Bridge Rectifier substituting to next model up - Page 1
Forum section: electronics / repair

author: L__J
author_rank: Newbie
timestamp: March 20, 2018, 03:16:51 am
content: Hey guys I got sent the KBJ408G instead of the KBJ406G would this be ok to substitute for the needed bridge rectifierPeak Repetitive Reverse VoltageWorking Peak Reverse VoltageDC Blocking Voltage:KBJ406G = 400v KBJ408 = 600VRMS Reverse Voltage:KBJ406G = 420v KBJ408 = 560vThe rest of characteristics are the same

author: digsys
author_rank: Unknown
timestamp: March 20, 2018, 03:30:00 am
content: Anything up to OZ mains voltage, you will be fine. Most bridges are well over-rated in voltage. If you're not directly rectifying mains,or at a much lower voltage, then even better. It's a very minor voltage difference.

author: L__J
author_rank: Newbie
timestamp: March 20, 2018, 03:58:31 am
content: Cheers I thought so..Bloody aliexpress sending wrong parts.

author: L__J
author_rank: Newbie
timestamp: March 20, 2018, 08:23:14 am
content: Also this is for a TV power supply just making sure it will work.

author: digsys
author_rank: Unknown
timestamp: March 20, 2018, 09:07:55 am
content: Even though they will rarely ever use a bridge close to spec, to be really sure, what voltage is across it? If you're not sure, check the voltagerating of any cap hanging off it.

author: The Soulman
author_rank: Super Contributor
timestamp: March 20, 2018, 09:45:12 am
content: The replacement has a higher maximum voltage rating than the original, never a problem.

author: glarsson
author_rank: Frequent Contributor
timestamp: March 20, 2018, 09:45:37 am
content: What is the problem? They sent a better product than ordered. No need to check voltages unless the wrong part was ordered initially.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 20, 2018, 09:04:07 pm
content: In theory, "better" depends on use. Diode Vf goes up slightly as Vrrm goes up.In practice, datasheets don't specify this; typically the 50-200V parts are specified together, and the 400-1000V parts together. It's not clear if, by getting a 600V part instead of 800V, you're getting a slight edge on Vf, or conversely, if they're actually all the same Vf and Vrrm in that set.If Vrrm satisfies your application, don't worry about it.Tim

author: L__J
author_rank: Newbie
timestamp: March 21, 2018, 02:16:34 am
content: Thanks guys I done a bit more googling on my question, came across several people saying they use the higher rated model all the time and manufactures only use the lower one because its cheaper.

author: james_s
author_rank: Super Contributor
timestamp: March 21, 2018, 03:26:28 am
content: That's generally true, speaking from experience you can nearly always get away with using a higher voltage rectifier. In this application it will be no problem at all.

author: L__J
author_rank: Newbie
timestamp: March 22, 2018, 06:37:59 am
content: Cheers guys I have the tv running again..I have parts for another 2 tv's with this signature fault.

author: digsys
author_rank: Unknown
timestamp: March 22, 2018, 07:03:25 am
content: Quote from: L__JMaybe it's an over-heating problem? Any indications that there is heat stress where it's mounted?

author: 6PTsocket
author_rank: Regular Contributor
timestamp: March 22, 2018, 07:22:25 pm
content: Not a problem. a little better prv is an improvement with no down side. As far as forward drop is concerned, once the current is higher than a few mills, the drop is around 0.7 volts for a silicon rectifier, no matter what the voltage rating. Industrially,saving a penny or two matters so they buy no more than they need but fol small quantity use, the difference in cost for a higher rating is negligible. I usually buy a bunch at the highest rating I might need and use it for everything. 50v prv works fine at 800 volts and has for me for the last 50 years. Ali did not screw you, they filled the order with a slightly better product.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 22, 2018, 08:21:08 pm
content: Quote from: 6PTsocket on March 22, 2018, 07:22:25 pmFYI, Vf is closer to 1V for power rectifiers, and even more for higher voltage types, and fast-switching types.Tim