Can i use 10v instead of6.8v cap ,cant find them. - Page 1
Forum section: electronics / beginners

author: nic77
author_rank: Contributor
timestamp: March 03, 2022, 02:15:33 pm
content: Hi to all , i just cant find certain ellectrolytic caps with low ESR ,can i use normal caps or must they be low esr in this PS board , ive been searching for about a month and nothing ,can i use a slightly higher voltage , say 10v or 25v instead of 6.8v , thanks to all ,nik

author: Mp3
author_rank: Frequent Contributor
timestamp: March 03, 2022, 02:17:38 pm
content: yesjust remember esr isn't everything. if it was, higher esr caps wouldn't exist.for power supply cap replacement i look for high ripple tolerance instead of low esr.i always go higher on voltage.i just replaced many 16v caps with 50v. no problem. always ok to go higher on voltage.

author: nic77
author_rank: Contributor
timestamp: March 03, 2022, 02:37:06 pm
content: Thank you Mp3 for your super response , as i dont want to throw my tds 210 in the junk bin , as i did change ccfl to led strip and works well , so now i am going hunting for caps thank you once again ,greetings and JESUS bless all.

author: golden_labels
author_rank: Super Contributor
timestamp: March 03, 2022, 04:40:43 pm
content: Voltage rating of a capacitor is the maximum voltage it can safely take. If 6.8V was fine, anything equal or above will be valid.In some circumstance even lower value may be ok: the manufacturer might’ve chosen higher value simply because it was better from BOM point of view or because the designer did not specify any particular value. Replacing with a lower rated capacitor always require proper understanding of the circuit and should be throroughly thinked over, but is not wrong. For example you may see many 50V eletrolytic caps that filter 5V lines.The reason lower rated capacitors are used is usually not their electric parameters, but size. The higher the voltage a capacitor may withstand, the larger it gets.

author: nic77
author_rank: Contributor
timestamp: March 03, 2022, 07:31:27 pm
content: Thank you very much golden_labels , another super lesson i now know ,i was struggling with this oscilloscope power board for over a month now ,i bought this tds210 and the seller said all it needed was a new lcd screen ,but to my misfortune ,i found that no power was getting through anywhere ,so i opened it up ,ordered a new lcd screen ,fitted the new lcd , and no ccfl backlight , so ordered a led strip and made the mod ,so far so good , because i had no way of testing the high voltage transformer that powers the ccfl lamp ,the scope powered up with 2 errors 1st power unit , 2nd acquisition , left it on for a few minutes then swtched off and on again , no errors worked fine , so i presume it is a capacitor issue ,have already done some searching ,and found almost all caps , thank you very much for the help ,greetings to all and JESUS may bless all.nik.

author: gamalot
author_rank: Super Contributor
timestamp: March 03, 2022, 07:37:44 pm
content: Please double-check to make sure there are no mistakes. I've never seen any 6.8V capacitors, I've never seen them mentioned, and I don't even believe they exist in this world.

author: magic
author_rank: Super Contributor
timestamp: March 03, 2022, 07:43:24 pm
content: Maybe it was 6.3V? A very common rating.Looks similar, but not the same

author: mariush
author_rank: Super Contributor
timestamp: March 03, 2022, 08:43:09 pm
content: You should double check things, like the others say.Your capacitor could be 6.8uF 35v - V may be the voltage rating - copy paste fromhttps://www.electronics-notes.com/articles/electronic_components/capacitors/capacitor-codes-markings.php:SMD Electrolytic Capacitor Voltage CodesLetter Voltagee 2.5G 4J 6.3A 10C 16D 20E 25V 35H 50Sometimes a manufacturer will use a voltage rating higher than required for various reasons...For example maybe there's nothing to gain going with lower voltage ratings (ex 35v rated one is 7mm diameter, the lower ratings are 5mm or same diameter, so minimal benefit)Maybe they needed a bigger volume capacitor for better lifetime rating (more hours @ 105c) ... bigger volume may resist more to heat from nearby heatsinks.Bigger diameter capacitors often have better ESR, can handle higher currents better..In the case of tantalum capacitors ... tantalum tends to blow up or burn if voltage is exceeded, so it's often suggested to use a tantalum capacitors rated 50% higher than voltage expected in circuit (ex 12v power supply, use 25v tantalum or higher)

author: nic77
author_rank: Contributor
timestamp: March 04, 2022, 10:20:30 am
content: Hi to all , yes you are correct it is a 6.3v , sorry for the typing mistake, i got confused ,these capacitors are in the power board of the tektronix tds 210 ,as for the help here i am very grateful to all ,at least i can get this scope working again,for me it is more than enough 60mhz (at this moment)So i will be looking for higher voltages and low current ripple caps ,as they are hardly any big heatsinks ,on the board and ample space ,greetings to all ,and may JESUS bless all.

author: golden_labels
author_rank: Super Contributor
timestamp: March 05, 2022, 06:40:07 pm
content: In today’s live Dave has mentioned a video from SlowMo Guys: blowing up electrolytic capacitors. I am not sure if what they produced is merely due to overvoltage or also reversed polarity and they don’t reveal the voltages used, it shows how the failure looks like. Here are some good videos comparing electrolytics and tantalum capacitor failures. Tantalums are not only having much thinner safety margins: when they die, they die really violently. In electrolytic capacitors the electrolyte boils and leaks (damaging the PCB), vents or causes explosion from pressure. Occassionally some short may cause fire. Tantalums always catch fire, massively and explosively.Electrolytics:https://youtube.com/watch?v=6WUxgmMDts4https://youtube.com/watch?v=BNaVokFOxjohttps://youtube.com/watch?v=QlgBwPUF9CcTantalums:https://youtube.com/watch?v=u1Gsf9Lzkyghttps://youtube.com/watch?v=Z-VGnizVZeMhttps://youtube.com/watch?v=rVYGZ2hFUswhttps://youtube.com/watch?v=nigE8xpQ4RMhttps://youtube.com/watch?v=o7CYATVZTmEhttps://youtube.com/watch?v=3Ll4Y3LHtSw