Test Equipment Anonymous (TEA) group therapy thread

[bd139]

@bd139, you are correct not a single DC blocking cap in sight, such is the design these days, it doesn't even have any speaker protection circuit either unlike the Kenwood receiver I have that checks the speaker connections before switching the output relay on to connect the amp to the speakers. Its all about penny pinching these days.

Not sure what part it is handling the output there (assume it's some kind of either push-pull arrangement or class D switcher) but the assumption that the output is never going to be DC because nothing is ever going to fail is a dangerous one for the manufacturer. Big thumbs down on that design

I don't think it's even penny pinching here but probably just verbatim copying of the output IC manufacturer's datasheet which probably doesn't mention anything like that because datasheets only carefully mention the "within spec" side of things and inside the SOA it won't blow anything up. Similar to the old original rev 1 LM386 datasheets which fail to mentoin the zobel network on the output which caused many a little shitty amp to go kaboom from oscillation way above audio frequencies.

"National does not assume any responsibility for use of any circuitry described"

This is why when designing things engineers should look at the output and input circuits inside the black box ICs so they can understand what the IC designers forgot or left out intentionally because of cost or practicality reasons. In fact I think it should be a requirement that you're not allowed to use an IC until you've build at least an approximation of the circuit out of transistors at least once in your life. Side issue; same with programmers. They should know roughly how the system they are using is constructed from the bottom up.

Step 1: MIT 6.002 "the abstraction". Worth a watch if you haven't seen it before. I wish my lecturers at the time were this good and informative:



Anyway well off tangent there.

Those caps were nasty in your Fluke, this is the one with the duff display right? Waiting to see the finished item and documented.

That is the one indeed. I'm going to replace the caps in the other one as well now as a precautionary measure.

Slightly distracted first as my new toy has arrived:

[Specmaster]

That HP35 is a fair less expensive than the Swiss Micros DM42, although it was a nice machine, it was very costly to boot as well. Fine if you use it professionally I would think but the HP35 is much more affordable and suitable for our level of usage.

[bd139]

Exactly why I bought it

I can afford three 35s units for the price of a DM42

[mnementh]

Oh, that would annoy me too.

I'd be inclined to move it to the back to keep it more "out of sight" - but it will never be "out of mind" until you find a replacement.

Since it looks to be in reasonable condition, I would put up with it if it checks out OK.

Yeeah, I'm with Brumby on this one... it is definitely more a matter of "should have been disclosed, but meh" status... in this case, with the age of the item, I'd say that one unobtanium missing foot being replaced with a generic substitute of decent quality comes under "normal wear and tear".

If it was advertised as "collectible" or something, then I'd be upset... but the lack of photo of the bottom should have been a clue when you bid that there might be something ugly.

Given the rest of the unit's pretty much original appearance, unless you paid "Collectible" money for the thing, I'd offer my mother's very sage advice:

"If this is the worst thing that happens to you in the course of a day, then it's been a damn fine day."

mnem
"Sometimes, you have to just chuck it in the 'FUCK IT' bucket and move on."

[bd139]

I would probably buy a 3d printer just to make a new foot so I didn’t have to know it was there’s like an invisible cancer inside me. But I’m an OCD weirdo.

[mnementh]

That's only because you changed your reference from 25 to 50 and you've fallen into the scale doubler trap.

If you are referring to me, then I haven't fallen into any trap. I am well aware of what is happening and why!

This is just a trivial reflection of something that is infecting the web nowadays: the presumption that your display device shows the same as my display device. That phenomenon is extremely irritating when web "designers" want either pixel identical reproduction on all devices, or they cripple what I can see based on their presumed lowest common denominator.

A classic example of the latter is where it is necessary to have a lot of columns displayed but the info is contained in a narrow viewport. Here's a particularly irritating example (scaled to 1000 pixels for brevity):

Yes, you have fallen into a trap. The trap of thinking that we care what you've changed on your display. We don't. And get this... we don't HAVE TO CARE.

