Re: [time-nuts] FE-5680A - Newbie capacitor question
Hi, Sorry, I had to jump in here. Ceramic capacitors are NOT less likely to suffer damage hand soldering. They are very susceptible to damage hand soldering. This is especially true if you are using the larger sizes (1206 and up). Placing the tip of a hot soldering iron against the end of ceramic capacitor causes very high localized heating and temperature gradients. This results high localized stress concentrations, which can result internal damage to the capacitor. The result is a shored capacitor immediately after soldering, or sometime later during operation. It's best to read up on the datasheet for the particular cap you are buying, but often times they state not to hand solder. I'd highly recommend using a hot air reflow station, even the cheap $40 chinese ones. If you can't use hot air, be sure to only touch the solder pad with the iron, and not the capacitor directly. Let the solder flow the heat to the capacitor through the pad. All the above said, the smaller sizes 0603 and 0402 don't seem to be particularly vulnerable to soldering irons. Higher voltage capacitors don't seem to be as vulnerable in the same size. And anything at or above 1206 seem to be much more sensitive. Also, minimize the solder between the cap and pad. Use the bare minimum necessary. Using a large 'blob' of solder or large fillet allows the board to transfer bending stresses to the cap, causing failure as well. I do agree, once they're on a board they're much more robust than the tants. But care needs to be taken getting them there. Just my very hard earned two cents! :) Dan On 5/2/2020 12:00 PM, time-nuts-requ...@lists.febo.com wrote: If it were me, and assuming it is at the input of a linear regulator, I would put a ceramic multilayer capacitor in its place. It will likely be much smaller (requiring a short jumper to match the solder pads of the larger tantalum) but a lot more reliable, and you are less likely to damage it by hand soldering. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] FE-5680A - Newbie capacitor question
On Sat, May 2, 2020 6:57 am, Didier Juges wrote: > Tantalum capacitors are known to occasionally short for no good reason. And traditional tantalum/manganese-dioxide devices can start a self-sustaining combustion as the manganese dioxide breaks down. I avoid solid tantalum caps because I have actually had some combust. > If it were me, and assuming it is at the input of a linear regulator, I > would put a ceramic multilayer capacitor in its place. If you cannot find a ceramic that fits (although you probably can these days) the tantalum polymer do not have the same problem of combustion that the pure tantalum capacitors do. If you look for ceramic, avoid Y5V, it has large decreases in capacitance with voltage and temperature. X5R or X7R are better, but double check the change in capacitance with voltage. You may also be able to find a surface mount polymer aluminum electrolytic that is close enough to the same size that you can get it soldered on. The polymer aluminum (should) have longer life than the traditional liquid electrolyte aluminum electrolytic caps. -- Chris Caudle ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] FE-5680A - Newbie capacitor question
Tantalum capacitors are known to occasionally short for no good reason. Give them a reason and they'll be happy to oblige. Things that can damage a tantalum cap in a hurry include excessive voltage, reverse polarity, overheating (likely with hand soldering) and current spikes. If it were me, and assuming it is at the input of a linear regulator, I would put a ceramic multilayer capacitor in its place. It will likely be much smaller (requiring a short jumper to match the solder pads of the larger tantalum) but a lot more reliable, and you are less likely to damage it by hand soldering. (some linear regulators are unstable with a large ceramic capacitor on the output without proper damping, but there is typically no issue at the input) Didier KO4BB On Sat, May 2, 2020 at 2:59 AM Matthias Welwarsky wrote: > On Freitag, 1. Mai 2020 23:42:46 CEST John Bievenour wrote: > > I'm an amateur electronics hobbyist who's still a newbie (especially to > > SMD), so please forgive the basic question. > > > > I recently acquired a FE-5680A that was failing to lock on frequency > (pin 3 > > never went low). It will power up, sweep up and down, and finally settle > to > > fluctuate around 9.999 to 10.000. > > > > When I opened the case, I found that one of the capacitors had blown, > which > > I believe might be the reason. Looking at the top