LC Fan and Speaker Clicking

[agg24]

I recently recapped a LC and TDK PSU that was entirely unresponsive. As seems to be somewhat typical for the LC, several caps had fallen off of the board and the traces were very corroded. Before I started the recap, I did the heating test on the PSU, which greeted me with some signs of life from the system. When the power supply was turned on, the LC speaker would begin clicking, and the fan would whirl for a short period, with a frequency of about 1 second, assumedly around the same frequency that LC PSUs typically click at when they're bad.

After a recap, I am still presented with these same results. I have checked the voltages of the PSU, both with and without load. Without load, the numbers seem fine, but under load (the LC itself), the voltages fluctuate up a bit, then dive towards 0 with the click. I assume this indicates that something is still bad in the PSU, but I thought I would ask those who are more knowledgeable than me. I am somewhat worried about the machine having been "powered" (even with this bad PSU) when caps were missing from the board, possibly messing up something else.

 

[AwkwardPotato]

If I'm not mistaken, the PSU voltages fluctuating the way you describe means one of the rails is shorted. If you're running any PDS cards or drives you might want to try removing them and then try powering on again.

 

[agg24]

To avoid issues like that (and to avoid damaging anything), I have removed everything except the logic board, PSU, and fan/speaker assembly.

 

[SalvationCoder]

I just started having the same problem with my LC about a week ago:

I turned my Mac on, only to get a popping sound which I traced to the speaker.  Opening it up, I saw that the fan was also twitching with each pop.  I pulled the fan/speaker assembly and got just a faint clicking from the power supply.  There was also a faint clicking from the hard drive, which stopped when I unhooked the drive and made it easier to hear the ticking power supply.  Disconnecting the drives changed nothing else about the Mac's behavior.  At this point I started guessing the power supply was the source of the trouble.

Through sheer persistence, I did get it to chime and start booting up a few times, but I got the "no disk" screen even though I could hear the hard drive starting to spin up.  A startup floppy would boot the machine.  Any time it booted to this point, I could restart it and it still worked, but a hard reboot usually resulted in the clicking/popping for many more tries.

Still guessing it might be the power supply, I pulled it and took a look.  There was one bad capacitor that had opened up.

I was pretty certain it was the power supply by now, so I checked eBay for a spare and found one for my LC.  The listing said "guaranteed to work."

Well, today it arrived, I hooked it up, and still almost the same problem.  The only difference is that the clicking keeps going for a couple of seconds after I cut the power (whereas previously the clicking stopped immediately after switching off the machine), and when it occasionally boots through persistence, I've been getting the smiling Mac and going partway through the boot process before it suddenly cuts off, everything goes black, and it's back to the popping/ticking.

I inspected the new one, and there's no evidence of any blown capacitors.

Did I get ripped off on the power supply, with a bad cap I just can't see, or could something else be bad?  I've disconnected every peripheral, both drives, and the fan/speaker assembly, so the only thing that could still be bad is the logic board or the SIMMs.

I'm reluctant to try replacing the logic board ore memory without knowing for sure it's not the power supply.  Likewise, I'm reluctant to try recapping either power supply without knowing for sure it's not something else.  I'm not even sure how to go about troubleshooting the SIMMs (will it even boot without them if everything else was fine?).

I'd appreciate some troubleshooting advice.  Aside from this, this Mac was otherwise in pristine condition.

 

[agg24]

I'm fairly certain it's not caps, as I just recapped mine (with the exception of the very large one, which supposedly doesn't go bad often). I have a broken LC III coming in with a supposedly good PSU, so hopefully I'll be able to shed some light in a few days.

 

[AwkwardPotato]

@SalvationCoder The way you describe your LC acting makes it sound more like a power supply issue than a motherboard one. Definitely try recapping one of the power supplies first; it'll be real difficult to determine if something other than the caps is wrong with the power supply unless you do that first. I'm almost certain you'll at least get death chimes without any RAM installed (at least the LC I used to have did). 

@agg24 I'll definitely be interested to hear if using your LC III's power supply is successful. Unfortunately I've had a fair number of LC-series machines that seemed unrepairable even after recaps and this may shed some light on them. Good luck!

 

[agg24]

Tested the voltage on the new PSU. Everything seems to be within specifications.

