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Sorry to hear you aren't well @pianokeyjoe, hope you will feel better soon! I cant find a schematic for the PT20 so far. But I was reading through the Casio vowel/consonant patent the other day and though that isn't model specific, it seems that volume envelopes are done at the digital level with the music LSI. Can we have a photo or two of the PCB to see what's on there?

In general I wouldn't put anything with significant dark/black areas particularly plastic in full sun. It can easily reach a temperature where it softens. Even individual dark buttons on a light coloured panel can warm up rapidly, as can displays. Objects can attain much higher temperatures than the ambient air temperatures.

VZV CZ Update! (bugfix again, sigh) Version 1.1.10 Fixed bug which caused a crash when clicking the "End" button when no envelope step is selected.

Going out on a limb a bit here but... Without looking at the circuit diagram, I'm guessing the headphone jack comes off the power amplifier somwhere via a resistance and thus a low impedance audio signal can perhaps backfeed into the power amp. Just guessing.

From the picture, I don't see damage to the LA4120 itself, though the top has clearly been dunked in gunk. It looks like there's metal on top, a small heatsink? This thing has a line out, right? That should be unaffected by the LA chip which is the power amp?

@AFG70that sounds pretty random. Just for now, let's put it down to random coincidence. If it keeps happening, I'll look further You can always contact me directly at support@veezeevee.net

@CasioForest The fact there are voltages on the power supply pins of an IC doesn't mean it is working; neither does the presence of voltages on the output pins of the internal gates. The output may be incorrect, or stuck at high or low voltage. Often a single gate can fail (e.g. one inverter out of the six in a hex inverter). They are commonly available as replacements fortunately, and cheap. Observe anti-static precautions as they are CMOS chips. Example here https://uk.farnell.com/texas-instruments/cd4049ube/inverting-buffer-hex-4000-cmos/dp/3119255 (it can be a bit tricky searching for part numbers as they tend to have extra letters; in this example note the CD4049UBE. Rusty pins isn't a good sign but that doesn't mean they are at fault also. I'm presuming you don't have an oscilloscope?

Hmm, okay. Can we have some photos of the PCB etc? First quick thing, when checking power voltages, don't use the ground pin of the IC as ground. Use some common ground reference point e.g. ground on the power supply or the negative terminal on the output jack. I see the LA4120 is a power amp, I can't find a pinout either (as of this posting) but it may be dual rail e.g. +5 and -5, hence your 10.76V. It probably isn't any standard position for the power pins. You should be able to trace the power connections to the rails though, by identifying the rails on the board (or we should be able to do it with photos). But the power amp sounds like it's working anyway so the problem would be elsewhere. It could just be a bad switch in the signal path, for instance. I Another possibility is the CMOS chips like the 4049s, one logic gate down could take out the signal. I wouldn't be surprised if it's one of those. The 773G is (I think) one of Casio's range of music LSIs, looking for info but can't find anything right now but it rings a bell. This is a small keyboard and I'm going to assume that the LSI puts out an analog signal that eventually reaches the amp via (probably) some other filtering circuitry but we don't know which pin that comes out of; a bare audio cable (shield to the keyboard's ground) could be used to find it and trace audio generally (the other ended plugged into an amplifier). I did find this company that says they have the service manual for download, they look legit to me but I've never used them https://www.samswebsite.com/en/photofact/details/index/id/31489 -but it is $23.00 to get it. If you go that route, I'd email them to check it's the right manual before ordering. My first guess is this will turn out to be one of the CMOS chips (the inverters or flip flops) but my first guesses are frequently wrong!

More piano, less forte!

@AFG70thanks, feel free to leave a review on the Store I considered tooltips but it probably does need a manual. I really should. Regarding the coding; the UI was quite easy. In UWP apps, it's coded using a XML type code called XAML with a visual editor which is verbose but straightforward to use. I used VB.net which is different to VB6. It's gradually dying on the vine as most people now use C# but I actually prefer it being a bit more wordy; I prefer structures with stated starts and ends (e.g. SUB... End SUB) rather than curly braces which I find less readable e.g. SUB{} Just personal taste. The UI just evolved based on what I wanted to be able to do and some suggestions here about improvements (e.g. initially it did not automatically update the synth, there was no Autosend Live option). It was very important to me to be ergonomic. It was also a part of my "design brief" for it to function on tablets well as I originally envisaged using one local to the keyboard so it all works with touch input, I bought a cheap Windows tablet for the purpose but ended up using it on a PC myself and I don't think that is much used by anyone else as Windows tablets are pretty thin on the ground compared to IOS and Android. Still, it's there for anyone with a Surface tablet etc... The "definitive" Casio CZ sysex document I got from the interwebs is... wrong! The formulas are mixed up and any app based on them will receive and send wrong values. That was the big head scratcher, not least because of the inevitable assumption that my code was buggy, whereas it was actually Garbage In Garbage Out. I think realising that was the one point where I nearly abandoned the project. I pushed ahead because there simply wasn't anything anyone else had written that could talk to my CT6500, which so far as I'm aware I am the first person in modern times to figure out how to repatch it (it is a preset keyboard with the CZ Phase Distortion engine, but the Live Patch can be edited... it's just Casio never bothered to tell anybody how!) Must admit I am quite proud of my work on this, it's just very pleasing to me that other people use it and leave positive comments instead of "total garbage, avoid" type stuff!

