Could that be the amplifier 2025? Sounds in games is ok when is low volume. But that 16bit sound in diagnose is also confuse me...

The problem can be caused by the pre-amplifier circuit, or the potentiometer. Are you using a riser? Also post a pic if you can.

butjer1010 wrote on 2025-08-04, 21:30:

on diagnose, 16bit sound was broken (8bit and synth were ok)

That would suggest a problem with the 16-bit DMA channel - by default DMA 5, ie. DRQ 5 and/or DACK 5 signals.

See what happens if you jumper it for DMA 6 or DMA 7 instead.

Here are the pics. No riser, and i cleaned the potentiometer with contact cleaner.
Will try with DMA7, but which jumpers are fot those channels?

I tried change DMA to 7 in diagnose.exe, but everything is same as before. Didn't changed any jumpers...

http://th99.infania.net/i/C-D/53583.htm

Jumper settings and software settings must match...

Also, it's always a good idea to remove all the jumpers, and install them again - they are prone to oxydation/bad contact.

No change with High DMA to 7, both jumpers and software settings. 16but sound still crackling. Would internal amplifier change anything, now it is on disable (jumpers OPSL and OPSR are on 1-2)? If i enable this?
On all pics online, those amplifier jumpers are just like on mine, so maybe the first pin is to the right?

Grzyb wrote on 2025-08-05, 13:58:

Also, it's always a good idea to remove all the jumpers, and install them again - they are prone to oxydation/bad contact.

I tried that just now... no change

Check the input and output for the TEA2025B amplifier chip.

https://www.alldatasheet.com/datasheet-pdf/vi … S/TEA2025B.html

+Vs is 8.97V (pin 16), same as on 7809, output 1 is 4.49V (pin 15), output 2 is 4.43V (pin 2)

This is the sound of testing 16bit, weird....
8 bit and synth are great...

And this is the sound in Monkey Island

Are sure you solder the right caps? Both the value and voltage, and what about the polarity?

dominusprog wrote on 2025-08-05, 18:03:

Are sure you solder the right caps? Both the value and voltage, and what about the polarity?

I have bought recapped card already. Didn't do the recap myself. I could check on pictures on net for the polarities, but i doubt this guy could put the wrong caps?!?
I can mark on picture the values of caps, if that helps?

Maybe You were right, it seems one cap is reversed????
Going to try and let You know....

I think the marking on the board is wrong, and that was the reason this guy solder this cap wrong!!! I looked at least 20 pics on internet of CT1750, and on every picture, plus is to the left!!! On this board on markings, plus is to the right!?!

I have reversed the Cap, but it is all the same. I will mark caps values now, and put it on picture, so if someone has same SB, please let me know if the caps are wrong values 🙁
I hope You can see which ones have which value!

What edition of Monkey Island are you using? If you use a version without speech output, Monkey Island is not supposed to use digital sound output, neither 8 bit nor 16 bit. If you get issues in Monkey Island (not the "CD talkie"), the issue is not related to 16-bit output.

I've seen a YouTube video with similar symptoms, and in that case, the 7809 was overheating, because IIRC the TEA2025 was broken and used too much current. When the 7809 overheats, it shuts down for a moment, then it cools down and turns on again. Depending on the external conditions and the load, the turn on/turn off oscillation of the 7809 can get into the audible range. So I recommend you to test carefully whether the voltage regulators get hot. You can burn your fingers! The overtemperature shutdown of the 78xx series kicks in above 125°C (way more than 300°F) inside the chip, so I would expect a case temperature above 100°C if the overtemperature shutdown activates.