Test Equipment Anonymous (TEA) : Discussion and Group Therapy Thread

[Robert]

I've not watched the whole thing, but it doesn't set a good example of how to approach a restoration. Just start pulling it apart. What about a visual inspection, power up testing and recording of faults. Taking lots of photos is a good idea too. "I know I'm "preaching to the choir" but just teing it apart without knowing the existing faults means you don't know what to fix or if there are faults when you finish if it as something you caused.

[Zenith]

I wonder what the odds of that ever working again are

We'll see, but as I doubt he's going to post videos about a failure, I assume he's already got it rebuilt and working.

I also assume he's a lot more meticulous and systematic than the video makes him appear, with notes, drawings and photos, otherwise, what are the odds of him ever getting it back together again?

I don't like the silly cat character presenting it.

[bd139]

I quite like the presentation method with the cat. It's creative and unique.

The word restoration usually entails a careful evaluation and low touch effort for the sake of maintaining as much of the original device as possible as discovered, fixing functional defects as found and doing preventative maintenance only. What we have here is a complete re-engineering effort which has a much higher risk of destroying the item irrecoverably from accidental damage etc.

There are things which are not said in the service manual or particular revisions and possible post construction fettling to get something working which are unknowns too.

You can get functionally good results without risking destroying it completely. Case in point...

6y1Uj85.jpg

Hy22d7y.jpg

Edit: I do worry that you only see his successful projects.

[Zenith]

Taking it to bits with gusto and apparent abandon, isn't the way I'd tackle it myself. Unnecessary dismantling is something I avoid, because apart from anything else, it makes a lot of unnecessary work. I will laugh if he manages to reassemble it and has a pile of parts left over, which don't seem to fit anywhere. But I doubt that's what the final video will be about.

There's a tendency for all of us to report our successes rather than disasters.

I have a failure with an HP3400A to report. I haven't yet given up hope of fixing it, I just got fed up with it and put it aside until feelings of rage subside and peace and love return. Part of the disaster was dealing with the meter, which has the flaking scale problem, but to the point where it interfered with the movement of the needle. It could so easily have been avoided. I now have to make another meter scale. Yes, they were supposed to be individually created for the meter movement, so some corners will need to be cut. I believe the other problems can be dealt with one way or another.

It didn't start with being a pristine example with minor faults, which I've managed to wreck.

I'll write it up after I've had another attempt. However it turns out, my insights into removing the meter and dealing with a badly flaking scale, without doing more damage, may help someone else to avoid the same mistakes.

[bd139]

I've done the flakey meter thing before. Boiled water with pritt stick melted into it and carefully run along the edge causes the edges to stick down if it's not too bad. I did a half respectable job of an HP 400E with that!

[vk6zgo]

I quite like the presentation method with the cat. It's creative and unique.

The word restoration usually entails a careful evaluation and low touch effort for the sake of maintaining as much of the original device as possible as discovered, fixing functional defects as found and doing preventative maintenance only. What we have here is a complete re-engineering effort which has a much higher risk of destroying the item irrecoverably from accidental damage etc.

There are things which are not said in the service manual or particular revisions and possible post construction fettling to get something working which are unknowns too.

You can get functionally good results without risking destroying it completely. Case in point...

6y1Uj85.jpg



Hy22d7y.jpg


Edit: I do worry that you only see his successful projects.

If I showed my unsuccessful projects, I would have to include two thirds of them.

The days when I could rat bits out of a Sony Profeel Picture Monitor till it just looked like a skeleton, then slowly accumulate the required bits & slap it back together in less than a day, are, alas, long gone, along with the purchasing power of a TV network!

[Zenith]

I've done the flakey meter thing before. Boiled water with pritt stick melted into it and carefully run along the edge causes the edges to stick down if it's not too bad. I did a half respectable job of an HP 400E with that!

A good tip, but I don't believe that alone would have done much good. This one was gruesome.

DSCN3369.JPG

I'll write it up when I've had another go at it, and have either fixed it, or decided it can't be fixed, or at least that I can't fix it.

[tggzzz]

I know it is heresy, but it looks like the plastic covering could be peeled off, leaving the legend underneath.

[Zenith]

The coating may be plastic, but it seems very brittle and has lifted in parts with age. Peeling it doesn't seem like an option.

I brushed off the loose lifted parts with a small, very soft artist's brush. That worked well and did no damage. You don't want flakes to get into the movement and interfere with hair springs, etc.

The scale under the flaked coating is not at all permanent like ink, it's more or less powder.

The mistake was to clean the mirror scale with a microfibre cloth. It only lightly touched the exposed scale and it erased it.

The better approach would have been to remove the worst of the lifted flakes as before. Remove the scale from the meter. Apply the bd139 treatment, where appropriate, and spray the scale with a clear lacquer, such as used to fix charcoal drawings. Then replace the scale. Spraying the scale in place would be asking for trouble.

