Are these real 1N4007? - Page 1
Forum section: electronics / projects

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: December 06, 2020, 02:12:39 am
content: The diode with the longer thicker leads is a vintage 1N4004 from my crap.The one with the shorter thinner leads in a 1N4007 from some random eBay seller.Both diodes test as diodes, 0.55V forward, open in reverse with a DMM.Those thin leads look more like cheap resistor leads. Are there legit 1N4007s built with such skinny legs? Surely there can't be any money in making counterfeit 1N400X diodes ??

author: bob91343
author_rank: Super Contributor
timestamp: December 06, 2020, 02:26:36 am
content: Take a sample of the questionable diodes and measure the leakage at the specified voltage, either 1000 V or somewhat higher, depending on the details in the EIA specification. If they pass, you have good diodes.I can think of no better way to verify the quality of what you have.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: December 06, 2020, 02:39:04 am
content: Yes, I'll have to try that next, only with 100V to start. But these skinny leads might also be legit cost reduction. I've seen new TO-220 packages from legit sources with a very thin metal tab, compared to the almost 1mm thick of my vintage parts.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 06, 2020, 02:45:44 am
content: To me the printing is ugly and not defined on your "thin" leads diode, i never saw any "bad" printing as this, i use in4004 and the leads are "thick"

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: December 06, 2020, 03:03:13 am
content: Yeah, the printing is thicker than the leads on the 1N4007. It might be a 1N4148 with an epoxy fake body molded over it...

author: Teledog
author_rank: Regular Contributor
timestamp: December 06, 2020, 03:31:03 am
content: Careful!Picked up some "supposedly" 10 amp diodes at an electronics surplus place in Toronto years ago.They certainly looked beefy, but..no,..all were junk..shorts &/or no rectification whatsoever!Also,.. ordered "supposedly" germanium diodes from china..not!!!Unless you're ordering from Digi-key ...Test them all!(even at that, have had a few parts packaged/mislabeled..really!)

author: trobbins
author_rank: Frequent Contributor
timestamp: December 06, 2020, 03:37:06 am
content: The die may pass all vintage 'datasheet' specs, except the package may not exactly align with the thermal ratings (due to the change in conduction by the leads). As suggested, use an insulation resistance megohmmeter at 1kVdc to confirm no measurable leakage from PIV. So I'd suggest they are legit, but like any design, you need to relate the spreadsheet average curremt rating to the applications current waveform and then die temperature, which is not trivial for many rectifier applications.UF4007 from ebay certainly have the slightly reduced lead diameter.

author: 0culus
author_rank: Super Contributor
timestamp: December 06, 2020, 03:52:40 am
content: Quote from: Teledog on December 06, 2020, 03:31:03 amNobody makes germanium diodes anymore (as far as I'm aware), so any you see for sale "new" are usually Schottky diodes.

author: rsjsouza
author_rank: Super Contributor
timestamp: December 06, 2020, 03:58:20 am
content: Quote from: 0culus on December 06, 2020, 03:52:40 amNTE Does (NTE109, NTE110A, NTE110MP, etc.)https://www.nteinc.com/diodes/general-purpose.php

author: bob91343
author_rank: Super Contributor
timestamp: December 06, 2020, 04:20:52 am
content: I was gifted with a box of resistors and diodes mostly. All look good and clean. A bunch of 220 Ohm resistors all measured way out of tolerance. Included were perhaps 50,000 diodes, 1N4148 which can serve as rectifiers in many places.Years ago I built a replica of a decimal counting unit to plug into an old counter. It used 10 tubes and many other parts. When finished, it didn't work. I was gobsmacked at the thought of troubleshooting it but bit the bullet and started testing. I found one diode marked backwards. Replaced it and the unit worked, nothing short of a miracle. I was torn between reversing the diode and replacing it and decided replacement made sense to simplify future troubleshooting.So don't assume if things look a bit odd that someone is trying to cheat you. The world is filled with surprises, many of which almost refute logic and common sense.

author: Pawelr98
author_rank: Regular Contributor
timestamp: December 06, 2020, 05:01:32 am
content: I have had some 4007 or similar diodes go short circuit in circuits where the backwards voltage was around 800-850V or so, still under 1000V.They could in fact work for several days before shorting.So try and apply a reverse voltage close to 1kV and let the diode sit there for several hours.

