Is it just me or is the pricing at Digikey getting ridiculous?

I just call them and have them look. Yes, they are good. Our Avnet rep is pretty good too. We get excellent prices from both.

Not completely. We received a small number of samples of the new transformer but without manufacturing quantities we don't _know_ that it's solved. Only something like 5% were failing in reflow so it's pretty hard to test three samples for the problem. We have a very good manual test for the failure now and an in-circuit test that tests ten out of fifteen of them. When we get production quantities we can remove the manual test and will then rely on ICT to flag any regression. Completely solved, no. We have a very good handle on it and it's no longer impacting deliveries, so it's 95% of the way there.

If there is time you could cook two transformers. One from the old batch and one of the new samples. Ratchet up the oven temp and see which one is going at what temp. At least that'll tell you whetehr they really used wire with better coating.

The "new" transformer only has the high temp wire on 1/2 of the primary, since that's what is exposed. The transformers have a thermal time constant of something like 8.5 minutes and are only baked for 3 minutes (about 10 seconds at 250C, according to the profile). It's going to be real hard to balance time and temperature to measure insulation melting with any confidence.

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Then the only option would be to send them through the reflow oven "dry" several times, together. Ratchet up the temp profile by 10C at a time and see when the old one fails and when (or whether) the new one fails. Of course if you have the SMT assy contracted out that isn't really going to work.

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With only a normal 5% failure, I'm not sure that would tell us anything useful. We do our own assembly.

After taking a few of the failed transformers apart, as was suggested by someone here, I found that the failures were all on the bottom of the transformer (horizontal core). The ones with a small number of turns shorted (the ones with a nominal DCR) appeared to be shorted in the corners where the winding changed direction. Perhaps the windings/insulation was damaged (piled up when changing direction?) or perhaps that's the hottest area in reflow. With the higher temp wire (200C vs. 130C.) it should be better. The first production batch should tell us pretty quickly. IIRC, a few hundred are due in a couple of weeks and 1500 or so a couple of weeks after that.

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It would be useful. At some point the old xfmr will fail. Then if you keep ratcheting up the temp profile until the new one fails you'd know how much more the new xfmr can take. It would reduce the wait time and risk.

Sharp bends often compromise an insulation just by stretching so that would be the area to go first.

The samples are not usually the problem. Quality has a tendency to grow fainter with time in some cases.

Best regards, Spehro Pefhany

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Well John I have no desire to argue anymore. I have better things to do with my time as I'm sure you do.

I'll leave it at this you do what works for you; I'll do what works for me.

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True, which is why I wanted a good in-circuit test to alert us if something goes wrong down the line. In this case, it's either the wire is right or it's not. If they switched wire on a batch it could be ugly. Unfortunately, we can only catch 2/3s of the failures but at least that's a good sampling plan. ;-)

I have used Newark several times, and I have experienced (a goodly decade ago) what I suspect as getting better-than-catalog prices to those who actually do some decent amount of business with them.

On the other hand, when I ordered from Newark more than 1 product line of part, sometimes I ran into them having having these different parts stocked in different warehouses. That often resulted in 2 shipping charges for 1 order.

Which is not much of a problem to the few doing electronic circuit/product production in USA, and a minor extra cost to those doing product development work.

Hobbyists appear to me to be something that Digi-Key caters to somewhat, especially in the times of Rat Shack doing many things that repelled hobbyists.

I also seem-to-think that Digi-Key has a bit of liking to electronics repair types, as well as for product development types. For one thing, back in the 1980's and early 1990's when I bought and read a lot of electronic hobbyist magazines, I remember Digi-Key advertizing significantly.

Back to Rat Shack:

Can I say: Some of their stores have 4 "sets of drawers" of small parts, and some of their stores have only 2 "sets of drawers", not stocking roughly half the parts that are in the 4-sets-of-drawers.

And they have a store in the University City section of Philadelphia, a little less than a mile from Drexel U. and even closer to University of Pennsylvania, both of which have engineering schools that have electrical engineering departments, and the Rat Shack there has only the

- Don Klipstein ( snipped-for-privacy@misty.com)

Check "SHIP ORDERS COMPLETE" and that wont happen.That happened to me once before I realized about the "SHIP ORDERS COMPLETE" I called their free number and they took the charge off.

In fairness the wide price discrepancy on PIC's between Digikey and Newark isnt as wide as it used to be. I havent compared in a while but I just did and Digkey is maybe 20-30% higher versus the last time I checked in which they were typically 2 times the price for the same PIC's.

I'm in Canada we have no RAT SHACK it's now the source we have two in the city. We also have a college and two universities that have EET and EE programs ( one of the Universities) so you would think places like the source would stock decent components but they dont.

I went into the source asked for a PCB blank and the guy gave me a blank look. He didnt have a clue what I was talking about. I bought a decent soldering iron there I went back about a month later looking for a replacement tip and they didnt stock one and didnt know where to get them. They now carry replacement tips for their current soldering irons so sometimes complaining does work.;-)

IIRC, Digikey's pricing for PICs is quite competitive at 25+ quantity. Maybe not so much at 1pc or 1000+ pcs.

Eg. PIC18F13K22-I/P

Digikey US site: 1.99 USD Digikey CAD site: 2.25 CAD = 2.20 USD Mouser US site: 1.99 USD Mousr CAD site: 2.25 CAD = 2.20 USD Microchip 1.99 USD Newark 1.99 USD Avnet 2.19 USD

Well yes they have started to become more competitive; it depends for example two of the more popular PICs.

Newark 2.34 CT singles $2.21 100+ quantities

Digikey same PIC Canadian site

$3.17 CT

That's the typical spread I'm seeing on PIC's I use.

It has improved significantly since the last time I did a direct comparison there would typically be a 2x spread on CT, and a much wider spread in quantities. The same for transistors (BJT'S FET). When I was comparing FETS with Newark; Digikey's T/R price was the same as Newark's CT price. I don't know about you but I'm not buying T/R's (2500+) of transistors so that price is irrelevant to me. Why anyone would buy production quantities off a distributor still boggles my mind.

A single FET example. This is a good jellybean FET neither currently has stock but Newark will soon. When Newark originally got these they were less then a quarter CT now they are 0.35 cents but they couldn't keep enough of them in stock 2500 one day 200 the next etc..

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Ones that both have in stock

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They still have some work to do on Transistors, for me anyway.

Before Digikey fans jump on me I know that there are some cheaper ones at Digikey then Newark, but for me Newark is always cheaper.

Everything I need for electronics arrives by courir. I rarely go to electronic shops for parts because they seldom have parts I need. If a shop has all the parts you need, you're probably not building something special.