Test Equipment Anonymous (TEA) group therapy thread

[BU508A]

Those Amphenol ACPR RCA plugs are nice, I like them. 



Source: https://www.tme.eu/html/DE/professionelle-rca-stecker-cinch-amphenol/ramka_4568_DE_pelny.html

[ch_scr]

Sneak-Peek at the 10MHz distribution amplifier - isolated with Gigabit Ethernet transformer. Input is fully isolated and two outputs each share a ground. I've tried to get as-much-as-possible out of the poor transformer in addition to the isolation - it split's the outputs into two, allows for push-pull amplification through the inverter IC, and the solder-bridge select-able input ratio can be 4:1 or 1:1 depending on drive strength. The little proto-board was the first draft with 2 NPN... More on this later 

[Specmaster]

question: would it be interesting to see a pinball repair thread ?

It's not really applied electronics but combines a multitude of tasks and I have not really a clue if it would be of any interest to anyone outside of our little community ?

Go for it, I'll be honest and say that sometimes pinballs don't float my boat particularly, but as I mentioned earlier, part of being an adult is the ability to understand that everyone doesn't have the same tastes, so we need to be tolerant of others. Yes it is applied electronics and even aspects of woodworking in the repair of things are all fair game in my book. We can all learn things from each other that may be useful later to us. So yes, go for it, variety is after all, the spice of life, fill ya boots.

[Saskia]

actually using WBT most of the time. but thanks for the amphenol hint.

[mnementh]

Does anyone buy useless (to them) low-price test equipment to just scavenge for parts?

For example here's a Sonet test set -

HP 37704A Sonet Test Set  $56

eBay auction: #295120014901

The thing is of no use to me, but it might have $56 worth of parts inside, I don't really know. What do you guys think, have you ever done this?

I used to do a lot of that with older Dept Store grade  AV/HT receivers. You get a deader for $10-20, and you can be almost assured of a 100-400VA power transformer good for making a 2-8A lab PSU, plus the rectifiers and brawny caps for the DC. You also got lots of op-amp ICSs and discrete transistors, and the large resistors used in MCP amp circuits. And usually, enough of the final output transistors survive to use as series pass elements.

Of course, these parts are also good for model hobbies, robotics and small motor speed control projects.

 mnem
 

[bd139]

That's got bugger all interesting stuff and a cranky 3rd party SMPS in it 

[xrunner]

Here's an hp 3551A Transmission Test 3 available for $55 or best offer, free shipping. Of no use to me as test kit but it does appear to have good knobs, buttons, binding posts which are desirable for older hp kit, maybe good innards as well.

eBay auction: #
403592921172

Oh what the hell, I'll make an offfer and strip it when it arrives. 

[bd139]

Quick google and picture of guts: https://www.barbouri.com/2022/05/27/hewlett-packard-3551a-transmission-test-set/

I'd pay 20 for it

The case is super cool. Would make a good project case. Lots of reasonable analogue bits in it.

I mostly bough the 3776A for the precision resistors and displays. Anything else was bonus.

[xrunner]

Quick google and picture of guts: https://www.barbouri.com/2022/05/27/hewlett-packard-3551a-transmission-test-set/

I'd pay 20 for it

The case is super cool. Would make a good project case. Lots of reasonable analogue bits in it.

I mostly bough the 3776A for the precision resistors and displays. Anything else was bonus.

Maybe I'll clean her up and turn it on when I have visitors. Since nobody that comes over knows what any of this stuff is anyway should look impressive!

 

[Robert763]

Does anyone buy useless (to them) low-price test equipment to just scavenge for parts?

For example here's a Sonet test set -

HP 37704A Sonet Test Set  $56

eBay auction: #295120014901

The thing is of no use to me, but it might have $56 worth of parts inside, I don't really know. What do you guys think, have you ever done this?

I buy a lot of kit to break for parts, but not mainstream T&E. It's mostly custom built kit that is toally unknown. Some of the HP digital test kit can yield bits but the 377704A is, as has been said, mostly SMD and basically a computer. There are few electronic parts for reuse. Quite a bit of hardware though.

