Need help with replacement caps for kzg series

[markusm]

I've seen some other posts from other people on here, and some others recommending which series from other manufacturers will work. My problem is I can't find anything that really matches...

I'm wondering how strict I need to be when trying to match the specs of the new capacitors. I know the voltage rating can be hire (and have had it recommended to me that I use a higher voltage by one person on another forum), and that the capacitance should be the same... But I'm not sure exactly about some of the other things...

If I understand correctly the ripple value should be as high or higher, but what about impedance? If it does't match should I err on the lower or higher side? And of all the specs, which ones are going to be more or less critical than others?

If it helps the caps I am replacing are 470uf 16v kzgs, and they are in an infocus projector. Also, is there any problem with using caps that are 2mm larger in diameter? Here is a picture: The caps in question are on the right...

[mariushm]

Re: Need help with replacement caps for kzg series

In general, impedance should be as close as possible or LOWER. Ripple value can be higher.

Even though the specs are not as good as the ones of the KZG, I would recommend going for Panasonic FM or FR , 470uF 25v. (there's room on the board, so go with 25v if you find them)

As it's a projector, the capacitors will run in a hot environment and those capacitors have a high lifetime and they should be "close enough".

[markusm]

Re: Need help with replacement caps for kzg series

Great thanks for the tip. I was leaning towards a 25v already. Partly due to a previous person telling me I ought to, and partly because some of the other series caps would have some specs right on, but the ripple was a lot lower. I looked those FMs up and they look to be the closest of any other series I've looked into.

One question... would it be better to go with the one of same diameter, but longer if clearance is okay? The one that's 2mm wider has slightly lower impedance and higher ripple. I'm not sure if the 1.5mm difference in lead spacing would have any ill effect?

Thanks again!

[momaka]

Re: Need help with replacement caps for kzg series

would it be better to go with the one of same diameter, but longer if clearance is okay? The one that's 2mm wider has slightly lower impedance and higher ripple. I'm not sure if the 1.5mm difference in lead spacing would have any ill effect?

If you have the clearance for the higher capacitor, then it doesn't really matter. The wider capacitor will just have to sit a few mm off the board since the lead spacing would be larger, thus not allowing the cap to go all the way down to the board (if you do go that route, don't force the cap to go all the way down to the board).
I doubt the slightly lower ESR and better ripple specs of the wider cap will make much of a difference (if any) in terms of longevity and performance.

[markusm]

Re: Need help with replacement caps for kzg series

If you have the clearance for the higher capacitor, then it doesn't really matter. The wider capacitor will just have to sit a few mm off the board since the lead spacing would be larger, thus not allowing the cap to go all the way down to the board (if you do go that route, don't force the cap to go all the way down to the board).
I doubt the slightly lower ESR and better ripple specs of the wider cap will make much of a difference (if any) in terms of longevity and performance.

Thanks for the reply. I've also been asking on audiokarma's DIY forum and it was suggested that I should go with one with the same lead spacing. Once I had a chance I checked my clearance and there was plenty of room so I ordered the longer ones.

I got them in today and planned to do the repair, but both my tips seem to be too big for the size of the pads around the holes on the circuit board. I successfully replaced one of the caps, but it was a pain in the rear so I'm going to wait until I order a smaller tip to do the rest.

[momaka]

Re: Need help with replacement caps for kzg series

Do you have pictures of your tip or link to your iron? I use a 5 mm bevel for almost all of my recapping. Haven't found a tip that is "too big" for removing caps so far .
If anything, bigger tips make the job easier as you have more "heat reserve" (helpful on thick traces) and can usually desolder leads on small caps at the same time so I can just pull the cap straight out vs. having to wiggle it out.

[markusm]

Re: Need help with replacement caps for kzg series

I can try to get pics after work today. I took another stab at it last night and desoldered the rest of the caps. I believe the tip that came with it was an 1/8" flat tip (the kind that's round on one side, flat on the other if I'm forgetting the name of it). Guessing, I'd say the solder pads are about 3mm or so in diameter... It's much smaller than I was expecting.
I think I can make it work with what I have, and am going to take another stab after work when my son can help me, as I need him to hold it steady to use my solder sucker to clear the holes to add the new caps.
It also seems like the solder on the original caps is hard to melt. I have my iron set at 750 deg. and it seems like it takes longer than it should for it to melt. Do I have my temp high enough? This is my 1st adjustable iron that has the temp settings shown on it, my butane iron is adjustable, but I always just turned it all the way up... now I'm trying to learn to do things the right way.

[momaka]

Re: Need help with replacement caps for kzg series

I believe the tip that came with it was an 1/8" flat tip (the kind that's round on one side, flat on the other if I'm forgetting the name of it).

Sounds like you have a chisel tip - which is always preferable over the bog-standard conical (pencil-like) tip.

It also seems like the solder on the original caps is hard to melt. I have my iron set at 750 deg. and it seems like it takes longer than it should for it to melt. Do I have my temp high enough? This is my 1st adjustable iron that has the temp settings shown on it

Yeah, that's probably lead-free solder. I definitely recommend you get some gel or liquid flux and put it on the joints before trying to desolder - it really helps. It also helps to add a blob of solder on the iron's tip.

I'm guessing you have one of those 936 clone stations with the Hakko clone tips? If so, I just found recently that their temperature probe is located very far from the tip, so when the tip conctacts the board, the tip temperature often drops much below what the LCD displays. For that reason, I usually crank mine to 350C (about 660F) or more. When I am impatient, I just put it on full tilt at 460-480C.

[markusm]

Re: Need help with replacement caps for kzg series

The iron is a weller WES51. I decided to try using my burtane iron to desolder the caps, before I knew I had replies to this, and have ruined the trace around one of the holes. The tip of the iron slipped into the hole while I had the solder sucker on the other side of the board, and I think ripped the trace off when I pulled it out. The rest of them seemed to have turned out fine.

So now I'm trying to figure out how to fix that. Its a two sided board so the trace coming from this hole is on the opposite side of the board from the trace that got ruined. I think my only option is to scrape of the plastic coating and solder that lead to the top side of the board... Unless someone has any other advice?

[momaka]

Re: Need help with replacement caps for kzg series

The iron is a weller WES51. I decided to try using my burtane iron to desolder the caps, before I knew I had replies to this, and have ruined the trace around one of the holes. The tip of the iron slipped into the hole while I had the solder sucker on the other side of the board, and I think ripped the trace off when I pulled it out.

Means the butane torch tip was way too hot. The only other time it can happen is if the board was heat-damaged before (usually an improper design where a certain component or two may cause darkening on the board).
Too cold of a tip can also damage the board. The normal reaction is to start pressing the iron harder on the board in hopes of better heat transfer. But what ends up happening is the tip often slips and scratches other traces or damages the current trace.

Its a two sided board so the trace coming from this hole is on the opposite side of the board from the trace that got ruined. I think my only option is to scrape of the plastic coating and solder that lead to the top side of the board...

Yes, that should be fine.

[mariushm]

Re: Need help with replacement caps for kzg series

Either tip too hot, or you pressed too hard on the pad.

View this video which should explain some things about how proper soldering is done:

https://www.youtube.com/watch?v=vIT4ra6Mo0s
https://www.youtube.com/watch?v=AY5M-lGxvzo

The video (and the series) seem dated but the information is still valid.