Test Equipment Anonymous (TEA) group therapy thread

[bd139]

BTW I have sketched up an analogue only controller for one of these irons.

Trying to get parts count down to below China. Reckon I can do it

Currently at 4 BJTs, 1 MOSFET, 6 resistors, 1 trimmer and two capacitors for fixed temperature output. This gives PWM proportional control no less

(voltage controlled current source, capacitor, pseudo-UJT/SCR circuit, MOSFET driver)

Need to shape the output a bit better though as it's currently spending too much time in the MOSFET's linear region which means "poof!"

How are you measuring TCPL voltage? The Hakko/OLED T12 controllers do this by turning everything off (actually, I think the original Hakko design did it with AC powering the heater, and the processor would shut off power while the AC voltage was swinging +2V/-2V) every 10th mS or somesuch.
 
I mean yeah you can make an analog comparator, but then you have to make sure it only samples while power is switched off. Seems to me this is a project that just screams "micro with a PID controller", which is why that's what everybody's using.


mnem
"Always some m***f***r tryin' to ice-skate uphill..." ~ Blade   

It's a bit sneaky. Fundamentally it's an analogue comparator but it's not just that. It has two states: heat and sample. During the sample phase it uses a current source controlled by the tip temperature (tip voltage drives divider, drives current source). This fills up the cap until the comparator (SCR/UJT) triggers based on the set point set by the trimmer. If the iron is hot the charge rate is low. If the iron is cold, the charge rate is fast. The thing heats for around 10ms after this cycle (naff implementation of a miller integrator on the driver transistor) and then the cycle starts again. Effectively it's modulating the off time based on the set point and the current temperature. It is really an intentionally unstable PID loop that resets its own state avoiding loop stability problems and ignores the derivative term.

It's a temperature controlled oscillator with feedback. There you go, that's what it is

It sort of works at the moment. Honestly it may need a couple more transistors or a rethink or two yet or a fire extinguisher. It may turn out to have a phase shift I didn't account for and oscillate itself into a fireball. If it does that i'll let it burn and smile gently at the lapping flames.

4 out of 5 things I built never get shown because of the charring and lumps of hair scattered around them.

[mnementh]

Damn, dude... that is downright poetic, in a "Zen and the Art of Motorcycle Maintenance" kindof way. 

Thanks, you provided a much-needed belly laugh; I'm at this moment in the process of paying my taxes. As you may imagine, it's a grim and grisly business; the Treasurer takes no prisoners.


mnem
"Death and Taxes, my son... Death and Taxes."

[bitseeker]

Just filed mine. Earliest ever, I think. And that's about the only good thing to say about tax time.

[GreyWoolfe]

We did ours Saturday.  Surprisingly, after paying the tax preparer, we ended up with a net refund of $82.  According to the preparer, next year will be much better with the new tax laws.  Be nice to get a break.  25% tax bracket down to 12% and a much better refund.

[bd139]

I love doing my tax return. Think I did it in October so I could file early. My only complaint is that they have made it too easy now. I like a forensic challenge.

I got an audit a few years ago and the inspector was extremely disappointed that I had everything to the penny 

Then again I’m one of those weirdos who runs their entire life in excel.

[Mr. Scram]

We did ours Saturday.  Surprisingly, after paying the tax preparer, we ended up with a net refund of $82.  According to the preparer, next year will be much better with the new tax laws.  Be nice to get a break.  25% tax bracket down to 12% and a much better refund.

Doesn't a refund mean you overpaid? I don't really see the advantage.

[mnementh]

I love doing my tax return. Think I did it in October so I could file early. My only complaint is that they have made it too easy now. I like a forensic challenge.

I got an audit a few years ago and the inspector was extremely disappointed that I had everything to the penny 

Then again I’m one of those weirdos who runs their entire life in excel.

*Crosses fingers and hisses, to ward off the evil portent* 


mnem
I have no idea. None whatsoever.

[ChrisLX200]

Definitely TEA - didn't need it really, got no room for it, but I bought it anyway

[Specmaster]

I love doing my tax return. Think I did it in October so I could file early. My only complaint is that they have made it too easy now. I like a forensic challenge.

I got an audit a few years ago and the inspector was extremely disappointed that I had everything to the penny 

Then again I’m one of those weirdos who runs their entire life in excel.

*Crosses fingers and hisses, to ward off the evil portent* 


mnem
I have no idea. None whatsoever.

I don't know which is worst, being employed with some money coming in and having to do tax returns... or...being retired with no money coming in apart from a small pension and not having to do tax returns 

[Mr. Scram]

I don't know which is worst, being employed with some money coming in and having to do tax returns... or...being retired with no money coming in apart from a small pension and not having to do tax returns 

There are countries where the latter means you still have to do tax returns. That's the best one.

