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Test Equipment Anonymous (TEA) group therapy thread

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mansaxel:

--- Quote from: m k on June 26, 2022, 09:11:21 pm ---Midnight, somewhere.

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the mosquitos...  :-DD :scared:

You're far norther than we are -- here, it's still 7 minutes to midnight and a lot darker.

Cubdriver:

--- Quote from: mnementh on June 26, 2022, 07:20:20 pm ---On the Bench Tonight: INFINITY RS-3000 Cabinet Rehabilitation And Assembly
One of these speakers had drop damage on the corner; it broke this corner of the grill frame and made a ding in the top edge of the speaker with a noticeable separation right at the seam.

I almost passed on these speakers as it had been a long time since I did such repairs; but then the fixer in me took over, saying "You know how to fix this; just do it ya fukkin' baby!" After a little goading from Pat, here they are on my bench.




Here I am doing rehab on the speaker grilles. This is the broken corner; as there is little contact area at the diagonal crack, I printed up a little corner bracket to make a lap joint with the epoxy. Note the little holes to give the epoxy something to sink into. This took about 5 minutes in fusion360, then 15 minutes to print at 0.28mm DRAFT Layer height. :-+

The broken support peg will just be epoxied in place; there's a lot of contact area there. To give the epoxy something to bond to, I've made a lot of crosshatch scoremarks with a sharp paring knife on the mating surfaces. Note the scrap of cardboard between the grillcloth and the frame as a drip barrier. Epoxy soaking through the grillcloth is very noticeable.  :P




The finished repair. I tacked down the edges of the grill cloth that had come loose by touching the edges with a soldering iron; I used the hot-knife blade and temp at 250°C. This is essentially how they make the grills at the factory.




The correct way to "renew" this speaker would be to replace the grillcloth; however I'm already into these for $40, and there isn't budget for that in either money or assache. I'll clean things up as best I can and see how good I can make it look.

Cleaning is done first with a towel soaked in Windex. I support the back of the grillcloth with my hand and arm and scrub gently against them; moving from area to area until the entire surface of the grill has been scrubbed. Any spots that don't come clean with Windex (like tracks on the back from marshmallowy speaker roll foam) will get followup with a towel soaked in IPA. In both cases stop and re-wet the towel frequently. If grillcloth rips or stays stretched when you try this, it was already past time to replace it. ;)




Next problem to address is slubs in the fabric from where it got snagged on stuff over its life. I used to do this with a Bic lighter, but I found that it is too easy to burn a hole in the cloth if you're just a moment too slow pulling it away.

A small hot air gun like this one for heat-shrink tubing works a treat; it makes the polyester threads shrink away and much less obvious. Start about a foot away and bring the nozzle in while watching the slub(s) you're working on; the instant you see them start to shrivel up tilt the nozzle away. Repeat until you stop "seeing just one more really ugly poker"... :o




Part of the damage was a split seam right along this edge with ~2mm gap; my repair was to mask right up to the edge of the seam, then poke epoxy into the gap with a paring knife. (Sorry; no before pic  :-[) Then wipe off excess with a IPA-soaked towel, clamp the seam as  seen here and wipe off the sqweezage with the IPA-soaked towel. Set it aside and wait til the next day. I SAID WAIT TIL NEXT THE DAY, DAMMIT!!! >:D




Next morning I undo the clamp and I'm greeted with this beautiful sight. I can see there is a tiny little bit of epoxy extruded right on the edge, and of course the first instinct is to pick at it and try to make it perfectly flush. *smacks own fingers* No. You know this only results in pain and misery, like picking at sunburn scabs...




Resisting the urge, I do as I know from painful experience is the right way to finish this repair: Peel off the masking tape, then wipe it all down with a IPA-soaked towel.  :phew: Not perfect, but close enough that I know only I will notice.  8)




If there's one thing that pisses me off with a used speaker, it's to find the bottom all tore up from monkey-butts who drag a bare speaker across the floor.






It takes pretty much nothing to just pop a few of these on the bottom, which will prevent easily 90% of such mishaps from scarring your speakers, and it helps decouple them from the floor so the bass doesn't make the house rattle.

Just do it, FFS.


   

Last step before reassembly is to do a quick checkup of the XOs; these are a nice compact design well-supported by the spring-connector bung and lots of hot-snot. No loose inductors, no leaking or bloaty caps and no cracked solder joints. Caps/resistors measure well within reasonable "sanity values" indicating no opens or shorts, so no motivation to dismantle for further testing.

