Please help -- SCSI stupidity on my part (?)

[orb85750]

OK, I must not understand SCSI.  Are there certain device assignments that need to be made in order for my computer even to turn on?  The A2000 was working fine until I tried to add a Vlab card to the SCSI chain and Zorro II slot.  Then, the computer would not even turn on -- not even the power supply fan.  I removed the board from the chain and everything powered up as usual.  Then, for some reason, I removed the Commodore 2091 and the end of the SCSI cable from it.  When I put it back together (in its Zorro slot), the computer would not power on, and it still won't.  The computer will power on only if I remove the 2091 from the Zorro slot too.  Of course, I am now prompted to insert a workbench floppy (which I don't have).  If you can, please help.  Each step I take seems to be making things progressively worse!  I'm pretty clueless here, but at least the power supply does not appear to be broken as I originally thought.  Thanks & please excuse my ignorance.

[orb85750]

Thanks, time to roll up my sleeves and check everything carefully.  Yes, I have a separate SCSI work disk at the end of the chain.  Does it matter where in the chain the Vlab motion board goes (and which Zorro slot it's in)??  

[orb85750]

Unfortunately, I cannot read German and there is no English manual available for Vlab motion.  On my first install attempt, I did not add the Vlab to the SCSI chain.  I just put it into the Zorro slot.  The software installation was successful, but every time I would start to load it, it simply froze up and I had to reboot the computer.  I noticed the SCSI-like connector and that's when I hooked in the ribbon cable.  Obviously, trial and error with electronics is stupid, but I was not aware of such non-SCSI connectors, so I thought this was a no-brainer!! (bad choice)

Looking at the computer from the front, which pin would be #1?
Left, closest to front?

I should reiterate that the power supply does work provided that nothing SCSI is plugged into the Zorro slots.  I was able to find an old WB1.2 floppy and booted up the system successfully with that.  BUT, with anything SCSI (including the 2091 itself) plugged in, even the power supply fan will not power on.

[orb85750]

Zac67 wrote:
Does the PSU fan give a slight jerk when turning on (look closely)? That would indicate a short circuit on the 2091 (the PSU's short protection needs a tiny moment to catch).

I think pin 1 is front right, but you can use the GND pins to check.

There's a slight flicker on my monitor screen when I attempt to turn on the system with a SCSI plugged in.  As for the Zorro voltages, I've tried all permuations regarding which could be pin #1 and something is wrong with some of the voltages no matter what.  Pin #5 (*if* I am measuring #5!) does give 5V, but then the other pins do not give correct voltages (way off, some 0 that shouldn't be 0).  Again, in guessing which is pin #1 (from all four possibilities), there is no combination that gives the correct voltages overall.  So something is wrong now with the Motherboard or power supply -- should I conclude???  Thanks, -Dave

[orb85750]

Matt_H wrote:
If I'm reading your posts right, you removed the VLab and everything was fine, then tinkered with the SCSI a bit and ended up in your current no-boot/no-fan situation. Is that accurate?

But the machine does boot from floppy with no 2091 plugged in?

Yes, the system boots flawlessly from a floppy so
long as the 2091 is removed.

The history of the debacle....
With the Vlab in the Zorro slot and attached to the SCSI chain, I had no power, no fan.  When I removed it from the Zorro, I was able to boot up the system from the hard drive initially.  But then I tinkered some more, trying different SCSI connections and Zorro slots for the Vlab.  I must have done more damage, because even with the Vlab completely out of the picture, I can no longer get anything associated with SCSI to work (so I cannot boot into OS2.1 -- now using old OS1.2 floppy for boot).  The computer will turn on only if no SCSI of any kind is plugged into the Zorro slots.  I'm very confused at this point.  -Dave

[orb85750]

Hmm...
amiga.resource.cx lists these features for the VLab Motion:
* optional digital YUV or RGB component transcoders (50 pin feature connector)
* no [...] dedicated hard drives are required
* additional adapter for direct interfacing with the Video Toaster

So the 50pin seems to be the feature connector and NOT SCSI. I figured orb had consulted the manual. Obviously that complicates matters as just about anything might have been killed. :-(

@orb85750: Try to find out which pins carry power or GND and post those here, possibly we can get an estimate of what might be damaged.
These Zorro II slot pins are relevant:
+5V: pins 5 & 6
-5V: pin 8
+12V: pin 10
-12V: pin 20
ground: 1-4, 13, 25, 37, 49, 61, 73, 85, 87-91, 99-100
The GNDs are probably all connected together so any of them will be fine for measuring.

MY VOLTAGES checked on a couple of Zorro slots:
PIN 5: +5V
PIN 6: 0V to +0.3V
PIN 8: +2V
PIN 10: +5V
PIN 20: +2.5V (some charts leave this pin blank/unknown)

In any event, my situation does not look good, given that only pin #5 is giving the expected voltage.  ANY SUGGESTIONS at this point or should I simply look to buy another Amiga 2000 and hope that most of my expansion boards still work?  I thank you for your input.  (One less working Amiga in this world, thanks to me.)

[orb85750]

If the SCSI board is the problem at this point, then why are my Zorro slot voltages so far off from what they should be showing, given that nothing SCSI is attached (not even the 2091) when using my voltmeter?  

[orb85750]

My Amiga is becoming crazier by the minute.   The good news is that I checked the *correct* pins now in a Zorro slot and they all checked out perfectly!  With no SCSI attached, the system  booted up fine with a floppy.  Then I inserted the Vlab motion board.  The computer powered up, but the floppy drive was never accessed and I had a black screen.  Tried again, but this time, the system turned on then off completely within 10 seconds.  Removed the Vlab motion.  System turned on and off again in 10 seconds.  So, now I cannot get the system to remain on or recognize the floppy drive even with no SCSI and no Vlab motion installed.  Whatever the problem is, it seems to be getting progressively worse.  Could it be some kind of grounding issue??  Is the power supply itself very suspect?

[orb85750]

Matt_H wrote:
So now with nothing installed things are going up and down? That points to a PSU issue.

That sounds reasonable.  But does it make sense that my tinkering over the past few days would make the issue worse?  Before the Vlab motion install attempt, the power supply worked 100% perfectly with not a single case of sketchiness.

[orb85750]

Thanks again for the sensible advice.  I will be overjoyed if the power supply turns out to be the solution and nothing else is destroyed.  -Dave

[orb85750]

What is the metal bar that goes across the A2000 case from front to back, parallel to the boards?  Is it a grounding device or is it simply there to support the structure?  It is movable, so if it is a grounding device, what is the best place for it?