haven't gained weight and haven't let myself go to pot. I still shower everyday and don't stink.  I see these other retirees out and about that look all disheveled, matted hair, wearing pajama bottoms for pants. That's not me. The only problem I have is getting back on a normal sleep schedule. That's been real tough and it's not getting any better. I may ask the doc for a week's supply of sleeping meds to force my body back to normal schedule but I don't really want to go that route. Other than that, life is good not working.   

[bd139]

Gee, I'm already a scope-nut and volt-nut. You want me to become RF-nut too? I may lose all my marbles, and my money. 

It's been 1 month retired and I'm loving it.  Not bored and keeping busy on my own terms. Haven't gained weight and haven't let myself go to pot. I still shower everyday and don't stink.  I see these other retirees out and about that look all disheveled, matted hair, wearing pajama bottoms for pants. That's not me. The only problem I have is getting back on a normal sleep schedule. That's been real tough and it's not getting any better. I may ask the doc for a week's supply of sleeping meds to force my body back to normal schedule but I don't really want to go that route. Other than that, life is good not working.   

That scares me when I see people do that. I worked with a guy a number of years ago who retired and turned into a starcraft playing morlock. Dropped in to see if he was still alive and I was greeted by a yeti and a green cloud of death. His entire place was about a foot deep in fag ash, beer cans and cat shit.

Decided I was never going to be that person. Now up at 6AM every morning, shower, clothes on, do the spreadsheet and todo list for the day.