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shadedream

Re-capping IIsi problems....

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I gave in to the inevitable, ordered a bunch of caps and have started learning to re-cap these old boards and clean them up. Unfortunately this board has not been a success. It was... mostly working... before re-capping, I've re-capped the board using the recap-a-mac references, have double/triple checked cap polarity, continuity tested cap connections etc.

Currently it turns on, soft boot works fine, hard drive powers up, but no boot process begins and I have no startup chime. It just sits on a gray screen which is occasionally yellow tinted.

Caps were removed with a hot air rework station w/ small tip and low air pressure (so I didn't end up blowing other small components off) and replaced with tantalum equivalents.

Any thoughts?

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I didn't see any notable corrosion on legs or traces but I have thoroughly cleaned the board and cleaned the pads before putting the new caps on. There really wasn't much cap goo on this board (I have another to do which is worse).

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No problem. I can take photos of the board a bit later if that will help. For the most part the screen is just normal gray. Once in a while when powering on it takes a yellow hue.

I also forgot to mention, I already successfully re-capped the power supply, so I'm quite confident it's not related to that. I've tested another one in it just in case. I've also removed it's RAM to just use onboard as well, just in case.

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Im dealing with same thing. Same screen and no sound. No broken traces. Mabie the leaking capacitors short out the chips or something? 

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8 hours ago, MrFahrenheit said:

Do you have a multimeter?  If so you can verify your capacitors are taking charge and discharging through traces on the board. 

I do have a multimeter but it doesn't have a specific mode for testing capacitors.... how do I go about testing them correctly? Do they need to be removed from the board or can I test them inline?

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Well I've removed the caps, given the pads a good clean fluxed it all back up and soldered caps back on and given it a clean. I've already done this before and nothing changed, but we'll see how it goes, it's in the oven drying for a few hours now.

Is it possible a heat gun could have damaged something else on board near the caps while using one to remove the caps? I wouldn't think so but feeling a bit at a loss at this point.

 

I have another IIsi in need of a recap but I'm hesitant to get started on it until I know where I've gone wrong with this one...

Edited by shadedream

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19 hours ago, shadedream said:

Well I've removed the caps, given the pads a good clean fluxed it all back up and soldered caps back on and given it a clean. I've already done this before and nothing changed, but we'll see how it goes, it's in the oven drying for a few hours now.

Is it possible a heat gun could have damaged something else on board near the caps while using one to remove the caps? I wouldn't think so but feeling a bit at a loss at this point.

 

I have another IIsi in need of a recap but I'm hesitant to get started on it until I know where I've gone wrong with this one...

Are you using a hot air heat gun to remove your caps?  
 

What temperature are you using to remove and to solder the caps ?

 

I’m not that experienced with a multimeter but there’s a setting on most that will measure the capacitance by charging or discharging depending upon whether you hold positive to positive and negative to negative (charges the cap) or other way around (discharges). I was told to make sure to discharge before trying to charge. 
 

Check YouTube there’s a bunch of videos but essentially you put your multimeter on a setting in range of the cap your testing and it tells you how full it charged (or inf if the cap holds a lot) but it demonstrates whether the cap is able to work on the board. This is how I found 5 that weren’t actually electricity connected to the circuit even though they were soldered on. 

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Yep, used hot air to remove old caps, small tip, heat directed on caps with low pressure. The hot air rework was at 350c.

I used my iron to solder the surface mount tants, ~370c on that. Through-hole soldering work so I might be running a bit high on that.
 

I've continuity tested the caps solder joints to points on the board multiple times and things seem to be connected well. I even replaced the caps with a new set. Same result.

FWIW It sound like I was similar to your experience, in that on my first boot, it chimed and worked... and then went down hill from there.

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20 hours ago, bibilit said:

All psu rails are present ?

 

Egret chip bad or contaminated ?

 

rom issue ?

I recently recapped the PSU and tested it working in another system. I've also tested that system's PSU in this one with the same results, so I don't think it's the PSU.

