So, I inheited a non-functional JTV-69 a few months ago. All I knew at the time was that the unit would not power on under battery and wouldn't be recognized by the Workbench adapter (likely because it wasn't powering on).
When it arrived, the first thing I did was charge up the battery and plugged it in to see what it was doing. Sure as advertised, the guitar wouldn't power on and the battery LED shows nothing. I checked the battery with a multimeter and I was getting 8.4v, so appeared to be charged and alive. For the heck of it, I checked the charger and I'm getting 12v at the adaptor and about 8.7v across the prongs on the charger. All seemed in line.
Based on this, I ended up ordering a replacement main PCB (from Full Compass). Three weeks later, that came in and I installed it. On first try after installing it, I got full LED appearance and finally got the guitar to power on. Played it for maybe 5 minutes, unplugged it. Came back later, tried it again and it worked again. Came back later and nope, stone dead and no battery LED again.
At this point I was a little freaked out because I thought the first PCB got fried and the new one was fine until some time plugged in and this one fried too. After I calmed down, I got a hold of someone with an HD500 to try seeing I'd it'd power on with the data cable. Tried it and it worked reliably for several days. So, confirmed the PCB is fine.
I started suspecting the battery was the issue. I've had Li-Ion batteries for drills and whatnot that show full charge right after a charge but die instantly on use.
So that in mind, I ordered a new battery from Sweetwater. Two days later, it arrived, I inserted it into the guitar just to test and I got LED readout, albeit one blinking light. I assume that they ship discharged. So, I put it in the charger, solid red light for about the prescribed 8 hours then blinking red light, so full.
Installeded into the guitar, shows full LED and guitar powers up. Works great and reliably on and off all day. I only check it for maybe 5 minutes at a time and a few times today, so no more than 30 minutes of playtime. I was also removing the battery between uses. Came back to use it this evening and uh oh, back to no LEDs and guitar is stone dead.
I plugged the battery in and it's reading full (blinking red light).
Pulling my hair out over here.... My last remaining cause I can think of is the battery holder itself. I pulled the batter holder out and used the multimeter on the back to make sure the battery is making full contact with the prongs and I'm showing full voltage. But there's a small PCB on the back, so I'm guessing it's possible the problem is there?
Just wondering if anyone has had this experience or has any ideas. I'm starting to miss my ol' 6 double-A Variax 300 haha