VOGONS


First post, by AppleSauce

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Hey anyone willing to help ,

So I'm in a bit of a pickle.
I've run into snag with my MS-DOS PC that was running beautifully up until I ran into a really strange problem.

Here's some idea of the system specs:

OS : MS-DOS 6.22 with Windows 3.11 installed on top
Motherboard: MS-5148
CPU: Intel Pentium MMX @ 233 MHZ
GPU: ELSA Winner 1000 T2D 2 (S3 Trio64V2 DX)
Sound Card: Sound Blaster Pro 2 CT1600
Ram Amount: 32MB Single SDRAM stick
Additional Expansion: MIF-IPC-B Clone card connected to real MPU-401 , with that connected to a Roland MT-32 Old

Hard Drive: 10 GB mechanical of some sort (I think)
CD Rom Drive: Sony CDU of some sort
Floppy 1: 1.44mb 3 1/2" of some sort
Floppy 2: 360kb Teac 5 1/4"

So here's the story:
I was playing Legend of Kyrandia Book 1 for pretty decent amount of time ,
with an MT-32 playing the music , CD-ROM doing the voice acting and the Sound Blaster taking care the sound effects.
I was at a point in the game where the main character was talking with a side character and all of a sudden the sound cut off at once.
Which was really jarring since the game was still running and the characters where moving their mouths and whatnot but there was no sound whatsoever.

Naturally I thought the game bugged out and rebooted.
I quickly went into Duke Nukem 3D's setup to do a quick sound check.
Strangely the setup program told me there was a DMA conflict and the sound wouldn't play.
So I went into the SBPRO Diagnose Utility and it told me it couldn't detect the DMA.

So fearing the worst I turned off my pc and pulled out the SbPro2 and inspected it but there was nothing obvious.
So I decided to disconnect the MIF-IPC , take it out , remove the CMOS battery and to then install another sound card.
I put in a Sound Blaster 16 CT2230 and tried to test that but I still got DMA conflicts in the Duke3D setup.
Finally I went into the SB16's Diagnose utility and it somehow detected everything , but when I went play the test sounds nothing came out.
I've tried different ISA slots to no avail.
Also mysteriously just like the sound card the Motherboard doesn't have anything obvious on it (popped caps etc.).

So yeah that's the story ,
if anyone can clue me into what the hell is going on such as:
bad Ram , bad CPU , bad caps , a weird conflict out of the blue or maybe something even worse ,
feel free to let me know cause this is a pretty nice rig that I put a lot of work into
and I'd be pretty sad if it turned out the motherboard was irreparable.

Reply 1 of 5, by Horun

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Have you run a Memtest on it ? Have you cleaned all the memory and card edge connectors? Have you checked the PSU for possible issues ?
What happens if you boot a clean DOS floppy with mininum drivers and try the SB Diag ? The CT1600 is all hardware based so really does not need drivers for DOS iirc.
Sorry too many variables and sounds like you loaded the machine up to a point it could be anything...

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 2 of 5, by AppleSauce

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Well I happened to have some extra Ram sticks and I swapped the Ram out just an hour or so ago and had the same problem
so it doesn't appear to be the ram.
I did a few tests in SB Diagnose and during one reboot and test the sound actually worked in the utility.
But after I rebooted and tried Duke 3D again it had the same DMA issue ,
after which I tried Diagnose again only to find , surprise surprise , no sound.
I'm beginning to suspect that some caps on the motherboard might be flaky and it might warrant a recap.
The PSU is a fair point and its a pretty old one I scavenged off another thrown out pc , so ill probably need to get a PSU tester just in case , and maybe a ESR meter for the caps.

Reply 3 of 5, by AppleSauce

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Horun wrote on 2021-07-25, 02:15:

Have you run a Memtest on it ? Have you cleaned all the memory and card edge connectors? Have you checked the PSU for possible issues ?
What happens if you boot a clean DOS floppy with mininum drivers and try the SB Diag ? The CT1600 is all hardware based so really does not need drivers for DOS iirc.
Sorry too many variables and sounds like you loaded the machine up to a point it could be anything...

So yet even more testing it turns out the SB16 was a red herring , I forgot it was corroded , which is why it probably had issues with the DMA.
I put the SBpro2 back in and it seems the audio is actually there, it was strong at first but after a reboot and another sound test it was faint.
Does that mean the caps on the Sound Blaster Pro 2 are failing?

Reply 4 of 5, by AppleSauce

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Okay so left the PC for a bit , came back cleaned the edge connectors and jacks on the pro2 and put it back in and tried the Duke Nukem 3D setup utility.
Volume was nice and clear at the beginning but after running the test 2 or three times over the course of each test the sound got weaker and weaker till you could barely hear it at all.
So I'm like 70% certain at this point that the caps have dried out and hold less charge as they get warmed up.

Reply 5 of 5, by AppleSauce

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Okay well it looks like the problem has been solved , and you wont believe what it was .
It was the speaker system.

I honestly don't know why on earth didn't check it before.

But after checking the motherboard caps , the PSU caps and the sound cards caps and them all looking perfectly fine ,
I decided it was time for a Hail Mary and plugged my phone into the speakers , left it for a bit and sure enough the sound cut out.
After doing some googling it turns out that the Corsair SP2500 Speaker set has a somewhat common issue with the caps failing taking the system with it.

So funnily enough in the end after all the blaming of the old hardware it was in fact the newer hardware that failed.