Test Equipment Anonymous (TEA) group therapy thread

[tautech]

Fluke 8012A update. ALL of the damn electrolytics have spewed their guts on the board. Major cleanup. Surprised it even came up.

Cool, looks like you caught it just in time. 

You might be spewing now but in a few days you'll be glad you opened 'er up. 

[mnementh]

Ahhh LOOOVE the smell of hot electrolyte in the morning! Smells like VICTORY!!! 

Been working on the Technics amp tonight and I have no idea what I was doing / thinking last night, must have been distracted or someit  , pulled the main board out and checked all tracks for bridges, could I see any, nah.

Refitted it and powered up without speakers this , connected 4 meters up (internally this time) and checked to see if the 36V was being switched by the AB speaker switch and darn it, it was so WTF did I not spot that last night???

Got a 5th meter and probed the main amp IC pins to see if there was an internal short when powered, and bugger it, there was (you were 100% bang on menmenth)  the right hand channel was instantly raised to 36V, left channel, not a problem.

New power amp IC on order, just got to wait for that slow boat to come now. Arh well onto the next item in line for the bench, an Aiwa XR-M500 whose CD player skips on tracks 1 and 2 and the tape drive doesn't work, otherwise performs really well. 

I fuckin' hate bein' right... *sigh* 

Some of the newer ones are actually 4 BTL channels... that means they COULD have 8 discrete channels in one IC, but they deliberately Siamese the inputs internally and the frontend on each channel is balanced with a DC servo circuit. Internally. With nothing discrete but individual feedback and mute lines for all the channels. 

That's what I guessed you were working with; I haven't seen actual switches in the speaker circuit in over a decade. And I like to work with old AIWA & TEAC shit.

mnem
*Time to be mauled by two small children for the weekend*

[Mr. Scram]

Does anyone recognize accepting that you need to spend money on something, then seeing one sell for a way too be good price and then not being quite so prepared to spend the money any more? Do we have a term for that? Envious Sale Reluctance, or ESR perhaps?

[mnementh]

It has to be some variant of "Grass is Always Greener" syndrome... Maybe "Shopper's Remorse"?

mnem
*Looking for a low-profile AC power switch to hack into a small space on a printer*

[bitseeker]

"Oh, NUTS! Now, where'd my frequency counter go?"

You remembered!  I feel honoured.

Still looking for the flipping thing.  I kept it in a cardboard box - one of several I had used to containerise all the smaller stuff.  It should be with the others ... but I haven found it yet.  Still annoyed about that.

You have my sympathies. Hope it turns up before you go bonkers.

PS  A vote for NUTS.  Not sure about MET as yet.

Looks like NUTS is going to win.

[bitseeker]

   A quick heads-up... something that just blew me away.

... I found and ordered one on AliExpress for $6.57 and got a $2 coupon since I hadn't ordered anything in a while. So, $4.57 with free shipping. Woot!

Let us know how you like them; and how you feel about the comfort vs sound quality.
...
Also let us know how the controls work, and on what breeds of phone you've had a chance to try them.

I shall. It may be a few weeks until arrival (free shipping ). I usually use over-the-ear headphones as most ear buds (especially cheap ones) don't sound good. So, your reputation is riding on this — just kidding, I appreciate your sharing your positive experience or I wouldn't have bothered trying them. I look forward to having some reasonable-quality buds because big cans don't offer much/any air circulation, which gets rather humid when working in the yard, for example.

[mnementh]

I spent the day housecleaning with them on... burned a whole battery in my Nano and eventually had to turn them down because they were just too loud.     The only part that was sore was my eardrums.   

I did not, however, notice the doorbell when FedUPS delivered my motor mount from slAmazon, and only noticed my wife calling me due to having the vibrate on as well as ring; guess the noise-canceling claims are legit. 

"Oh, NUTS! Now, where'd my frequency counter go?"

You remembered!  I feel honoured. Still looking for the flipping thing.  I kept it in a cardboard box - one of several I had used to containerise all the smaller stuff.  It should be with the others ... but I haven found it yet.  Still annoyed about that.

You have my sympathies. Hope it turns up before you go bonkers.

PS  A vote for NUTS.  Not sure about MET as yet.

Looks like NUTS is going to win.

Have we MET? Everybody's NUTS in here!   

mnem
Sweet Hypnos, carry me away in you tender embrace...

[mnementh]

Lucky page 777!!!

mnem
That is all.

[bitseeker]

With all this Fluke talk, I shall join in as well. Actually, I need a group insanity check.