of the board, with the > > DB9 on your left, the capacitor in question directly across from the > right > > hand 2941 voltage regulator. It has 105 on the first row, 35 followed by > a > > stylized K on the second row, and 333 on the last row. > > > > I'd like to attempt to replace the blown cap. After doing lots of > searching > > and reading, I'm pretty sure this is a Kemet 35 VDC 1uF SMD Tantalum > > Capacitor (never knew these existed until yesterday). I've narrowed down > > the options on Mouser, but I can't figure out: > > > > 1) is my identification correct? > > Sounds about right, going by the images I found. > > > 2) is it a T489, T491, T494, T495, T496, T498, or T499 (the band at the > top > > makes me think it's a T498, T491, T494, T495, T498, or a T499) ? 3) is > the > > tolerance 10% or 20% (I think it's 10%)? > > > 4) what is the ESR (I have options from 1 Ohm to 83 mOhms)? > > I don't think you need to worry about that too much. The capacitor is > probably > for filtering on the input of the regulator. For output filtering it's too > small. The datasheet for the LM2941 I found says at least 22µF is needed > for > stable operation and ESR between 100mOhm 1 Ohm. So, the output filter cap > must > be somewhere else. > > Just make sure the size matches. The band on the top only marks the > positive > side of the capacitor. > > > 5) for future reference, how am I able to tell the tolerance, ESR, and > > series just by decoding the writing on it? > > Without knowing the exact part number and looking up the values in the > data > sheet it's impossible to know these details. I usually compare the top > markings against manufacturer data sheets until I find a close match and > then > go from there. > > > > > Thank you very much in advance. > > - John > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and > follow > > the instructions there. > > > > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] FE-5680A - Newbie capacitor question
On Freitag, 1. Mai 2020 23:42:46 CEST John Bievenour wrote: > I'm an amateur electronics hobbyist who's still a newbie (especially to > SMD), so please forgive the basic question. > > I recently acquired a FE-5680A that was failing to lock on frequency (pin 3 > never went low). It will power up, sweep up and down, and finally settle to > fluctuate around 9.999 to 10.000. > > When I opened the case, I found that one of the capacitors had blown, which > I believe might be the reason. Looking at the top of the board, with the > DB9 on your left, the capacitor in question directly across from the right > hand 2941 voltage regulator. It has 105 on the first row, 35 followed by a > stylized K on the second row, and 333 on the last row. > > I'd like to attempt to replace the blown cap. After doing lots of searching > and reading, I'm pretty sure this is a Kemet 35 VDC 1uF SMD Tantalum > Capacitor (never knew these existed until yesterday). I've narrowed down > the options on Mouser, but I can't figure out: > > 1) is my identification correct? Sounds about right, going by the images I found. > 2) is it a T489, T491, T494, T495, T496, T498, or T499 (the band at the top > makes me think it's a T498, T491, T494, T495, T498, or a T499) ? 3) is the > tolerance 10% or 20% (I think it's 10%)? > 4) what is the ESR (I have options from 1 Ohm to 83 mOhms)? I don't think you need to worry about that too much. The capacitor is probably for filtering on the input of the regulator. For output filtering it's too small. The datasheet for the LM2941 I found says at least 22µF is needed for stable operation and ESR between 100mOhm 1 Ohm. So, the output filter cap must be somewhere else. Just make sure the size matches. The band on the top only marks the positive side of the capacitor. > 5) for future reference, how am I able to tell the tolerance, ESR, and > series just by decoding the writing on it? Without knowing the exact part number and looking up the values in the data sheet it's impossible to know these details. I usually compare the top markings against manufacturer data sheets until I find a close match and then go from there. > > Thank you very much in advance. > - John > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow > the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] FE-5680A - Newbie capacitor question
