Fried Defender RAM

Peale

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I converted my Defender to 4164 RAM a few years back.

The machine has been in storage. While it was there I took the 4114 -> 4164 adapter so that I could build another (I'd lost my notes on how I built the first).

I forgot that I did that. So, when I brought the machine to my apartment, I saw the disconnected connector, plugged it in, fired it up, and smoked some RAM.

Right now I don't have the $$$ to plunk down on all new 4164, so I'm trying to see if any of them are salvageable. I have a few replacements that I can swap out.

The 2nd and 4th LEDs are lit. According to the manual, this means that there's something blown in the 4th bank, correct? Replaced them with no change.

Others had definitely blown (shorted, and HOT) and those have already been replaced.
 
Dude...

Last time I saw a 4164 put in a socket wired for a 4116 it took out the 4164 AND the 2/1 data selectors feeding it. You probably have more damage than just the RAM chips.
 
Dude...

Last time I saw a 4164 put in a socket wired for a 4116 it took out the 4164 AND the 2/1 data selectors feeding it. You probably have more damage than just the RAM chips.

I was afraid of that, too. The error I'm getting seems to lead to other things being toasted, also. I noted the error above.
 
Dude...

Last time I saw a 4164 put in a socket wired for a 4116 it took out the 4164 AND the 2/1 data selectors feeding it. You probably have more damage than just the RAM chips.

Can you tell me which chips those are? I've looked at the schematics, but I honestly don't know what I'm looking at.
 
Fried Defender RAM? Does that taste good with jam?

Seriously though, Unicorn electronics has the best prices on these; good luck. I have made this mistake BRIEFLY and did not fry the whole lot. The question is: which are deep fried and which are salvageable. The finger temperature probe can assist here.

Best of luck, and ease up on the fried foods,
Saltbreez


I converted my Defender to 4164 RAM a few years back.

The machine has been in storage. While it was there I took the 4114 -> 4164 adapter so that I could build another (I'd lost my notes on how I built the first).

I forgot that I did that. So, when I brought the machine to my apartment, I saw the disconnected connector, plugged it in, fired it up, and smoked some RAM.

Right now I don't have the $$$ to plunk down on all new 4164, so I'm trying to see if any of them are salvageable. I have a few replacements that I can swap out.

The 2nd and 4th LEDs are lit. According to the manual, this means that there's something blown in the 4th bank, correct? Replaced them with no change.

Others had definitely blown (shorted, and HOT) and those have already been replaced.
 
Can you tell me which chips those are? I've looked at the schematics, but I honestly don't know what I'm looking at.

That was on an Apple II+ computer.

Look at the address lines on the RAM and see what is feeding them. The way the DRAM works is that the address lines are multiplexed. This is how you get a chip that is only 16 pins in size yet holds far more data than 16 pins can address. You feed part of the address to the chips, toggle a line, then feed the rest of the address to the chips. The chips that are feeding that multiplexed data will most likely be toasted.
 
So, if I'm looking at this correctly, the 74153 @ 4F is likely bad. As is 3G, 3I and 4H.

Right now I'm getting a RAM error 12. Which is more of an error than I got before.

Also, the text doesn't look quite right.

There's also some kind of weird monitor blob, that I think that's a monitor issue.
 
If it were on my bench I would replace those 4 multiplexers for sure.

Next step after that would be to check the latches the data pins connect to.
 
Start with the RAMs and then move on to the 74153s. Socket them if they aren't already socketed.

ken
 
Have I mentioned that I'm unemployed, and at this moment, pennies count? :) I can unsolder a chip in less than a minute.
 
I have to place a Mouser parts order anyway, so I thought I'd add these parts in there.

Mouser doesn't seem to have 74153s, but they have 74ls153s. Are they compatible?
 
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