Amiga 500 IC issues

[SuperSpork]

Hello all,

I am now the proud owner of an Amiga 500 with 512k expansion.  This is my first Amiga to date, so I don't know everything yet, but I am learning quickly.

I'm having intermittent issues, however.  Two issues plague me the most -- the flashing power light, and scrambled video.  (For reference, I'm using the mono/greyscale video port for the moment, as I don't yet have a modulator or an RGB monitor.)

Seems to me that the IC's just do not want to stay in their sockets, as pressing firmly on the CPU usually fixes a flashing power light, and pressing on the Denise chip usually fixes scrambled video. But it doesn't usually stay fixed, and that doesn't always solve the issue. So, my question is, what's the safest and most effective way of cleaning the contacts on an IC?  I've done the trick with a hard eraser to remove oxidation, but that might have made things worse to an extent.  I also know I could solder the chips into their sockets for the best reliability, but I don't really want to do that.

Also, what other things (other than the power supply -- which I can't currently test because I don't have a multimeter handy) should I check?  I know everything individually is working alright, as when it does work, it works wonderfully, just not 100% of the time.

Finally, the CPU has been replaced with a Vortex ATOnce, which is piggybacked over a stock 68k.  Can I replace this back to a regular 68000, or shouldn't I?  I don't really have any use for it.

Thanks

[Zac67]

If the socket contacts have gone bad the best option is to replace the sockets with quality ones...

[rossb]

Hi,
 
 I had a similar problem, and removed all the socketed IC's and used electrical contact cleaner on the pins and replaced them. Also I had an issue where after 10-25 mins the A500 would just shut down (no restart). I tested the PSU when this happened and I had lost the +5V feed. I have since hacked up an ATX power and all runs great now.
 
 HTH,
 
 Ross.

[save2600]

I'd yank that silly IBM ATOnce clone thing but quick. Probably the point of contention in the system too. Yes, yank the 68000 off of that and reinstall directly into the CPU socket. Be careful to observe correct notch orientation.

Best way to clean IC pins is to simply remove and re-insert them. The friction of the sockets is usually enough to "clean" 'em. If they're truly oxidized, get yourself some very light grit sandpaper or a fiberglass brush to clean 'em up.

I'd be willing to be though most all of your problems will be solved once you get that AtOnce board out. All the chips, but especially the Kickstart, CPU and Agnus chips all deserve to be re-seated.

[amigaksi]

Hello all,

I am now the proud owner of an Amiga 500 with 512k expansion.  This is my first Amiga to date, so I don't know everything yet, but I am learning quickly.

I'm having intermittent issues, however.  Two issues plague me the most -- the flashing power light, and scrambled video.  (For reference, I'm using the mono/greyscale video port for the moment, as I don't yet have a modulator or an RGB monitor.)

Seems to me that the IC's just do not want to stay in their sockets, as pressing firmly on the CPU usually fixes a flashing power light, and pressing on the Denise chip usually fixes scrambled video. But it doesn't usually stay fixed, and that doesn't always solve the issue. So, my question is, what's the safest and most effective way of cleaning the contacts on an IC?  I've done the trick with a hard eraser to remove oxidation, but that might have made things worse to an extent.  I also know I could solder the chips into their sockets for the best reliability, but I don't really want to do that.

Also, what other things (other than the power supply -- which I can't currently test because I don't have a multimeter handy) should I check?  I know everything individually is working alright, as when it does work, it works wonderfully, just not 100% of the time.

Finally, the CPU has been replaced with a Vortex ATOnce, which is piggybacked over a stock 68k.  Can I replace this back to a regular 68000, or shouldn't I?  I don't really have any use for it.

Thanks

Just some more possibilities:

The ATOnce I had for A500 wasn't that tight fit in the socket plus could cause power issues depending on what else is connected to your A500.  Having said that the flashing LED doesn't necessarily mean a 68K issue.  Also, if pressing on the ICs make things work it can mean that some pins are bent or partly broken so they aren't making contact (on the edge of making contact).

[JimS]

I agree with save2600.... pull that AtOnce board & put the 68000 back in it's socket.... then take the AtOnce outside, run a Humvee over it a couple times, burn it, then scatter the ashes at midnight in a graveyard. ;-) I used to work at an Amiga store, and we had nothing but trouble with those. If you need a peecee, well, much better machines than a 286 can be had for nothing these days.

