Test Equipment Anonymous (TEA) group therapy thread

[mnementh]

How does that work then? Surely if your probing along a supply rail measuring resistance / voltage or volt drop then the same contact resistance each time you probe as you mention is also just as affective in those modes as well?

Contact resistance doesn't really matter when measuring voltages with a 10M input resistance meter, but it is a different story trying to measure mOhms.

You would think... in all the intervening years since they were invented and since abandoned as too dangerous for delicate modern components, that SOMEONE would have developed an ultra-low-current version of the ShortSqweek. They were the bomb for this work back when everything was discrete Si components. 

Got my Fluke 8050A. Arrived with some serious problems. Decided to attack it rather than look after myself. Looks like the front end has been blown up. Varistors and the big 1k protection resistor have been replaced and the board has burned where the first set of varistors went up. Whoops. So it reads wrong by about ten percent on 20V and above. Popped 87V on the front end and input impedance registered as 8.5M which is low. Traced out front end and found Q2, a 2n3904 used as clamp was short. Replaced that and the other clamp transistor just to be sure, cleaned out the switches and it’s bang on cal  . Just needs a good clean now. Display is good too.

Going back to bed now though 

Thanks for braving the wilds of your test bench in your indisposed disposition to bring us this tale of daring and electro-surgery! 

Sounds like you've had yourself a big steaming cuppa TEA (good for both mind and soul); now take care of the body and get some rest, you fool. 

mnem

[BU508A]

I present to you bastard 15uf tant. Reads 0.20 ohms. 

Hmm, I cannot spot it on this board:

[Specmaster]

While you guys have been standing around the water cooler debating the merits of one short finding technique vs another I've been working.  And after hours of tracing and dealing with schematics that DON'T match the board (How many times have I had THAT happen) I have FINALLY found the source of the +15V short. 

I present to you bastard 15uf tant. Reads 0.20 ohms. 



It's going to take me at least an hour to restore all the pulled parts on the supply board then install it. Then apply power and see what happens. If I get power up that's great but I'm definitely going order replacement caps for the PSU and do a total recap.   

Well done med, we all knew that you'd get there in the end, so what method did you use in the end? There is absolutely no doubt that the liquid and evaporation method while passing a current through it is going to be the fastest method, even with TH parts like that because of the radiated heat would cause the liquid on the PCB in the vicinity to evaporate quicker then the rest of board so that would have pinpointed the faulty item in minutes rather then hours.

[mnementh]

New multi-meter came in yesterday.  This one effectively replaces the old Radio Shack one that has gone to the great multimeter repository in the sky...

Anyway, this thing is a complete Wun Hung Low brand, but I'm relatively impressed with it given the price. It feels solidly built, came with two sets of leads, and the one set appear to be "gold plated" to some extent, and they pass the Dave "how quickly does the continuity buzz go off" test.  And the flip-stand thing seems relatively solid.  On the downside, you have to use a screwdriver to open the battery compartment, and it runs on one 9v battery, so not expecting great battery life.

Nice big screen 

Normally those meters are not that bad with DC voltage. Got a cheap 15$ 4.5 digits here and it's pretty accurate. Just don't try to probe main with it 

Awww... mains over here is just 120V; you can probe that with your fingers. Hurrrrrrhhhurrrrrr!!! 



No, seriously.... I keep its older brother, the Ragu 17B on my mnemTest stand pretty much all the time now. I keep the DE-5000 between it and my Fluke 189, so I don't seem to have any bickering or miscegenation. 

As long as you don't eff around with stuff right on the mV/uV threshold, a fine little meter (especially to use as a "sacrificial element" for when I'm about to do something stupid  ); the firmware bug that makes it flaky down there was a known issue when I bought it, and was probably the reason I caught it on slAmazon for $9.99.

now you need a couple of the ANENG AN800x family for when you need to watch 3 or 4 things at once and you'll be ready for almost anything! 

mnem
*tzzzzt*

[mnementh]

(SNIP)
Here Louis Rossmann uses alcohol    https://youtu.be/t5fICjcaJ3E   and in this one uses petrol    https://youtu.be/CW87dyYIimE   and see just how quick this proves the theory.