[bd139]

Quick google and picture of guts: https://www.barbouri.com/2022/05/27/hewlett-packard-3551a-transmission-test-set/

I'd pay 20 for it

The case is super cool. Would make a good project case. Lots of reasonable analogue bits in it.

I mostly bough the 3776A for the precision resistors and displays. Anything else was bonus.

Maybe I'll clean her up and turn it on when I have visitors. Since nobody that comes over knows what any of this stuff is anyway should look impressive!

 

"Ah yes the embogulator. Would you like to be bogulated? I won't even charge you!"

Edit: Actually on that I need a conversation piece for the new place that won't scare the opposite gender away immediately 

[Zenith]

Here's an hp 3551A Transmission Test 3 available for $55 or best offer, free shipping. Of no use to me as test kit but it does appear to have good knobs, buttons, binding posts which are desirable for older hp kit, maybe good innards as well.

eBay auction: #
403592921172

Oh what the hell, I'll make an offfer and strip it when it arrives. 

Maybe. See if you can find the service manual on line, and have a quick flip through to see if there's anything of interest in it first. The knobs and other HP bits might be useful.

When I've bought that sort of stuff, it's very often been some specialised piece of test kit for something obsolete or obscure, and  a few times I've bought it for the case, which came with an IEC connector and switch and probably a useful transformer, and with a front panel which could be replaced. I'd have some project in mind when I bought it, and paid two or three quid. New cases are quite dear.

[TERRA Operative]

Tonight on the bench, the HP 8112A 50MHz Pulse Generator.
The original fan was busted, so a new fan just got installed. All nice and breezy now.

Unfortunately the busted fan means one of the custom HP chips (U220) has cooked.

So....... If anyone has a spare HP 1DD6-0002 they want to sell, let me know! 

[Robert763]

Here's an hp 3551A Transmission Test 3 available for $55 or best offer, free shipping. Of no use to me as test kit but it does appear to have good knobs, buttons, binding posts which are desirable for older hp kit, maybe good innards as well.

eBay auction: #
403592921172

Oh what the hell, I'll make an offfer and strip it when it arrives. 

NOOOO
Don't break that up. It's a brilliant little Audio oscillator, level meter and and frequency counter in a box.
Great for all sorts of bench applications.

I have two....

[mnementh]

That's got bugger all interesting stuff and a cranky 3rd party SMPS in it 

Given the nature of the OP, I assumed xrunner intended to research the thing before plonking his money down. 

I was talking about those old AV receivers as an example since they are something I used to do all the time, so I knew them viscerally well and could triage at a glance, the same way Saskia triages a pin.

Though honestly... I've never ever lost money parting anything out... it doesn't take much to add up to $20-50 worth when you're looking at a thing in terms of future project potential. Anything you can sell comes out of that, then you keep/strip the carcass as spoils of war.

Even if you can't sell enough of the carcass to make a profit, you have to buy really dumb to not be able to get "reasonable return" in terms of bits & pieces for future misuse.

mnem
 

[xrunner]

Here's an hp 3551A Transmission Test 3 available for $55 or best offer, free shipping. Of no use to me as test kit but it does appear to have good knobs, buttons, binding posts which are desirable for older hp kit, maybe good innards as well.

eBay auction: #
403592921172

Oh what the hell, I'll make an offfer and strip it when it arrives. 

NOOOO
Don't break that up. It's a brilliant little Audio oscillator, level meter and and frequency counter in a box.
Great for all sorts of bench applications.

I have two....

Now I can picture a little devil on one shoulder and an angel on the other one tugging at me, whispering hints from both sides. 

Let's see what arrives first ...

[mnementh]

Wait... what...? You have a devil and a angel...?

Is that normal, cuz I only ever had a devil... and sometimes another devil. 

mnem

[25 CPS]

The test equipment purchase I was looking forward to turned into quite a disappointment last night.  I was really looking forward to this curve tracer.

I scrounged out and tested a set of PNP and NPN transistors out of a junk box, packed a couple of multimeters and a portable scope into the truck, picked up a friend who decided to come along at the train station, stopped at the bank, got a coffee, then headed out to the seller's place where he had it set up ready to go on a work table in his garage.



