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Started 600XL 64K upgrade, now getting only a black screen


x=usr(1536)

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1 minute ago, DrVenkman said:

The 600XL is the only A8 that uses that particular flavor of DRAMs, I think. 

I believe you're correct on that.  There is another 600XL here, but that one is the it's-staying-stock beauty queen.  Not opening it up anytime soon.

 

In any event, I found a problem that, with luck, is the problem.  It appears as though I managed to crack R36 in the process of removing or inserting the new RAM.  It was a very light crack, and, until I put pressure on it in just the right direction, wasn't obvious.  Read all of the resistors in the area and had good readings, but R36 metered out at 0Ω.  In moving the meter's probes around, I managed to disturb it just enough to make the crack visible from above.

 

I'll check tomorrow to see if I can find one at the local R/C / model train hobby store; if not, Mouser will be getting another order from me.

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It sounds very suspicious and I suspect a socket or some other component damaged in your chip swap process. That is, of course, if I correctly understood the sequence of events. It sounds like the machine was working, you swapped the RAM chips, it didn't work, you put the old RAM back in, it still didn't work. That pretty much narrows down the when. Now you just need to determine the what. It sounds like you may have a good suspect in that cracked resistor.

 

Good luck!

 

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10 hours ago, x=usr(1536) said:

I believe you're correct on that.  There is another 600XL here, but that one is the it's-staying-stock beauty queen.  Not opening it up anytime soon.

 

In any event, I found a problem that, with luck, is the problem.  It appears as though I managed to crack R36 in the process of removing or inserting the new RAM.  It was a very light crack, and, until I put pressure on it in just the right direction, wasn't obvious.  Read all of the resistors in the area and had good readings, but R36 metered out at 0Ω.  In moving the meter's probes around, I managed to disturb it just enough to make the crack visible from above.

 

I'll check tomorrow to see if I can find one at the local R/C / model train hobby store; if not, Mouser will be getting another order from me.

When you say 0Ω, do you actually mean zero Ohms (short circuit) or infinity Ohms (open circuit)?

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XEGS and 2/4 chip 65/130XE use that same 64k x 4 DRAM type so you could use those for testing whether the mod has been done or not.

Of course there is that risk factor of blowing them if it is the 600XL at fault.

 

ed - (posted that not realising I wasn't on the last page of the thread)

Edited by Rybags
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2 hours ago, bfollowell said:

It sounds very suspicious and I suspect a socket or some other component damaged in your chip swap process. That is, of course, if I correctly understood the sequence of events. It sounds like the machine was working, you swapped the RAM chips, it didn't work, you put the old RAM back in, it still didn't work. That pretty much narrows down the when. Now you just need to determine the what. It sounds like you may have a good suspect in that cracked resistor.

 

Good luck!

Thanks, and I'll know more when Amazon gets here with resistors later today.  Not ruling out the possibility of further damage, but want to deal with the obvious issue first and move on from there.

2 hours ago, HyperDriver said:

When you say 0Ω, do you actually mean zero Ohms (short circuit) or infinity Ohms (open circuit)?

Infinity, as in open.  Should've been clearer about that.

 

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11 hours ago, bfollowell said:

Hopefully, that will be the extent of your damage.

Thankfully, that appears to have been all that it was.  Replaced R36, fired up with the original 16K chips, no problems.  Swapped the 16K ICs for the 64K ones: came right up and only saw the first 16K of memory.  This made my evening :D

 

Anyway, I ended up doing @Mathy's Internal upgrade to bring the 600XL up to 64kB and everything is working perfectly.  The main reason for choosing this upgrade vs. the others was that all of the alterations are made to 74-series ICs that are cheap and easily-obtainable if something goes wrong.  I'd rather spend $0.65 on a 74LS158 if I cook or damage it than have to deal with pad repair, etc.

 

Anyway, the proof of the pudding is in the eating, so here it is running the FujiNet for the first time without PBI-connected RAM:

 

IMG_0124.thumb.jpg.32ecdc9e23903d9246f38d88cb3406bc.jpg

 

Thanks for all of the suggestions and assistance.  It's very much appreciated!

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44 minutes ago, Mazzspeed said:

You have a secret TNFS host?

It's not a total secret, but I'm not ready to make it public yet, either.  What I'm working on is this:

 

 

The basic idea is that a FujiNet can connect to any of the root servers and browse a list of TNFS servers the same way it would browse files.  Registering a TNFS server in the directory is neither mandatory nor automatic, so unless a server admin opts in to be listed, the server remains unlisted and effectively private by default.

 

There is some other stuff I want to implement in there, like being able to browse the directory by country or other criteria.  However, I really need to get back to working on it - right now I've got about 80% of the basic functionality implemented, but there are a couple of things holding me up at the moment.  Time's one of them.

54 minutes ago, Mazzspeed said:

Is this Atari porn! ?

Yes, but only Gigantic Gerry and the Smurfette page-flip animation :P

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9 minutes ago, x=usr(1536) said:

It's not a total secret, but I'm not ready to make it public yet, either.  What I'm working on is this:

 

 

The basic idea is that a FujiNet can connect to any of the root servers and browse a list of TNFS servers the same way it would browse files.  Registering a TNFS server in the directory is neither mandatory nor automatic, so unless a server admin opts in to be listed, the server remains unlisted and effectively private by default.

 

There is some other stuff I want to implement in there, like being able to browse the directory by country or other criteria.  However, I really need to get back to working on it - right now I've got about 80% of the basic functionality implemented, but there are a couple of things holding me up at the moment.  Time's one of them.

Yes, but only Gigantic Gerry and the Smurfette page-flip animation :P

I see, very cool!

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I agree with DrVenkman.  I'd look at the sockets real hard.  Atari was known for putting cheap sockets in their computers.  I have on occasion even

pulled socket pieces up still attached to the IC pins when removing IC's.  I think I posted some pictures of that about 3 or four years ago.

   Plug the chips in and test for continuity between the top of the pins coming out of the IC's and the under side of the motherboard.  I would stand

the board on edge and wedge it up with a couple of heavy books to do this testing.

 

David  

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