When plugged into the LC, at first the machine didn't do anything other than turn the fan on (solidly though, this time). After a few power cycles, I got a lot of static from the speaker, which appeared to be continuous, so likely not a garbled startup chime. While the speaker was making noise, the fan was running normally. I have not been able to get any signs of life from it since. I did notice that the floppy drive clicks once on startup, but I think that is normal. I will investigate my solder joints (this was my first time doing SMT caps), and maybe do a wash to see if that improves the situation.

 

[AwkwardPotato]

Given that the stock caps had leaked to the point where they fell off the board, I'd definitely wash it to make sure any residual electrolyte is cleaned off. The fact that you're getting static from the speaker is also a sign of remaining electrolyte left on the board. There are 4 little SOIC-8 packages nestled between the caps behind the '030, one of which is needed for the system to reset (rest are for sound), so I'd make absolutely sure there's no signs of corrosion on them.

 

[agg24]

Did a dishwasher cycle (low heat, no soap) on both this LC board, and the new LC III one that came with my new PSU. After sitting in the oven at 170F for an hour to dry, both boards show no changes. The OP LC board does have corrosion on several of those 8 pin ICs, but I don't know how to solve that issue without removing the component completely (an exercise that will likely result in that component never being installed again). Would reflowing each of the pins manually help at all? If so, do you know which IC in particular controls the reset?

I didn't buy spare caps, so I'm very tempted to just lift some of the new caps on the LC to install on the LC III, since it is at least chiming (but no other activity, other than a death chime if a RAM stick is installed).

 

[AwkwardPotato]

The 8-pin IC needed for reset should be labeled "36064" (the EGRET it sits next to is needed for reset too). Reflowing the pins may help, at least it got an LC II I used to have from showing no signs of life to getting to the blinking "?" screen (albeit without sound). Before reflowing the pins though, turn the LC on and measure the voltage at pin 15 of the EGRET chip. If the reset circuit is functioning properly, it should read around +5V after a couple of seconds. If it reads considerably lower or stays at 0V, then try reflowing the 36064 (and EGRET too if just reflowing the 36064 doesn't work).

 

[agg24]

Just to clarify, this is an original LC, which doesn't appear to have "36064" (it instead has "34064") and has a 020.

Pin 15 is immediately (or as quickly as I can get my probes on it) pegged at 5.08V, so at very least it doesn't seem to have the same issue that you mentioned. I wish I had a better method of reflowing, as there are quite a few bad joints that may be causing issues (see images).

 

[AwkwardPotato]

Just to clarify, this is an original LC, which doesn't appear to have "36064" (it instead has "34064")

Sorry about that, my mistake. Yes, the 34064 is needed for reset.

Pin 15 is immediately (or as quickly as I can get my probes on it) pegged at 5.08V

That's good, the reset circuit is fine then. I do spot at least one corroded trace in your last photo, though, so there may be some others that could be causing problems. If you can take some more pictures of the top and bottom of the board, we may be able to spot more.

 

[agg24]

Which is the corroded trace in that image? The one right down the center, to the left of Y1?

Pictures are here, as the uploader seems to be having issues.

Thank you so much for your assistance.

 

[AwkwardPotato]

Yeah, that trace near Y1 is definitely bad. Also, are you trying to turn it on with or without the PRAM battery?

 

[agg24]

Without. I have tried toggling the power supply on and off to prevent any issues with not having a battery in, but I think I read that wasn't a LC I issue anyway. I can put one in, but in the past it has made no difference.

Is there any way to know where that trace goes, or do I have to scrape off the top near the ROM to get a connection point?

 

[AwkwardPotato]

Scraping the solder mask off the trace near the ROM will work. I'd put a battery in when testing just to be safe (take it out of course when working on the board though).

 

[AwkwardPotato]

Here's another corroded trace:

 

[agg24]

Nice eyes. That trace actually tested fine, though I should probably fix it up anyway. Unfortunately, fixing the first trace you noticed didn't seem to change anything.

Is it possible that powering a machine on with missing caps or leaked elecrolyte bridging some traces could permanently ruin something on the board (some chip, mainly)? I wouldn't be surprised if that happened, particularly since I powered the machine on without noticing that one or two of the caps fell off.

 

[AwkwardPotato]

It's certainly possible that one of the missing caps rolling around on the board and shorting things out could've damaged it, but leaked electrolyte typically won't cause permanent electrical damage aside from corrosion, etc. I'm not sure if the caps not being in circuit would cause damage, though.