Yeah; if you ever needed proof he's a a-hole, there it is. APPLE USERS watch his videos (and he KNOWS it); one or more of them is gonna try and fix their own crac-Book by pouring it full of alcohol and poking it with a red-hot coathanger and burn his/her own damn fool face off. And BECAUSE they're Apple (L)users, they'll file a class-action suit against him and he's gonna DESERVE it. 

That other guy using gasoline though... I've seen other videos of his and he really should know better. 

mnem
But as long as the feeding cycle of spite and acrimony holds out, he'll keep making more money on those assoholic videos than I ever made as a repair technician... 

[mindcrime]

Awww... mains over here is just 120V; you can probe that with your fingers. Hurrrrrrhhhurrrrrr!!! 

I might not go that far, but I'd feel OK using it for a quick "is this outlet live and delivering 120V test." or something. But I really don't do much of anything that involves working with mains voltages... and I have a separate dedicated "outlet tester" device for testing AC outlets to see if they're wired correctly and all that jazz.  So this thing will rarely, if ever, see anything more than 12V ... at least intentionally.   

No, seriously.... I keep its older brother, the Ragu 17B on my mnemTest stand pretty much all the time now. I keep the DE-5000 between it and my Fluke 189, so I don't seem to have any bickering or miscegenation. 

As long as you don't eff around with stuff right on the mV/uV threshold, a fine little meter (especially to use as a "sacrificial element" for when I'm about to do something stupid  ); the firmware bug that makes it flaky down there was a known issue when I bought it, and was probably the reason I caught it on slAmazon for $9.99.

Nice. I didn't even know it had an "older brother". I was just looking for a cheap-but-hopefully-semi-decent meter to replace one that died.  I picked this more or less at random to be honest.   

now you need a couple of the ANENG AN800x family for when you need to watch 3 or 4 things at once and you'll be ready for almost anything! 

Well, I have this one, my other Radio Shack handheld meter, and my Rigol DM3068, so I think I'll be OK in the short-term.  My next multi-meter purchase will likely be one of the "official EEVBlog" ones.  But now that I've started down the rabbit-hole, I'm sure pretty soon I'll be buying more meters because "Oooh, I don't have one with a green case yet" and "oooh, look, a pink multi-meter", etc., etc., yada, yada. 

[mnementh]

The Brymen meter Dave flogs is a decent little unit, but you can get it cheaper elsewhere. You can also get into a much better meter from Brymen as well, if you think you want to. Ultimately, I had a Fluke 87-sizeded hole in my bench that just was not going to be filled with anything less than another 87 or a 189 (87 on steroids), so that's what I scoured eBay for for months. You can read about those misadventures in this thread and over here. 

mnem
moo. Or don't; it's entirely up to you.

[med6753]

While you guys have been standing around the water cooler debating the merits of one short finding technique vs another I've been working.  And after hours of tracing and dealing with schematics that DON'T match the board (How many times have I had THAT happen) I have FINALLY found the source of the +15V short. 

I present to you bastard 15uf tant. Reads 0.20 ohms. 



It's going to take me at least an hour to restore all the pulled parts on the supply board then install it. Then apply power and see what happens. If I get power up that's great but I'm definitely going order replacement caps for the PSU and do a total recap.   

Well done med, we all knew that you'd get there in the end, so what method did you use in the end? There is absolutely no doubt that the liquid and evaporation method while passing a current through it is going to be the fastest method, even with TH parts like that because of the radiated heat would cause the liquid on the PCB in the vicinity to evaporate quicker then the rest of board so that would have pinpointed the faulty item in minutes rather then hours.

I had to physically the trace the patterns on this board because the +15V runs all over and this board is not just the PSU. That's what really took the time. The technique I used to track it down was actually quite simple. Follow the lowering resistance. The short at the edge connectors showed about 0.50 ohms. I kept tracing back following the lower resistance. I eventually got to about 0.39 ohms and I knew I was getting close. But what stymied me for a while was the schematic did not match the actual circuit.

