Microbotics Starboard 2 for A500 HELP

[Metalguy66]

Somehow I don't believe you. Your "stock" A500 PSU is probably a custom one. I had/still have an A500 with the TRUE stock PSU, and it could BARELY power the 512K belly memory expansion and one external floppy. NOTHING else. Period. End of discussion. New and more powerful PSUs for the A500 did a brisk business in those days as the stock supply was good for nothing. Wherever you got your A500 from, the dealer almost certainly swapped your PSU for something more powerful.

The stock supply for the A1200 was even worse. Go to any Amiga magazine or any Amiga site and you'll see the same thing - those stock supplies couldn't power virtually anything at all. It's why things like the GVP had their own supply in the first place. They wouldn't have put it on there if it wasn't necessary.

I have 4 A500 PSUs.. They came from all different sources and I use them interchangably between systems with no problems whatsoever. They all bear the same part number (312503-01), but one is noticably heavier than the other three.. And interestingly, the heavier one is rated at less current (4.3a) on the 5v circuit than the other three which are rated at 4.5a...  The 12v circuits on all 4 are rated at 1a, and the -12v circuits are all rated at 100ma(.1a).

All of my machines are rev 8a or rev 6a..  And all three run fine (and have for years) fully loaded with side-car, internal hardisk, and extra ram... and NO ADDITIONAL PSU..

If you have a hard time believeing this, than I dont know what to tell you other than "sucks to be you"...  I sympathise with your past problems, and I suspect that you had earlier and more "power-hogging" designed hardware than is employed in the systems/add-ons that I have..

I guess I could hook my ammeter in-line with the 5v circuit on the PSU of each machine, to see exactly what they are drawing in terms of current, but I really havent the inclination to do so.. Like I said.. It's all worked great for years..
 

[jj]

@ JLF65

Nope your mistaken.  The A500 power supply was more than enough for A500 with expansions.  I even used to use one to power my A1200 with expansions because the A1200 supply was so flakey.

I remember that most magazines would suggest using A500 power supply first if you were having problems with an expanded A1200.

Maybe different regions has better or power supplies, or maybe its down to different regions having different/better power grids.

[Metalguy66]

I dont think anyone is "mistaken". I just think weve had different experiences..

For example: And A500 rev3/rev5 board has 16 (256kx1)ram chips just to make 512k. This pulls significantly more current than 4 (256kx4) chips on a rev 6a (or later board). You throw in an early model A501 expansion, and guess what.. ANOTHER 16 chips.. Thats 32 ram chips instead of 8 on the later models.

Also, look at the size difference in the stepper motors on the early floppy drives (like the A1010 and early "all metal" mechs used in the first A500s & A1011s) versus the new "plastic" ones used in the later A500s. Floppy drives are consntantly starting & stopping spindles and "grinding away" at the disks moving the head steppers.. Also remember with MFM, it cant start & stop one drive spindle independantly, it does both simulatneously.

Also, look at early hardisk controllers that used all DIP package logic, and tons of it, versus the newer designs that only had one or two small surface mount package custom chips. (eg. the A590 versus the GVP A500 HD+/8)... big difference..

Its also possible that commodore "beefed up" the PSUs in later A500s after so many people b!tched about them burning up in earlier units.

I would expect the A1200/A600 motherboards to be significantly less power-hungry than an A500 due to the fact that almost everything had been replaced with newer, smaller, surface-mount components.

So you see, there's quite a few factors here. I believe him when he says he had problems. Ive heard others say the same thing. Im just glad my particular combinations work with a single stock PSU. Id hate to have YET ANOTHER power cord to deal with, or some "hacked PC unit" looking PSU..

[JLF65]

Metalguy66 wrote:
I dont think anyone is "mistaken". I just think weve had different experiences..

For example: And A500 rev3/rev5 board has 16 (256kx1)ram chips just to make 512k. This pulls significantly more current than 4 (256kx4) chips on a rev 6a (or later board). You throw in an early model A501 expansion, and guess what.. ANOTHER 16 chips.. Thats 32 ram chips instead of 8 on the later models.

Also, look at the size difference in the stepper motors on the early floppy drives (like the A1010 and early "all metal" mechs used in the first A500s & A1011s) versus the new "plastic" ones used in the later A500s. Floppy drives are consntantly starting & stopping spindles and "grinding away" at the disks moving the head steppers.. Also remember with MFM, it cant start & stop one drive spindle independantly, it does both simulatneously.