[Tenacious]

Multimeters are cheap.  If you know how to use it, never be caught without one.  I would suspect the PS until it's proven.

Examine the pins of the square chips to see if all are correctly formed.  If one is abinormal, gently bend it like its neighbors.  Don't overdo it.  Same with the dips.

Don't GeorgeBush the Atonce!  I'd be interested in buying or trading for it if it has no use to you.  I have spare 68000s and other options.  Let me know.

[SuperSpork]

Thanks everyone.  Hopefully next week I'll have a little time to sit down with the thing to do a little more thorough cleaning.

Looks like I'll need a PLCC puller as well.  The Agnus is pretty firmly seated in its socket... I'll take that as a good sign.  Might as well invest in a good DIP puller as well while I'm at it.  (I know where to get them cheap too.)

The ATOnce actually caught me off-guard at first.  There's a badge on the case of the unit that says 386dx/33, but I assumed it was on there by accident.  Then I spent a while wondering how the heck they managed to emulate a 68k on a 286 until I realized that there was a 68k underneath.  What is it actually good for, anyway?  As far as I can tell it's hardware emulation of the IBM PC, but I'm not sure why that would be important.

[save2600]

What is it actually good for, anyway?  As far as I can tell it's hardware emulation of the IBM PC, but I'm not sure why that would be important.

LOL! Amen brother.

[dougal]

Taken from Amiga-Hardware.com

"Connects into the CPU slot of the A500, or providing you have the A2000 adaptor card you can also plug this unit into the CPU Fast slot of the A2000.

This card may have problems with A500 motherboards which are older than Rev 6A. The card has printer support, serial support, support for various graphics modes as well as basic MS-DOS sound"

[trip6]

Thats brings up a good question... Anybody Know a good source where to get sockets for A500 style IC's? I believe they are all 40-pin dip style sockets right?

[save2600]

I get most all my electronics stuff from Mouser or Digikey.

[Tenacious]

Might be prudent to pull and inspect PLCC chips last, unless you're very experienced doing this.

As for the dips, I usually pry a little at each end with a screw driver.  If I work slow, in 5 or 6 passes the chip comes out without a bent pin.

Maybe the problem is with the power supply after all.  How many amps is the 5 volt rail rated for?

Do you intend to expand this 500?

[Dandy]

I'd yank that silly IBM ATOnce clone thing but quick. Probably the point of contention in the system too. Yes, yank the 68000 off of that and reinstall directly into the CPU socket. Be careful to observe correct notch orientation.

Why "silly" AtOnce?
What's so silly about it?
Back in the early ninetees I was really glad to have a Vortex AtOnce286 classic in my A500 because it allowed me to run all the MS-Dos soft we used at the CAD school (dbase, word, fortran, c and qb).
(For CAD itself I had DynaCadd plus a tool to convert the 3d CAD data to CNC files for the CNC milling machine and CNC lathe - was slooooowwly, but worked)

Best way to clean IC pins is to simply remove and re-insert them. The friction of the sockets is usually enough to "clean" 'em. If they're truly oxidized, get yourself some very light grit sandpaper or a fiberglass brush to clean 'em up.

Why not an angle grinder? (just kidding)

I always use commercial contact sprays for contact problems, as they're non-destructive in contrary to sandpaper and the like.

I'd be willing to be though most all of your problems will be solved once you get that AtOnce board out.

Really not sure why you thing the AtOnce causes all the problems...

All the chips, but especially the Kickstart, CPU and Agnus chips all deserve to be re-seated.

Fully agreed - but do not forget to treat them with contact spray...

[Dandy]

Hello all,

...
Finally, the CPU has been replaced with a Vortex ATOnce, which is piggybacked over a stock 68k.  Can I replace this back to a regular 68000, or shouldn't I?  I don't really have any use for it.

As you bought the A550 for retro computing/gaming, you might be interested to compare it to a "PC" of that time (I even ran Win3.1 in monochrome mode on it).

Motorola 68000 @ 7.14 mHz vs. Intel 80286 @ 8mHz

In case you don't have the AtOnce manual or boot disk, I could send you a copy of all via e-mail...