The board wasn't heavily contaminated with cap goo fortunately. No idea how to test the Egret chip though (or which it is).

Would a ROM Issue be likely if the system was working fine before recap?

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10 hours ago, shadedream said:

Through-hole soldering work so I might be running a bit high on that.

Clarification, I do a lot of through hole soldering work, so I might be running my temp a bit high for surface mounts.

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Attaching a photo of the board currently if that helps. There are two pads that lifted or partially lifted, so I've scraped a bit off the connected traces and soldered them to the traces (hence why they're crooked). They're at C5 and C31. I also noticed a couple of stray black bristles from the brush I was scrubbing the board with on there currently, so disregard those.

If a closer view of any component or area would be helpful, let me know and I can take them.

DSC_5779.jpg

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Take a dental pick and gently probe the solder vias (holes that go through the board, with no component legs in them).   These carry signal from one layer of the board to another.   They are also low laying areas where cap goo tends to pool and have an intensified corrosive effect.

 

When I recapped my IIci back in the mid-90s, one of my vias looked fine, but was actually corroded through ("solder" was soft, rather than hard).  I had to run a bypass wire to run the signal around the corroded via.   Fortunately, the connected traces were on the top and bottom layers and not on an inner layer.

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Visually it looks very clean.  I've also had pads come off and I've done as you have, solder to a scraped off trace, and it works just fine that way, providing it actually is making contact.  I also checked some of your components for bent pins that would touch, and don't see any (I had a IIci that wouldn't boot, and I found something had pushed two CPU pins together).  Caps all look oriented the correct way.  Do you get anything from powering on?  Can you confirm your PSU is working correctly?  The IIsi has 1MB of on-board soldered RAM, used for the integrated on-board video display.  If somehow that RAM gets damaged or affected, it would cause the machine to not boot properly.  Not sure what else to tell you.  

 

In cases like this, I'm saving up the motherboards, an I plan to ship them off to Branchus Creations in AUS in one lot (shipping to AUS is expensive!).

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Yep the PSU is recapped and working, tested with another working PSU also. I turns on, HD gets power, soft power works, but no sound and just a gray (or tinted gray) screen. I've re-done and continuity tested the caps more times than I can count now (went through three sets, just in case) and nothing has changed so I'm pretty sure it's not the caps at this point.

My planned next steps are look into the vias as @trag mentioned as well as re-examine all the chip contacts and potentially re-flow some/all of them.

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8 hours ago, shadedream said:

Yep the PSU is recapped and working, tested with another working PSU also. I turns on, HD gets power, soft power works, but no sound and just a gray (or tinted gray) screen. I've re-done and continuity tested the caps more times than I can count now (went through three sets, just in case) and nothing has changed so I'm pretty sure it's not the caps at this point.

My planned next steps are look into the vias as @trag mentioned as well as re-examine all the chip contacts and potentially re-flow some/all of them.

Have you plugged in an external speak to see if you get any tones externally?  Are you able to hear a click sound through the speaker indicating the board powers up ?

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8 hours ago, shadedream said:

I hadn't plugged in speakers externally, I'll give that a try. It does click quietly when the board powers up.

It probably wont work. I tried it didnt work but theres a pop when it starts up. 

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Well... some good news and some bad news... I made a poor decision and learned a lesson about trying to re-flow very small pins gently with a soldering iron. I will not be fixing that IIsi any time soon, unfortunately.

 

On the other hand, I re-capped the other IIsi, which was the one in worse shape of the two as far as cap goo goes, flawlessly and it's up and running.

 

szKnPNf.thumb.jpg.4c747d6b7ba010951d16ac6f597de2db.jpg

 

https://imgur.com/a/iSla5SN

 

I appreciate everyone's help with troubleshooting the first one anyway. I'll worry about getting back to it when I'm a bit more experience with dealing with smaller pinned surface mounts.

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