Bridge rectifier testing. - Page 1
Forum section: electronics / beginners

author: Birstall
author_rank: Contributor
timestamp: July 25, 2020, 04:42:31 pm
content: I have a D15XB60OH bridge rectifier in an audio amp. Can I test this in circuit? The reason I ask is that I am getting a 0.49v reading across the ~ to +DC and ~ to -DC. I get the same reading when I reverse the polarity.I have spent hours trying to remove the effin thing using wick with fresh solder and also a manual sucker but the solder hardens the instant I remove the iron. The pads are fairly clean but I can't pull it from around the pinsIf I can be sure the diodes have failed, I can cut the pins and deal with them separately.Thanks

author: retiredcaps
author_rank: Super Contributor
timestamp: July 25, 2020, 05:52:05 pm
content: I do a simple in circuit bridge rectifier test to see if it's shorted.With power off and big cap discharged (or showing less than 5V DC across the legs of the big main capacitor), I measure the resistance between legs 1-2, 1-3, 1-4, 2-3, 2-4 and 3-4.Any reading under 20ohm is suspicious.

author: james_s
author_rank: Super Contributor
timestamp: July 25, 2020, 05:54:21 pm
content: You can usually test them in circuit because a bad one will usually be a dead short, 0.0V drop between at least two of the pins. It can be slightly tricky though because you have the DC resistance of the power transformer secondary across the two AC pins.Wick is less than ideal for this sort of thing although dipping it in flux helps a lot. I never had any luck at all with those manual solder sucker things, you need a proper vacuum desoldering gun.

author: Birstall
author_rank: Contributor
timestamp: July 25, 2020, 06:58:25 pm
content: Well that was a learning curve, I don't have a vacuum machine and I thought "bollocks to this" its better for my health and temper to cut it out which is what I did.Of course it turns out to be perfect out of circuit. Ah well I'll put that down to the cost of an education.I got the pins out fairly quickly after I upped the temperature on the iron I'm not sure what it was but over 360c. I'm afraid of ungluing the pads but they were fine

author: JustMeHere
author_rank: Frequent Contributor
timestamp: July 25, 2020, 07:56:18 pm
content: Hot air works better for this type of work. Look for a rework station.

author: james_s
author_rank: Super Contributor
timestamp: July 25, 2020, 08:13:11 pm
content: I've never used hot air for through-hole work, unless you know what you're doing that's a good way to have a bunch of smaller parts fall off the board. Vacuum desoldering tools are not really much more expensive than hot air, there are used ones and some decent Chinese ones on the market. For a really low budget there are those rubber squeeze bulb desoldering irons, I used one of those for years before I finally bought a Hakko 808.

author: MosherIV
author_rank: Super Contributor
timestamp: July 26, 2020, 09:39:32 am
content: One trick you can do to remove through hole components is to flood and join the legs of the component with solder. This makes all the solder for all legs molten so that you can just pull the conponent out.I have used this technique for transistors with in line foot print.With that diode pack, the 4th leg may be too far apart.I have seen (but not tried myself) wrapping a thick copper wire around the iron and long enough to touch all the legs of the device so that they are all molten at once, then you can pull the component.Clean up the extra solder after.