In the Mkt for a HP Bench DMM

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Thanks for the info. I had several 5V dip relays that I got from rat shack long ago on clearance. Probably stuck away in the garage in some box, still in their blister packs. I wish I could get an old Strowger switch from the '50s telephone surplus stuff. They're a rotary stepping switch, with lots of contacts.

Hi Watson, Great! I don't know why people are bidding up that guy that has *zero* sales, and a *trust-me* price on shipping. He is already up to $76! And as you know, your tucker meter was sitting there unmolested.

I bet another TE 3478A appears, exactly the same terms, before the week is out.

As to the manual, a complete 3478A manual can be downloaded for free from

click on the icon for test and equiptment publications, accept their "terms" (believe me, you have a right to be there!), and enter a title search on "3478A" (caps are important!) And there it will be.

It appears to be the standard HP manual.

HP sold a hpib controlled relay actuator, HP59306A. It usually goes for spit on ebay. It is simple to program, and makes these kind of chores easy.

-Chuck

The rotary steppers sometimes show up in ham electronic flea markets; otherwise snoop in electronic surplus stores.

My browser sez "

could not be found". What's up?

It's the usual thing, I thought I remembered the address, and didn't double check. The actual address is:

Your browser must have 128bit encription, or better, or they won't let you play.

-Chuck

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The final bid was $143.50 so it looks like the bidders trusted the seller. Somewhat. Some 3478As go for over $200.

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That didn't work, so I added

I got time out error on that, tho. I tried again just now, and again got a timeout error. Looks like they're blocking me, and I'll never be able to access that website.

Looks like I'm stuck with buying one. I've seen some on CD-R, for cheap. I wonder how good or bad the image quality is.

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I found a few on Ebay for anywhere from $15 to almost $200. I checked out a pic of one, and it looks like it is connected to the outside world with a GPIB or HPIB cable. I don't have one of those and from what I've seen they cost major money new, and they're uncommon in the used or surplus world.

I suppose that the thing can be actuated manually. But then I've already got the rotary switch that I mickey moused, which works to a certain point. And I feel real confident about its simplicty and operation.

Thanks for the info.

That works! Thanks.

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Thanks. I finally got on, and d/l'd the .PDF, almost 2.5 megs. I saw that it has some gotchas. Like it has a CMOS mem backup battery, which can go bad or leak. I haven't had a chance to look at the parts list but hopefully it's a lithium, which don't seem to get thegrunge like some old batteries. Back in the late '80s we upgraded over 300 ATs with

386 MoBos, and I used to pull off the Varta mem backup batteries that were on the old 286 MoBos and I put 'em in a cardboard box in a cupboard. Later, the whole bottom of the box turned brown from the leakage and I had to almost treat them as toxic waste.

The 3478A that I bid on looke a bit beat up in the pic. I'm hoping that the thing's in working order. I haven't yet heard from the company, which is supposed to contact me in two business days. I'll have to contct them tomorrows.

I suppose, that this being a binaries group, I could post the manual for you.

I presumed that, if you were planning on using your new 3478A as part of the automation rig, you would be using HPIB.

I designed an HPIB controlled relay driver as part of the gear I automated for my thesis. It uses a few TTL chips. I can post that if you'd like.

Yes, but that is hardly what I would call automation.

-Chuck

It looked to me like it had one nick on the bezel, but the rest was sticker grunge. Sticker grunge comes off nicely with lighter fluid (VM&P Naptha). Mine cleaned up and looks like new... There were 6 or 7 stickers on it.

The battery is a very long life nonrechargable lithium. I think it will be just fine.

If you paid Tucker by paypal or bidpay, you will probably find the instrument is at your door. I received no contact from them, and after 3 days I got curious, and emailed them. I got the package, and then I got the reply.

-Chuck

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I finally got it d/l'd and posted a followup. The d/l is a standard Army Technical Manual. No problemo, it does have the schems and PCB layout in the back.

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No automation rig, just the 3478A and something else to switch the probe leads.

