LCII Death Chimes (Already Recapped)

[NickH93]

Hey all, 

I recently took a gamble on an as-is LCII, which has the death chimes immediately upon booting, and a blank white screen. Here's all I've done

Seeing leaky capacitors, I washed and recapped the board, checked it, at this point, about 20 times for broken traces, and they're all good. Any suspect looking things tested okay on my multimeter. I have successfully recapped a Mac Classic, and my current SE/30, so I'm fairly confident of my work.

The power supply desperately needs capacitors (even though it still worked), but for the time being, I've rigged this thing up to an ATX power supply with no change in behavior. I've double checked that all the voltages are correct. 

I have a fresh, 3.6 PRAM battery, and no leakage from the old one. 

The only thing I could think is that for the SE/30, when I recapped it, I bought the caps as a kit from a reputable dealer. This time, I happened to have everything I needed from an assortment pack I bought from eBay about a year ago. I've heard that these could have values different than what they say, and I don't have an LCR meter to check them with. However, if the caps were off, would it even power on enough to give me the chimes?

Are there any other common suggestions? 

 

[NickH93]

I should clarify, and for some reason I cannot edit the post, but the cap assortment was a no-name assortment from China. Probably a big no-no, but I'm not sure if the caps are the issue if it is booting to a death chime. 

 

[just.in.time]

If you haven’t already, try removing any extra ram sticks (should have 4mb soldered in), and make sure the vram stick is seated properly (I believe it is required, but may be wrong), as well as the ROMs. Also, disconnect the floppy disk drive and hard drive. Then try powering on. If that works, begin to slowly add things back to find what causes the chimes of death.

 

[NickH93]

If you haven’t already, try removing any extra ram sticks (should have 4mb soldered in), and make sure the vram stick is seated properly (I believe it is required, but may be wrong), as well as the ROMs. Also, disconnect the floppy disk drive and hard drive. Then try powering on. If that works, begin to slowly add things back to find what causes the chimes of death.

Thanks for the reply. I have the board stripped of everything non-essential with no change. It just has the ROM, VRAM stick, no additional RAM, no FD or HD. Adding or removing the VRAM makes no difference in behavior, either. 

 

[bibilit]

I have a board doing the same, never found the issue so far.

As you have the chimes immediately (as i do) soldered Ram or Rom can be bad... or anything to be honest.

 

[just.in.time]

@bibilit

im thinking it may be soldered RAM then. Fixable, but not fun to do so.

 

[NickH93]

@just.in.time
That's kind of what I was worried about, but figured. I found some good RAM ICs on eBay that would work. I have had success with piggybacking RAM chips on other restorations I've done (for testing purposes), but then again, these are TSOP chips...

At any rate, I suppose I'll wait for the RAM, and in the meantime see if I can find any RAM with a stuck output, etc. My scope doesn't have the bandwidth, but perhaps it can function enough to tell me if a bit is stuck.

 

[NickH93]

So, as an update, in case this helps:

I probed the data lines of the RAM with my oscilloscope. It only goes up to 2mhz, though, so the idea was just to use it as some sort of logic probe. 

That being said, the left 4 RAM chips had a noticeable pulse on the data lines, (though the frequency was out of range) at a voltage of about 1.26. I'm guessing since the frequency was too high for my scope, the voltage is just some average between a logical 1 and 0 depending on the speed.

The right 4 chips had the same voltage as the left 4 on every data line, but no obvious pulse like on the other 4. The signal was just flat. Not sure if this says anything. (I really just need a logic probe or a faster scope)