This happens to a lot of HP meter scales. I'm sure it's caused by damp, rather than UV or just age. A lot of TE I come across gives the impression it's suffered from being kept in a garage or loft for a time. Mostly it causes mold and grottiness, and switches to act up, but causes surprisingly little actual damage.

The flaking scale is something to look out for when buying HP meters. It's easily missed.

I now have the problem of replacing the scale, which I could either print, or try photocopying another scale, or look out for a tatty HP 3400A as a parts donor for the meter and the photochopper (which is a tale for another day). The thing is this was close to a parts mule as any I've seen. I have another two HP 3400As. They are not very big and they are occasionally useful. I seldom come across them on my travels.

[Cerebus]

The better approach would have been to remove the worst of the lifted flakes as before. Remove the scale from the meter. Apply the bd139 treatment, where appropriate, and spray the scale with a clear lacquer, such as used to fix charcoal drawings. Then replace the scale. Spraying the scale in place would be asking for trouble.

Museum conservators, when trying to fix flaking paint into place, apply a very fine mist of dilute water based glue using a nebuliser of the type used for delivering inhaled drugs. Ultrasonic nebulisers are also cheaply available for creating a mist effect on indoor water features or as humidifiers.

[tggzzz]

Glue plus nebulizer minus fume cupboard plus lungs.

What could possibly go wrong?

[Zenith]

It would be a once in a blue moon job, which would take a few seconds. It would be different if it were being done for hours at a time. Wearing a mask would be a sensible precaution. It would be water soluble glue, not a solution of ricin or a suspension of beryllium oxide.

Worth thinking about, but I'm more inclined to the soft paint brush, bd139 and then charcoal fixer approach. I'd have to have a nebuliser to start with.

I came across someone very eager to warn about inhaling solder flux fumes and talking about the terrible lung damage they can do. It turns out he worked for years on a badly ventilated hand soldering production line, making tellies or similar. He hadn't got it from assembling a Heathkit amplifier.

[bd139]

The legend is printed on gelatin which is the issue. Once you get it a bit damp it sort of settles where it was.

[Zenith]

Interesting and it makes sense.

Unfortunately this one is beyond dilute Pritt solution, charcoal drawing fixer or nebulisers with their dangers, because part of the scale was erased. It has to be another meter, or printing a scale somehow.

However, it's all to be considered next time, as well as when tempted to buy another, examining the meter scale carefully and allowing for its state in the price.

[bd139]

Wise move. I am actually avoiding anything until it's one of the very late models from the 1980s on that front.

[Zenith]

That's a very sound position, but I'd say it depends on the price. At a fiver I couldn't resist one in almost any condition. Then they went through several major revisions. The photochopper was swapped for an IC based chopper amp and the nuvistor based input stage was swapped for a FET version. Then they produced the 3400B, which I've never seen.

And of course, if you got one from the very late 80s, assuming the meter was the same, with the gelatin layer, if it showed signs of flaking you'd have to factor that in. It's a disgrace the way some people treat these beautiful things, chucking them in damp cellars and garages.

I feel like a heretic for saying it, but the Ballantine 323 seems the better instrument.

http://www.ballantinelabs.com/323/

I've never got my hands on the Racal TRMS meters.

[bd139]

On the subject of rotten test gear from sheds I did purchase a risky looking HP 6200B a few years back. Turned out it was literally coated in rust inside. It worked fine though!

[Zenith]

A lot of the grotty looking stuff cleans up very easily, with a bit of general purpose surface cleaner and a nail brush if needed. Very often there's not much wrong with it. I wish I saw more of it about - for a suitable price of course.

A thing I don't like is dealing with festering NiCd packs.

[mansaxel]

I'm all for the "minimal intrusion" school. What Atkelar did to the 410C was in part reasonable, in part ever so slightly over the top. I told him as much -- the transformer rewinding was what was required, but the power inlet replacement would have been better with a Schurter C6 -- which is a better fit for a PH-163 hole.

I tend to leave things as they are as much as possible, only correcting what needs doing to get a functional instrument that is not a health hazard.

[MED6753]

I think Blondie is mad at me.



But when do women need a reason to be mad at you?

[nixiefreqq]

maybe its just the perspective.....or the way you zoomed the shot?

but............are her feet really that big?

and for the love of God, don't say I called her "bigfoot".

ps swmbo just got over not talking to me for 3 days after I asked her stop ranting about politics. I avoid tv news like the plague, and therefore she felt the need to constantly update me on the latest nonsense going on with our pinhead vote chasing wanna' be leaders. my voter registration says "non affiliated" for a reason. I will give it my attention on the first Tuesday in november, and refuse to expend any time or effort until then.

[Zenith]

Just an invitation for you to tickle the soles of her feet.

[AVGresponding]

Those are great socks, I want a pair!

[MED6753]

Those are great socks, I want a pair!

Search "fuck off socks" on Amazon and bingo!

[dl6lr]

Since Saturday I am now owner of a Tek 575 in good condition accompanied with a 175. Haven't tested it yet. Was a trip to Heidelberg over the weekend. And as a by-catch: I got CoViD