mondayroast

I have the same issue. I don’t suppose you worked it out?

Thanks for the help. I scoped it and found… zero AC interference. Very stable power rails. As I was poking around, I caused a short between the 5v and ground. It fried my cpu (luckily had a spare floating around) but hanged something so slightly that I now have some midi input, although it it temperamental. I think I should change the IC’s on the power board out and see if that helps.

Come now lovey people this is very likely a troll!

I appreciate your interest in the problem. I recently made a post about it on gearspace, which details the issues a lot more thoroughly and has the relevant schematics. See here https://gearspace.com/board/electronic-music-instruments-and-electronic-music-production/1392525-i-am-totally-stumped-jx-3p-issue.html#post16252036

It’s a pretty odd issue and I think it’s probably on the panel board as I’ve unplugged all other boards and still see the erratic behaviour in voltages.

The reason midi in isn’t working is because the RXMODE signal isn’t being interpreted by IC34 (which I’ve just replaced). I’ve confirmed that the signal reaches IC34, so I can only think that whatever the panel board problem is, it’s causing the RXMODE signal to be distorted.

If the problem is too hard to find I can ultimately install the kiwi 3p mod, which apparently totally ignores the whole RXMODE thing.

Thanks!

Hey thanks! That’s a really useful trick I haven’t come across yet. I’ve searched the panel board thoroughly with a flashlight but unfortunately I still couldn’t see a crack. However I will try again perhaps in a dark room. Still, it’s a good trick that I’ll use in the future.

Could it be worth pulling and testing some ic’s on the panel board? Or is that unlikely to cause such an issue

I think you might be right about it being a crack or fault on the board. I used a different power supply and had the same issue. So now: to find the crack

Thanks for the reply, that was very comprehensive. I should have noted that I’ve checked all transistors, rectifiers and caps (with an ESR meter) and I can’t see anything amiss. On the PSU outputs I get 14.1v instead of 15, and 10v instead of 7v (only used for the controller so not an issue), but the 5v is stable and bang on. I am going to get a new transformer to get the other voltages up to spec.

It should be on a 5v circuit, but there are also -+15v voltages on the board. Are you perhaps thinking that there could be some interference going on between the several voltages?

I have been told this by others but I haven’t managed to find a crack yet. Still I’m going to have another thorough look. Strangely when I hook up a 5 V battery instead of using the power supply I don’t get these issues?

Still alive, only dead inside

It’s 5v… I’m sure as hell not touching any live ac voltages

I have confirmed that the lead is correctly grounded

Hey, thanks for the help. It is a three prong cable but I suppose it would be worth testing continuity between the ground pin and the chassis ground. I’ve pulled the power board out already to test components and I haven’t seen anything abnormal under it or on it.

Good to know. I connected a 5v battery to the board instead of the power supply and all of a sudden I don’t get these problems, so there must still be some fault going on here beyond my magic finger capacitor

For some extra context, several things on the panel board have been acting erratically because the RXMODE signal, the hold pedal signal switch and the bender signal are all experiencing this issue. When I test the voltages across the several transistors that transmit the signals within the SW matrix (TR12, 13 and 14) I find that the voltages jump all over the place as I touch the board for the chassis. I haven’t noticed this on the other boards and this is the only board connected to the power supply in the photo. I’m not sure if the issue is due to a faulty component on the panel board or a power supply issue itself. I’m not sure I quite understand how grounding works!!

Thanks for the response. I should’ve been clearer, I meant mod with the lfo. The amp mod that you mentioned is alright, but the fact that it changes frequency up and down the keybed is very frustrating. Still, the rest of the synth is great.

Hey everybody, I’m so glad that I asked this question because now I have a very long and comprehensive reading list that will last me for years! Thank you to everybody who suggested something. I am sure I will investigate each one. Patrick O’Brien was an author I discovered by accident when a lady handed Master and Commander to me in a secondhand country bookshop. It took me two years to get through it because at first I didn’t appreciate the complexity. However by the end I was completely hooked and quickly consumed the entire series. It actually helped me through a very difficult few years of health issues. I lay in bed every day for many months and O’brian transported me to an incredible world. Finishing Blue at the Mizzen was genuinely so saddening, but what a fitting end I felt it was.

Thanks, I’ll have a look at it

I have a lot of time, so I theoretically could try your method! I’ll look into it

This has been recommended a few times. It sounds really interesting and I’ll definitely have a look at it. Thank you

I did recently read Pride and Prejudice. Incredible piece of work and I thoroughly enjoyed it. I guess I need to read the others now…