NeXT Turbo Color No Video

Started by Rob Blessin Black Hole, March 20, 2019, 10:43:31 pm

Previous topic - Next topic

Rob Blessin Black Hole

Hello NeXT Community:
So I have 2 NeXT Turbo Color Motherboards with no video.
Both have new ceramic capacitors
Both power up
Green light blinks 5 times on motherboard and repeats!
known good ram
good power supply
good bios battery
will also try swapping out rom chip (thinking out loud)
known good power cable
known good monitor
known good monitor cable
known good sound box
known good keyboard and mouse though not related to video issues
known good sd drive with openstep

Any idea what the 5 light beep code is?

Seems to be a plague of issues developing with component failure on Turbo Color motherboards for me this week , another one does not power up ....

13w3 connector looks ok on the motherboard
and the schematics, anyone fixed this issue before...
I also have many 25Mhz Color donor boards ....


http://www.nextcomputers.org/NeXTfiles/Docs/Hardware/Schematics/Turbo_slab/CSlab33-06.pdf
Rob Blessin President computerpowwow ebay  sales@blackholeinc.com http://www.blackholeinc.com
303-741-9998 Serving the NeXT Community  since 2/9/93

barcher174

5 blinks is RAM. Try filling all the banks and see if you can get a picture.

rumbeard

Quote from: "barcher174"5 blinks is RAM. Try filling all the banks and see if you can get a picture.


Are the RAM bank pins prone to dry solder or contact gunk?

Rob Blessin Black Hole

Hello Brian: I tried different ram as well and the ram works in another turbo color board also swapped the rom chip and it works . I'll try cleaning the ram slots in the morning and check for any anomolies !  Thanks  .... I have another Turbo Color motherboard missing BNC that is booting using the same ram with the rom chip.
Rob Blessin President computerpowwow ebay  sales@blackholeinc.com http://www.blackholeinc.com
303-741-9998 Serving the NeXT Community  since 2/9/93

rumbeard

Thanks for your work.  What I meant was turning the board over and checking the ram socket attachment to the board and seeing if all pins have a proper solder glob or if any are chipped/corroded/need solder reflow... then flip over and check for any bent, torqued, or missing pins.  All of this is really rare if you have a board that was always babied but I've seen it on maybe 8-10 boards in my entire history of computer repair over 30 years... so that's a very small % but I always give that a glance when pulling stuff.  My thought also would be if POST tests bank 0 and 1 first that those would probably be the ones with issue.

Rob Blessin Black Hole

Quote from: "rumbeard"Thanks for your work.  What I meant was turning the board over and checking the ram socket attachment to the board and seeing if all pins have a proper solder glob or if any are chipped/corroded/need solder reflow... then flip over and check for any bent, torqued, or missing pins.  All of this is really rare if you have a board that was always babied but I've seen it on maybe 8-10 boards in my entire history of computer repair over 30 years... so that's a very small % but I always give that a glance when pulling stuff.  My thought also would be if POST tests bank 0 and 1 first that those would probably be the ones with issue.
Great advice here as well, thank you Rumbeard
I've examined the back of the board as well as the physical simm slots and both appear to be in good order no signs of misuse are age , fatigue or rust .   Knowing the 5 blinks is ram related should help as well , the ram does work in an alternate Turbo Color motherboard  so I think that helps with the cross comparison troubleshooting.  I'll have Matt try and reflow the solder as well that is a excellent suggestion .
Further testing
I tried a different rom chip same 5 blinks on the motherboard  and different ram .
I'm tempted to try swapping in a known good 68040 33Mhz processor , question .
In looking closer at the board  it appears 2 of the replaced ceramic capacitors right above the simm slots have pools , this may have been a board Charles at MacCaps did for me as Mat's work is usually much cleaner so on a hunch I'm going to have Matt swap these caps on this particular board.
Now as far as the board that won't power up with new caps ,  I think I will have him try and reflow the battery connector also is there a cap that may affect power on off , my guess is this one is probably an easy fix  once we figure it out.
I know this thread will also help others with same symptoms so feel free to check in we are friendly.
Rob Blessin President computerpowwow ebay  sales@blackholeinc.com http://www.blackholeinc.com
303-741-9998 Serving the NeXT Community  since 2/9/93

Rob Blessin Black Hole

Hello NeXT Community:

All Turbo Color Motherboards:

Matt my capacitor guru came by and we checked the boards.

No video on one board and because there was no motherboard beep code , inspecting the actual video connector appears to be a cold solder joint on the board. So hopefully reflowing that will fix the issue.

No video board with 5 blinks repeating which indicates a ram issue , we did not recap this particular board and the past cap work  appears to have left pools of flux, hopefully they did not pull a pad as this may have caused the issue so we are  going to just recap it to see if that works.

No power up motherboard with new caps , nothing stands out after inspection , this one I'll send to Brian .... would a bad crystal cause this ?

Missing BNC Connector boots has new caps.... we are going to attach a new bnc connector from a donor board and it should continue to work.

Another board with new caps stalls on boot at checking ethernet so we are replacing both the rj 45 and bnc connectors to see if it resolves the issue.

My head hurts from eyes straining lol , I'll keep you all posted.

Rumbeard , we should have a nice working solution for you by Monday!

Also have Started a Cube project for a Museum in Moscow and multiple item orders makes time pass quickly!

best Regards Rob Blessin
Rob Blessin President computerpowwow ebay  sales@blackholeinc.com http://www.blackholeinc.com
303-741-9998 Serving the NeXT Community  since 2/9/93

barcher174

Hopefully it should be obvious to everyone by now to replace the capacitors before wasting your time doing any board level debug. Some personal notes I have:

1) The boards seem to be much easier to damage by mishandling. The mask is much easier to damage than the older boards and the traces more fragile. First step is a -very- thorough board inspection. Be sure to check the surface mount ASICs for bent pins causing a short.

2) The boards generally generate more heat. This includes the ASICs and the 74F543D transceivers in the memory path. The memory path is not very fun to debug even with a schematic. The ASICs are -much- more fragile than the old ceramic style. If one is dead, that may just be a parts board. They can be swapped from another turbo board but I don't recommend unless you have really nice rework equipment.

3) Bad video RAM will still allow you to boot and view errors, with the exception of the first 4 chips (counting from the 72pin simm side of the board). These are connected directly to the ROM

4) Always check the traces around the ROM chip. Using the wrong tool can easily damage the traces around it and leads to a whole host of strange behaviors.

Rob,

In reference to your boards:

1) No Video:  Did you see the LED light up at all? It should have and then turned off. This can also be a bad BT463.

2) 5 blinks: You can replicate this behavior by removing the RAM entirely or sometimes if the RAM is in the wrong bank (curiously it will also sometimes boot like that). I think generally this code means there is not enough system memory to bring the system alive. After you have cleared the capacitors of suspicion I would check the 74F543Ds.

3) No Power: You pretty much have to start from the power on signal and work your way back. Bad crystals are very rare I've been told. Either way it should power up with other issues.

4) missing BNC: I've had to replace so many of these...

5) Ethernet hang: Check the VIA connections around where the electrolytic capacitors are/were. I've had to replace a few ethernet chips as well.