So, I bought a Fluke A90 to go along with my Fluke 8100A. It might also be useful to provide 10A current measuring capability for my 2A- and 3A-limited DMMs.



The item looked to be in good condition and the seller disclosed that the buttons were a bit hesitant/sticky. Since he said that the shunts measured correctly, I went for it.

Imagine my horror when I unpacked it today and discovered




I sent the seller a message about the discrepancy and he claimed that he didn't look at the bottom.  Then, stated that I must be a collector to be bothered by it. As if only a collector would be bothered by receiving a four-leg table with one leg that doesn't match the other three.

It's getting exasperating how many sellers on eBay try to get away with this kind of nonsense, feigning ignorance. Some even have 100% rating with over a thousand feedback. I've already returned several items this year because they weren't as described and I just get tired of dealing with it.

But I'm not sure about this one. I probably should return it out of principle. But the shunt resistors measure good and look fine (not fried). The switches should clean up and operate well thereafter. The rest of the enclosure is in good condition. I'm inclined to keep it and post neutral feedback since it was packed well and the seller's response was prompt. But finding a replacement foot for these ancient things is going to be a long journey.

In the meantime, I suppose I could move that goofball foot to the rear. Out of site, out of mind?

[Brumby]

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.

[Neomys Sapiens]

My mother was a calculator for a bit (true story!)

I am seriously tempted by one of these bad boys from Swiss Micros:

Yup, I found them too. Have 2 HP28S, an 48Emu and 'RPNCalc', but they are severely tempting.

[med6753]

Nasty. No stonking great big DC blocking cap I bet either!


8012A power supply and caps done. Didn't notice it was a bit slow to start up initially. Turns out bad caps!

....snip...


 
And I'm off to bed now. Display replacement tomorrow!

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.

[bitseeker]

Glad to hear she's doing better, med. I missed your original post about that and your close call, too. Quite the week, eh?

[bitseeker]

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.

Yeah, since the switches are dirty and affecting the readings at the binding posts, I checked the strip and wirewound shunts directly inside and they're pretty close to what they should be. The 10mΩ for the 10A range is a tad high, but may have been affected by the dirty switch contacts being engaged.

I haven't been able to find any specs on what the tolerances are for these shunts. The 8100A manual has a short description of the A90, but no specs. Instead it has specs for other accessories such as probes. I haven't found an A90 manual online.

Incidentally, I saw that Fluke made a 500 MHz AC probe for the 8100A. That seems like an awful lot of bandwidth for an AC probe when the meter's AC mode measures at frequencies from 30 Hz to 20 kHz.

[tggzzz]

Lucky page 777!!!

Nope, but page 400 approaches:

[Brumby]

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

[Ero-Shan]

I didn't have a 120 ohm resistor or I would have used 120+150. Since taking this photo I've added a small run of epoxy on the bottom of the board to support the floating resistors better.

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. 

[Ero-Shan]

Late, as usual, here's my contribution to the Tower of Flukes exhibition. Non of the highly esteemed ones (its 'mass instead of class'). And my 75 is on permanent loan at a friend.

[bd139]

I didn't have a 120 ohm resistor or I would have used 120+150. Since taking this photo I've added a small run of epoxy on the bottom of the board to support the floating resistors better.

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.


On subject of calculators, Amazon are dropping off an HP35s today. Wonder if it’ll suck or not. Not used that series yet.

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.

All the gory details will be presented once complete. I have to do some mundane tasks first unfortunately as SWMBO has buggered off for the weekend. That means shopping, washing duty for me.

Good to hear she is recovering nicely. Not a nice situation.

[bd139]

Late, as usual, here's my contribution to the Tower of Flukes exhibition. Non of the highly esteemed ones (its 'mass instead of class'). And my 75 is on permanent loan at a friend.

Holy shitballs!  I think the IEC leads for that pile would cost more than my entire collection of flukes!

[Specmaster]

Late, as usual, here's my contribution to the Tower of Flukes exhibition. Non of the highly esteemed ones (its 'mass instead of class'). And my 75 is on permanent loan at a friend.

Holy shitballs!  I think the IEC leads for that pile would cost more than my entire collection of flukes!

@Ero-Shan That's the benefit of having a world famous dumpster to dive in. Your the only other person I know next to Dave who comes across these incredible dumpster finds. [emoji53]

[tggzzz]

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):

[bd139]

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.

[Specmaster]

@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.

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

[Specmaster]

@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.