author: 0culus
author_rank: Super Contributor
timestamp: December 06, 2020, 06:01:57 am
content: Quote from: rsjsouza on December 06, 2020, 03:58:20 amHah, TIL. Nice.

author: amyk
author_rank: Super Contributor
timestamp: December 06, 2020, 06:11:55 am
content: At the scale these things are made, I suspect the reduction in packaging and lead diameter made a significant reduction in cost.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 06, 2020, 09:25:34 am
content: That might well be out of spec. At least, one or the other, the wire diameters don' t look like they can both be in tolerance:https://en.wikipedia.org/wiki/DO-204DO-41 specifically (DO-204AL).The leads dissipate a significant amount of heat; I'd be worried the thin one can't handle rated current at max ambient. Easy enough to check, with a power supply and ballast resistor.Tim

author: Tom45
author_rank: Frequent Contributor
timestamp: December 06, 2020, 12:14:53 pm
content: Regarding testing the diodes with 1 KV. These days I wonder how many of us have a power supply that can output 1 KV.

author: trobbins
author_rank: Frequent Contributor
timestamp: December 06, 2020, 12:59:01 pm
content: Need to use a 'megger', or alternately known as an insulation resistance tester. Some countries require that type of test on any mains ac circuitry as part of verification of installation, so the meters are quite common (but the meters are not common in countries that don't require much in the way of testing, such as USA). The modern testers typically have 250, 500 and 1kV DC levels and are current limited, and will confirm diode has reverse leakage below at least 0.5uA for a 2Gigohm max reading (vintage datasheet nominal level is 0.3uA at 1kV at 25C).

author: exe
author_rank: Unknown
timestamp: December 06, 2020, 04:04:08 pm
content: These diodes are produced by so many manufacturer (and I suspect many of them just rebranded), so just by appearance it's hard to judge. I suggest just buy parts from a reputable distributor and don't bother with guesswork and testing. Although, I like testing components, it's fun by itself, but sometimes gets boring when I want things to "just work".

author: Pawelr98
author_rank: Regular Contributor
timestamp: December 06, 2020, 11:29:29 pm
content: Quote from: Tom45 on December 06, 2020, 12:14:53 pmA lot of folks have it in their homes without even realizing it.European folks can just use a doubler from 380-400V 3 phase mains which are very common.US folks can get away with a tripler from 240V mains.From there just make a voltage divider using resistors or use series zener diodes to adjust to 1kV.You can build that in several minutes.

author: 0culus
author_rank: Super Contributor
timestamp: December 07, 2020, 01:46:56 am
content: Quote from: Pawelr98 on December 06, 2020, 11:29:29 pmI hope you have some kind of current limit on that, like at least a fuse that won't let you dump 15 or 20 amps (or more) through a short.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 07, 2020, 06:40:03 am
content: Well, an isolation transformer might be highest priority!Half-wave type multipliers are AC coupled, i.e., mains flows through a capacitor, so the value of that capacitor limits the peak current even under short-circuit conditions. Using say 10nF caps limits it to a few mA.You need a series resistor anyway to limit avalanche current, in case it breaks down at a lower voltage; some megs is a good idea at least as a starting point.You probably also need a specialized meter, or a dropping resistor for a more conventional one: most don't read over 1000V, or are rated to tolerate such. A 10M DMM (or VTVM if you're old school) with a 90M 1% resistor in series will give a 10x reading easily enough.Tim

author: Kleinstein
author_rank: Super Contributor
timestamp: December 07, 2020, 08:45:58 am
content: The thinner leads may be just cost reductions. However much of the heat has to go through the leads. So I would not use the thin lead version for higher currents, like > 500 mA.There is a chance they are fake ( someone here even reported fake 0 ohms resistors - so there is nothing to cheap to get faked). If fake, it could be lower maximum voltage, more series resistance (so compare at some 500 mA with good cooling) and also more leakage. The original 1N4007 are usually quite slow, which helps to get low leakage. One could do a quick reverse recovery check (scope and a +-2.5 V with 50 Ohms impedance rectangular signal): 1n400x are more like 1-10 µs, most small diodes like 1N4148 are < 50 ns.

author: CJay
author_rank: Super Contributor
timestamp: December 07, 2020, 09:28:09 am
content: I dunno, I've seen weird off brand 1N400x diodes with thin legs like that, question is, would you want to take a chance on them or is it better to just dump them and buy something from a reliable distie?Especially as they're mains rated.

