(AU) Ebay, Hewlett Packard 34401A multimeter.  - Page 1
Forum section: electronics / general

author: wilfred
author_rank: Super Contributor
timestamp: February 02, 2013, 11:33:30 am
content: /.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 05, 2013, 10:55:23 am
content: Some nice things, but I'd be a bit concerned about the seller's feedback, or lack of it. And some odd details:Only two previous items sold: a laser printer and cartridges for it, in Sept last year. To the same buyer.The seller joined ebay the same day as he sold those two items. Huh?$99 for laser printer cartridge(s)?Same price ($99) for the two previous items, and now he starts listings at $0.99?The item listings are expired, so we can't see them.And... how does he show '3' in the feedback count, but only two in the feedback listing?Buyer beware.This is a pity, there's a couple of items I'd be interested in bidding on - if the seller didn't seem really suspicious.

author: paulsev
author_rank: Contributor
timestamp: February 05, 2013, 11:42:06 am
content: Just Pay with PayPal and you get buyer protection, also hes offering COD which is a good idea if you live locally. Hes selling allot of other things too...I wouldn't be worried just ask for his phone number to call him about the item.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 05, 2013, 01:02:07 pm
content: Quote from: wilfred on February 05, 2013, 12:24:13 pmOops! Yeah, I'm not _usually_ dyslexic. But taht tmie...Sure, everyone has to start, but I'm nervous paying potentially a few hundred to someone with very little history.QuoteMaybe. I lost track of what ebay is doing with the feedback system.QuoteActually, I've had a few ebay experiences where the seller sounded fine, but wasn't. Not many, very small percentage of my 400+ ebay buys, but enough to be wary.In this case I just thought I'd mention the sparse history. Still undecided about bidding...

author: johnh
author_rank: Regular Contributor
timestamp: February 06, 2013, 09:12:09 am
content: No photos showing the units working!

author: TerraHertz
author_rank: Super Contributor
timestamp: February 15, 2013, 05:16:09 pm
content: I ended up buying three of those items. Here's the story of how it went, including two teardowns with lots of photos.http://everist.org/tales/20130215_The_Q_meter.htmWhat's the general opinion is here - should I give the seller a negative ebay feedback for the stupidly negligent packing? I haven't decided yet.

author: PaulAm
author_rank: Frequent Contributor
timestamp: February 15, 2013, 06:26:33 pm
content: I'd say ask for a rebate to cover your time to make a part. Depends on what you got it for, but at least $20. If they're amenable give them positive feedback and if they blow you off, give them negative.I recently bought a TM500 module from Tektronix surplus and the one they shipped didn't match the one specified in the auction (it was dirty, had a broken locking tab and a bad control). Not only did they send the original unit, they told me to keep the one sent in error as parts.I had a scope shipped that was reasonably well packaged, but it must have been dropped on a corner since the B trigger level control was completely smashed. The seller credited me $20 for that one after sending along a picture.

author: Nirios
author_rank: Regular Contributor
timestamp: February 16, 2013, 01:19:17 am
content: Quote from: PaulAm on February 15, 2013, 06:26:33 pm+1 on the rebate. I've asked and received money back for items damaged in shipping or part of the device did not work even though the listing said "tested".

author: TerraHertz
author_rank: Super Contributor
timestamp: February 16, 2013, 09:26:38 am
content: Trouble is, the Q-meter cost me Au$355, but the time and cost required to get the part out, try correcting the bend (failed), then making a new one (and getting it gold plated) is going to be more than that, if I factored a reasonable hourly rate.Also I realize some people would have just shrugged and used it with the bent connector. But I like to get test gear like this to as close to new looking as possible. The bent connector would perpetually bug me.Oh well.The currently annoying thing is, I thought I had some suitable brass rod in stock, but turns out I don't. What I have is just a little too small diameter. So can't do anything more on this till Monday.

author: SLJ
author_rank: Frequent Contributor
timestamp: February 16, 2013, 01:24:27 pm
content: Looks like a lot of shill bidding went on to run up the price. I wouldn't have touched it.