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like.

I found a "Kelvin Clips" 4-wire probes on Ebay, it's more than what I paid for the 3478A! Eighty-five bucks! And that's the cheaper one!

My guess is that a couple GPIB cables will go for over a hundred total, so I really don't see that I'm gonna save a lot by making my own GPIB stuff. I would just as well buy a used setup if I wanted to do that much automation. I think for now the rotary switch is as far as I need to go.

I'm not really looking for automation, I'm looking for not having to hold the probes at a half dozen test points and change them around a half dozen times when I make an adjustment with a pot ot two, for esample. I think some people probably just buy a half dozen ten dollar DMMs and connect them up to the various test points. But they aren't all that accurate ($10 DMMs have an AC range that's 200VAC, no lower), and the batteries run down after several hours. I'd rather use a bench DMM that I can leave on for awhile until the circuit reaches thermal equilibrium, for example.

I have a couple wiggle stick D'arsonval meters that I use for current measurements, and they work okay, and take no power. But one, for example, has a full-scale reading of 15 mA, but it has an internal resistance of 8 ohms. And that resistance in series with the supply can distort the performance of the circuit. So I would rather put a 0.1 ohm resistor in series with the supply lead, and then use a sensitive DVM to get the current thru it. I suppose that I could put an opamp with a couple precision resistors across the current resistor to give it a gain of 10 or 100. That way, I could use a cheap DVM to do the measurement. But I would need 2 or 3 or 4 of these to measure the current at various points, so it looks like the whole measurement jig starts to get too complicated. And then there's the problem with isolating the measuring circuits from the circuit being measured.

One example that I've run into is when I measure the current draw of a circuit. I break the + lead and insert the DMM, and get 90mA. But when I reconnect the circuit without the DMM, it's drawing more current, like

100mA, and putting out more power. The DC resistance of the DMM is disturbing the circuit. So I would rather leave a low value current sensing resistor in the + supply lead permanently so the readings don't change with every measurement change.

Thanks for putting up with my ramblings. But these are real world problems for which I'm trying to find solutions.

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Well, the auction said that if the buyer is in Tx or Calif or ?? that they had to wait to be contacted within two business days for the final cost, apparently because of sales tax. So I still haven't heard from them as of this afternoon, so I guess I'll have to rattle their cage with an email.

What's odd is that the prices are so variable. I see one go for a hundred, another for two hundred, another for one fifty, etc. etc. I'm wondering if the buyers know something that I don't. Like with the Tek

2235(?) scopes there is one custom chip that often dies, and it's no longer available, so the only way is to cannibalize to get one. Or if you're wise, don't buy the scope to begin with. Or if you bought it, then sell it for parts. I'm concerned that I might have bought a turkey and I'll never know it.

Just pay them using paypal. Include the CA sales tax, if you want. Your calculator works as well as theirs. Note, you probably don't need to tax your shipping cost.

2465

there is one custom chip that often dies, and it's no

The 2465 is my hands down all time favorite o'scope. The problem with the horizontal chip that blows is they let it dissipate just a tiny bit too much power for its lack of a heatsink. If the scope gets hot, usually because it is choked up with hair and dust, the chip dies. The easy answer is if you get a good one, add a heatsink to that chip. I did a simple thermal study of my 2465, and found that that one chip runs 10F hotter than all the rest. After the heatsink, it runs cooler.

Or if

Consider this, most people are so ignorant about how to use computers that when they finally figure out how to use a service like ebay, they still are clueless about how to use the search function. So, what they do is haunt the catagory that has their kind of stuff, and look through the listings that come in every day. I am quite sure that some of these guys that are bidding up one 3478A don't even know that there are others up for auction.

-Chuck

It is a problem when trying to measure current with a dvm. The more sensitive the scale the more resistance the meter has. It can throw things way off as you have noted.