Also, look at early hardisk controllers that used all DIP package logic, and tons of it, versus the newer designs that only had one or two small surface mount package custom chips. (eg. the A590 versus the GVP A500 HD+/8)... big difference..

Its also possible that commodore "beefed up" the PSUs in later A500s after so many people b!tched about them burning up in earlier units.

I would expect the A1200/A600 motherboards to be significantly less power-hungry than an A500 due to the fact that almost everything had been replaced with newer, smaller, surface-mount components.

So you see, there's quite a few factors here. I believe him when he says he had problems. Ive heard others say the same thing. Im just glad my particular combinations work with a single stock PSU. Id hate to have YET ANOTHER power cord to deal with, or some "hacked PC unit" looking PSU..

Now that all makes more sense. I got one of the early A500s, so the RAM was just like you described. Floppies in '89 or so were definitely a far cry from one in the middle to late '90s. The A500 manual itself said to not use more than the RAM expansion and ONE floppy without replacing the PSU... which I one of the first things I did, getting a Phoenix PSU, which had a handy on/off switch as well.  :-D

I eventually chopped up one of my A500 PSUs for the cable, which I attached to a 125 W PSU. That was able to drive my A500 with one of those funky 512K extra chip RAM + 2.5 MB of slow RAM expansion cards (Fatter Agnus required), 68030 with 8MB, two external floppies, and a Slingshot with an EMPLANT and HYDRA ethernet cards. That wouldn't work without TWICE the power of an A500 stock PSU.  8-)

[TjLaZer]

I have not had a chance to crack it open, but there is no markings on the rear as to what volt AC adaptor to use.  Bummer.  So what am I looking for inside?  I guess I will just take some pics and post 'em here.    

As a side note I am using a R&D 200 Watt PS with this A500. I wish the damn side car would just use the power off the bus.  I also have another 1200 that has a Apollo 1240 card, with 64MB and I use that with my internal 8GB HD off a stock A1200 PS and it works great!  

[TjLaZer]

OK I opened it up and took some pics, see this post:

[Metalguy66]

The PSU circuits are on the bottom board. Your gonna have to get a good close-up shot of the bottom board if you want my input..

I would definitely NOT try any more AC voltages unless you know for sure it requires AC... DC voltages will not hurt it even if it's designed for AC, but the opposite is not necessarily true.. You could fry it..

If you can remove those upper boards and get me a good hi-res shot of the lower board (the one the power connector is actually hooked to) I can tell you for sure an appropriate supply voltage for it, as well as the required polarity if necessary.

[Methuselas]

Hey Guys, Metalguy66 knows what he's talking about. He's the only guy in H-Town that I'd ever let touch any of my amigas.

Well, other than myself, that is....


But I trust his judgment more than my own.


Just my 2p.

Speaking of, when am I going to get to your house to have some indian food, Ken? =D I'm going back to Cali in about 3 months. Got a job working for DC Comics. :-D

[TjLaZer]

I did not use AC sorry, I used two DC5V power supplies and nothing happened.  I then tried a DC6V and it seemed to come alive!  A500 finally booted and the LED on the StarBoard2 stayed on but there is nothing there.  No mem or stardrive.device is present.  Hmmm  (NOTE: LED on StarBoard2 flashes when no PS is attached, and A500 will either lock up or Guru on powerup)   I have a DC7.5 PS I am temped to try but I do not want to fry this thing!   :madashell:

Unfortunately I do not want to dismantle this thing as I might break it.  I am not anxious to get it running so I might wait until I can possibly find out more info on what kind of PS it needs.  Is there a way to determine this with a volt meter?

[TjLaZer]

A little necrobump!

Got around to messing with this again.  Tried it on my A1000 and it would not show the Kickstart screen with it hooked up.  Screen would stay dark gray then turn different colors and just sit there.  Tried it with a 5V DC 2amp Zip drive power pack and it would just show a black screen.  With nothing else to lose (does not work!) tried a 12V DC powerpack.  Smelled something burning!  DOH (yeah yeah).  Decide at this point I need to just dismantle the damned thing.  Took it apart, and hooked up the main board to my A1000, and it works!  So the Zorry but adaptor part seems to be toast.  And there are 3 crisp looking caps.  Previous owner probably did what I did and fried it