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SB16 issues

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First post, by Murugan

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Maybe I am missing something important,but after installing the drivers for my CT2290 on a DX2-66, I get no output on the speaker jack but on the line-out. It 'works' but I hear a lot of other noises too and not a clear,crisp sound.
So I switched it for a CT2920 and the same thing happens.

Is this some configuration error?

My retro collection: too much...

Reply 1 of 15, by mkarcher

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Murugan wrote on 2021-01-18, 21:03:

Maybe I am missing something important,but after installing the drivers for my CT2290 on a DX2-66, I get no output on the speaker jack but on the line-out. It 'works' but I hear a lot of other noises too and not a clear,crisp sound.
So I switched it for a CT2920 and the same thing happens.

Is this some configuration error?

The analog section of the sound blaster 16 cards require +12V from the ISA bus. If the connector from the AT power supply to the mainboard makes bad contact on the +12V line, this might cause issues like you describe. Try re-seating the power supply connector.

Reply 3 of 15, by TechieDude

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mkarcher wrote on 2021-01-18, 21:26:
Murugan wrote on 2021-01-18, 21:03:

Maybe I am missing something important,but after installing the drivers for my CT2290 on a DX2-66, I get no output on the speaker jack but on the line-out. It 'works' but I hear a lot of other noises too and not a clear,crisp sound.
So I switched it for a CT2920 and the same thing happens.

Is this some configuration error?

The analog section of the sound blaster 16 cards require +12V from the ISA bus. If the connector from the AT power supply to the mainboard makes bad contact on the +12V line, this might cause issues like you describe. Try re-seating the power supply connector.

I think you mean -12V because if it was +12V, it wouldn't POST to begin with.

Reply 4 of 15, by mkarcher

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TechieDude wrote on 2021-01-18, 21:45:
mkarcher wrote on 2021-01-18, 21:26:

The analog section of the sound blaster 16 cards require +12V from the ISA bus. If the connector from the AT power supply to the mainboard makes bad contact on the +12V line, this might cause issues like you describe. Try re-seating the power supply connector.

I think you mean -12V because if it was +12V, it wouldn't POST to begin with.

No, I don't mean -12V. It is true that hard drives and many floppy drives don't work without +12V. It's also true that a power supply should not indicate "power good" is +12V is out of spec (inside the supply). Yet, many mainboards work without +12V if they rely on POWERGOOD instead of probing voltages on the board. I am not suggesting the power supply is broken, I am just suggesting that the mainboard doesn't receive the +12V properly.

Reply 5 of 15, by TechieDude

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mkarcher wrote on 2021-01-18, 21:50:

No, I don't mean -12V. It is true that hard drives and many floppy drives don't work without +12V. It's also true that a power supply should not indicate "power good" is +12V is out of spec (inside the supply). Yet, many mainboards work without +12V if they rely on POWERGOOD instead of probing voltages on the board. I am not suggesting the power supply is broken, I am just suggesting that the mainboard doesn't receive the +12V properly.

Whoops, forgot these old boards rely more on +5V, my bad. Still though, don't SB16s also use -12V?

Reply 6 of 15, by mkarcher

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TechieDude wrote on 2021-01-18, 22:10:
mkarcher wrote on 2021-01-18, 21:50:

No, I don't mean -12V. It is true that hard drives and many floppy drives don't work without +12V. It's also true that a power supply should not indicate "power good" is +12V is out of spec (inside the supply). Yet, many mainboards work without +12V if they rely on POWERGOOD instead of probing voltages on the board. I am not suggesting the power supply is broken, I am just suggesting that the mainboard doesn't receive the +12V properly.

Whoops, forgot these old boards rely more on +5V, my bad. Still though, don't SB16s also use -12V?

I'm unsure. Maybe they do, but the two big regulators on classic SB16s are 7805 and 7809, with step +12V down to +9V and +5V. If the card uses -12V, it uses either low current (such that a TO92 negative regulator like a 79Lxx) would do, or it uses -12V unregulated and relies on power supply rejection. It's definitely a good idea to check -12V, too.

Reply 8 of 15, by appiah4

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Check out JP18 and JP19.

Both JP18 and the third and fourth pins (counting from top to bottom) of JP19 have to be jumpered for the SPK out to work AFAIK.

Like this:

      O 
O
X X
X X
O
JP18 JP19

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Reply 10 of 15, by appiah4

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Murugan wrote on 2021-01-19, 14:50:

These are jumpered.

That is strange.. It sounds like the amp IC on both cards is misbehaving. Can you post photos? My 2290 had a TEA2025B IIRC which means it uses 12V. You may have filtering issues on your 12V line, or a device that is shorting it somehow. Can you try running the card without any other 12V peripherals such as CDROM, HDD, Floppy etc?

Last edited by appiah4 on 2021-01-19, 15:05. Edited 1 time in total.

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Reply 11 of 15, by Murugan

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I took only one of the jumpers.
I also have two pnp models but haven't found the courage to try install them,drivers etc...
I believe I have another pc with the same card but which is it... 😒

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Reply 12 of 15, by appiah4

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First order of business would be to try that card in another PC. I have a suspicion that either ISA power delivery on your motherboard is damaged (corroded power rail from the power connector, bad caps, etc.) or some other device in the build (floppy with bad caps, etc.) is messing with the 12V rail in general. Have you measured it with a multimeter yet? If you are weak of heart you can just measure from a molex connector, but that won't tell you as much as measuring it from the appropriate 12V and G solder pads behind the ISA slot while the card is in there. Try not to short anything though 🤣.

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Reply 13 of 15, by Murugan

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Lol my cheap multimeter broke and haven't replaced it yet.
I'll try to find the machine with the other SB16 in.
I wonder if the battery leakage might caused some damage...

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Reply 14 of 15, by appiah4

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Murugan wrote on 2021-01-19, 15:10:

Lol my cheap multimeter broke and haven't replaced it yet.
I'll try to find the machine with the other SB16 in.
I wonder if the battery leakage might caused some damage...

You should have mentioned battery damage earlier. Battery leakages tend to corrode power delivery lanes from the AT power connector to the PCI/ISA bus very often. Your board may be getting 12V but your ISA slots may not. You can confirm this by checking continuity between the motherboard AT connector's 12V pin against the ISA slot's 12V pin. If there is no contact, there you have your answer. Fortunately, this can be fixed with a simple bodge wire under the board once you locate where the damage is, if you don't mind a bit of soldering.

Posting detailed photos of the top and bottom sides your motherboard could help, now I know where to look for the damage, maybe I can visually spot it.

Retronautics: A digital gallery of my retro computers, hardware and projects.