GF1 uses 44100 * 448 as its clock freq which is a bit unfortunate as it isn't used by anything else. It shouldn't be hard to synthesize with the PLL chips available now though, you can use a standard 44100 * 256/384/512/768/1024 clock as reference and get exact freq : (((44100 * 256) * 7) / 4) = 44100 * 448

Tiido wrote on 2023-01-03, 09:45:

GF1 uses 44100 * 448 as its clock freq which is a bit unfortunate as it isn't used by anything else. It shouldn't be hard to synthesize with the PLL chips available now though, you can use a standard 44100 * 256/384/512/768/1024 clock as reference and get exact freq : (((44100 * 256) * 7) / 4) = 44100 * 448

Thanks for the info. I have zero experience doing modifications like that, but I can solder. How big are the components that would be needed for that particular clock?

I have seen SOP and TSSOP things with 8...16 pins. Definitely hand solderable with the right techniques. The chips will have to be programmed too, and that may not be straightforward at all and it is all manufacturer specific too.

And then, sometimes things seem to align with an undeservedly still much too small channel I just happened to run across in my feed: https://m.youtube.com/watch?v=ASouxxQyABk

Almost at the end, you can see Mike / vswitchzero deal with issues of the ECS crystal on his Ultrasound Classic and using a close replacement one.
But, there's also one good extra information: it seems he was able to get an (albeit also broken) replacement from Ian Polpo, whom I've found to be working on another fun project over here:
PicoGUS: ISA sound card emulator with Raspberry Pi Pico (Gravis Ultrasound, AdLib, MPU-401, Tandy, CMS)

Who knows, maybe there's still one more in his drawers... 😀

MJay99 wrote on 2023-01-18, 23:56:

And then, sometimes things seem to align with an undeservedly still much too small channel I just happened to run across in my f […]
Show full quote

And then, sometimes things seem to align with an undeservedly still much too small channel I just happened to run across in my feed: https://m.youtube.com/watch?v=ASouxxQyABk

Almost at the end, you can see Mike / vswitchzero deal with issues of the ECS crystal on his Ultrasound Classic and using a close replacement one.
But, there's also one good extra information: it seems he was able to get an (albeit also broken) replacement from Ian Polpo, whom I've found to be working on another fun project over here:
PicoGUS: ISA sound card emulator with Raspberry Pi Pico (Gravis Ultrasound, AdLib, MPU-401, Tandy, CMS)

Who knows, maybe there's still one more in his drawers... 😀

Wow, thank you so much for the lead! I bet Ian is the one that bought all of the stock from RCFreelance at some point in the last 4 years. 😁

I have sent him a PM.

I watched the video, and it is odd that he was getting some kind of intermittent problem related to grounding\capacitance, and that it did it with both crystals. I don't know much about circuits, but I'm inclined to agree with the other commenters on the video saying that the card likely has a capacitor issue. The newer crystal is probably less susceptible to the issue, so it seems to fix the problem.

Hopefully my card doesn't develop such issues if I'm able to get a proper crystal for it, but if it does I will focus on capacitors.

You have actually helped me with two other projects though as well! I have an Nvidia NV1 and an Alliance AT3D that both have odd issues that seem to respond to touch. I have replaced electrolytic caps on both of them, but now that I have actually seen someone experience similar issues I will probably try two things: replacing any clock crystals with identical replacements, replacing other capacitors on the card.

Thank you again for taking the time to post about this. 😀

Touch related things are usually mechanical issues, some bad connection somewhere. When a signal is open, the input will float and since they are very high impedance they're easy to affect. Finger nearby will be a big capacitor that can divert all the neighboring signals into that input. This is why "finger test" can be quite revealing, a well behaving digital circuit will withstand finger in most of its areas (except directly on crystals as they rely on minuscule capacitances to be exactly right to function). Analog bits will be much more suspectible to it, and it can be a good diagnostic tool, i.e in an audio path you can use finger to follow the buzz and find something that is upset 🤣

Some crystals are now on the way to @Ozzuneoj. I ordered the 22 crystal minimum from Freestyle Electronics back when they had stock, as a part of my own GUS repair saga, outlined here: Bringing a Gravis Ultrasound back from the dead

In the video linked above, the crystal that I sent vswitchzero had issues, so I was a bit worried about the state of the crystals I had, despite the one that I used in my own GUS working fine. So I've added a socket to my GUS so I could test each one in my stash... so far each one I've tested works just fine! I'm thinking about putting the rest of my stock up on eBay, Tindie, or some other place because there's not much point in sitting on a hoard of these, so being able to test them will be good.

polpo wrote on 2023-01-25, 00:05:

Some crystals are now on the way to @Ozzuneoj. I ordered the 22 crystal minimum from Freestyle Electronics back when they had stock, as a part of my own GUS repair saga, outlined here: Bringing a Gravis Ultrasound back from the dead

In the video linked above, the crystal that I sent vswitchzero had issues, so I was a bit worried about the state of the crystals I had, despite the one that I used in my own GUS working fine. So I've added a socket to my GUS so I could test each one in my stash... so far each one I've tested works just fine! I'm thinking about putting the rest of my stock up on eBay, Tindie, or some other place because there's not much point in sitting on a hoard of these, so being able to test them will be good.

Really looking forward to getting that shipment. 😁

For some reason I keep hearing this when I look at your newly socketed GUS...

Thanks again!

In watching the vswitchzero video recently and seeing the issue being resolved via touching the crystal, it made me take a look at my Gravis Ultrasound Extreme. The GUS Extreme also uses the GF1 chip and a 19.7568 MHz crystal.

However, the design of the board includes a grounded plane under the crystal.

This is something obviously omitted in the design of the original GUS. It makes me wonder if the GUS Extreme would be less susceptible to this issue given the inclusion of the grounded plane.

In the case of the GUS Classic would it be possible to jury-rig a similar solution? Would even just adding a grounded bodge wire accomplish the same?

Shponglefan wrote on 2023-07-13, 10:54:

In watching the vswitchzero video recently and seeing the issue being resolved via touching the crystal, it made me take a look […]
Show full quote

In watching the vswitchzero video recently and seeing the issue being resolved via touching the crystal, it made me take a look at my Gravis Ultrasound Extreme. The GUS Extreme also uses the GF1 chip and a 19.7568 MHz crystal.

However, the design of the board includes a grounded plane under the crystal.

This is something obviously omitted in the design of the original GUS. It makes me wonder if the GUS Extreme would be less susceptible to this issue given the inclusion of the grounded plane.

In the case of the GUS Classic would it be possible to jury-rig a similar solution? Would even just adding a grounded bodge wire accomplish the same?

The problem with the Pierce generator is that it always works, except when it doesn't.
Page 2 "Pierce-Gate Design Example Design a 20MHz CLOCK using the Pierce-Gate topology given the following requirements:
Frequency: 20MHz"
An example of the values ​​​​of capacitors and resistors for a similar generator from a quartz manufacturer.
https://www.crystek.com/documents/appnotes/pi … ntroduction.pdf