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.

[Zac67]

This can't be connected to the SCSI config, at least not directly. Make sure there are no loose metal parts inside the case causing shorts - may have been moved while reconfiguring.

The only thing you can do fundamentally wrong in SCSI is to plug in the cable upside down, but even that can't cause damage when everything accords to standards. Plus the machine would still power up.

Amiga PSUs are dumb ones, i.e. they don't care if anything is attached to them. When they fail to power up (fan spinning?), it's a matter of
- no mains
- PSU broken
- short somewhere (there's a short protection built-in, otherwise some board traces would burn up)

Check out the mains lead - I've had occasions where the contacts were bent/bad. If nothing happens when switching on, switch off again, disconnect the PSU plug from mainboard and try again. If it does power up now, something is short-circuited. (Don't let the PSU run unloaded for lengthy periods.)

Additionally, I think the VLab (Motion?) requires a dedicated HDD and can't share the system disk.

[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)??  

[Zac67]

Usually you can connect the host adapter to any connector of the SCSI cable - provided the bus is terminated at both ends. The BBoAH pics don't look like the VLab provides any means for termination, so you'd have to make sure to terminate the HDD and use a cable terminator behind the VLab.

The Zorro slot shouldn't matter, but depending on what else is hooked up it might. Most of the time you'd put the SCSI adapter in the rightmost slot and add the rest of the boards to the left with decending speed requirements.

[Matt_H]

I've never used a VLab Motion before, but something tells me that you shouldn't be hooking it up to the SCSI chain, but rather giving it its own chain. That's how other video cards work, at least.

It doesn't seem like it would make sense to attach it to the existing chain since it should already be able to access the existing chain through the Zorro interface.

One last point: are you absolutely certain that it's a SCSI port on the card? There are a few cards from other manufacturers (DPS) that have 50pin headers that are not SCSI ports.

[Zac67]

One last point: are you absolutely certain that it's a SCSI port on the card? There are a few cards from other manufacturers (DPS) that have 50pin headers that are not SCSI ports.

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.

[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.

[Zac67]

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.

[Matt_H]

Tell us more about the machine: Kickstart, accelerator, other cards, etc.

You should really get a set of Workbench disks. Any dealer can fix you up.

[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

[Matt_H]

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?

[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.)

[rkauer]

 I think you just burned the SCSI chip on the A2091.

 A friend is selling some of them in this very forum. Do a search for WD33C93.

 Also never connect two boards if you don't know about 'em.

 Or better buy another type of SCSI controller. A2091 is too slow and rubbish, anyway. Grab a GVP SCSI+ or SCSI+8 for a little more than the sluggish 2091 if you can afford it.

 

[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?