author: Haenk
author_rank: Super Contributor
timestamp: December 07, 2020, 10:39:06 am
content: Quote from: Pawelr98 on December 06, 2020, 11:29:29 pmErm, at least by german standards (and probably EU standard by now), 3-phase stuff requires handling by a certified electrician. For a reason.However a used DIN tester is rather cheap on ebay, and even if out of certification, it will still give you 1kV without the need to tinker around and try to blast yourself directly to Heaven's Gate.

author: cdev
author_rank: Super Contributor
timestamp: December 09, 2020, 01:34:05 am
content: I bought a bunch recently to experiment on as they can sometimes sub for PIN diodes in circuits. I was thinking they could be used as RF switches, in things like preselectors and similar, Maybe there would be a way to exploit that property, if present, to evaluate the likelihood of them being bogus without needing the high voltage?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 09, 2020, 09:47:25 am
content: Well, for PIN purposes, you can test them to only whatever voltage you need, and can measure reverse recovery easily enough, and capacitance.Tim

author: David Hess
author_rank: Super Contributor
timestamp: December 09, 2020, 05:27:20 pm
content: Quote from: Alex Eisenhut on December 06, 2020, 03:03:13 amPower rectifiers use copper leads for their heat sinking, and cheap parts might use thinner leads.Glass packaged signal diodes like the 1N4148 use Kovar to support the glass to metal seal, so it should be easy to detect if they were repackaged by checking to see if the leads are magnetic.

author: magic
author_rank: Super Contributor
timestamp: December 10, 2020, 09:08:27 pm
content: It is probably cheaper to produce or buy bare 1N4148 dice and package them as whatever you want. I tore down a bunch of ultra cheap shady opamps and that's exactly how they were made - size-reduced clones of common parts like LM358 and RC4558, cleanly packaged with no signs of tampering and pristine false markings on the outside.I still have a few of them, one day I may power them up and see if they meet the maximum output current and power dissipation ratings. That could be funQuote from: exe on December 06, 2020, 04:04:08 pmQuote from: Haenk on December 07, 2020, 10:39:06 amUnenforceable regulation is unenforceable. But I wouldn't build such a thing connected to live mains

author: trobbins
author_rank: Frequent Contributor
timestamp: December 11, 2020, 12:56:01 am
content: The OP hasn't said he is using the diodes for mains side rectification.

author: Vovk_Z
author_rank: Super Contributor
timestamp: December 11, 2020, 04:17:14 am
content: Quote from: Pawelr98 on December 06, 2020, 11:29:29 pmThat is not a way to do it.It has to be safe first, so this voltage source definitely has to be isolated from the mains. So it needs something like a low-power rated transformer (like for tubes).(And a current limiter of cause. With a limit somewhere between 1...10 mA to it was really safe).

author: dcac
author_rank: Frequent Contributor
timestamp: December 11, 2020, 07:55:20 am
content: There seems to be an /L type but I've actually never heard of this before or probably even seen one - but it has thinner leads.

author: CJay
author_rank: Super Contributor
timestamp: December 11, 2020, 12:10:50 pm
content: Quote from: trobbins on December 11, 2020, 12:56:01 amNope, he hasn't, I'd still bin them and buy from a reputable source if I were uncertain about them, who knows what other parameter might be screwed up or not met.

author: Pawelr98
author_rank: Regular Contributor
timestamp: December 13, 2020, 12:46:26 am
content: Quote from: Haenk on December 07, 2020, 10:39:06 amWell, single phase 230V can, just like US 240V be rectified using a tripler and it will still end up at around 1kV, which is good enough.And for one, I don't think anything will blow into your face, it's just a few basic components, how much would you have to screw up ?3 diodes, 3 capacitors, nothing more than that is required to achieve 1kV out of commonly available mains.Worst case scenario install a 100mA fuse or a 20W light bulb in series and nothing will go wrong there, even if someone does manage to screw up such a basic circuit.Oh, and maybe 10Mohm parallel resistors for extra protection, just to discharge the stuff.In fact, a lot of common mains bug zappers use such triplers.They are everywhere, manufactured using questionable chinese standards (and components), yet many work for years.Isolation is another matter.When powering a circuit directly from mains I just adhere to a simple rule.An extension cord and power up the circuit while standing 1 meter (~3.3 feet) away, the current/voltage at the multimeter remains clearly visible.Or just use back-to-back transformers. It's not like much power is required for such testing, few VA is perfectly fine. Older mains adapters are a good source of such transformers.In the end I would even say that getting right up to 1kV is pointless anyway, 900-ish V is sufficient, if the diode is not having a breakdown for several dozen hours then I would call it good enough.The long, continued test is why I propose mains supply.It can go on for hours or days if needed, keeping sustained voltage at the diode leads.I have had 400V diodes that could survive something like an hour of 800Vdc testing, so just zapping such a diode with an isolation tester may not be enough.