[Specmaster]

I don't know which is worst, being employed with some money coming in and having to do tax returns... or...being retired with no money coming in apart from a small pension and not having to do tax returns 

There are countries where the latter means you still have to do tax returns. That's the best one.

If I was lucky enough to gain some paid work of some sort, I'd have to start doing tax returns again here.

[Specmaster]

Definitely TEA - didn't need it really, got no room for it, but I bought it anyway

I could hear your great sigh of relief from here Nice meter though 

[Ero-Shan]

Definitely TEA - didn't need it really, got no room for it, but I bought it anyway

A fine acquisition, congrats!

Looks great and new. I've changed to a 34401A as my standard DMM some weeks ago. I'm very happy with it, except for the VFD, which is rather dim. Got to check out the other two, maybe their's are brighter (if they work at all).

[mnementh]

Probably more than you paid for the whole instrument  , but there is [MAKE OFFER] on the listing.

The 34401* is one of the models I peek in on from time to time on fleaBay in hopes of a steal... I do love a crisp VFD.


mnem
*putter-tinker-putter*

[bd139]

Heads up U.K. peeps. There’s a 2467B on eBay for a respectable £230 at the moment in Basildon. Would go for it but I need a spectrum analyser and signal generator more.

[Specmaster]

Heads up U.K. peeps. There’s a 2467B on eBay for a respectable £230 at the moment in Basildon. Would go for it but I need a spectrum analyser and signal generator more.

Beware, seller thinks that these go for loads of money over here in the UK on Ebay, just checked on the completed listings and there is not a single recorded UK based one sold.

Loads from overseas, mainly the USA however and they do sell over there is true. The unit is absolutely caked in dust and fluff, so it might be a similar tale internally, that might not be a bad thing though, just giving you a heads as the photos of it are low res and small sized.

[bd139]

They sell well here usually. They're just rare. One of the finest analogue scopes ever made.

Marketing video - worth a watch:

[Specmaster]

Yep, you're right, I used a poor choice of words there, but the point I was making was that the seller might not be aware of the origins of the ones that they researched or the significant price difference between the locations. 

[mnementh]

I'd consider the proper value of one of these to be approx US$1040; as that is what user 2465b sells a Cal'd Refurb unit for with shipping. These being the best of the best of the breed, hard to argue with that price really. Anything less than that you get one for is a bargain... especially considering they cost like 13K in the late 90s (Over $25K adjusted for inflation).

The only model better, or so I've heard, was the HD version you see in that video, which is supposed to have an extra long latency, extra-fine grain phosphor that is even crisper and more sensitive than the standard micro-plate CRT. It was supposed to have been optimized to be able to reliably capture 1 nS events legibly enough to photograph.


Cheers and good hunting,


mnem
I'll let the moose do the talking.

[bitseeker]

We did ours Saturday.  Surprisingly, after paying the tax preparer, we ended up with a net refund of $82.  According to the preparer, next year will be much better with the new tax laws.  Be nice to get a break.  25% tax bracket down to 12% and a much better refund.

Doesn't a refund mean you overpaid? I don't really see the advantage.

Yes, it does mean you overpaid. However, it's better than getting fined for underpaying. Ideally, you'd owe just enough to avoid getting fined, but there isn't a huge margin for error.

[bitseeker]

Definitely TEA - didn't need it really, got no room for it, but I bought it anyway

And a fine meter it is. I have one that looks to be about the same age. It's more stable than my 34410A that's more expensive.

The prices of the 34401A have been rising the past couple years. So, you might come out ahead even if you decide not to keep it long term. It's a good meter, though, and yours looks pristine.

[ChrisLX200]

Definitely TEA - didn't need it really, got no room for it, but I bought it anyway

And a fine meter it is. I have one that looks to be about the same age. It's more stable than my 34410A that's more expensive.

The prices of the 34401A have been rising the past couple years. So, you might come out ahead even if you decide not to keep it long term. It's a good meter, though, and yours looks pristine.

Cosmetically very good, and functionally I see no issues. Calibrated 8 months ago. Decided to buy a 82357B USB/GPIB interface for it but only the Chinese clones seem readily available. I bought a used one but expect it's fake anyway, there are so many fakes around but apparently they do work (mostly).

[beanflying]

My Fake GPIB has been great since I sorted out the 34401a setup (as per the clone thread). For a bench meter it works great and I swing between it and the GW121 or both.

Beware however as it was recently calibrated to keep an eye on it over time you need accurate voltage and resistance standards then a better meter to check it and ........ 

[bitseeker]

... and that's why you're here.

[Specmaster]

Yep, even if you don't need actually that level of accuracy, you will need to know if that last wavering digit is correct or not or you'll never be able to trust the rest of them, and so it begins 

Not too sure however at what number of digits it starts at but there is a level where at below it we all seem to accept the readings as being right, or near enough right and above we are cautious at best about the readings, its tied in to the rate of the last digit changes at IMHO