author: PaulAm
author_rank: Frequent Contributor
timestamp: February 16, 2013, 02:16:51 pm
content: Since actual shop rates to make the part would exceed your cost, that's not realistic. If I were making one of those for a friend, I'd probably charge $15-20 or take a few pints in trade.Really, if they make some movement, consider it good. And you have the fun of making a replacement OEM part. If you're a closet machinist with a lathe, you probably haven't recovered the cost of that yet, so you can also congratulate yourself on the forethought involved with acquiring that

author: TerraHertz
author_rank: Super Contributor
timestamp: February 18, 2013, 09:31:56 am
content: Quote from: SLJ on February 16, 2013, 01:24:27 pmDo you mean the multimeter, or the Q-meter?I think perhaps you're not used to the way auctions go here in Australia. It's a starved market, for any kind of quality 2nd hand test gear. Partly due to the import shipping costs, and also due to the small size of the industrial user base. Then there's some local buyers who are too timid to buy direct from overseas, so they bid up the price of local auctions even more. Try subtracting the likely shipping cost (USA to Aus, say $100+) from the price, to get the real price.It would not surprise me much if the Q-meter is the only one of these in the country. Or at most one of a small handful.As for the bidding, the seller is a moderate sized company, that markets airport/transport security systems worldwide. The guy who listed them is busy with a company premises move (and hardly ever sold on ebay before.) Plus the bids jumped a fairly typical amount via snipe bidders (about +50%) and I don't think shill-sniping is a very likely strategy.Making a new part for that connector post is underway. Today bought the brass and the two button UNF thread dies needed. Currently making a button die holder jig to ensure exactly axial thread cutting, since I don't tend to be able to get that quite right by hand.Once that's done, making the part won't take long. It's all the running around getting materials and tools that chews time. Then there'll be the problem of getting it gold plated.While I'm at it I may get all of the connector posts and the mounting plate re-plated, as the original plating was too thin, and tarnished badly. In the case of the mounting plate, it wore off completely while buffing it up.Quote from: PaulAm on February 16, 2013, 02:16:51 pmHey, if I knew someone who'd make a duplicate for $20, I'd definitely do that. But I don't. Did consider taking it to local engineering shops and getting a quote, but decided the cost would certainly be so far above what I can do it for, that the time spent getting the quote would be wasted.So far, it's cost $32 for the two button dies. Not going to count the $90 for a selection of brass rod stock, since the amount used for this will be tiny, and I've been meaning to get an assortment of brass rod sizes anyway. Already had some, just none above 10mm diameter.QuoteExactly. I enjoy doing stuff like this. Not even 'closet' - see the last pic ofhttp://everist.org/pics/workshop/20121129_workshop.htmHowever it would have been better if the idiot had packed it properly, and this wasn't necessary.Since it's delaying other things I'd rather be doing.'Cost recovery'? What's that?

author: PaulAm
author_rank: Frequent Contributor
timestamp: February 18, 2013, 05:55:08 pm
content: That's a pretty impressive setup.I totally agree though, it's much better if they spend 5 minutes and pack the stuff correctly in the first place.

author: lowimpedance
author_rank: Super Contributor
timestamp: February 19, 2013, 01:41:33 am
content: QuoteChecked out your teardown link, Some nice old gear there. Utter bugga about the bent post.Check out these guys for platingIndustrial & Decorative Gold Plating Co Pty Ltd in Milperra, NSW.Many moons ago when they were near where I work (moved to Milperra some time now), I used them for variousplating jobs with good results at a good price. (Don't know what they are like now though!).Enjoy the 'new' toys.LowZ

author: TerraHertz
author_rank: Super Contributor
timestamp: February 19, 2013, 09:18:20 am
content: Quote from: lowimpedance on February 19, 2013, 01:41:33 amOh my gosh, that's serendipitous! I'm in East Hills and that's about one minute drive from my place. Thank you very much. I was expecting I'd have to hunt all over to find such a service. I drive past there often, but didn't notice they were there due to their being down a side lane.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 20, 2013, 08:11:17 am
content: Finished making the replacement mounting post, and got a quote for the gold plating today. Rather than just plate the replacement post, I'm going to get all six posts and the support plate re-plated, since the old plating was very thin and tarnished, and in the case of the mounting plate so thin it completely wore off while removing the tarnish.The new post (on right, shiny brass colour), together with the unbroken 2nd original one of the same shape. Also the tool I made for producing exactly axial threads using button dies.

author: ddavidebor
author_rank: Super Contributor
timestamp: February 20, 2013, 12:54:09 pm
content: Why you would gold plate the banana input?

author: TerraHertz
author_rank: Super Contributor
timestamp: February 20, 2013, 03:35:50 pm
content: Both practical and aesthetic reasons.Practical, because gold doesn't oxidize, and thus reliably provides a very low resistance contact. This is important for measuring Q, since stray circuit resistance degrades resonance.Aesthetic - because that's the way the instrument originally was.Today I found a nice history and good photos of the HP 4342A here:http://www.hpmemory.org/wb_pages/wall_b_page_09.htmScroll down the page to it. The 'zoom view' they show gives a good idea of how it should look. Compared to how tarnished the ports on my one are, here:http://everist.org/tales/20130215_The_Q_meter.htm

author: ddavidebor
author_rank: Super Contributor
timestamp: February 20, 2013, 04:15:25 pm
content: If you want to have better contact, you've to buy better cables with better banana jack.