The fact you bring it up EVERY GAWDDAMN TIME someone mentions the page number is narcissistic to the extreme. You are part of a group that is so small it falls within the margin of error that would be discarded anyways... meaning that in this case, you are literally statistically insignificant. Every time you bring it up, you remind EVERYBODY of that fact, and the fact that you STILL demand to have allowances made for you, when the sane thing to do is just get the fuck over it and let it slide.

Do you REALLY want to be THAT person?   

Again... "If this is the worst thing that happens to you in the course of a day, then it's been a damn fine day."


mnem
You can be HAPPY, or you can be RIGHT. Rarely do the two coincide.

[bd139]

Perhaps he is like Pythagoras who believed numbers had souls magical powers. I want some of whatever he was on

Anyway must stop slacking and start hacking

[Specmaster]

Meanwhile in other news.....

My KZ-ZSE ear buds have arrived and they do look rather nice and do a very good job of blocking external noises I agree, that said however I can't help but feel underwhelmed by them, the really deep bass I was expecting simply wasn't there for me, there was bass it's true but I have heard better namely some cheap Sony ones  that I have and also another pair of Sony ones of the earlier design that don't have the rubber bungs but the earpieces lodge in the ear sort of sideways, these are shown in the first photo. The Sony earbuds I have currently put somewhere safe and it's so bloody safe that I can't remember where that is 

The absolute best headphones I have ever heard and use a lot are ones made by Lindy, over ear enclosed type with built in active noise cancelling, switchable and has a volume control built in, photo 2. These really do deliver that deep bass and you actually feel the deep vibrations on the really low notes.

The music I use to test headphones out on is Pink Floyd Dark side of the moon, The Division Bell etc and also some pipe organ music such as Widor - Toccata (Allegro) which has some really deep bass as well clear treble. My computer sound system (5.1) is a Cinema THX rated system with 2 x 10" subwoofers and that really is a fantastic system and when I hear that Widor Toccata on that it transports me back to the time when I stood in a theatre hearing that being played on a massive Wurlitzer and when those deep notes came out, you could literally feel your whole body pulsating with the frequencies.

That has long been my mantra for a yard stick, if your system can reproduce that without sounding distorted or the speaker destroying itself then its a good system that is capable of some fantastic clarity and will never sound flat.

[mnementh]

Don't forget you promised me pictures of the ugly display surgery. 

No TEA here this weekend. The lady is here, currently sleeping and I'm sneaking some time on the computer.  She's still sore from the fight incident on Wednesday but recovering nicely. Tomorrow (Saturday) will be a busy day taking her shopping.

Hooray Ms. med! Hope you were a good "old man" and snuggled her to sleep.

I can't believe that. You're building electronics gadgets by the dozen and repair stuff frequently, yet you do not have a 120 Ω resistor? Seriously, I never thought anybody posting here wouldn't have at least a complete E6 series of resistors from 10 Ω to 1 MΩ. But then, 240 Ω saves a wee bit of current. 

I have a full Royal Ohm dev kit. I should say that in this case the issue is not that I don’t have them but more it looks like I accidentally put the 120 ohm ones in the bench sweepings box and I couldn’t be bothered to go and find them

240 because you can do the maths easier in your head. 1.25 volts over 240 is about 5mA. So I need to drop 3-1.25=1.75 volts. 1.75 / 5m is 350 (5 goes into 17.5 three and a half times)  so pick a 330. Close enough! Build, measure, 3.0004v. Close enough. Sorted. The minimum stable standing current of an LM317 is about 10mA but that’s only if you have a capacitive load attached so 5mA was fine here. 120/150 is better if you have that.

Thus the whole thing was at the lazy engineering maxima. Also because calculator and phone were buried under parts and schematics.

I have at least a dozen "baggie kits" of axial lead and SMD resistors I've never ever bothered to sort into the RAACO boxes like I should have; they all reside in a plastic shoebox along with several baggie kits of trim pots, 10-turn pots and carded Radiddio Shank resistors rubber-banded together for so long I've had to change the bands at least a dozen times.  At the bottom of the shoebox is my "fuckit" pile... a big old swarm of bench sweepings, random single resistors that have fallen off of the sprag or card, all sorts of random scavenged power and precision resistors and pots, etc.