The power light came on and the CRT displayed a dot in the middle of the screen and there was humming but no fan noise.  I couldn't get any deflection on the CRT by turning either of the position knobs or by throwing the -10 division test switches, and then the dot faded out after a minute or two.  This was not off to a good start so we switched off and I asked it it was ok to take the covers off and see if there were any visual indications of problems inside.  I was a bit concerned because the two covers were bulged out of the front by the plastic clips that are supposed to turn inside to hold the covers on, not outside of the frame as they were in this case.

First off, two of the rubber mounts for the fan had rotted away and it had fallen in.  Luckily it only jammed and hadn't shorted out a selenium rectifier behind it.  We moved the fan outside the back of the case so it could spin freely once stood on something.







My friend noticed the missing tubes before I did.  It's hard to see from the picture I took from the side but there are a bunch of tubes missing from the underside of the top chassis.  That would explain no deflection since about 9 tubes total were missing from the sweep and stairstep generation circuits.  Someone at some point in time raided it for tubes and then did a slapdash job of forcing the case closed not bothering to do it properly since they must've figured it was junk after they poached the tubes they wanted.

Since the seller had already powered it up several times for us, for pictures, at a garage sale on his street, and it had time to cool down from the brief first power up, we attempted another startup again now that the fan was out of the way to investigate the dimming CRT display issue.  At least the fan ran freely.  I got a measurement on the -150V reference of about -128V and the CRT dimmed right out again after a minute, so the high voltage is failing quickly whether it's the high voltage transformer at fault or something else.

Nobody knows who or when the piece of tape labelled "Works" was put on the front but the curve tracer cannot have worked once the missing tubes were removed somewhere along the way and the CRT high voltage supply failing in the first 1-2 minutes of runtime, setting aside the issue of the fan which could've fallen while the unit was in dead storage.  I don't know what kind of storage conditions it was in but the machine was in far dirtier condition than I expected based on the photos.  If it was an issue of getting the fan remounted and sourcing the missing tubes in order to get started, I might have considered taking it on, but not with the possible bad high voltage transformer.

The friend and I went for dinner after and we enjoyed a nice long countryside drive on the back roads on the way home.  Dropped him off at his place and then I went home still feeling pretty disappointed because I really was looking forward to that curve tracer but it just didn't work out with the condition it turned out to be in.

[McBryce]

Here's an hp 3551A Transmission Test 3 available for $55 or best offer, free shipping. Of no use to me as test kit but it does appear to have good knobs, buttons, binding posts which are desirable for older hp kit, maybe good innards as well.

eBay auction: #
403592921172

Oh what the hell, I'll make an offfer and strip it when it arrives. 

The buttons are well worth having. That style was used on many HP devices and are often missing or broken and are impossible to buy separately.

McBryce.

[AVGresponding]

Very boring repair. I'm disappointed 

Black Star 600 arrived. Spent £20 on it including delivery. Seller described it as "*Spares or repairs*. Initially powered on. No flashes on and off."

Plugged it in, yep it does indeed turn on and off with some clicking. Suspicious!

Cracked it open. Mostly empty space but in good condition overall.



Decided the first thing to do was bisect the problem so I hooked up a bench supply to the internal lines and pushed 5V into it. And it entirely works. So it's the mains side end.



After some inspection the culprit was found. All too simple 



After redoing this joint completely it works perfectly!



Aaand into the cupboard until I've moved. Told you it was a boring fix

Total time elapsed was about 15 minutes. I expect more trouble for my money!!!!!! 

Send it to me. I'll break it in some unexpected and difficult to diagnose way and send it back to you.   

[AVGresponding]

The idea of audible differences is of course plain and utter nonsense.

But there is indeed a problem with cheap ready-made audio cables. The amount of copper, especially for the screening, has been reduced drastically over the last years. Three strands of copper aren't a proper screen!