author: TerraHertz
author_rank: Super Contributor
timestamp: February 21, 2013, 12:04:31 am
content: Cables? What cables? The component under test mounts directly on top of the Q-meter, with the absolute minimum of connection parasitic capacitance, inductance and of course, resistance.That's why the thing is such an odd shape, instead of the usual rack-mountable case with connectors on the front panel. Some of the coils the Q-meter would be used to characterize would be bulky and heavy, and they still need to be right next to the test port. Hence the port is on top.Perhaps with very large value components and LF measurement, cables would be used. But then they'd be heavy copper with spade lugs, preferably silver or gold plated.

author: ddavidebor
author_rank: Super Contributor
timestamp: February 21, 2013, 05:47:18 am
content: Ok

author: TerraHertz
author_rank: Super Contributor
timestamp: February 28, 2013, 07:01:22 am
content: An update:http://everist.org/tales/20130228_repairing_Q_meter.htmI probably should be posting this on a machine tools forum, rather than electronics. So far I haven't even got to try using the Q Meter for what it's meant to do.

author: AlfBaz
author_rank: Super Contributor
timestamp: February 28, 2013, 09:13:53 am
content: Very, very nice. You have to be happy with that resultI have done enough lathing to know that what you have done there is not a simple task, especially if you have an old flogged out lathe. +1 on your machining skills.As an aside, a friend of mine who's a fitter/turner once showed me this thing he made on a lathe as part of his apprenticeship. I don't have access to a lathe anymore, if I did I'd have a crack at it.Its a brass cube about an inch in size. It has about a half inch hole in each face. Inside the hollow cube is a smaller, loose solid brass cube and it was all made from a large, solid brass rod, using nothing but a lathe.I'll knock up some 3d drawings of what it looks like and how he did it

author: AlfBaz
author_rank: Super Contributor
timestamp: February 28, 2013, 12:03:47 pm
content: Sorry if you already know this stuff TerraHertzPicture of the cube should give you an idea of what I'm talking about. The inner one is detached from the external one.You'll probably need a 4 jaw chuck to turn up the original cubeYou then need to drill holes on each face to the depth of the wall thickness you want plus how much smaller you want the inner cube (or the width of the tool). Clearly you have to grind the end of the drill so that both cutting edges from a straight line (don't know what the name of it is... milling drill?)Once that's done you mount the specially ground cutting tool so that its flat with the cutting tip facing you. Wind it in until the flat edge is flush with the bottom of the hole and that when you turn the chuck, the cutting tool sits in the middle of the hole without touvhing anything. You then simply wind the tool out toward you creating a cut that is inside the cube. Repeat this for every whole.hope that made some senseEDIT: I drew the tool backwards, the way I drew it you would have to wind the tool away from you to work

author: TerraHertz
author_rank: Super Contributor
timestamp: February 28, 2013, 02:12:02 pm
content: Heh. Actually, I figured out how to do that from your original description. I do have a 4-jaw, and could do this if I wanted to. The tool to cut the flat bottomed holes initially is called an end mill. And there are other ways to do both the cube shaping and the final undercuts. For instance with the cube clamped on the bed of a milling machine. Which I could also do. This is a better method because it allows the circular holes to be any size, not just the size of your end-mill.The one trap is being careful of what happens when you finally cut through the last attachments of the inner cube to the outer body. Strong chance of that 'sudden expensive bang' as shifting workpiece jams and breaks rapidly rotating cutting tool. It's not the cutting that takes skill, it's avoiding the bangs.For this exercise you'd arrange a clamping system holding the inner cube in place during the final cuts.But... I won't be doing this, because I already have too many machining, electrical & electronic 'todo' list items on a main project that's going to take years. Life provides enough unwanted time-killing sidetracks already. For example this week discovering that of my four Tek R7903 rackmount scopes, all of which worked a couple of years ago, now I find all four are dead. And all with power supply module problems. Rats, I hate that 'brick' PS, it's really hard to work on.Plus the extra troubles I create for myself, like the Q-meter, who's utility for the main project is perhaps a stretch. But definitely fun.Every now and then I get to do some work on the actual primary project. Like adding braces to the vacuum chamber support frame recently:

author: AlfBaz
author_rank: Super Contributor
timestamp: February 28, 2013, 03:48:25 pm
content: Yeah that was one of the problems I foresaw in making that gizmo, the final cut.What is that big project you are doing, if you don't mind me asking? I tend to recall someone here talking about something big like this but I was relatively new here at the time.