Yes, I really should write a user manual...

@AFG70 Hi there When you do a Get Live, the patch settings will show up in the controls. However they are not yet ready to save. In the File tab, you need to save them to a patch in one of the 16 patch slots (in banks 00 and 01). So click the Add dropdown and choose which slot to store them in. (If you make changes after this you also need to click Store on the Control panel to update that patch slot). Now, you can save the sysex file and it will contain that patch. If you didn't do this, you could still save the sysex file but it would have no patches in it! Now any time you load the sysex, the patch(es) you saved into it will appear in the File tab. You can load them into the app's patch controls just by clicking the patch in the Bank in the File tab. If the "Live" switch at the top of the File tab is on, it will also send it to the synth (if not, you'll need to hit Send Live on the Control panel). Or, you can send all the patches in the Banks by clicking "Send All". Hope this helps.

@pianokeyjoe @Ridley According to the manual (included below in this post) it receives and sends tone sysex data in Normal and Combi modes. I've never used or owned a VZ so have no personal experience I'm afraid. Casio VZ-1_MIDI_Sysex_Manual.pdf

The CZs can send and receive patch dump sysex (that's how VZV CZ works) but the computer has to send the request, there is a "handshake" in which the computer sends a request, and the CZ then replies with the patch dump. The CZ has no onboard function to just send a patch dump without a request from the computer.

Fascinating and informative thread!

The Casiotone 701/601 textbook shows two Music LSIs, two DACs and analogue mixing of the signals (also with the percussion source) so it should be possible to trace the audio on the circuit board to see if one or both DACs are outputting sound. The mixer will presumably be a simple op amp virtual ground mixer, probably inverting. A simple audio probe, that is just a wire connected to the input of an amplifier (highest impedance you have) should be sufficient to do that. Casio_Casiotone_CT-701 601 Casiotone_Textbook_701_601.pdf

Ah, so it's likely the DAC multiplexer that's faulty then...

Have you checked all the power supplies at the chips themselves? Ideally I'd get an oscilloscope on them to see what is happening. The recap may have introduced a problem.

@pianokeyjoeOn the other hand, these chips are just very old and all chips eventually fail with enough time.

VZV CZ Update! Version 1.1.9 Fixed bug which was causing "Get 16" function to write corrupted sysex files (they couldn't be reloaded by the app due to an extra byte in each patch dump). Changed number of Banks in "Synth" tab to 8 (it was 6) to access all patch banks in 32+32 synths e.g. CZ5000

@Chasthanks, I've also found an online manual and that seems to agree. Strikingly the manual for the 230 at least states explicitly it can be sysex programmed- but then gives no further useful information about how. A little better than the 6500 which is positively shy about its sysex capabilities! It's a bit of an oddball, but then Casio had a habit of oddball keyboards! @pianokeyjoemake sure they don't get crushed under the pile!

Sorry @pianokeyjoe, I thought you have a CZ230S. No worries. On the CT6500 it's the second preset from the left with "Select" lit up. I've verified it's identical to CZ patch 00 thanks to my VZV-CZ bug reporter who has a CZ5000 (lucky devil). And yes it's great to be chatting old synths again! "Bump" just refers to when one forces an old forum thread to appear at the top of the forum again by posting to it, so it is "bumped up to the top".

Also @pianokeyjoecan you help me by explaining to me (as I don't have one) how many patches a CZ230S has, which ones are user programmable and how are they recalled (are they banked or just a list of numbers from 1 to X)? Cheers mate.

*Bump* haha Fixing a VZV CZ bug reported by a CZ5000 owner, I went back to this Brass Ensemble malarkey and finally found my error; the preset on CZ synths is their Preset 01, literally the first one. It's Brass Ensemble *2* on the CT6500, which is patch number 24 (with 1 based counting). The sysex file I posted at the top of this page is for CT6500 patch number 02, which is the first Brass sound- so it's a completely different patch. I also looked again at that weird -5 rate value in DCW1 step 4 and can't make any sense of it; it's coming from the CT6500 as 129 decimal, which is an illegal value, so I'm guessing it's some kind of bug in the ROM. Since it doesn't happen on any of the other presets I've just kludged it out. So anyway to reiterate, @pianokeyjoe's much loved patch is the first patch on a CZ and patch 25 on a CT6500.

Microsoft can't settle on a coding standard because every time they decide what the future is, it doesn't get enough adopters and they abandon it. With VZV CZ I committed to UWP (Universal Windows Platform), the "app" style, but they've effectively abandoned that now. And of course every time they do this it makes devs less willing to commit to MS's next big idea because so it's a negative feedback loop. But that's why in my case VZV CZ won't run on Win 7, it's Win10+ only.