I've gotten in the habit of FORCING myself to at least LOOK there for a few minutes for any single resistor I need before rummaging in the baggie kits; but only over the last few years.   

We won't talk about the pitiful state of my capacitor collection... I just did a massive haul to the dumpster of capacitors I KNOW were at least 10-20 years old. Ashamed I didn't do it 10 years ago.  But I still haven't braved the hallowed halls of Mouser, DigiKey and Newark to find replacements.

@bd139, you are correct not a single DC blocking cap in sight, such is the design these days, it doesn't even have any speaker protection circuit either unlike the Kenwood receiver I have that checks the speaker connections before switching the output relay on to connect the amp to the speakers. Its all about penny pinching these days.

Not sure what part it is handling the output there (assume it's some kind of either push-pull arrangement or class D switcher) but the assumption that the output is never going to be DC because nothing is ever going to fail is a dangerous one for the manufacturer. Big thumbs down on that design

I don't think it's even penny pinching here but probably just verbatim copying of the output IC manufacturer's datasheet which probably doesn't mention anything like that because datasheets only carefully mention the "within spec" side of things and inside the SOA it won't blow anything up. Similar to the old original rev 1 LM386 datasheets which fail to mentoin the zobel network on the output which caused many a little shitty amp to go kaboom from oscillation way above audio frequencies.

"National does not assume any responsibility for use of any circuitry described"

This is why when designing things engineers should look at the output and input circuits inside the black box ICs so they can understand what the IC designers forgot or left out intentionally because of cost or practicality reasons. In fact I think it should be a requirement that you're not allowed to use an IC until you've build at least an approximation of the circuit out of transistors at least once in your life. Side issue; same with programmers. They should know roughly how the system they are using is constructed from the bottom up.

Step 1: MIT 6.002 "the abstraction". Worth a watch if you haven't seen it before. I wish my lecturers at the time were this good and informative:



Anyway well off tangent there.

I tend to agree as well... more a matter of lazy engineering (in the bad way) by way of using the bare minimum shown by the manufacturer and possibly a little of the good old "What? We can shave a few cents per unit here AND increase turnover by 10% over the next 5 years? WIN-WIN!" Stef Murky brand of management decision-making process.   

I like this professor... he reminds me of very few great professors I've been lucky enough to have; that not only teach you the rote material, but teach you to THINK in new and larger ways. To grok in fullness. I had one such professor in my junior year at high school; when he taught math he both made it interesting and enlightening, AND he helped you understand how the fundamental concepts build upon each other.

Any professor who can make SELF-DISCIPLINE literally part of the equation qualifies as a great professor.

I had another such professor at SACC; without his incisive insight into the abstractions of modern networking, I'd never have grokked the OSI model. *Sigh*

@mnementh
Here are the 2 pages that cover the circuit of interest, amp and the speaker/headphone circuits and as you will see the speaker selection switch most definitely sits within the path between power amp and the speakers.

Oh, I believe you... especially after you traced it back to the IC. It's funny how "general design ethic" seems to go in cycles... something new comes along (Like multi-channel monolithic amplifier ICs you can mute individual channels on, making soft-switching cheap & easy) and for a while, everybody is using it... then maybe the bottom falls out of some component like a certain type of switch, and suddenly the old-school way is notably cheaper again so regains favor.

There could be (and should be) a whole SEPARATE school of actuarial and statistical science devoted to just this aspect of modern manufacturing... it would help the few smart leaders we have left position our workforces to be producing what is really needed rather than bouncing around from one manufacturing fad to the next like lemming ping-pong balls.   

mnem

[tggzzz]

That’s terrible that. This is probably because to get the static headers in the table they have had to resort to all sorts of unholy hacks and if they don’t fix the width it’ll shit a brick if the table is wider than the max-width css declaration.

I don’t know whether we should blame the web devs here or the muppets who hacked together the pile of shit that is the web.

