Thanks, John! Do you know if carbon comp resistors do this? I will know more in an hour as I have some semi-exotic resistors being delivered today. The original resistor came from Amazon so who knows what their characteristics are!
Doug Smith Sent from my iPhone IPhone: 408-858-4528 Office: 702-570-6108 Email: [email protected] Website: http://dsmith.org ________________________________ From: John Woodgate <[email protected]> Sent: Wednesday, April 30, 2025 09:05 To: [email protected] <[email protected]> Subject: Re: [PSES] [SI-LIST] Re: Interesting resistor response Those 1% resistors are probably thick film, where the element is micro-granular, and what you are seeing is discharges at the grain boundaries. On 2025-04-30 05:37, doug emcesd.com wrote: Thanks, Andrew! I have some rather expensive resistors coming in tomorrow, picture attached. On 10k 2W resistors I have only 1% laser trimmed and carbon comp resistors and don't trust either with high voltage pulses. The trimmed 1% resistors came from Amazon so who knows what they are. Doug Smith Sent from my iPhone IPhone: 408-858-4528 Office: 702-570-6108 Email: [email protected]<mailto:[email protected]> Website: http://dsmith.org<https://urldefense.proofpoint.com/v2/url?u=http-3A__dsmith.org&d=DwMDaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=2hl-B8d09gOYsuXCAwwFfA4xrCLCHgsIKt4faibIExuGP0jB0nDj5WdUN2qO6zw-&s=AxwQDTakM29eHOE1PJkYydT2g35EtXlbOl8-qLzPP70&e=> ________________________________ From: Andrew Zonenberg <[email protected]><mailto:[email protected]> Sent: Tuesday, April 29, 2025 15:58 To: doug emcesd.com <[email protected]><mailto:[email protected]>; [email protected]<mailto:[email protected]> <[email protected]><mailto:[email protected]>; [email protected]<mailto:[email protected]> <[email protected]><mailto:[email protected]> Subject: Re: [SI-LIST] Re: Interesting resistor response Do you have an exact resistor make/model number that exhibited this effect? It might be interesting to polish off the overcoat and look at the actual thin/thick film pattern under a microscope. I have all of the lab equipment to do this and would love to give it a try if I know which resistor to test. On 4/29/25 15:19, doug https://urldefense.proofpoint.com/v2/url?u=http-3A__emcesd.com&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=LL7H7KPHw8RVjM46XsiH9JOYKkJ9R7Pzr2YvvMon1ackmnLqEa-y6deNTRho587T&s=KBRFnCAF7dQ_xUsTp7oxlcdMgVFblUfDquoaZJ2q38c&e= wrote: > Hi All, > > One correction to my message below. The pulse width was 70 ns into a short > but several microseconds into a high impedance. During the first few > microseconds the breakdown effect was observed in the 10 K resistor. > > Resistors acting poorly to high amplitude pulses is not new. The 470 K Ohm > resistors that are used in ESD testing of equipment to drain charge from the > horizontal coupling plane often fail if the right resistors are not used, and > they are often not. 1% laser trimmed resistors are to be avoided in ESD > testing. > > In this case, the lengthened pulse to micorseconds and the inductance of my > leads (significant) caused a relaxation oscillator of sorts to be formed with > arcing over the laser cut in the resistor leading do lots of discharges > across the cut. > > Takeaway summary: Do not use 1% laser trimmed resistors in high pulse > amplitude applications unless the resistor is rated for it, few resistors > are, or you will get a lot of interesting noise from the resistors in your > system. > > At some point I will post another of my Technical Tidbit articles including > more details, circuit drawings, and scope plots. That link will likely not be > allowed over on the IEEE EMC-PSTC list as links to sites with any commercial > content are prohibited these days and I have a tiny portion (probably 0.1% of > the byte content of the site) of my site containing seminar information. > > I posted the original message on April 28th. It has not yet showed up on the > IEEE-PSTC list server. The admin there is deciding if my technical content is > acceptable. Currently he is not allowing links to my 300 technical articles > and papers written over the last 30 years. > > Doug Smith > IPhone: 408-858-4528 > Office: 702-570-6108 > Email: [email protected]<mailto:[email protected]> > Website: > https://urldefense.proofpoint.com/v2/url?u=https-3A__emcesd.com&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=LL7H7KPHw8RVjM46XsiH9JOYKkJ9R7Pzr2YvvMon1ackmnLqEa-y6deNTRho587T&s=yEuDE0E7MbQ_c7IAMNaUAiuHnctRuo-xvAVgL4BNyhc&e= > > -----Original Message----- > From: [email protected]<mailto:[email protected]> > <[email protected]><mailto:[email protected]> On Behalf > Of doug > https://urldefense.proofpoint.com/v2/url?u=http-3A__emcesd.com&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=LL7H7KPHw8RVjM46XsiH9JOYKkJ9R7Pzr2YvvMon1ackmnLqEa-y6deNTRho587T&s=KBRFnCAF7dQ_xUsTp7oxlcdMgVFblUfDquoaZJ2q38c&e= > Sent: Monday, April 28, 2025 21:11 > To: [email