The problem is made worse by the fact that our local energy supplier uses 1350 Hz tones transmitted via the mains to control street lighting, switching counters from day to night rates etc. Other cities do this at frequencies between 200 und 400 Hz. 1350 Hz is the point where our ear is most sensitive. I've had to throw away a number of cables bought lately and I'm now making my own with high-grade microphone cable stock.

That's why you use balanced audio. It's common mode noise then and thus rejected

A shitty balanced XLR cable is better than a good 1/4" patch...

you are certainly right about that, but I cannot refrickle my stuff to balanced audio. It would involve f*ckering up the cases which I am not inclined to do. I will however use decent shielded cable. And decent connectors. Such as https://www.amazon.de/Oehlbach-High-End-Cinch-Stecker-Kabelquerschnitt-Vollmetallstecker-Gold/dp/B000FS9AJE/ref=sr_1_7?keywords=WBT&qid=1659621689&s=home-theater&sr=1-7

Just run it off an inverter. You're getting a solar PV install at some point right?

[bd139]

Send it to me. I'll break it in some unexpected and difficult to diagnose way and send it back to you.   

That’s actually an interesting idea: diagnostics practice as a service 

[AVGresponding]

Oh, meant to say also, another lot of Unilab modules arrived; collecting them in order to bully the grandkids into learning electronics. I'll glue them to their Lego or something...

Also, going to be selling some meters soon. HP 3468A, Thandar 1905a, TTi 1906, Solartron 7150 for starters. I'll clean the 3468 this weekend, do some comparisons against The Quorum (Fluke 8840A, recent cal, Keithley 2015, less recent cal, Agilent 34401A, recentish cal), then pack it up and wait for a sucker buyer. Will be sold in the BSW sub-forum here, not going near ebay.

[Zoli]

Still $572 for a 6 foot RCA cable. That’s bananas. There is no measurable difference between those cables and a $5 radio shack cable at line level. I’d expect triax blessed by the ghost of Bob Pease for that money.
...

Scientific instrument fly-lead: $400
Materials used: $30
Time to build: 10 minutes
I've made a few ten on a previous job(rest of the details under NDA).
Bananas? No, market price for first word custom engineered and and built cable; I'm sure that are experts here who can confirm the pricing.
Measurable difference: can you point me to proper engineering tests(time/group delay, impedance(the good old engineering units characteristic to cables/transmission lines) etc. vs. frequency, current, etc.) between the Radio Shack and Iconoclast? Similar comparison between properly engineered and mass produced cheap cables are acceptable; worst case double blind ABX test is OK.
And in case if you've missed it:

These designs are all, in a certain sense, "impractical." They represent optimization of design constrained only by what can feasibly be manufactured, without regard for cost of manufacture -- engineering unconstrained by budget. As a result, they are substantially more costly to make than conventional products are, while also being priced substantially below some of the stratospheric prices one sees in the high-end audio world. Whether this is an expense which will be worthwhile for you is precisely the judgment that only you, not we, can make; but if you are seeking the best in audio performance, we encourage you to give Iconoclast a try(https://www.iconoclastcable.com/story/index.htm).

Conclusion: certainly not for a ferengi spirit  Well, except when some profit(or ear-lob increase) is involved 

...
re cables - I try to use good connectors such as WBT and reasonably good cable. with up to 70 amps of current going over the speaker cable a 22 ga cable would create a bad feeling ... so I am using 4 mm^2 or an over the top cable out of the surplus bin of my friend the speaker developer.
...

24AWG(=0.25mm²)*24=6mm²
I think it would fulfill your requirements(except price). For the rest, see above.

...
Now, if only they would make a crimp type 1/4" mono plug...

Crimp and ultrasonic weld is only for speaker cables:
https://www.bluejeanscable.com/articles/ultrasonic-welding.htm

[ch_scr]

Send it to me. I'll break it in some unexpected and difficult to diagnose way and send it back to you.   

That’s actually an interesting idea: diagnostics practice as a service 

That's literally the way they do it for e.g. TV repair servicemen certification - they have a guy which job it is to put faults (e.g. faulty components) into the exercise devices. As far as I've heard, the trainees that thought "no problem, I'll be able to see where he soldered" had a very hard time passing