M70 power but won't turn on - no functions.

R

rootsu

New Member
Nov 15, 2021
5
0
1
Seattle, WA
Hi everyone,

I just got an M70 and trying to troubleshoot it. When plugged in via cord, there is no light, no power LED, nothing when I push it to "ON" under any setting, line in, phono, tape or radio.

I've removed the back panel, and verified the fuse for the power supply is in tact and it gives off 14-16V that plugs into the Amplifier board.I'm 100% satisfied the power-supply/transformer is good.

I did some disassembly and troubleshooting via the service manual and saw the contacts on the X505 pins were all broken. Re soldered that back on, and still nothing - continuity through the first and 3rd pin though..

I pulled all the cords and reseated them w/ contact cleaner, nothing. I'm not sure where to look at next, I though I could perhaps do a limp mode where I just plug the transformer into the Amplifier board but I can't seem to bring it to life for phono/line-in.

Any advice where to look? I also have a spare M70 that I can swap parts to and from, but from what I see that could be tricky indeed. :D
 
R

rootsu

New Member
Nov 15, 2021
5
0
1
Seattle, WA
JVC Floyd said:
have you verified the power switch itself is functioning and also that there is power present at the switch.
Click to expand...
Yep, this I did. Power switch isn't an issue, and I re flowed the solder on the three wires and tested continuity. The switch works.



caution said:
Sounds like a shorted transistor
Click to expand...
:( Yeah, I guess the only way is to go one by one?

--
Meanwhile on my other M70, I turn it on, it works 100% for line in/phono, but for radio it instantly mutes after 2 seconds. I guess the culprit there is the muting circuit. Common failure?
 
You must log in or register to reply here.
Top Bottom