Re: Sound Blaster 16 CT1740 - Left Channel Not Working - Repair or Return?

Posted on 2022-11-11, 08:34

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

Would you find it advantageous to replace all four of the opamps, even if they are currently working? No. I would also have left all the caps alone, had I known the problem. Some are very tricky to desolder due to the thick ground plane. I see in the pic you posted in your thread that your …

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Re: Sound Blaster 16 CT1740 - Left Channel Not Working - Repair or Return?

Posted on 2022-11-10, 09:14

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

TLDR (the guy from the other thread): After identifying the problem, it was easily fixed but you would need a voltmeter, around $ 10 for the replacement parts and a hot air/smd soldering station. If you are trying to determine if it is the same problem, probe the outer pins of the opamps U15 and U22 …

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-09, 09:34

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

It wasn't over... This card is like a super-villain, who jump-scares you after you think, you've definitely beaten him. Turns out the WT header wasnt working and I was getting garbled sound or none at all. Again, the DC voltage on the opamp closest to the WT-header (U10) was inconsistent (0.8 V on …

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-08, 14:04

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by Frunzl

in Marvin \ Sound

in Marvin \ Sound

A LOT easier for U19 on the CT2290. Also fixed the issues completely.

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-08, 13:31

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

Replaced U22. Works perfectly now. Thank you both for your extremely valuable help. I am pretty surprised that this issue is not discussed in detail anywhere else, since even I myself have a second model with exactly the same problem. So it seems to be fairly common. I found a handful of forum …

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-05, 19:37

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

C105 next to the opamp has a little hole in top, I'm sure that cap is not happy. As far as the rest goes, interesting... I located the boxes where my computer hardware is, but they are packed full with layers and layers of cards and for the time being, I will not disturb them yet. I know I have two …

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-04, 23:05

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

Are you certain about that? At this point, I tend to believe that the problem is within U22. Interesting: DC voltage at the output pins that work correctly is +2.5 or -2.5 V, whereas on the faulty one it is -4.2 V (input voltage is correct at +5 or -5V). So you are getting -4.2V constant with very …

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-04, 22:09

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

If the output of U22 were not connected to anything, you would get the full output of U15 at -in of U22. Are you certain about that? At this point, I tend to believe that the problem is within U22. Interesting: DC voltage at the output pins that work correctly is +2.5 or -2.5 V, whereas on the …

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-04, 19:44

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

"Unfortunately", the U22 output is not shorted to ground (6 MOhm)... By the way, below are the connections, stupidly drawn.

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-04, 19:36

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

Thanks!! Damn... i had just corrected my +/- mistake in my post, but obviously too late 😉

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-04, 19:04

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

After measuring and probing and so on, I discovered that for the right channel, which is working, the signal travels from the DAC to the input pins of opamp U15 (directly next to the OPL). It then leaves the opamp again with some phase shifting going on and seems to arrive at the output pins of U22. …

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-04, 09:43

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

I was afraid, I would have to do that :) Thanks for your help until this point. Do you think that the small smd caps also have a significant probability of failure (I actually don’t think so)? Otherwise, I would focus on the resistors, especially any 0 Ohm ones, which may have blown during an ESD …

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-03, 16:46

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

Tiido wrote on 2022-11-03, 16:30: Including the C41 which is missing on the circled area ? I actually missed it on the initial photo, that one is 100% definitely needed 🤣 🤣, yes, including that one 😀

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-03, 16:02

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

Replaced all the caps in the red circle below. no improvement... All caps were within specs. Well I guess it's good, I didn't kill it for good in the process (or is it..)

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Re: Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-03, 13:32

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

DAC output goes to some opamps first for filtering, gain adjust and to mix with WB header sound. Pins 42 and 43 should be the ones carrying FM+MIDI mix into the mixer chip. The problem is most likely in one of the tiny capacitors near the mixer chip, they are easy to bend and it is possible one has …

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Sound Blaster 16 CT1740 - one FM/MIDI channel almost dead

Posted on 2022-11-03, 11:29

by

by Frunzl

in Marvin \ Sound

in Marvin \ Sound

Hi, I recently found a cheap SB16 CT1740 with DSP 4.04, which I would very much like to save. The seller said that it was partially working, but that the left channel was dead, so I hoped it might be an easy fix, maybe a dead Cap in the amplifier circuitry. Turns out, it's not easy at all. At first, …

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Re: PowerLeap PL-370/T

Posted on 2022-10-01, 23:59

by

by Frunzl

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

When I removed X4 from my modded chip, I unfortunately ripped off the pad :( When I was modding motherboards for coppermines back in ~2000 I would drill socket plastic a little bigger and sleeve insulation stripped from thin wire over the pin I wanted disconnected. I know, for a normal board, that …

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Re: PowerLeap PL-370/T

Posted on 2022-10-01, 23:23

by

by Frunzl

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Im getting old :) and posting nonsense :( sorry. 1.25V refers to AGTL+ bus voltage and not Vcore, so no, you dont need to mod anything to run at 1.3V. Tualatins bus runs at a lower voltage because they were made on newer process node, but you can safely run them on 1.5V like Coppermines and …

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Re: PowerLeap PL-370/T

Posted on 2022-10-01, 22:20

by

by Frunzl

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Ah, sorry for my ignorance, I only knew that from the MMX and K6 CPUs, where it often was an issue if the board could do split voltage or not... After socket 7, that ceased to be a problem for me, but should have been clear that this actually persisted, especially if attempting to run a chip from …

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Re: PowerLeap PL-370/T

Posted on 2022-10-01, 21:26

by

by Frunzl

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Im getting old :) and posting nonsense :( sorry. 1.25V refers to AGTL+ bus voltage and not Vcore, so no, you dont need to mod anything to run at 1.3V. Tualatins bus runs at a lower voltage because they were made on newer process node, but you can safely run them on 1.5V like Coppermines and …

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