Electrolytic Capacitors: Are these bad? - Page 1
Forum section: electronics / beginners

author: rmel
author_rank: Regular Contributor
timestamp: March 04, 2015, 05:36:33 am
content: My GE washing machine motor went bad. Repair tech came out and said the motor is shot because the indicator LED is not blinking and the fuse is not blown.Research on the net indicates that the LED is supposed to blink any error codes, so I was thinking that if the LED is not blinking at all, the board is bad and not necessarily the motor.So I pulled out the motor and removed the control board. There are a couple of really large capacitors: G-Luxon, 820uF, 200V, 105 C temp. I measured their values in-circuit with my DE-5000 and it showed a value of 699uF. I tried it at 120Hz and at 1kHz for both of them. To be sure, I desoldered one of them and measured it out of circuit. I got the same value.I can't tell if these caps are bad. I'm not sure at what point the capacitance is too low, and I haven't been able to find a datasheet for them. 699 is about 15% of 820, so I'm not really sure.Can someone tell me if these are good or bad, or point me to a datasheet?I'll attach pics of the board and one of the caps, in case it helps.Thanks

author: Huluvu
author_rank: Regular Contributor
timestamp: March 04, 2015, 06:36:06 am
content: 699uF are most probably the right Value because it is within Spec.The ESR Vaule is much more intresting and I would check this first (should be a couple of mili Ohms)Gl-Luxon....

author: sean0118
author_rank: Frequent Contributor
timestamp: March 04, 2015, 08:36:42 am
content: I know it's not what your asking, but did you check all the basic things with the motor? Like if the windings have gone short or open circuit? Are the brushes ok (assuming it's not brushless)? Also, did you actually measure the fuse to be sure it's not blown?

author: Seekonk
author_rank: Super Contributor
timestamp: March 04, 2015, 02:56:46 pm
content: I have a washer board sitting on my desk right now. It has two bad FETs. Dream if you must, but those caps are not likely bad. Check the resistance of the FET gates with a meter, the two outside pins. Generally the problem shows up on the gate. You have six fets, if one or two are different they are likely bad.

author: rmel
author_rank: Regular Contributor
timestamp: March 05, 2015, 06:37:40 am
content: Thanks for the suggestions.I double checked the voltages and the fuse on the washer itself and didn't find any problems. There was voltage/continuity on all the pins.So I went back and traced the board to understand where the voltages go. Eventually I noticed that there was no continuity on one side of the big coil, and it turned out that one side had cracked just above the solder joint. I am not trying to figure out how I can repair this. Can I just flow in a bunch of solder in the hole hoping it will flow to the top of the board and onto the wire? I guess I could remove the coil completely and solder a piece of wire to extend it enough to go through the board.Any suggestions?Edit: I decided to try and fix it by shoving flux in the hole. Then I put the end of a resistor in the hole and added solder until it filled. This seems to have worked and I'm getting continuity. I wonder how strong this bond would be, long term, with all the vibration. I'll have to wait until tomorrow to test it out. Crossing my fingers!

author: Seekonk
author_rank: Super Contributor
timestamp: March 05, 2015, 01:30:03 pm
content: Obviously it wasn't strong enough the first time, must be a lot of unbalanced washer loads creating vibration. This is an EMI filter. You could unsolder it and unwrap one turn to get more wire, OR extend it with a section of wire, OR you could just bridge a wire on the bottom. The FCC won't be knocking on your door.

author: rmel
author_rank: Regular Contributor
timestamp: March 05, 2015, 02:06:03 pm
content: Quote from: Seekonk on March 05, 2015, 01:30:03 pmThanks for identifying the function of that coil. I had assumed it was a transformer or something like that, and it confused me for a while when I was tracing the circuit. I'll do some reading up on EMI filters.Just curious, but I counted the number of turns on each side and they're not even. Now I wasn't completely careful about counting but it came out to about 30 turns on the 120v side and 25 turns on the ground side (he break is on ground side). Did I miscount or is that normal?

author: rmel
author_rank: Regular Contributor
timestamp: March 05, 2015, 02:18:56 pm
content: I did a smoke test this morning and it seems to be working.Now I guess I have to reinforce the components I removed while debugging this problem. Is that white gunk they used some special material? It looks like silicon sealant. Or can I use hot glue?Oh, the the entire board was sealed in a clear rubbery coating. I poke quite a few holes through it with my multimeter probes. Any idea if it's necessary to reseal this board?

author: Seekonk
author_rank: Super Contributor
timestamp: March 05, 2015, 02:19:29 pm
content: They will always be the same in a common mode inductor. The inductance of just one side is quite low and has little effect at power line frequencies.That silicone was there to dampen vibration, it obviously needed it. Hot melt glue does not have very good adhesion, not the import type anyway. Wouldn't worry about resealing.

author: rmel
author_rank: Regular Contributor
timestamp: March 10, 2015, 03:23:18 am
content: Well, I did some googling and found that there's such a thing as electronics grade silicon. I had to order it from Amazon, as I can't seem to find any of it locally here.I am assuming that this stuff won't stick to the rubber coating on the board, nor to the old goop that was on there before. I am not sure how much I'll be able to scrap off with my knife. I plan to just be really generous in applying it.Thanks, everyone, for all the suggestions and info.

author: c4757p
author_rank: Super Contributor
timestamp: March 10, 2015, 03:25:05 am
content: Quote from: rmel on March 10, 2015, 03:23:18 amIndeed there is.

author: Monittosan
author_rank: Regular Contributor
timestamp: March 10, 2015, 03:51:58 am
content: some silicon is conductive when not 100% cured.For future testing the motor windings test should be done with an insulation resistance tester at twice its rated voltage ie US 110v test at 250v AUS 230v test at 500v ac

author: rmel
author_rank: Regular Contributor
timestamp: March 10, 2015, 04:41:08 am
content: Quote from: Monittosan on March 10, 2015, 03:51:58 amThanks for the warning. I'll be extra careful to be sure the stuff is cured before I apply power.

author: timb
author_rank: Super Contributor
timestamp: March 10, 2015, 05:02:11 am
content: Quote from: rmel on March 10, 2015, 04:41:08 amThrow the board in the center rack of your oven at 100f overnight. That should do it.Sent from my Smartphone

author: android
author_rank: Regular Contributor
timestamp: March 10, 2015, 11:25:15 am
content: siliconevssilicon

author: Monittosan
author_rank: Regular Contributor
timestamp: March 11, 2015, 06:21:34 am
content: HAHA i actually typed "silicone" then squinted and backspaced to "Silicon"Now I'll remember

author: rmel
author_rank: Regular Contributor
timestamp: March 19, 2015, 08:05:51 pm
content: Quote from: android on March 10, 2015, 11:25:15 amThanks, I didn't realize there was a difference.

author: rmel
author_rank: Regular Contributor
timestamp: March 19, 2015, 08:12:46 pm
content: Update:The washing machine is working now, but it took a couple of tries.My first attempt of putting flux in the hole and hoping the that solder would flow all the way through and make a good connection was unsuccessful. It seemed to work when I did it, but after I gobbed all that silicone around (and possibly between the inductor and the board), it didn't work. In fact, I could hear a bunch of arcing when I plugged the machine into the wall.Taking it apart again, I found that connection had failed again. I should have checked it before reinstalling everything.This time, I pulled the entire inductor out and soldered an extension. That did the trick. Hopefully, it will last.I learned a lot from this experience. Part of me is glad this failed.