protected]<mailto:[email protected]>; > [email protected]<mailto:[email protected]> > Subject: [SI-LIST] Interesting resistor response > > Hi All. You may know I have been doing research on switching power supply > response to EFT like pulses. In the process of building a low cost pulser to > use instead of an ESD simulator or EFT generator, I accidentally found an > interesting characteristic of some resistors. > I can apply a 1500 Volt by 70 ns long pulse (exponential decay) to a 10k Ohm > 2 Watt 1% resistor and watch it breakdown many times internally (using a > current probe) at a rate of 2 to 20 MHz!!! The resistor and its leads > radiated some strong fields during the discharges. I changed over to a 5% > carbon composition resistor (been in my tool box for about 65 years now and > is likely 80ish years old) and no longer see the effect. Problem is carbon > comp resistors are not linear with voltage so I will look around for a better > resistor. > > Some resistors, like the one above, should not be used on the mains side of a > power supply where it may generate a lot of noise in response to EFT coming > down the power line. And one see anything like this in the literature? > > Doug Smith > Sent from my iPhone > IPhone: 408-858-4528 > Office: 702-570-6108 > Email: [email protected]<mailto:[email protected]> > Website: > https://urldefense.proofpoint.com/v2/url?u=https-3A__emcesd.com&d=DwIDAQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=AuHHvCC49gbCVxyUUn7R_xxeE1fVhA5NpFnWNe_HTXlnmWxWP1IaRT6c2FmUEbSD&s=SIvG35ui7qDLbTfpfcHDH_-QRwn8ljwLGRP64-jm0mo&e= > > ------------------------------------------------------------------ > To unsubscribe from si-list: > [email protected]<mailto:[email protected]> with > 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > https://urldefense.proofpoint.com/v2/url?u=http-3A__www.freelists.org_webpage_si-2Dlist&d=DwIDAQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=AuHHvCC49gbCVxyUUn7R_xxeE1fVhA5NpFnWNe_HTXlnmWxWP1IaRT6c2FmUEbSD&s=05mwNPVcaMbxl3Uf97nE2Z108yILUuIXrNzWexEBz3U&e= > > For help: > [email protected]<mailto:[email protected]> with > 'help' in the Subject field > > > List forum is accessible at: > > https://urldefense.proofpoint.com/v2/url?u=http-3A__tech.groups.yahoo.com_group_si-2Dlist&d=DwIDAQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=AuHHvCC49gbCVxyUUn7R_xxeE1fVhA5NpFnWNe_HTXlnmWxWP1IaRT6c2FmUEbSD&s=u8xstrGRGz566MUDyYtGbVysdi3nHK9s2mVnG_aTI4A&e= > > List archives are viewable at: > > https://urldefense.proofpoint.com/v2/url?u=http-3A__www.freelists.org_archives_si-2Dlist&d=DwIDAQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=AuHHvCC49gbCVxyUUn7R_xxeE1fVhA5NpFnWNe_HTXlnmWxWP1IaRT6c2FmUEbSD&s=HR5xGgkvX4JB9EQEYEzbl_1peI9iPvR4OH9UDHqSlWE&e= > > Old (prior to June 6, 2001) list archives are viewable at: > > https://urldefense.proofpoint.com/v2/url?u=http-3A__www.qsl.net_wb6tpu&d=DwIDAQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=AuHHvCC49gbCVxyUUn7R_xxeE1fVhA5NpFnWNe_HTXlnmWxWP1IaRT6c2FmUEbSD&s=6vkgY11CFf5OIMg5sy8FALn77NiaXFzD57XtpypKvlI&e= > > > ------------------------------------------------------------------ > To unsubscribe from si-list: > [email protected]<mailto:[email protected]> with > 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > https://urldefense.proofpoint.com/v2/url?u=http-3A__www.freelists.org_webpage_si-2Dlist&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=LL7H7KPHw8RVjM46XsiH9JOYKkJ9R7Pzr2YvvMon1ackmnLqEa-y6deNTRho587T&s=OOdjPeqPSdlT1an8m6pnqmHkrmxOzn4_eNb2DSdNFPY&e= > > For help: > [email protected]<mailto:[email protected]> with > 'help' in the Subject field > > > List forum is accessible at: > > https://urldefense.proofpoint.com/v2/url?u=http-3A__tech.groups.yahoo.com_group_si-2Dlist&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=LL7H7KPHw8RVjM46XsiH9JOYKkJ9R7Pzr2YvvMon1ackmnLqEa-y6deNTRho587T&s=7yU3bcNfbRAGL_dqFDBCqTYYHJMuPO2St8RupbFfEKs&e= > > List archives are viewable at: > > https://urldefense.proofpoint.com/v2/url?u=http-3A__www.freelists.org_archives_si-2Dlist&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=LL7H7KPHw8RVjM46XsiH9JOYKkJ9R7Pzr2YvvMon1ackmnLqEa-y6deNTRho587T&s=ujFXjD4npFmhBOPT7VeJJW3KpROpdZu_rM7dDJVbGow&e= > > Old (prior to June 6, 2001) list archives are viewable at: > > https://urldefense.proofpoint.com/v2/url?u=http-3A__www.qsl.net_wb6tpu&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=LL7H7KPHw8RVjM46XsiH9JOYKkJ9R7Pzr2YvvMon1ackmnLqEa-y6deNTRho587T&s=u37jK7B-XAJii1uvhWk2LQN7nLWSk9mDR_x0lTDk_8s&e= > > -- Andrew D. Zonenberg, Ph.D Antikernel Labs https://urldefense.proofpoint.com/v2/url?u=https-3A__www.antikernel.net_&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=LL7H7KPHw8RVjM46XsiH9JOYKkJ9R7Pzr2YvvMon1ackmnLqEa-y6deNTRho587T&s=I8JavfK84Dih5arIDCJlesOAA-EsXZWzgQtPWBSocC0&e= ________________________________ This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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