Need help with a iic that won’t boot anymore

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Need help with a iic that won’t boot anymore

Hello fellow members,

i recently picked up my first iic. The seller described it as no beep and no video.  To my surprise the machine had an Ultra 2 board with a zip chip 4.  The PCB looked clean. No corrosion  anywhere.  I removed the memory board and installed a 65C02 on the motherboard  and the machine booted.  Vertical scroll on the video but a monitor adjustment corrected that. Self test showed ram was all good.  But something was  still wrong.  I had to readjust the scrolling several times after the machine was powered down and powered back up.   After being on for about 10 minutes , the video would get messed up occasionally and I self tested again. Now it tells me there are bad main memory ram. But every time I would run the test it gave me different results. Then when I would get a “system ok” it would boot again. Then one day I just lost all video while it was running . And now it won’t boot. No beep and no video, just as the seller had described. The self test showed 5 ram as faulty. Not all the same time, over multiple self tests but these 5 at one point kept showing up. Some tests would show a certain ram bad then run it again and now it says it’s good but something else is bad. So I removed the 5 that seemed to always come up and I put them in a working iie PCB and it boots fine. Passes self test and no issues in the iie.  I’ve tried different PSUs in the iic and no improvement.  So now the machine doesn’t even boot at all. What could be causing this situation?  Hopefully someone has experienced something similar and has a solution.  Also just to mention the iic came with a ROM0 ROM and I upgraded it to ROM4X, since the board had been modded already, and was working fine until I lost video. I re-verified the ROM and nothing appears to have happened to the 4X ROM so I doubt that’s the issue. 

Thanks 

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If it has RAM issues and they

If it has RAM issues and they're "MT" branded RAM, I'd replace them all as a matter of course before proceeding

 

Next I'd suspect the CPU socket...It did have that ZIP in it, and you did have luck powering up at some point with a replacement 65C02.

 

 

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The RAM are NOT MT ram.  I

The RAM are NOT MT ram.  I never tried booting the system with the ultra board or the zip chip.  I just put a 65C02 on the motherboard  where the ultra board plugged in. 

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You have lots going on there

You have lots going on there so may be best to step back and start with the basics.The radom tests with RAM are odd, almost has me wondering about power. Any chance you're a person with a oscilliscope? If so, may be worth checking all voltage lines.  The fact that video goes out also kinda suggest power may be a factor. The video generator is one of the few parts of the board that use -5V so that's interesting to me. 

 

The //c's external supply could be checked first, it gives something like 16V on the dual lins into the case. Once inside the case those lines go into the power supply which is filled with everyone's favorite 30 year old electorlytics! Monitoring those outputs may be helpful to rule power out. 

 

I'm also wondering about the CPU socket. Apple is known for using cheap-ass sockets, mainly because they never expected people to be pulling chips other than maybe once. 

 

One last comment, I recently started working on a platinum //e which was working. I pulled the ROM to image and I got a great image which verified with known images from the web. But reinstalling the ROM.... no work. I've found the data being read by the 65C02 was garbage. Replacing the ROM with an EPROM burnt from the previously read image... works perfect. In my case it appears the ROM may have been damaged to the point it's just not stable in the //e but stable in the reader. I found bad continuity from the ROM legs to the 6502 on almost all of the data lines so I replaced the crappy original single-wipe socket with a new double-wipe socket and continuity was restored. I too did not supsect the ROM given the read and verify, but damn the ROM is bad! I'm not convinced there's not other capacitance issue or similar affecting signal integrity, but that will require some extra analysis.

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Thanks Jeff,Interesting what

Thanks Jeff,

Interesting what you mentioned about the ROM going bad. Testing good on the reader but not so in the machine. I know Apple liked to use cheap sockets but hey by 1984 you were lucky to get any socket at all.  I socketed and replaced the 5 ram which kept coming up bad, (the ones I removed I put in a iie and are fine). Something  came to mind that I think is important to mention. After I had the machine working good, all ram constantly testing good and I’d shut it down for the night, I would move it to another table, then move it back the next day to power it up and that’s when it would start acting up. Moving the machine may have been flexing it to cause problems.  Pushing on the drive connector “used” to correct a bad boot, but it doesn’t correct a no boot. I tried pressing on the ROM, CPU, MMU and IOU while attempting to boot several times but still just a green power light. That’s it. I recently got a scope but haven’t learned how to use it yet.  But in the meantime do you think I should write another eeprom and/or replace the ROM socket?

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mochatea396 wrote:But in the
mochatea396 wrote:

But in the meantime do you think I should write another eeprom and/or replace the ROM socket?

 

 

 

The easiest (if you have the needed resoureces) would be burn an EPROM (actually 2 unless it's a platinum) and try those. I was floored to see the EPROM work after the ROM failed. What was stranger for me was while the ROM didn't work and the EPROM did, checking continuity between data pins on the cpu and ROM there was one  good connection, all other data pins were open. That was with the ROM installed so I thought it was the socket but still puzzled why the EPROM would be different but given the way pins can be flared vs straight I'm ok believing it was a bad socket so I installed the new socket and while the data lines are tone out correctly the ROM still doesn't work.

 

As for moving flexing the motherboard, that seems a bit extreme, but... if you don't know the history of the machine I guess there's a chance any joint could be damages. May be worth inspecting the bottom of the board with a critical eye.  The other thing to consider, is tin contacts on the chips paired with tin contacts on the sockets can produce mineral growth along with the tin oxidation. Big stretch but if you see stuff that could be something to explore.  Along with Tin/Tin contacts gold/tin can be worse with dissimilar metals issues, but we're heading into possible but very likely situations.  All that being said, the one thing which really can't be easily resolved is corrosion on the socktet contacts and those packages are never fun to rework. 

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I’ll program another ROM

I’ll program another ROM today and try that. Could you tell me if a iic only uses its main 64k of ram to boot or it needs the full 128k.  Reason I’m asking is I’ve replaced 5 of the 8 main ram and I’ll replace the other 3 so all main ram are new but if the iic doesn’t use the auxiliary ram to boot I’m not going to bother replacing them at this point. If the iic in fact does need the full 128k then I’ll replace them as well. But I’ll try burning a new rom first and see if that corrects the issue. Then perhaps sockets if no improvement. Also just a note, I opened the internal PSU and I didn’t see anything bulging, leaking or anything out of the ordinary. 

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