Okay, I think I'm beginning to get it. I reread some articles about ESR with fresh eyes and what you wrote makes sense. Since I won't be ordering many of them, it looks like a safer bet to purchase a 10%, 1.5 Ohm ESR capacitor (Kemet PN: T495B105K035ATE1K5, Mouser PN: 80-T495B105K35ATE1K5). I figured the lower tolerance was good, but at the late hour I was researching everything, the ESR was messing me up. Thank you for helping me understand more about these capacitors, I really appreciate it. - John N5JT ‐‐‐ Original Message ‐‐‐ On Friday, May 1, 2020 6:02 PM, Bob kb8tq wrote: > Hi > > The only way to work out what you have is to find the data sheet on that > part. It should translate > between the manufacturer’s markings and the exact part number. That part > number will tell you as > much as can be known about the part. Some data sheets are a lot more complete > than others. > > There is no risk (other than financial) in putting a 5% part in place of a > 20%. There also is very little > risk in going for the low(er) ESR. > > If the part is just a bypass, even the value is a bit open. If the cap is in > a filter or on the output of a switcher, > things may be a bit tighter. > > Bob > > > On May 1, 2020, at 5:42 PM, John Bievenour j...@bvnhr.net wrote: > > I'm an amateur electronics hobbyist who's still a newbie (especially to > > SMD), so please forgive the basic question. > > I recently acquired a FE-5680A that was failing to lock on frequency (pin 3 > > never went low). It will power up, sweep up and down, and finally settle to > > fluctuate around 9.999 to 10.000. > > When I opened the case, I found that one of the capacitors had blown, which > > I believe might be the reason. Looking at the top of the board, with the > > DB9 on your left, the capacitor in question directly across from the right > > hand 2941 voltage regulator. It has 105 on the first row, 35 followed by a > > stylized K on the second row, and 333 on the last row. > > I'd like to attempt to replace the blown cap. After doing lots of searching > > and reading, I'm pretty sure this is a Kemet 35 VDC 1uF SMD Tantalum > > Capacitor (never knew these existed until yesterday). I've narrowed down > > the options on Mouser, but I can't figure out: > > > > 1. is my identification correct? > > 2. is it a T489, T491, T494, T495, T496, T498, or T499 (the band at the > > top makes me think it's a T498, T491, T494, T495, T498, or a T499) ? > > 3. is the tolerance 10% or 20% (I think it's 10%)? > > 4. what is the ESR (I have options from 1 Ohm to 83 mOhms)? > > 5. for future reference, how am I able to tell the tolerance, ESR, and > > series just by decoding the writing on it? > > > > Thank you very much in advance. > > > > - John > > > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] FE-5680A - Newbie capacitor question
Hi The only way to work out what you have is to find the data sheet on that part. It *should* translate between the manufacturer’s markings and the exact part number. That part number will tell you as much as can be known about the part. Some data sheets are a lot more complete than others. There is no risk (other than financial) in putting a 5% part in place of a 20%. There also is very little risk in going for the low(er) ESR. If the part is just a bypass, even the value is a bit open. If the cap is in a filter or on the output of a switcher, things may be a bit tighter. Bob > On May 1, 2020, at 5:42 PM, John Bievenour wrote: > > I'm an amateur electronics hobbyist who's still a newbie (especially to SMD), > so please forgive the basic question. > > I recently acquired a FE-5680A that was failing to lock on frequency (pin 3 > never went low). It will power up, sweep up and down, and finally settle to > fluctuate around 9.999 to 10.000. > > When I opened the case, I found that one of the capacitors had blown, which I > believe might be the reason. Looking at the top of the board, with the DB9 on > your left, the capacitor in question directly across from the right hand 2941 > voltage regulator. It has 105 on the first row, 35 followed by a stylized K > on the second row, and 333 on the last row. > > I'd like to attempt to replace the blown cap. After doing lots of searching > and reading, I'm pretty sure this is a Kemet 35 VDC 1uF SMD Tantalum > Capacitor (never knew these existed until yesterday). I've narrowed down the > options on Mouser, but I can't figure out: > > 1) is my identification correct? > 2) is it a T489, T491, T494, T495, T496, T498, or T499 (the band at the top > makes me think it's a T498, T491, T494, T495, T498, or a T499) ? > 3) is the tolerance 10% or 20% (I think it's 10%)? > 4) what is the ESR (I have options from 1 Ohm to 83 mOhms)? > 5) for future reference, how am I able to tell the tolerance, ESR, and series > just by decoding the writing on it? > > Thank you very much in advance. > - John > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
