IIfx C1 Capacitor - Does it always blow?

[olePigeon]

Both of my IIfxes had the C1 capacitor blow up. If I remember correctly, so did quite a few other users on here. I'm beginning to think that the general recommendation for any IIfx should be to replace the C1 capacitor with a higher rated capacitor. It's possible it can crater the pads, forcing you to use the other set (which is what happened on the NASA IIfx.)

 

[MrFahrenheit]

Both of my IIfx had a blown tantalum there. I had to resort to soldering the replacement tantalum to the electrolytic pads. At the time I didn’t think of upgrading the voltage. Likely a very good idea to do. At least 25v I would say.

 

[Trash80toHP_Mini]

Thanks guys, now I really do need to unearth my IIfx. Didn't know these were a problem. Looks like it blew spectacularly while under load. Is that magic smoke stain on the logic board?

When someone comes up with a suitable, higher capacity part. That info and supplier part number will be much appreciated. Might it be advisable to upgrade all capacitors or is that a bad idea?Wondering because a marginal spec capacitor is the typical failure point of DuoDock PSUs.

 

[joshc]

Yeah, this is a known thing. Not sure why exactly it happens but there's clearly a design flaw/fault with IIfx's as many have done this.

IIFX, burned capacitor and more.

Hi. I buy second hand an IIFX. Replace the batteries and turn it on. At powering it came smoke from capacitor C1 (476 16) and exploded L3 (I do not know what component it is) Anyone know which component is the L3? How can I turn on the power supply to measure if it is giving the correct voltage...

68kmla.org

That said, I haven't replaced C1 on mine yet...

 

[MrFahrenheit]

Thanks guys, now I really do need to unearth my IIfx. Didn't know these were a problem. Looks like it blew spectacularly while under load. Is that magic smoke stain on the logic board?

When someone comes up with a suitable, higher capacity part. That info and supplier part number will be much appreciated. Might it be advisable to upgrade all capacitors or is that a bad idea?Wondering because a marginal spec capacitor is the typical failure point of DuoDock PSUs.

I don't really know if resistance really matters, but this looks like a very good candidate from just a quick search:

TCNX476M035R0150E Kyocera AVX | C2895719 - LCSC Electronics

TCNX476M035R0150E Kyocera AVX $1.1041 - 47uF 35V 150mΩ@100kHz ±20% CASE-X-7343 Tantalum Capacitors ROHS datasheet, price, inventory C2895719

www.lcsc.com

 

[Pushpull76]

Oww this looks like a thread with a good advice. I need to check the C3 cap of mine.....

 

[olePigeon]

@Pushpull76 It's actually the C1 cap. Looks like C3 from that angle, though.

@joshc My IIfx thread was lost in the forum crash, but I seem to recall the C1 capacitor had something to do with the SCSI BUS. I think when it blows the only thing that happens is that the external SCSI might not work. When mine blew, it caused an unexpected reset. I quickly turned off the power when I heard the pop.

 

[olePigeon]

Looks like it blew spectacularly while under load. Is that magic smoke stain on the logic board?

Sure is. The scariest part was that it splattered ash all over my now-not-so-inexpensive Radius 24X card. So on initial inspection it looked like my Radius card blew something up. Then I remembered the C1 cap, so I looked at the motherboard and saw what was left, then gave a huge sigh of relief.

 

[Concorde1993]

Is C1 still prone to explosion even after recapping the entire board?

 

[Pushpull76]

Is C1 still prone to explosion even after recapping the entire board?

I don't thinks so. This is an old tantalum cap, they are very well known to be spicy electronic little friends. Use a valid substitute, especially with higher voltage rate (25volts) as someone already mentioned earlier.

 

[Concorde1993]

Good to know. My board was recapped before I bought it. Haven’t had any issues with it in the 8+ years of ownership minus swapping the power supply