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Two NeXTStations to Fix
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hawkman



Joined: 25 Apr 2016
Posts: 16

PostPosted: Sun Apr 02, 2017 2:14 pm    Post subject: Two NeXTStations to Fix Reply with quote

Hi all,

I have decided to try to fix the two NeXTStations that I have neglected for far too long. Here is what I have:

1. NeXTStation Color 25MHz
- Model N1200
- Serial ABC0054059
- ROM 2.5 v66
- 8 SIMMs for 32 MB
- Non-ADB

This is my personal machine that I've owned for decades. It works. The hard drive finally failed so it boots to ROM monitor but no further, so I bought this:

- RaizinMonster CF-SCSI adaptor, jumper setting SCSI 1
- 4 GB CF card

Now the problem is, how do I find / install OpenStep / NeXTStep onto this?

2. NeXTStation Turbo Color 33MHz
- Model N1200, Part No: 3005
- Serial ABC0005664
- ROM 3.3 v74
- 4x NEC MC-422000A32B-70 SIMMs (I think this means 32 MB)

This one is completely dead, although in fairness it never worked since I bought it "untested" on eBay. The capacitors all appear fine. None appear to be bubbly. I've swapped the BIOS battery and the power supply from the good one to this one and nothing happens when you press power on the non-ADB sound box.

I can't see any problems with caps or anything else obvious. Any ideas?
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Rob Blessin Black Hole
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Joined: 05 Sep 2006
Posts: 597
Location: Ft. Collins, Colorado

PostPosted: Sun Apr 02, 2017 2:42 pm    Post subject: Reply with quote

So it is the same keyboard, mouse, power supply , ycable? I would look at the bios battery connector as some times they come loose.... or where the connector for the power supply plugs in .... Brian Archer may have further insite.... I'm guessing the video connector where the video cable plugs into check those traces as well.
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Rob Blessin President computerpowwow ebay sales@blackholeinc.com http://www.blackholeinc.com
303-741-9998 Serving the NeXT Community since 2/9/93
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hawkman



Joined: 25 Apr 2016
Posts: 16

PostPosted: Sun Apr 02, 2017 3:02 pm    Post subject: Reply with quote

Hi Rob -

Thanks for your really quick email response and for answering on the public forum.

Yes, I am using the same keyboard, mouse, power supply, battery, y-cable and sound box.

I just pulled the motherboard and went through what I could with my multimeter. My findings:

- Battery connector is good and battery reads 3V.
- Power supply connector is also good, all connections tested.
- Video connector tests good as well.

I think my next step (haha) will be to clean the board with contact cleaner. Any other ideas?

Thanks again.
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Rob Blessin Black Hole
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Joined: 05 Sep 2006
Posts: 597
Location: Ft. Collins, Colorado

PostPosted: Sun Apr 02, 2017 3:10 pm    Post subject: Reply with quote

Hello : May be the schematics will help with the trouble shooting :

http://www.nextcomputers.org/NeXTfiles/Docs/Hardware/Schematics/Turbo_slab/CSlab33_Schematics.README
http://www.nextcomputers.org/NeXTfiles/Docs/Hardware/Schematics/Turbo_slab/CSlab33-map.pdf

http://www.nextcomputers.org/NeXTfiles/Docs/Hardware/Schematics/Turbo_slab/CSlab33-03.pdf
Best Regards Rob Blessin
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Rob Blessin President computerpowwow ebay sales@blackholeinc.com http://www.blackholeinc.com
303-741-9998 Serving the NeXT Community since 2/9/93
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barcher174



Joined: 07 Dec 2012
Posts: 560

PostPosted: Sun Apr 02, 2017 4:14 pm    Post subject: Reply with quote

I don't have enough samples of the turbo color to figure out any pattern to these failures. Try booting with nothing connected to the board (floppy, SCSI, fan). First thing to do is replace the capacitors and reflow the solder on the power connector. If that doesn't get you anywhere, I would start at the RTC and work your way around to the system controller IC. Do you get a red light on the logic board?
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hawkman



Joined: 25 Apr 2016
Posts: 16

PostPosted: Sun Apr 02, 2017 4:19 pm    Post subject: Reply with quote

No red light. No fan movement. No click... nothing.

I've now blasted canned air and cleaned all connectors with contact cleaner. I've checked the PSU connector, battery and the video/sound box connectors with a multimeter and all are good.

Next steps are to review the schematics, particularly the RTC and system controller.

Failing that, it looks like it could be the capacitors. I'm in another country so I might buy the kit from Rob and get a local person to install them.
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hawkman



Joined: 25 Apr 2016
Posts: 16

PostPosted: Sun Apr 02, 2017 9:30 pm    Post subject: Reply with quote

Some weird progress to report on the Turbo Color.

I re-read an email from Rob which said to swap the battery direction - basically install it wrong - then install it the correct way.

To my absolute surprise, the machine flashed a (green - not red it turns out) light on the mainboard and booted right up! No power button though... weird.

I noticed that the fan connector was not very good so the fan wasn't running. I have since examined the pins and they are quite corroded.

I was able to do a few things in the monitor before I chickened out, fearing the lack of fan. It read the memory correctly (32 MB as I suspected) and everything else looked normal. It showed v74 which also was correct.

One weird thing is that I couldn't hit the power button to shut it down.

I got it to boot a second time this way but since then, no luck.

Does anyone know what I should check next?

Thanks!
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Rob Blessin Black Hole
Site Admin


Joined: 05 Sep 2006
Posts: 597
Location: Ft. Collins, Colorado

PostPosted: Mon Apr 03, 2017 6:13 pm    Post subject: Reply with quote

Hello Matt:
We may be able to narrow it down significantly because you have the luxury of a Color Station and Turbo Color.