I don't know how accurate you are trying to measure but also be aware that the kind of material in your connections will make a difference too. For example if you use steel alligator clips to a copper connection it can generate a small galvanic voltage at the junction. That will distort your reading. I ran into that when trying to calibrate some meters. My readings were different every time I hooked things up. Finally figured out it was the connections. Changed them and things were then stable.

Be careful of the switch that you are using to switch the meter from circuit to circuit with. Any poor contacts can have a big effect on accuracy too.

Regards Gary K4FMX

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The guy who sells those Kelvin Clips on Ebay for $85 says they're gold plated contacts. I think I will make up a mickey mouse pair out of a pair of clothespins. I used them for a button cell holder. I drilled a hole thru the jaws and put two #2 screws in the holes. I filed the heads somewhat flat to make good contact. I can use brass screws to minimize the galvanic action. Or I could put a length of heavy copper wire thru a pair of holes and really minimize it. I gather that it's not a good idea to use solder because it's also a bimetallic junction. I have some flexible 5-wire cable that should make a good test lead.

I had to squirt contact cleaner in the switches of the 30+ yr old PSes that I got. But I'm not really worried about accuracy. I just want to get something together that'll allow me to monitor a few points for V and I and allow me to calculate power in, power out and efficiency.

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I just wanna let people know what's going on with these seemingly clueless people at teoutlet (Tucker).

I won the bid on the 3478A, and as the instructions in the bid said, I waited for two days for them to contact me. Well, I didn't hear from them, so on the third day I did "ask seller a for the total price" and they replied back that it was $75 plus $16 shipping, total $91. So I paypaled them $91.

Then I get back this message that they have a sales presence in Calif so they have to charge me 7.75% tax. So please send them $7.05. Well, DUH! They said exactly that in the auction, and that's why I waited for them to contact me with the total price. And when I asked them for the total price they told me $91 total, no tax. So why didn't they say so then, instead of after I paypaled them? Duh.

But then I figured out that they were charging me $7.05 tax on both the item and shipping. So I replied to them that the shipping wasn't taxable and that I would paypal them 7.75% of the $75, or $5.81 if that was acceptable. So I expect to get a reply back tomorrow with the correct amount. But then one never knows since they have been nearly clueless up to this point. :-?

Sheesh! I have done over 2000 eBay transactions and have met many clueless eBay sellers. But what you describe above hardly fits the definition of clueless, as I have come to know it. In point of fact, Tucker is one of the better eBay sellers.

--
 Thanks,
    - Win

I'll have to agree with that. The last transaction I did, the ol' HP721 (like the one you bid on and won) came with a bad main filter cap (it's probably 40 yrs old). It took me three emails just to get the seller (obviously trying to avoid responsibility) to reply back, and more than a half dozen to resolve it (I got a partial refund).

And then there are the outright liars that I've had to deal with. The Consumer Sentinel

says auction fraud is their largest complaint category, with 1/6 of all complaints. nt%20categories.pdf Indeed, I've had to deal with several bad sellers, and I've only done a few score transctions. Sad, really.

I've read that you should run, don't walk, away from a seller that has a feedback rating of below 98%. But I've found that reading the bad feedbacks gives an insight into the mindset and attitude, bad or good, of the seller.

One burning question is, what do I do if Tucker insists that I pay taxes on the shipping? Do I pay it and file a complaint with ebay? Or not pay it, and hold up the tranaction? Ooh, today is Friday the Thirteenth. Ominous. I hope it's not going to be that bad...

First off, I don't think they will. If you don't get satisfaction with a simple email, call them. They are good folk. I don't like the quality of their repair work, but they go out of their way to please.

In the event that they are having a bad day, and they insist on taxing the shipping, pay it. We are only talking about $0.30. They have done a hell of a lot for your $95. You are getting a tested instrument, a foamed-in-place box, and a copy of the operators manual. Look at what the others are giving you for 50% to 150% more.

Tucker is a very respected, well known entity; that is why I made a point of aiming you at that auction. It worked just the way I hoped it would.

Smile, be happy.

-Chuck