Not sure what this particular variant of the ubiquitous 2nd order L-R filter is called; but I'm sure there are plenty in here who can bust my chops aboot it. :-DD




Any time I open up a speaker, I re-tension the connectors before reassembling. It takes just the gentlest squeeze with the pliers; I usually prefer something with smooth jaws, like my Xuron 3mm flat-bill pliers here.




And here's the fixer's moment of joy: finally time to reinstall the drivers. I do this by hand with a bit-type driver; the magnetized end holds the screw so you can balance the speaker while getting it started, and by choosing a new bit I can make sure I minimize slippage which leaves ugly scars on the screw heads. Plus it's just too damned easy with the drill/driver to slip and poke a hole in your just refurbished driver. Much  :'( follows.

As with anything assembled using machine screws, by hand you can turn the screw backwards and feel the bump at the edge of the old "thread"; looking for this with self-tapping screws in wood and plastic helps you make sure not to strip out the hole and makes reinstalling the screw much easier.

This tactic also helps you make sure easily-deformed sheetmetal like the speaker basket doesn't get bunged up, making the speaker not seal properly. This can cause buzzing or whistling as moving air passes through that gap.


   

And here are the money shots: Both speakers finished and ready to go into service.   

Guess I need to get this     up on the bench next...

mnem
 :-/O

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Excellent write up - thanks.  I still need to sand and refinish the Dynacos that pushed you along this journey; they got put aside when more pressing things arose, and then a week ago I buggered up my back overdoing it working with a friend refinishing a deck and pair of doors, so I’ve been hobbling around this past week like a 95 year old.  (This has also slowed progress on the NLS meter, though I have done a little more with it.  Needless to say, the 50 kg counters will not be moving until my back is well and truly better.)

-Pat

Cerebus:

--- Quote from: tggzzz on June 26, 2022, 09:09:02 pm ---
--- Quote from: bd139 on June 26, 2022, 07:38:12 pm ---My original copy of it I stole from the local library but they sent me a postal shit-o-gram with a large fine so I handed it back on an amnesty day about a year later  :-DD

--- End quote ---

I had a slightly different trick.

The senior library staff mentioned to my parents that I was borrowing books from the adult library on my junior library ticket, and maybe I would like a senior library ticket. My parents didn't let on that I had spotted that juniors didn't pay fines :)

--- End quote ---

Back in the pre-Internet days when I worked in a university attached science park, one of the perks for companies in the science park was their employees were entitled to use the university library. You got given a library ticket with a senior lecturer's privileges. This added up to a borrowing entitlement of something ridiculous like 20 books simultaneously, which you could keep for a whole term, no fines, and borrowing from restricted collections that weren't available for borrowing by undergraduates, research students or mere junior lecturers. As pig in shit, happy I was, when card I got.

One of the other 'perks' was access to the senior common room. Probably the dullest room on campus, including the various janitor's cupboard. We went in there for a drink, precisely once, to see what it was like. We had our drinks served to us by an ancient waitress in full 'silver service' style, swiftly drank them, and rapidly retired to the Red Lion up the road. We never subsequently bothered with investigating the silver service senior dining room, to which we also had access. I suppose we might possibly have considered using it to impress a certain snobbish sort of client, but the issue never arose.

syau:

--- Quote from: factory on June 26, 2022, 08:36:16 pm ---
Random web search find for TE feet (searched for tilting bail), found these Hammond feet & bail sets, they look very much the same as those used on old Systron Donner, Eldorado, Wavetek, Hickok and probably some other US TE brands, the tilting bails are available in three lengths.

https://www.hammfg.com/electronics/small-case/accessories/1427d



David

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Looks like those used by Stanford Research  :-+

Specmaster:

--- Quote from: bd139 on June 26, 2022, 07:38:12 pm ---
--- Quote from: ch_scr on June 26, 2022, 06:56:57 pm ---
--- Quote from: bd139 on June 26, 2022, 03:14:23 pm ---Ok Newbury megapost. It has been 3 years since the last one. Bloody COVID.

So what did I bag?

(...)
The Mullard Transistor Circuits Manual ...

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Damn that is nice bedtime lecture, I can see why it's highly sought after!

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Yes it's an excellent book.

My original copy of it I stole from the local library but they sent me a postal shit-o-gram with a large fine so I handed it back on an amnesty day about a year later  :-DD

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Its available free online to download as a PDF.

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