We know the color station powers up so lets try swapping components.

Try the power supply from the Turbo Color in the color slab ? Does it power up immediately?
Try the bios Battery from the turbo Color in the color slab? Does it power up immediately?

If yes we have narrowed it down to a Turbo Color motherboard problem , because the keyboard, soundbox , y cable , battery and power supply all wor k on the color station. You can also try swapping the bios battery and power supply from the color station to the turbo color to make sure, if they both work on one but not other we are narrowing it way down.

So then I would look at the battery socket on the Turbo Color, if its loose that would explain why it is intermittent works sometimes and not others.

NeXT would be the onboard connector for the power supply ....

then the video connector internally I've seen them separate right where the cable plugs in from fatigue,

if all those check good then it may be a failing or failed capacitor, with new caps, if it has the same problem then it would be a board level component open or short ... the gurus may have further insight

Best regards Rob Very Happy
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Rob Blessin President computerpowwow ebay sales@blackholeinc.com http://www.blackholeinc.com
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barcher174



Joined: 07 Dec 2012
Posts: 560

PostPosted: Mon Apr 03, 2017 9:53 pm    Post subject: Reply with quote

I would definitely be suspicious of the RTC circuit based on this behavior.

http://www.nextcomputers.org/NeXTfiles/Docs/Hardware/Schematics/Turbo_slab/CSlab33-03.pdf

http://www.nextcomputers.org/NeXTfiles/Docs/Hardware/Datasheets/MCCS1850%20(2).pdf

Check the battery voltage across pins 8 and 1. Then check the diodes around it. It looks like you can short pin 12 to ground to force a startup.
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hawkman



Joined: 25 Apr 2016
Posts: 16

PostPosted: Tue Apr 04, 2017 9:36 am    Post subject: Reply with quote

The RTC circuit is definitely in my sights now.

I've discovered that if you leave the computer plugged in with the battery connected correctly for a few hours, reverse the battery and then install it correctly, it boots. It's still strange to me that the power key does nothing but I have no experience with Turbo slabs so this may be normal. But anything that needs to "charge up" strikes me as a capacitor problem. I've emailed Rob to order the capacitor kit.

Some other information that supports the RTC issue: upon booting, it gives a "System test failed" message in the graphical startup screen. In the ROM monitor, typing "ec" gives "Last error code: 91" which appears to be a RTC error code.

I've also ordered a SCSI2SD kit. If anyone knows a source for a soundbox, Y cable and non-ADB keyboard, I'm in the market for these too!

I'm determined to get this machine working...!
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hawkman



Joined: 25 Apr 2016
Posts: 16

PostPosted: Tue Apr 04, 2017 9:40 am    Post subject: Reply with quote

FYI, I found this post:

http://www.nextcomputers.org/forums/viewtopic.php?p=18175&sid=320c042061bf28bb1e7214ea8dbdc4bd

I'll try reflowing the battery connector this afternoon.
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hawkman



Joined: 25 Apr 2016
Posts: 16

PostPosted: Tue Apr 04, 2017 2:41 pm    Post subject: Reply with quote

I reflowed the battery connector - no change. So that's not the issue.

I then looked at the RTC chip. There's a bit of green corrosion around the pins which I'm going to clean a bit. Pin 1 has the battery voltage on it, as does pin 12. I tried shorting pin 12 to the negative battery terminal and the machine started right up.

This time I put the working flash disk from my 25MHz Color into it. It booted with no drama. Mouse and sound box are working fine.

I'm coming to the conclusion that this machine works perfectly except that it is not responding to the power key. Even inside Nextstep, the power key doesn't register. There is some weird hardware failure going on here.

I'm going to look more specifically for how the power key is wired up in the schematics. This is a real head-scratcher.

EDIT:

I looked at the schematics again and it appears pin 12 is connected through inductor FL1 to the power switch. I tried to figure out how this is wired on the actual board and I found something troubling.

The most likely trace for this runs from underneath the RTC chip, under the battery and power connector and between the middle SIMM slots to the back of the computer which would be logical because that's where the keyboard plugs in via the soundbox.

This trace is really corroded near the RTC chip and looks almost burned in between the SIMM connectors. This leads me to believe that the trace is damaged and that's why the power button isn't being recognized.

Now, my questions are:

- Can I just run a wire from PIN 12 to wherever the power switch is being read from, presumably FL1?
- Where is FL1?

Getting close!
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barcher174



Joined: 07 Dec 2012
Posts: 560

PostPosted: Tue Apr 04, 2017 3:21 pm    Post subject: Reply with quote

FL1 should be close to the 13W3 connector I would assume. You can run a patch wire directly to the RTC from there, but make sure you cut the remaining connection in case it's shorting. I have fixed a couple of 68040 cube boards in the same way.
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barcher174



Joined: 07 Dec 2012
Posts: 560

PostPosted: Tue Apr 04, 2017 3:32 pm    Post subject: Reply with quote

I should mention that to fix this properly you would want to remove the RTC completely and clean the area/inspect the traces under a microscope. In reality you can probably get away with just scrubbing with a toothbrush and high grade alcohol. Then cut the trace going to the RTC with a razor blade or small screwdriver and lay a patch wire across to the good connection at the 13w3 side. Finally, I use hot glue to anchor the wire to the logic board.
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hawkman



Joined: 25 Apr 2016
Posts: 16

PostPosted: Thu Apr 06, 2017 9:26 am    Post subject: Reply with quote

I've ordered a high-quality soldering iron for this project so that I don't wreck this piece of computing history.

In examining the board, I'm having trouble identifying where FL1 actually is. Does anyone know which pin it connects to on the 13W3 connector?
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