JVC A-X900 power on but front panel no light

music soothes the savage beast
Joined 2004
Paid Member
Hello.
Need help for JVC A-X900 Amplifier.
Amplifier power on,but no front panel light.
No relay click.
It was 2 resistors blown R403 and R327.
After replacing no change.
We're I need control the voltages for front panel.
Regards.

SM
https://elektrotanya.com/jvc_a-x900b.pdf/download.html
Have you measured output transistors?
Resistors burn for a reason, and are rarely the reason why they burn. Typicaly something else caused excessive current to run through.
Do the homework, come back.
 
Power transistors desoldered and tested ok.
Without power transistors

Q513
E.....-57v
C......-65v
B....-62.5v

Q511

E....-57.2v
C.....+65.6v
B.........-59.0v


Second channel with power transistors

Q512

E........0v
C........+65.5v
B.......0v


Q514

E.....0v
C......-65.2v
B.....0v
 
Last edited:
Hello.
the amplifier works, there is sound on two channels, but if I touch the volume button, it goes into protection. Same if I press the button SUBSONIC.
With or without speakers goes into PROTECT. The voltage on the wires 2 and 5 of FW504 connector rises 2....4v when I turn the volume up.
Thanks