68kMLA Classic Interface

This is a version of the 68kMLA forums for viewing on your favorite old mac. Visitors on modern platforms may prefer the main site.

Click here to select a new forum.
IIFX, burned capacitor and more.
Posted by: Franchute13 on 2017-06-21 16:32:26 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? Any suggestions on why these components were burned? Thanks for your time. (This is not my motherboard)
Posted by: Unknown_K on 2017-06-21 16:41:02 L's are inductors.
Posted by: Franchute13 on 2017-06-22 02:03:45 Hi. Thanks for your answer. Do you know the value of the inductor? I could not find a schematic of the IIFX 🙁 Greetings.
Posted by: Franchute13 on 2017-06-22 16:08:39 http://maccaps.com/MacCaps/Schematics.html Anyone buy the schematics on this page? Is it recommended to buy there? Thank you
Posted by: Unknown_K on 2017-06-22 20:57:26 Probably the same part as L4. I would check the values of the other inductors and if they are all the same go with it.
Posted by: Franchute13 on 2017-06-23 05:58:11 Hi. Thanks for your reply. I do not have oscilloscope to do that type of measurements 🙁 and my capacimeter does not tell me the value.
Posted by: CelGen on 2017-06-23 07:00:43 C1 is a tantalum. Your power supply is fine. It's just old tantalum becoming unstable with age. It's hard to tell from the photo but I'm willing to be the inductor burned up due to the heavy shorting load from the tantalum.
Posted by: Unknown_K on 2017-06-23 13:42:19 The downside of tants is they short when they die, and will take any chip in line with them.
Posted by: Franchute13 on 2017-06-25 05:07:28 Hello! I removed the L4 and measured with a multimeter on the smaller scale (2mH) and L4 is smaller. I will change the capacitor and test if you turn on the computer without L3
Posted by: samurai-j on 2017-06-28 03:52:17 I checked some spare IIfx logic boards, On the surface of L3, consider 0R0 notation, 0 Ω. I burned C1 tantalum capacitor in the past, I could exchange it and repair it.
Posted by: Franchute13 on 2017-06-29 03:41:21 I checked some spare IIfx logic boards, On the surface of L3, consider 0R0 notation, 0 Ω. Hello Samurai-j. Thankyou for information!!!
Posted by: Franchute13 on 2017-07-08 04:27:22 Hi. Change the C1 and L3 (use a cable for L3). I turned on the IIFX with floppy disk but no hard drive. The IIFX turned on correctly, showing video and asking for SO. Turn off IIFX, connect the HDD, turn on the IIFX and PLUFFFF, again explode the C1. Measuring the continuity of C1 and L3, these end in the 12V of the HDD. Perhaps the hard drive malfunction or being old is generating a lot of consumption and so explode the C1. I will continue investigating and I will comment. Summary. If you have an IIFX and you do not have 12v on the hard drive, you have problems on L3 and / or C1.
Posted by: Franchute13 on 2017-07-12 07:23:41 Hello.! I replace the hard drive with a newer one that consumes less and it works and now the IIFX works correctly. Greetings and thanks!
Posted by: joethezombie on 2017-07-12 07:32:50 Nice. Good troubleshooting there. Can I ask what you used for L3?
Posted by: Franchute13 on 2017-07-12 08:03:21 Nice. Good troubleshooting there. Can I ask what you used for L3? Small copper wire. In the week I upload an image!
Posted by: Franchute13 on 2017-07-17 07:39:57 Hi. joethezombie, Here is the photo L3 uses a small cable. C1 was replaced.
Posted by: Franchute13 on 2017-08-01 18:31:33 Sorry, here photo
1