[med6753]

Veni, Vidi, Vici. 

Here it is. Powers up. But all is not kosher. Intensity is fixed at full. And after a few seconds the CRT beam starts flashing off and on. And I smell something burning. But it's progress! 

Time to celebrate a small victory! 

[med6753]

I present to you bastard 15uf tant. Reads 0.20 ohms. 

Hmm, I cannot spot it on this board:

That's because there are so MANY of them. You think 465/475 has a lot of tantalum's? Tek must have gotten a good deal from AVX and Kemet for tantalums because the 485 is absolutely loaded with them.

[bd139]

Upgrade it! 

I did consider that but I genuinely can't be arsed. I might flip it yet as I'd rather have one that I know hasn't had a nuclear disaster inside it.

I present to you bastard 15uf tant. Reads 0.20 ohms. 

Conflatulations! The moment you fix it another one will go.

Now I've had some sleep I'm going to hit the coffee then attack as much of the PM3217 supply as possible. Unfortunately CPC being the incompetent fucknuggets that they are missed 4 entire line items from my capacitor order and got another line wrong. That's what happens with you have proto-Morlocks from Preston running your warehouse:



The woman on the phone thought I was lying as well 

I'm done with fixing shit after this at least until the 25th of August 

[Specmaster]

Why the 25th August??

[bd139]

https://www.mkars.org.uk/index.php/milton-keynes-amateur-radio-society-2019-rally/

@med: meant to say. no post today other than tax return statement - will let you know when it arrives.

[Kosmic]

Awww... mains over here is just 120V; you can probe that with your fingers. Hurrrrrrhhhurrrrrr!!! 

Sure was also doing that in the past. I also ended up soldering an screwdriver to a electrical box because I was not careful. I'm trying to flip the breaker now when working on a circuit. 

Here 220v is more frequent than you think. Heating is mostly electric and all on 220v.

[mnementh]

Hence the dumbass "Hurrrrrrhhhurrrrrr!!!" with  prominently proclaiming the suggestion AS utter dumb-assery. 

mnem

[Kosmic]

Hence the dumbass "Hurrrrrrhhhurrrrrr!!!" with  prominently proclaiming the suggestion AS utter dumb-assery. 

mnem

 

[mnementh]

Veni, Vidi, Vici.     Here it is. Powers up. But all is not kosher. Intensity is fixed at full. And after a few seconds the CRT beam starts flashing off and on. And I smell something burning. But it's progress! 

   Time to celebrate a small victory! 

In vino veritas.

mnem
*off to seek a little liquid truth to soothe frazzled nerves*

[med6753]

Veni, Vidi, Vici.     Here it is. Powers up. But all is not kosher. Intensity is fixed at full. And after a few seconds the CRT beam starts flashing off and on. And I smell something burning. But it's progress! 

   Time to celebrate a small victory! 

In vino veritas.

mnem
*off to seek a little liquid truth to sooth frazzled nerves*

I'm not drunk you dumbass. 

[factory]

The 3460A is only 5 1/2 digit unless you got the H04 option, but the standard 5 1/2 version does accept the option PCB's for the 3461A AC/ohms converter.

Is it possible to add this H04 option afterwards? Are there any schematics around?
Or has somebody done this before and described it by any chance?

I have bought the scanned OSM for the 3460A here: https://www.artekmanuals.com

The scan quality is very good.
Example:



Thanks.

Option H04 could be complicated, some of the display PCB's are a little bit different, as are some of the other boards in the display area, also an extra LSD board is also needed. I did buy at great expense an original manual for my H04 3460A.

Here are a couple of pictures of what is inside mine (taken a long time ago), compare these with what is inside the 3460B Pat has.

[snip]
And a link to assorted photos of its innards, and the removal of the grunge that coated mine when I got it:

https://pmanning.smugmug.com/Electronics/HP-3460B-Digital-Voltmeter

Enjoy your 'new' anchor - tis a thing of beauty!

