Are you playing several games in a row without restarting the computer in-between? That makes the card sound weird since sound patches from a previous game will remain when starting a new game if the card isn't reset by restarting the computer.
Also, which jumper did you set for the IRQ? For IRQ2 you should set J1, which is the last jumper i the row and could be mistaken for a J7.

sounds to me some sort of capacitor/resistor failure, just like the amigas loosing audio... you might lose one channel and the other sounds like it's coming through a pillow with added static...
DK don't let the card die, send it to service!!! There are some ppl at amibay that repair stuff, maybe one can help...?

if you need any kind of measurement from a working card don't hesitate to ask me 😊

Its definitely not incorrect patches or jumpers. Playing just one game for long enough will make the sound unrecognizable as it slowly turns to static.

I fear you are correct keropi. I can see one cap nearest the RCA jacks has been replaced already. I can replace caps myself, there are just so damn many on this board 🙁

I did a quick test with my multimeter and all the electrolytics seem to increase in resistance rapdly unril they block DC after a very short time as I'd expect. I'll have to play around later.

While I'm at it I don't suppose there are newer ROM versions available for the LAPC-I? Ive only got 1.0.0

so it seems the previous owner attempted repair... yeah the card is a mess with a gazillion little components, I am scared when I think what will happen when I need to replace one... not the actual replacing but finding which 🤣
I'll check my rom version tomorrow, IIRC it is 1.0.0 as well... and the other boxed one I used to own was the same too

Well I think the first step is to replace the electrolytic caps.

Is it worth replacing the ceramic and epoxy caps as well? I'm under the impression that these are much less likely to fail than electrolytic...

Electrolytic caps fail because the electrolyte either leaks or evaporates. (SCIENCE! 😀)

If they've leaked, you should be able to see on the PCB where the fluid has settled. This is bad, because the electrolyte is conductive. It was a huge problem in early Macs. One or two leaked caps, and the system would just fall over dead.

In any case, I'd just replace the caps, maybe divide the board up into sections and do them a section at a time. Use acetone or isopro to clean up electrolyte.

Also, testing caps in-situ can give false results, they ideally should be isolated for testing.

Yep, understand all that, I'm just wondering if the other types are likely to fail, or at least loose their capacitance over time as well. Because if there's little point to replacing them I'd rather save myself the time and effort 😀
I've had tantalums go BANG before but I haven't done much with these other types.

In any case, there is no observable damage to any of the components on the board. All the caps look fine.

I figured you probably would, but I reckon it's good to have the info out there for someone who might Google this page later, looking for info. 😀

@DK:

I forgot where you find the rom version of the lapc-i , care to enlighten me? 😁

There should be a sticker on the ROM chip. Mine has 3 sets of the numbers 0-1 with 1, 0 and 0 highlighted in seperate rows.

EDIT: Keropi while you're at it can you tell me what cap is at C96 on your board? The one closest to the MIDI port. I've got a 100uF 50V in there but its not the same colour or brand as the others and looks to have been resoldered at some point

C96 is 100μF 16v 😀 so yours is fine too.

my lapc-i has no stickers though... never had as far as I can tell , take a look:
http://i42.tinypic.com/1zbat6x.jpg
http://i42.tinypic.com/1902eb.jpg

Hmm, yours must be a different revision. Mine has a socketed 27C512 ROM chip where the 'R15209214-01' chip is.

I wonder if there is a way to compare rom data... or a util to tell us versions...

well I can dump the ROM on mine pretty easily with my programmer. Not sure about yours without physically removing it 😜

keropi wrote:

C96 is 100μF 16v :) so yours is fine too. […]
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C96 is 100μF 16v 😀 so yours is fine too.

my lapc-i has no stickers though... never had as far as I can tell , take a look:
http://i42.tinypic.com/1zbat6x.jpg
http://i42.tinypic.com/1902eb.jpg

Mine is the same you also have.. Mine doesnt have a socketed ROM also.

Is there any test software for this card?

There are two versions of the ROM for a LAPC-I or CM-32L. The socketed EPROM is v1.0 and the soldered Mask ROM is v1.2. The OP has the latter. His caps may be dead or dying, and I think it is worth the effort to replace them even if there is no guarantee that it will solve the problem. Just remember that Electrolytic Capacitors have polarity.

ah, thanks for the version infos Great Hierophant 😀
do we know what the differences (if any) between the versions are?

And more importantly is the later version available anywhere on the Internet for me to upgrade my card? 😀

or a tool to grab from mine.... 😁