Leaky Electrolitic Capacitor - Page 1
Forum section: electronics / beginners

author: Illuminate
author_rank: Newbie
timestamp: November 01, 2012, 09:43:49 am
content: Hi All,I have some issues with a TEAC MV 6000 VCR. On a first look at the power supply area of the board an electrolitic capacitor appears to have a white hard substance around the base (see photo). Is this capacitor leaking and unservicable or is there something obvious I don't know?Any wisdom appreciated.

author: Rerouter
author_rank: Super Contributor
timestamp: November 01, 2012, 09:46:59 am
content: that is a glue, used to secure large capacitors, try taking some wider images and one of us might be able to spot something obvious,

author: d0ss
author_rank: Contributor
timestamp: November 01, 2012, 09:53:35 am
content: Appears to be glue, leaking capacitors tend to have a white powdery substance (not always) on them.EDIT: as above, not sure how I missed your answer. sleepy I guess.

author: PA0PBZ
author_rank: Super Contributor
timestamp: November 01, 2012, 12:35:56 pm
content: Quote from: Rerouter on November 01, 2012, 09:46:59 amMight also help to tell what issues you have...

author: amyk
author_rank: Super Contributor
timestamp: November 01, 2012, 03:53:21 pm
content: Quote from: d0ss on November 01, 2012, 09:53:35 amElectrolyte is also brownish in colour (Google "bad caps" and take a look...) but a cap doesn't have to leak or bulge to be bad.

author: Kremmen
author_rank: Super Contributor
timestamp: November 01, 2012, 04:03:27 pm
content: The primary side 400V electrolytics leak surprisingly seldom. Of course they can, but usually the busted ones are on the switcher side, i.e. after the isolation transformer. If your gadget behaves erratically the first approximation for fix is to replace all psu electrolytics save the primary side one. Replace that too if it shows obvious signs of distress, which this one in the pic does not.If you aim for long life then by all means avoid the gruesome Chinese crap and pick something like Matsushita/Panasonic, Nippon Chemi-Con, Nichicon, Cornell Dubilier which are all i ever use, and maybe Rubycon would do as well.That fixes the problems 80% of the time in your average consumer gizmo. The rest are then considerably trickier to put right.

author: d0ss
author_rank: Contributor
timestamp: November 01, 2012, 05:17:09 pm
content: Quote from: amyk on November 01, 2012, 03:53:21 pmI probably shouldn't give advice when I'm tired.Yes, you are correct the majority do leak a brown/orangey colour. However I've seen a fair few which have leaked and left a fair amount of white powder (much like an old battery) I'm guessing this is a salt of some description.And as Kremmen said above primary side capacitors are usually fine, the amount of low voltage CapXon I've replaced is astounding.

author: Illuminate
author_rank: Newbie
timestamp: November 02, 2012, 03:16:14 am
content: Thank you for the responses so far, much appreciated.The symptoms for this machine are as follows:1. Clock LED display Illuminates as normal2. Pressing function button illuminates red function led on display3. Insert tape into machine, tape lowers and rewinds between 2 and 5 seconds, winds forward 1 second and stops. (several different tapes behave the same).4. Tape raises and ejects itself.5. Occasionally (1 in 20 tape loads) the tape is drawn from the cassette to the rotating drum and this starts to rotate.I will uploaded some board photographs in case there is something obvious I Have not seen.Thanks

author: Illuminate
author_rank: Newbie
timestamp: November 02, 2012, 03:39:47 am
content: Board jpegs uploaded.

author: SeanB
author_rank: Super Contributor
timestamp: November 02, 2012, 04:48:15 am
content: Likely dirty mode switch, it provides mechanical position info to the microcontroller. also slipping belts on the loading mechanism. Clean switch and try again.

author: ptricks
author_rank: Frequent Contributor
timestamp: November 02, 2012, 11:35:17 am
content: If you look at the center of where the tape comes down when loading there is a little photo sensor sticking up that fits in a hole in the tap cassette . That is used to tell the micro that the cassette is now down. You can tell if it is working by using a camera. If you look at the sensor area through a camera you should be able to see some IR light sources either coming from the post in the center or from the sides pointed at the post.There are many VCR on the market with terrible firmware that can easily get confused if you do anything to break the order of steps it expects. So if it detects the tape is now not there from an intermittent sensor it will hang the processor until the eject signal.

author: PA4TIM
author_rank: Super Contributor
timestamp: November 02, 2012, 07:06:24 pm
content: Electrolyte is rather colourless. I believe the liquid elcos ( 1930's) had brownish electolyteIt is also not that a cap is filled with it. Only the material between the foils is soacked with electrolyte.Electrolyte oxidises the aluminium to form the delectric oxidelayer.vIf the cap starts leaking DC the electrolyte is dried/cooked and not able to form an oxide layer anymore. The leaking also heats the cap and this speeds up the killing like a chainreaction.The exploding/popping open ( top or under) is because the gass pressure gets to high. The gass is part of the chemical reaction.The white stuff is glue.Pictures of cap surgeryhttp://www.pa4tim.nl/?p=1385

author: peter.mitchell
author_rank: Super Contributor
timestamp: November 03, 2012, 10:42:00 am
content: https://www.eevblog.com/forum/beginners/leaky-electrolitic-capacitor/?action=dlattach;attach=32497;imageWhat are the caps like on this shot? They ok?

author: PA4TIM
author_rank: Super Contributor
timestamp: November 03, 2012, 11:24:33 am
content: It is very hard to see if caps are OK except if they pop open and in that case they were allready bad before that. Like putting a pizza in the oven. If black smoke comes out the oven you know its burned, but some time before that you allready were to late, it was then not burned but already to brown and hard as a rock.If they are not popped oen you can meaure DC leakage, capacitance and ESR ( or D, or loss angle) and that tells you more. That is, in some cases only if you have the datasheet. An ESR of 50 Ohm or a 1A DC leakage are very clear, 10 uF instead of 1000 uF is also no problem but there is a lot in between good and this.Second problem, this picture is not focussed, over exposed and it is only possible to recognise some shapes as electrolytic caps. But even if was was popped open I do not think I was vissible here.( did you use a camera that hase a phone option)

author: Illuminate
author_rank: Newbie
timestamp: November 03, 2012, 11:53:28 am
content: Thanks all.Following SEANB I evenyually found a very small mode switch under and attached to the board (see Photos).The mode switch was very dirty and the very fine contacts in the cap were bent and distorted.Both have been cleaned and the contacts gently realigned as best I can.On reassembly the tape is loaded and the screen flashes a code 4 which I assume is a fault code of some sort?Thanks to SEANB who was spot on with the mode switch.Any ideas where to go next or what the fault code 4 means please?