Mac IIfx - No Video - Need to identify C29

[JRotar]

I just got a Mac IIfx (a dream machine ever since I used one in a middle school journalism class...the fx was the teacher's computer, of course, but we could use it to do Pagemaker faster).  The photos showed a lot of rust on the RF shield so I was worried the battery exploded...but they didn't!  Must have been stored outside, plus the thing was covered in bugs - As I kept cleaning more dead (I hope they were dead) things came out over and over so I had to take the RF shield out just to make sure I got them all.  I was expecting to need to do a full re-cap, but much like others on here, I only had 2 aluminum leaky caps, which I replaced.  I replaced the axials, although I'm waiting on the 10uF 16v and 1000uF 10v axials near the RAM to be delivered, so I don't know if that could be part of the problem.

It turns on and chimes, but I can't get any video.  I've tried several adapter dip switch settings to nothing.  It came with the Mac II Video card but I also tried a High Resolution card to no success.

So here's where it gets interesting:  The small component C29 next to the Nubus slot closest to the power supply was rusty.  C28 above it looks like the same component, as well as C31.  These are all connected directly to the axial C224 near the power connector, so I'm assuming this is the main power, ergo if it's bad the Nubus won't get power.  I cleaned the rust off and tried to reflow the solder.  Plugged it in and hitting the power button caused the fan to start, and then the supply to click off.  I re-flowed again, and now I get the chime but still no video.  So C29 has an effect on the entire system.  It has a marking that looks like IA4.  Google brought up many different things, so I wondering how to interpret that marking so I can order a new one.  IE, what is this thing? 

Thanks everyone!  I'm sure there will be more adventures with this thing!

- Josh

 

[Unknown_K]

Are you using a CRT or LCD monitor?

The Toby card does 640x480 and probably at 60hz or slightly less.

 

[JRotar]

It's an LCD.  This model of Samsung is surprisingly compatible with a lot of things.  It seems to sync down to 15khz as I got an Atari 1040st to display on it I'm less likely to blame the LCD, granted not perfect but it did work...The adapter in 640x480 works on my IIcx (until I accidentally broke it), IIci, LCs, etc.  I tried the non-dip switch adapter with no luck, and on the dip switch one: 640x480, 512x384, VGA 640/800 all in each composite sync 1, separate sync, and sync on green.  

Also randomly just now after trying all day it now starts up as soon as I plug it in and restarts when I turn it off.  Definitely was not doing that earlier so that must mean there's something worse going on.  I need to check the power supply and I hope it's not one of the HC132s since replacing those (and more) in my IIcx is how I made it worse, but that's another thread...

The 5v and 12v lines look fine as well as -5v I believe I saw.  Now, the lone white cable at pin 15 on the other hand was behaving erratically going up and down, starting at 4v and going up past 12 so I unplugged it immediately. What is the pin 15 white cable supposed to read?  Looks like I will be needing to take a closer look at the power supply.  Any details about that pin 15 would be appreciated

 

[Arisotura]

I don't know about the Mac II video card, but I have a high-resolution video card too, and it outputs interlaced video. That may be part of your problem. My LCD doesn't like the interlaced signal, it atleast displays something but it's real ugly.

 

[JRotar]

It's possible that my LCD doesn't like the Tobey card, although I still couldn't get video on a known working High Resolution card so I think that still points to the IIfx for now.  

I decided to take the power supply apart and it was so caked in dust that wouldn't wipe off and dead bugs that I made it take a bath so it's down for a few days so I will order replacement caps.  They actually look pretty good but the weird voltage on the white line is concerning me

EDIT: I've used the high resolution card with this LCD panel on a IIci, IIcx with no issues