Digikey are the only ones who get this whole thing about right.

Digikey do get that right, so do McMaster-Carr in a different way. RS chooses to get it wrong.

There's nothing wrong with the web nor the fundamental protocols; they are well-tuned to the underlying eight fallacies of distributed programming https://en.wikipedia.org/wiki/Fallacies_of_distributed_computing  The problem lies with those that "customise" things in ways that conflict with the eight fallacies.

Examples: SOAP (a.k.a. RPC over the internet), or anything that presumes something non-trivial about my output device. HTML was, after all carefully designed so that the output device dictated how the information is displayed, not the server. CSS et al can be used in a similar way, but marketing muppets worry about trivial things like "branding" and "common appearance".

[Specmaster]

I agree, lecturers need to make learning fun and engaging. I used to like watching the Christmas Lectures they used to on TV, always enjoyable, much more beneficial than the current garbish based on reality TV etc.

[Specmaster]

@bd139
Yes I think your right about the bad design and assuming that nothing could go wrong. If that amp had smoked my Wharfdale Dovedale speakers I used to have I'd have been fuming. Lesser known makes of HiFi amps even fit fuses in the speaker lines to try and mitigate damage and yet Technics don't [emoji107]

[bitseeker]

That’s terrible that. This is probably because to get the static headers in the table they have had to resort to all sorts of unholy hacks and if they don’t fix the width it’ll shit a brick if the table is wider than the max-width css declaration.

I don’t know whether we should blame the web devs here or the muppets who hacked together the pile of shit that is the web.

Digikey are the only ones who get this whole thing about right.

It can be done. We have the technology. We have the capability to make web pages that adjust to the size, orientation, and pixel density of the display device. However, those in charge must be aware of it and choose to do it correctly. That is a whole other can of worms.

[bitseeker]

Oh, that would annoy me too.
...
Since it looks to be in reasonable condition, I would put up with it if it checks out OK.

Yeeah, I'm with Brumby on this one... it is definitely more a matter of "should have been disclosed, but meh" status... in this case, with the age of the item, I'd say that one unobtanium missing foot being replaced with a generic substitute of decent quality comes under "normal wear and tear".

If it was advertised as "collectible" or something, then I'd be upset... but the lack of photo of the bottom should have been a clue when you bid that there might be something ugly.

Given the rest of the unit's pretty much original appearance, unless you paid "Collectible" money for the thing, I'd offer my mother's very sage advice:

"If this is the worst thing that happens to you in the course of a day, then it's been a damn fine day."

Thanks for the insanity check, guys. It's been a long week. Fortunately, I was able to get it for a little under the recent selling prices (the listing prices are ridiculous) or it would've gone back instantly.

Without the specs for the shunts, I can't tell if these things are technically special or easily exceeded via DIY (it's all passive stuff), but it is nice to have the mostly matching enclosure and hardware as the 8100A.

[mnementh]

Meanwhile in other news.....

My KZ-ZSE ear buds have arrived and they do look rather nice and do a very good job of blocking external noises I agree, that said however I can't help but feel underwhelmed by them, the really deep bass I was expecting simply wasn't there for me, there was bass it's true but I have heard better namely some cheap Sony ones  that I have and also another pair of Sony ones of the earlier design that don't have the rubber bungs but the earpieces lodge in the ear sort of sideways, these are shown in the first photo. The Sony earbuds I have currently put somewhere safe and it's so bloody safe that I can't remember where that is 

The absolute best headphones I have ever heard and use a lot are ones made by Lindy, over ear enclosed type with built in active noise cancelling, switchable and has a volume control built in, photo 2. These really do deliver that deep bass and you actually feel the deep vibrations on the really low notes.

The music I use to test headphones out on is Pink Floyd Dark side of the moon, The Division Bell etc and also some pipe organ music such as Widor - Toccata (Allegro) which has some really deep bass as well clear treble. My computer sound system (5.1) is a Cinema THX rated system with 2 x 10" subwoofers and that really is a fantastic system and when I hear that Widor Toccata on that it transports me back to the time when I stood in a theatre hearing that being played on a massive Wurlitzer and when those deep notes came out, you could literally feel your whole body pulsating with the frequencies.

