68kMLA Classic Interface
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| Bench testing AA15830 from IIcx | |
| Posted by: ClintonGoodfellow on 2023-12-09 13:33:43 Hi, The rifa's went in my IIcx astec power supply, machine is now totally dead, wont turn on. Have ordered the replacement caps and wondered if there was a safe way to start the psu on the bench for testing of output voltages much like how you would start an atx one. Have ordered the full set of caps from console5 so should hopefully sort things. I find it strange however it being totally dead when the rifas blew as i thought these were more for mains filtering. Cheers. | |
| Posted by: cheesestraws on 2023-12-09 13:45:32 They are - if the PSU is totally dead when the RIFAs went, something else has gone wrong with it. Though it may just be the fuse and a fluke of the way the RIFAs went. You should be able to power it up on the bench by doing something similar that you'd do with ATX ones - take the soft power pin high using the trickle voltage (on macs it goes high, not low like it does for ATX). I can't remember the pinout for the IIcx off the top of my head, though, I'm afraid | |
| Posted by: ClintonGoodfellow on 2023-12-09 14:46:40 Cheers, will test this in the morning before i attempt recapping. Have seen the +5v continuous and the pfw pins, thanks for confirming it should be safe to bridge. Hopefully can sort it as its a great wee machine. Will report back. | |
| Posted by: chue on 2023-12-09 17:30:44 You need to put a load of about 0.75 A on the 5V rail. Otherwise the power supply may fail to output the correct voltages. | |
| Posted by: ClintonGoodfellow on 2023-12-10 06:37:43 Will def do that if I can get it going. Had a chance this morning to test for trickle, showing 5v, joining to pfw fails to start the psu. Can confirm the fuses are fine and power is getting around the mains side of the board. Kinda grubby inside and can see a couple bulging caps along with the blown rifa. Will change these out and see where we are. | |
| Posted by: ClintonGoodfellow on 2023-12-10 06:40:50 Also noticed this resistor has been snipped? Assuming it’s a factory thing as there’s no remnants inside? Can’t imagine it’s vapourised!  | |
| Posted by: chue on 2023-12-10 07:26:03 Here's a photo of mine, just for reference | |
| Posted by: ClintonGoodfellow on 2023-12-10 07:32:26 Yikes, should I reinstall it? 150k ohm? | |
| Posted by: chue on 2023-12-10 07:36:11 The bands are Red, Green, Yellow, and Gold. I believe that to be 250k +/- 5% | |
| Posted by: ClintonGoodfellow on 2023-12-10 07:43:28 Ah! I seen brown green yellow. Thank you. | |
| Posted by: chue on 2023-12-10 07:53:22 Now you have me second guessing myself... I think we need confirmation from someone else. Unfortunately my PSU is not in a position for me to look directly. | |
| Posted by: chue on 2023-12-10 08:41:37 I searched the interwebs for another image of R325, but all were blurry so I took apart my PSU. I took another image and it looks red here; it also looks red when looking at the resistor with my eyes.  | |
| Posted by: ClintonGoodfellow on 2023-12-10 16:25:34 That def looks red to me also. Any chance you can see what R322 is, mine looks a tad toasty here. Might swap it if I can work out what it is. Found this site which has some images, but still hard to see. https://oldcrap.org/2019/09/01/apple-macintosh-iicx/  | |
| Posted by: chue on 2023-12-10 18:53:30 I have some old images from a couple of different angles. It looks like brown, black, black, gold. But I'm not totally sure on the blacks. They could be blue. I'll see if I can get a better view tomorrow.   | |
| Posted by: ClintonGoodfellow on 2023-12-11 02:15:21 Can’t thank you enough. Def think it’s brown black black gold. Will take mine out and confirm if it’s 10 ohm and likely replace it regardless. | |
| Posted by: ClintonGoodfellow on 2023-12-11 06:37:49 Pulled that resistor, it was showing as a 10ohm right enough. Replaced it whilst it was out. Several of the caps were well past their best, showing signs of leakage/swelling etc. All were replaced along with the filter caps. PSU now soft starts with the jumper. Put the psu back in the machine and all is well, machine starts again now. So all clear hopefully for a few more years. I still haven’t replaced that snipped resistor though as it was working beforehand. Will continue testing and look toward replacing it, still a bit odd, but we never know the history of these things. Cheers | |
Posted by: cheesestraws on 2023-12-11 07:38:37Put the psu back in the machine and all is well, machine starts again now. So all clear hopefully for a few more years. Good stuff! Well done. I still haven’t replaced that snipped resistor though as it was working beforehand. Yeah - to me the snips look pretty neat, like it was done intentionally. It doesn't look like a blown part or an accident. If it's working, it might be best not to fiddle with it unless you can work out why. | |
| Posted by: chue on 2023-12-11 12:19:45 Glad you got it working! | |
| Posted by: ClintonGoodfellow on 2023-12-12 01:32:08 Really appreciate all your help folks. Will report back with any further testing. Thank you! 🙂 | |
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