my favorite 486 machine

[oblivion]

pieced this one together over several years

specs
HDD - 1.4GB SCSI, 500MB IDE (in the caddy for easy removal)
1.44 floppy drive
1.2 mb floppy drive
100MB SCSI Zip drive
CD-ROM drive IDE
UM 486V AIO motherboard
66mhz Intel 486 DX2
32MB fpm RAM
256kb L2 cache
BusLogic BT-445S VLB SCSI card
Tseng Labs ET4000 VLB video card 2MB
Roland mpu-401-T midi card
Gravis Ultrasound ACE
Sound Blaster 16 CT2900







I was able to get this thing running thanks to the help of some of the people here, especially with the SCSI issues I was having. One minor issues I have with this machine that only started recently is sometimes it doesn't quite power up. I hit the power button and the HDD's spin up and the lights come on and the fans but I get no video output and the RAM doesn't count up. sometimes I have to shut it down completely and power it up 2 or 3 times before it actually starts for real. thinking maybe I need a new PSU. 250 Watts should be plenty for this era right? Once its up and running its completely stable.

 

[luvit]

Some starting points..unplug everything but the processor fan, motherboard, and hard drive.
This will let you boot with bare minimum configuration just to verify that the problem is/is not a low powered PSU.
I'm sure your PSU is plenty powerful.

Next thing you could do is remove some ram and boot with just bare minimum ram.
Check for reliable booting, if no matter the results take out one chip and rotate-in another chip until you potentialy pinpoint which chip may be bad.

Another easier check is to disable cache memory in your BIOS.
Disable motherboard cache memory, if the problem is the same, try to disable CPU cache memory.

When you have an intermittent problem as you describe, it's going to take some time to reboot over and over and over.
Just simply disassembling everything (RAM and anything that plugs into the motherboard) could correct a slightly loose or dirty connection.

I can't tell you how many PCs I could NOT resolve at a customers desk, I place the PC in my vehicle, and when I arrive to my bench everything works well.
The vibrations of the car ride solved a poor connection... of course I still tore-down the PC and cleaned connectors.

 

[oblivion]

Some starting points..unplug everything but the processor fan, motherboard, and hard drive.
This will let you boot with bare minimum configuration just to verify that the problem is/is not a low powered PSU.
I'm sure your PSU is plenty powerful.

Next thing you could do is remove some ram and boot with just bare minimum ram.
Check for reliable booting, if no matter the results take out one chip and rotate-in another chip until you potentialy pinpoint which chip may be bad.

Another easier check is to disable cache memory in your BIOS.
Disable motherboard cache memory, if the problem is the same, try to disable CPU cache memory.

When you have an intermittent problem as you describe, it's going to take some time to reboot over and over and over.
Just simply disassembling everything (RAM and anything that plugs into the motherboard) could correct a slightly loose or dirty connection.

I can't tell you how many PCs I could NOT resolve at a customers desk, I place the PC in my vehicle, and when I arrive to my bench everything works well.
The vibrations of the car ride solved a poor connection... of course I still tore-down the PC and cleaned connectors.

now that you mention it the machine has been jostled a bit lately with opening it up and adding cards, ect...it wouldnt be to suprising if a card, ram was lose. I'll take your advice and do that today or tommarow, thanks.

 

[Stone]

If that board has electrolytics on it it could be in need of recapping. The symptoms you have described are quite similar to those of aging/failing caps. Sooner or later it just won't start at all.

 

[EverythingIBM]

More importantly, that board has *tantalums*! Tantalums can explode and/or short over time which is even worse than a failed electrolytic. Shorting damage from a bad tantalum can take out hard-to-replace ICs. Although in this case it's probably unlikely.

It's important to recap any capacitor that's 20 years old. Pretty soon the systems that folks didn't recap will all be dead.
Only use quality electrolytics when recapping (rubycon, chemicon, ELNA, sanyo, panasonic, etc).

 

[oblivion]

lot of doom and gloom guys, not even a single "nice build man". I know the monitor doesnt match but....

but yhea, seriously now that you all have me thoroughly terrified it will spontaneously combust I do think its maybe a good idea to have it sent to a friend I know for a recapping.

 

[luvit]

nice build man.
lol. really. i think you're in it for the long run. i'm looking at the surrounding vintage stuff in the background of you pic.
you got that case nearly stuffed to the hilt. i'm interested in seeing your results to reliable boots, too. :D

 

[oblivion]

thanks Luvit, I think so to.

I fixed the issue today. took it all apart and slowly reassembled while checking. best I can see the IDE connection to the MB was kinda loose. don't know if that can cause what it was doing but it seems to boot reliably now which is nice.

I know its not a 486 "hot rod" and I actually do have a extra 133mhz AMD chip here but the 66mhz just seems perfect for the era so I decided to just leave it at that. baring a new motherboard that maybe could take EDO RAM and provide more cache I don't think there's any more I can add. 256kb cache seems like more then enough anyways for the early/mid 90's.

yeah, in the background are 2 of my current projects in the works. I'm trying to make that SE/30 "32 bit clean" with the whole ROM switch and then upgrading to system 7.6 but since I'm not a Mac guy I've been dragging my feet on that project. To the left in the image you cant really see but its my poor beloved Amiga 4000 all disassembled. Has major sound issues that I cant seem to get fixed. It has really poor stereo and I sent it out to be recapped but now I just get a horrible screeching sound when its powered on and unfortunately there's not many Amiga technical types on this side of the Atlantic that can help me.