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Need help rescuing an LAPC-i

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First post, by Machforr

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Good day! First post here, even if I've been following this place for a while and found a wealth of information that saved my bacon.

I'm one of the lucky few with a marvellous LAPC-i and a pretty decent retro rig. (350mhz P-II with windows 98SE)

I tried to make sure the rig was stable before testing the few sound cards I still have, including the LAPC-i.

The card worked wonderfully for about a week before it would intermittently not output any sound. Sometimes a reboot would solve it, sometimes not. Windows detects the MPU-401 out and would show a Midi file playing if I start one.
At first I thought it would be a conflict with the present sounblaster card, (AWE64 gold, but having had a Roland SCC-1 installed beforehand, I knew not to have the SB's general midi at address 330).

I gave a shot with a SB16 value as well as a SBpro (in case manually having the IRQ and DMA set manually would help).
It sadly didn't work. However when the LAPC-i is the only sound card in the system, I can hear the mouse pointer move as static (coil wind?) in Win98 SE. Again, it's still detected, it just gradually stopped outputting sound it seems.
The jumpers are also at the default positions (irq-2, 330-331h)

Based on the topics here, caps might be a good start as well as, maybe, the opamp. Not sure what would cause this to happen or how sensitive the card is to possible PSU issues, as I had to replace it due to it not turning on reliably.

Any help is appreciated, I would really like to save this wonderful piece of technology!

Thanks 😀

Reply 2 of 6, by Machforr

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heckyeah wrote on 2022-04-17, 15:24:

New PSU has a -5v rail? LAPC-I requires one.

I don't believe it does. It's new and quite recent, though it also has the proper length ATX connector to fit the P2B motherboard.
It's a 500w thermaltake. The basics of basic. (even if really overkill for that p2 system, too)

Note that I did research beforehand if the LAPC-i required a -5v. I either did not research properly or gave up too soon, but it was inconclusive. I just didn't know.

Consequently, I'll check the PSU's rails as well, hopefully the other PSU might have had a faulty -5v and I didnt know either.
Thanks for the reply 😀

EDIT -
I researched here, on vogons, for 5 seconds and got confirmation that yes, I do need a -5v rail. The old, failing PSU did have that rail (it't written on the sticker!), the new one does not. I remember Phil's computer lab talking about a "voltage blaster'' for just those occasions. Hopefully, the lack of that -5v, or the failing psu did not damage the card, for that matter. I would hate for that beauty to be broken.

Reply 3 of 6, by heckyeah

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Glad I could assist, let's hope it's indeed just that and nothing severe. I don't think there's any harm in the -5v rail missing but I don't have any experience with LAPC-I (not for lack of trying though!)

Voltage blasters can still be acquired on Ebay it seems which you probably noticed already. There might have been some ATX-AT conversion adapters with -5v adapters installed as well but I might be confusing that with something else.

Reply 4 of 6, by Machforr

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heckyeah wrote on 2022-04-17, 15:56:

Glad I could assist, let's hope it's indeed just that and nothing severe. I don't think there's any harm in the -5v rail missing but I don't have any experience with LAPC-I (not for lack of trying though!)

Voltage blasters can still be acquired on Ebay it seems which you probably noticed already. There might have been some ATX-AT conversion adapters with -5v adapters installed as well but I might be confusing that with something else.

You were indeed a great help with figuring out, I do feel dumb for not pushing my researches further beforehand though.

I'll keep you posted 😀

Reply 5 of 6, by Machforr

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heckyeah wrote on 2022-04-17, 15:56:

Glad I could assist, let's hope it's indeed just that and nothing severe. I don't think there's any harm in the -5v rail missing but I don't have any experience with LAPC-I (not for lack of trying though!)

Voltage blasters can still be acquired on Ebay it seems which you probably noticed already. There might have been some ATX-AT conversion adapters with -5v adapters installed as well but I might be confusing that with something else.

Problem solved: All is well and nothing is broken (whew)

Long story short, I had a spare ATX power supply with a beefier -5V rail (0.5 amps instead of 0.3... go fig.)
Now LAPC-i actually works even more reliably than the SB16 value that is next to it!

Thanks so much again for making me reconsider that option! I didnt have to break out the soldering iron 😁

Thumbs up!

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