That has long been my mantra for a yard stick, if your system can reproduce that without sounding distorted or the speaker destroying itself then its a good system that is capable of some fantastic clarity and will never sound flat.

   

Hmm... maybe it's a matter of perspective, or maybe you just weren't getting a good seal. Did you try the next size larger mushroom tips? I found that seal to be absolutely critical with these, for both bass and clear highs.

I'm used to massive subwoofer abuse on my home stereo, and grew up pretty much living right by the stage for every rock concert I could get into... so pretty sure I'm not just a bass wimp.

Sorry you weren't as impressed as I was.     My review was predicated on them being awesome for earbuds, and specifically as used with an iPod. I don't like how they sound with any of my phones, but I don't like how ANY of my phones sound no matter what you plug them into, short of a home stereo. Then they are just passable. Barely.

As for bass you can feel in your chest... we both know you aren't going to get that with anything you can hang on your head; even my old favorite Sennheiser Ovation series.   

In Other News...

I've continued listening to bd's video of that MIT professor and the 6.002 "abstraction" principle:

"...If I really believe in my own BS, anything is a 'lumped element.'  So here's a pickle."

*Lab assistant connects pickle to a set of electrodes; much hilarity ensues*

*fnaaaarrrf*

Well-played, bd. Well-played. 

mnem
*Back to my spring cleaning*

[mnementh]

That’s terrible that. This is probably because to get the static headers in the table they have had to resort to all sorts of unholy hacks and if they don’t fix the width it’ll shit a brick if the table is wider than the max-width css declaration.

I don’t know whether we should blame the web devs here or the muppets who hacked together the pile of shit that is the web.

Digikey are the only ones who get this whole thing about right.

It can be done. We have the technology. We have the capability to make web pages that adjust to the size, orientation, and pixel density of the display device. However, those in charge must be aware of it and choose to do it correctly. That is a whole other can of worms.

Yeah, but that requires paying somebody who knows what the fuck they're doing, and paying them enough that they give a fuck. Such decisions are always made by someone of the Stef Murky mindset; which means roughly "Yeah, imagine that."

mnem
"In the race to the bottom, there are no winners." ~ mom

[Specmaster]

Hmm... maybe it's a matter of perspective, or maybe you just weren't getting a good seal. Did you try the next size larger mushroom tips? I found that seal to be absolutely critical with these, for both bass and high clarity.

I'm used to massive subwoofer abuse on my home stereo, and grew up pretty much living right by the stage for every rock concert I could get into... so pretty sure I'm not just a bass wimp.

Sorry you weren't as impressed as I was.     My review was predicated on them being awesome for earbuds, and specifically as used with an iPod. I don't like how they sound with any of my phones, but I don't like how ANY of my phones sound no matter what you plug them into, short of a home stereo. Then they are just passable. Barely.

As for bass you can feel... we both know you aren't going to get that with anything you can hang on your head; even my old favorite Sennheiser Ovation series.   

mnem
*Back to my spring cleaning*

Hmm, the bass can be felt in the case of the Lindy headphones, possibly because of the volume of air and good seal they make, I feel the vibration on my ears or whatever.

Yes I'm using the larger size of mushroom tips so I'm getting a good seal (I've got big ears you see  ) One thing I did note however was just how high I had to turn the volume up in order to get any sound from them so it's possible that either they are very insensitive or maybe I have a duff pair, anyway I'll continue to try them out over the next few days.

The sound overall is quite well balanced and clear, the only time I tend to use headphones of any sort is late at night as I'm a bit of night owl and everyone else with the exception of my youngest son.

[tggzzz]

That’s terrible that. This is probably because to get the static headers in the table they have had to resort to all sorts of unholy hacks and if they don’t fix the width it’ll shit a brick if the table is wider than the max-width css declaration.

