Possible help on MIDI Controller Casio Digital Guitar 20?

[danvex]

Good day/evening everyone, I'd like to know if there are any problematic cases for such MIDI synths? Mine came from Japanese auction and was sold "untested", therefore I had high hopes I'd get a working unit (naive from my side, as it seems), later on I discovered that it doesn't power on. Tried with SUM-1 (D sized) batteries for now, as was suggested in the manual, therefore I also thought of trying with AC Power Adapter (9v), but would it be worth trying? As of now I have it on my table, de-soldered ground wire to get further, in order to check both PCB's for any problems, however I cannot recall any problems, as visually they seem alright. Sadly I do not have voltmeter with me as of now and I can't really say that I'm experienced in electronics, help would be appreciated, thank you in advance! 

(I tried to follow this video below, they state that usually the problem is with the T3 Diode and Capacitor)
https://www.youtube.com/watch?v=26cBDE9Ac4I

[danvex]

As a possible guide I was using Parts & Service Manual which I found online as well: https://www.manualslib.com/manual/908821/Casio-Dg-20.html?

[Chas]

It would certainly be worth trying it with an ac adapter, though ensure the one you use outputs the correct voltage (the DG likely needs 7.5 or 9v) and that it has the correct polarity. Most Casios of that era used centre negative, which was the opposite of which most others AC adapter powered devices used.

 

Hope you get your DG-20 working, they're both fun and unique. And with MIDI Out they're also useful to use to trigger other midi devices. I've had the DG-20 on my radar for quite a while now,  but prices have shot up over the past few years. 

Edited January 17, 2023 by Chas

[danvex]

12 hours ago, Chas said:

It would certainly be worth trying it with an ac adapter, though ensure the one you use outputs the correct voltage (the DG likely needs 7.5 or 9v) and that it has the correct polarity. Most Casios of that era used centre negative, which was the opposite of which most others AC adapter powered devices used.

 

Hope you get your DG-20 working, they're both fun and unique. And with MIDI Out they're also useful to use to trigger other midi devices. I've had the DG-20 on my radar for quite a while now,  but prices have shot up over the past few years. 

Thank you so much! Just got one today, it has different voltages and hot-swappable head (You screw in two philips head/cross screws to hold the + and - wires), but yeah, you were indeed correct on 9v power, as well as polarity, as it is - c +, still haven't received a transistor or diode, so I might as well as try resoldering the ground wire to it's initial state and try with adapter

[danvex]

Strangely enough I don't get any readings on the diode (T3) and transistors near it.. Will update with anything good when possible

[danvex]

It worked with the adapter, but no luck with batteries, since the headstock was beaten up (Which I assume was the reason) - one may also find a screw in it, locking the strings and preventing them from rattling around.. With that being said - the strings are less responsive than they should be, so I plan to get a donor for my project to completely finish it, so in case you don't have a way or a fix - getting a dummy donor is always a way!

[danvex]

Welp, ordered a donor and what would you guess - the seller said that it didn't turn on, but it did using the AC adapter! Haven't tried batteries yet, but this one has one string popped off the base, which means that I'll have to figure out how the string mechanism works..