author: trobbins
author_rank: Frequent Contributor
timestamp: December 13, 2020, 02:53:44 am
content: Thanks dcac for the /L infoI will see if I can identify any /L datasheet ratings that show a difference to the older datasheets that show thermal resistance to ambient and lead length, as a higher thermal resistance would mean some additional derating risk when used in equipment like valve amps.There have been a few references of PIV testing of 1N4007, and 'lower rated' parts like 1N4004, and as a general comment leakage has only started to rise above about 1.2kV, as would be expected of a mature product. It is highly likely that 1N4004 will be the same as 1N4007, as it costs more to grade them than just to confirm PIV > 1kV.Imho one would have to be pretty deficient in test equipment to have to resort to a direct mains rectified test supply to get to 1kV, and the key outcome is to actually measure that leakage current remains below a set level at rated PIV, rather than confirm the part fails.

author: David Hess
author_rank: Super Contributor
timestamp: December 13, 2020, 03:27:10 am
content: Quote from: trobbins on December 13, 2020, 02:53:44 amHigher voltage diodes usually use PIN (p-type, intrinsic, n-type) construction. So for instance the NTE datasheet reveals a difference in junction capacitance between the 1N4001 through 1N4004 and 1N4005 through 1N4007 which indicates a difference in construction:https://www.nteinc.com/specs/original/1N4001_07.pdf

author: KRISTOFFER
author_rank: Contributor
timestamp: December 13, 2020, 08:39:08 pm
content: The Volts x Amps rating is 0.6 x 1 = 0.6 Watts. There does not appear to be any need for thick leads or body to dissipate heat. I think it is more costly to manufacture fakes than the real thing with 1N series diodes for sale on ebay. A lot of stuff is classed as 'generic' and can be manufactured by a lot of electronics companies in the far east for little cost. Some obsolete devices are now being cloned and work perfectly well which is a blessing. Unfortunately some do not. The last batch of TL071 op amps I got from ebay had no offset trim function. Similarly I got two 'genuine' XR2206 function generator chips from a well known shop in Cricklewood for quite a high price. Both were fakes from ebay. Trial and error all the time unfortunately.

author: CJay
author_rank: Super Contributor
timestamp: December 13, 2020, 09:10:25 pm
content: Quote from: KRISTOFFER on December 13, 2020, 08:39:08 pmAh yeah, that famous Electronics shop in Cricklewood. Name escapes me right now

author: David Hess
author_rank: Super Contributor
timestamp: December 14, 2020, 12:10:17 am
content: Quote from: KRISTOFFER on December 13, 2020, 08:39:08 pmPower rectifiers have to operate under realistic conditions which includes elevated ambient temperature as part of an assembly, so the DO-41 case is rated to dissipate 0.6 watts at 75C which is considerably different than 0.6 watts at 25C. And if you extend the lead length, the current rating is lower.QuoteCopper leads are a lot more expensive than Kovar leads. The DO-35 package is specified for 500 milliwatts at 25C as measured at the lead adjacent to the case and that results in the 150 milliamp current rating of a 1N4148. A copper leaded 1N4148 would have a higher current rating only because of the better thermal conductivity of copper.

author: trobbins
author_rank: Frequent Contributor
timestamp: December 14, 2020, 05:23:37 am
content: The A-405 case style has thinner diameter leads, and is identified by a /L appendix to the part number. For all the datasheets I have come across, whether it be the 1N400x series, or other similar types, there are no datasheet rating differences for any performance parameters for diodes of either the A-405 or DO-41 case style. That's not to say that the A-405 package style with the thinner leads is a worse device, just that the design ratings presented by the various manufacturers are the same.Kristoffer, the thermal design of the basic 1N4007 can get quite detailed even when used in generic mains type power supplies. Many people just assume the part can be used in a power supply that provides up to 1Adc, but that is way to simplistic a view, and the actual situation can be more towards the diode coping only with up to 0.3-0.4A(av) through it - due to the peakiness of the current pulses, and thermal derating to keep the die temperature adequately low.