I don’t know whether we should blame the web devs here or the muppets who hacked together the pile of shit that is the web.

Digikey are the only ones who get this whole thing about right.

It can be done. We have the technology. We have the capability to make web pages that adjust to the size, orientation, and pixel density of the display device. However, those in charge must be aware of it and choose to do it correctly.

That's the default! It takes special techniques and deliberate effort to avoid it.

Hence it is indeed a can of (self-inflicted) worms, may the fleas of a thousand camels infest graphic artistes' armpits.

That is a whole other can of worms.

[mnementh]

Hmm, the bass can be felt in the case of the Lindy headphones, possibly because of the volume of air and good seal they make, I feel the vibration on my ears or whatever.

Yes I'm using the larger size of mushroom tips so I'm getting a good seal (I've got big ears you see  ) One thing I did note however was just how high I had to turn the volume up in order to get any sound from them so it's possible that either they are very insensitive or maybe I have a duff pair, anyway I'll continue to try them out over the next few days.

The sound overall is quite well balanced and clear, the only time I tend to use headphones of any sort is late at night as I'm a bit of night owl and everyone else with the exception of my youngest son.

Yeah, you read my response before I realized an important omission and edited for clarity; "As for bass you can feel in your chest..."  

I know what you mean about bass you can feel... my Ovations were like that.    But still no comparison to some good long-excursion 18" drivers from a few feet away. What you're describing really sounds like either a poor seal or maybe a android phone actively limiting the absolute volume; they've gotten to be total dicks about that over the last few iterations.     Like I said... mine the sensitivity is definitely above average.



One thing I did find was that when fitting the mushroom tips, it was easy to slide them all the way down like the one on the right. They have a ridge inside the tube; they're only supposed to go on as far as the one on the left, so they extend into the actual ear canal instead of trying to seal against the irregular ridge right at the outer ear.

With mine, they are very tight fit... like I said, JUST this side of uncomfortable. When I tap on each of the wires coming down past my shoulders, I can hear the "thoom-thoom" in that ear like when you tap on a hot mic. 

Another thing I do remember is that a couple reviewers stated they have had a QC issue wherein they arrive with the bass driver loose, dangling off the wires inside. Those reports said that was very obvious if you looked for it though.

Cheers,

mnem
*YMMV*

[bd139]

Small break to eat (pizza and coke like a proper engineer). Fluke repair going well so far. New display module in and in process of wiring it to the board.  I’ll do a separate thread on this as it’s going to be image heavy.

[neo]

Went to another hamfest today, bought a tube tester. Don't know why, but i did. 

B&K model 607 tube tester, solid state in good condition with original documentation for 50 bucks.

Also, bitseeker, shame to hear about the mismatched foot on that. I had hoped i could help you though after rifling through my spare parts i couldn't find one, if i do find one in my stock of spare parts i'll let you know.

[bitseeker]

That tube tester looks quite clean, neo. So, what is solid state about a basic good/bad-type tube tester, the power supply?

Thanks for keeping an eye out for Fluke feet. Much appreciated.

[Specmaster]

Small break to eat (pizza and coke like a proper engineer). Fluke repair going well so far. New display module in and in process of wiring it to the board.  I’ll do a separate thread on this as it’s going to be image heavy.

We are all eagerly awaiting your thread on it with baited breath. 

Speaking off eating reminds that is something that I should go and do right now 

[neo]

That tube tester looks quite clean, neo. So, what is solid state about a basic good/bad-type tube tester, the power supply?

Thanks for keeping an eye out for Fluke feet. Much appreciated.

Well in this exact case it is exactly 3 diodes and a transistor in the, you guessed it, power supply. Actually, interestingly enough, there is almost nothing to this one, a transformer, a couple of capacitors, the above mentioned solid state and a handful of resistors.

[bitseeker]

Yeah, that's about what I figured. The older tube types that I've seen are essentially a box of sockets and wires routed via switches to transport electrons from the power supply to the meter via the TUT (tube under test).

I haven't looked into the transconductance types. I imagine there's more to those ones.