-Pat

David

[mnementh]

Veni, Vidi, Vici.     Here it is. Powers up. But all is not kosher. Intensity is fixed at full. And after a few seconds the CRT beam starts flashing off and on. And I smell something burning. But it's progress! 

   Time to celebrate a small victory! 

In vino veritas.

mnem
*off to seek a little liquid truth to soothe frazzled nerves*

I'm not drunk you dumbass. 

Guilty as charged.    But I was suggesting that perhaps you should seek the counsel of a "little too much" liquid truth, as I am currently doing.   

mnem
Ooooh.... that is some GOOOOOD truth right there...

[med6753]

For those of you wondering why I didn't use many of suggestions for finding this shorted tant on the 485 let me give you a quick synopsis as to why:

1. I don't own any thermal imaging devices.

2. None of my power supplies have current limiting. So if it WAS a board short I ran the risk of burning the board and permanently damaging it.

3. There is NO WAY in hell am I EVER going to use lighter fluid on a circuit board.  That is just plain dumb and I don't care who's done it. They are asking for trouble. Besides, I don't have any.

4. Having a schematic that matched the board would have cut the troubleshooting time. Seems I run into this often because Tek is always making updates and improvements during a product run.

 

[factory]

This Dana 5330 voltmeter listed on ePay.com in the wrong category may be of interest here, it has nixie bulbs:
eBay auction: #254237958335

David

Damn you!!!       

Hmm. Does that mean you own it now? Looking forward to the teardown.

I was hesitant to answer this earlier, given my experience a year or so ago with the Fluke that I bought that turned out to be either lost or "failed testing and was scrapped" by the vendor (after having been listed and sold as "for parts or not working"  ), but it has now been marked as shipped, so I hope I am safe in saying yes, I bought it.  Why, you might ask?  Well, it has nixies in it, and I don't have one of THAT particular model yet.  Reason enough for a TEA addict.  (And I'd been doing kind of well with staying off the Bay of Iniquity, too, dammit!)

-Pat

Sorry Pat, as I couldn't find much of interest in the UK I was searching on ePay.com for digital counters & voltmeters and that is how I found the Dana, I'm looking forward to the teardown too.

I did end up buying this reversible counter though.   



David

[Specmaster]

For those of you wondering why I didn't use many of suggestions for finding this shorted tant on the 485 let me give you a quick synopsis as to why:

1. I don't own any thermal imaging devices.

2. None of my power supplies have current limiting. So if it WAS a board short I ran the risk of burning the board and permanently damaging it.

3. There is NO WAY in hell am I EVER going to use lighter fluid on a circuit board.  That is just plain dumb and I don't care who's done it. They are asking for trouble. Besides, I don't have any.

4. Having a schematic that matched the board would have cut the troubleshooting time. Seems I run into this often because Tek is always making updates and improvements during a product run.

 

Yeh, in one video the person wound up his power supply to max which was in my view pretty dangerous as you said, runs the risk of burning out tracks etc  so it makes perfect sense to limit the current and let the voltage collapse to almost zero in the event of a real major short. I'd have no qualms about using lighter fuel or IPA because you do not use a lot of it and you only do small areas at a time and both will evaporate pretty damn quickly so is not an issue (with current limiting ignition is almost impossible) If anything was getting hot enough to cause ignition then it would have been visible before so no need to do liquid testing.

The practise does indeed seem to be pretty wide spread in the professional sphere as I have seen it done before by professional engineers but it is of course done with care, you certainly do not apply the power within the vicinity of the liquid for obvious reasons and I've never seen it used for anything above 19v. 

[BU508A]

3. There is NO WAY in hell am I EVER going to use lighter fluid on a circuit board.  That is just plain dumb and I don't care who's done it. They are asking for trouble. Besides, I don't have any.

How do you clean the board from flux after soldering? I'm using for this IPA.

[bitseeker]

Limited forum partition over next day or two as have terrible man flu. Going back to bed

Feel better soon, bd! Otherwise, we'll have to get our TE out and do some debugging.