Problem with Amiga 3000T , Please help !

[mechy]

Well he doesnt believe me that the A3000T SCSI NVRam settings are stored on the batt. He doesnt have one installed. This could be a solution.

When the 3000(t) does not have a battery,it falls back to the default scsi settings, worst case it is just not set to synchronous usually. It should still work fine.

[mechy]

6 feet long?! That's way too long. That causes errors, and data loss may occur.
Try shorter cables of 10" - 15" inch max.

That is absolutely wrong, where do you get this stuff. a 6ft cable is fine.

SCSI I standard specifies up to 6 METERS(over 18ft~) for cable length.
SCSI II standard specifies 3 meters which is over 9ft.
 I run long cables in my 3000t's with no issues whatsoever for many years.
Besides,you would be lucky to reach anything in a 3000t with 15" cable.

If anything the revision 4 WD scsi chip is a problem child. Many times you cannot use multiple devices on this and i believe its known to have a broken scsi II command set, it can also be a source of scsi going haywire and giving errors when a A3640 is added into the mix.
Updating to the western digital rev 8 or the Amd chip solves most scsi woes on the 3000.

It might be wise to learn a bit more about scsi instead of putting out bad information on the forums that gets repeated year after year.

Mech

[mechy]

Some good suggestions from Zac67 regarding the memory, certainly worth checking all of the ZIPs are the same.  More information here.





As for the RTC backup power supply; you're far better off using a small signal Schottky diode as opposed to a standard silicon diode (e.g. 1N914, 1N4148, 1N400x, etc).

To look at the maths behind it...
From the RP5C01 datasheet we can see the minimum input voltage is 2.2V at a current of 15µA.  The RTC has a 1.2k Ohm resistor in series with the battery (see schematic).  So it'll develop (1.2k x 15µA) = 18mV, or round to 20mV across it.  So the actual minimum voltage at the RTC becomes (2.2V + 20mV) = 2.22V

If a 1N914 diode was used, we can see it has a forward voltage drop of around 0.55V at 15µA.  So it'll only provide a clock backup until the cell reaches a voltage of (2.22V + 0.55) = 2.77V.  The CR2032 cell is 3V nominal, meaning it only has to discharge by 0.23V to a terminal voltage of 2.77V before it'll need to be replaced, so that's using well under half of the cell's capacity.

If a Schottky diode was used instead, say a common BAT85 for example, we can see the forward voltage drop will be less than 0.24V at 15µA.  So the cell can discharge further to (2.22V + 0.24) = 2.46V before it needs to be replaced.  You still won't get to use the full rated capacity of the cell (230mAHr), but at a guess you'd still get about 60% of that (140mAHr).  At a current draw of 15µA, I'd expect a clock backup time of 389 days or 13 months.  Of course that depends on the exact cell being used, age/condition of the cell, exact current draw of the RTC on standby and the temperature.

So in summary, while the silicon diode will work, you'll get far longer out of the coin cell if you use a small signal Schottky diode.

May i also add the LIR2032 3.6v lithium is a direct replacement for the cr2032 coin cell and is rechargeable,but should NOT be recharged by the amiga,Use the diode as you normally would.Because it starts at 3.6v you will also buy some time before its dead. They make external wall chargers to recharge these coin cells.

[mechy]

Oh and mechy, your post counter is the number of the beast 666. Post a reply or something quickly, before bad things might happen with you... :nervous:  

:razz:

BOO! hehehe :angryfire:

[mechy]

Many thanks for the thoughtful reply. Measuring a 0.3V drop here, and 3.05V total on the anode side - looks like it'll go a few more years yet, with the potential to do a bit better with a Schottky.

This is probably obvious, but it's worth mentioning I've had great luck with the Renata (or anything made in Japan) 2032's. The Chinese ones die quickly.

No problem with original sony coin cells here, i guess the people having capacity problems are buying those cheap china cells.

Also if there is a bad diode in the circuit or left over leakage from a bad battery that was not cleaned well and can be conductive in some cases.
 it can drain the batteries prematurely.


Mech

[mechy]

Dude, why waste your time trying to fix that POS computer?  Everyone knows that the best computer is the Amiga 2000.  (The great Doom Master even thinks so!)   It's a work horse and never has issues like this!  

My A3000T is also not working. I think it has a flakey CPU slot on it.  It's just a big hunk of metal right now.  Dead as a doornail.  I have to open it up every so often and reset the CPU card on it to get it to work.  Never have this problem with my Amiga 2000's...

I cant tell if you are joking or what,but siding with doomy has already blown it for you.. :biglaugh:

The 3000(t) can be as reliable as anything if its in good condition, 90% of these i have fixed have been problems with bad connections somewhere, the rest were power supplies,bad factory chip socket here and there,etc.

Its a known problem the accelerators can work their way out with heating/cooling cycles on big box machines. That is why there are metal standoffs to secure it to. Use them,they stop many problems of bad connections to the accelerator boards.Socketed machines will eventually all suffer more connection problems than surface mount machines down the road..Commodore did not exactly use the best sockets.
While i did start on a A2000 in 87' and loved the old girl,nothing beats a proper 32bit amiga :knuddel:

Let me know if you get tired of the 3000T and want to sell it.

Mech

[mechy]

Thanks, I think I need to find some better ones, and maybe some that will screw the cpu card down.  I have a Cyberstorm MKII 060 in there now.

some 3000/3000t's came with the wrong length standoffs so beware of this. If you need i can take some measurements of the proper length ones.

mech