On Feb 4, 2023, at 5:45, belzrebuth s via <belzrebuth@...> wrote:

I would troubleshoot with a midi editor like SoundQuest or whatever to see exactly what gets changed realtime.

With an init patch you may be missing something.

If you get the other operator levels back to zero do they stay at zero after saving?

Can you make a patch? from scratch set levels back to zero and then set them like 10 20 30 then save and recall that patch?

If you're able to recall that patch I would compare the original and the modified one (modified by the machine I mean) to verify my findings.

If it's indeed *only* the OP output levels that get scrambled only then I would proceed further chasing that error.

In fact one could take it even further and take a screenshot of a patch with ALL values set in a custom way and check what else gets changed before going into a single direction.

On 2/3/2023 10:31 PM, José Juan wrote:

Hi,

I did a full recap of the TX802, and it sounded awesome afterwards.

Electrolytic capacitors are dead on most 80s Yamaha Roland Korg gear.

To change all capacitors is a PITA, but the machine gets new expected life.

Just my suggest. Not every tech guy is capable of doing that without damaging the unit.

Good luck, and take care.?

JJ

El vie, 3 feb 2023, 21:24, <contact@...> escribió:

Hello group,

I would like to share a troubleshooting story I am in the middle of.

I bought a broken TX802 on the internet. I knew it was broken when I bought it, I felt like taking a chance. The seller said it worked but has "digital noise".

It turns out this TX802 is in pretty good shape. Everything works except that the sounds are wrong. There appears to be something wrong with the output levels of the operators.

If I make an init sound, I am supposed to get a single operator sine wave with an organ envelope. The user interface shows the expected parameters. But when I play it, I get more or less the sound of algorithm 1 with all operators at 99. A harsh overmodulated FM sound. When I then change the algorithm to 32, I get a clean sine wave sound.

It's a fascinating puzzle for me. Almost all the explanations I can come up with would make the TX sound more broken than it actually does. The EGM and OPS2 chips cannot be broken because they can make clean sounds. (I have a DX7II which is my reference.) Data is getting corrupted only in a very specific place, which happens to affect the output levels.

My best guess at the moment is that there is a problem with the chip enable line of the EGM chip that causes it to latch bad output level data when it should not be reading data in the first place. But I have not seen evidence of that yet on my oscilloscope.

I don't know if anyone else finds this interesting, but if there is someone who finds it interesting, they are probably on this list. :)

Cheers, Jacob