JVC XL-EX70 no power on stanby

[ex250]

Hello guys, I purchased this week this CD changer to add to my old Pioneer Hifi, well, just lasted 1 CD playing, tried to open the tray to change it and add a full set of three, but got stuck, no opening tray and no response from any button, power but was not responsive and finally unplugged it. Plugged again and no standby led and nothing works.

Opened the case and there is almost one zenner diode that gets quite hot, enough to evaporate quickly the alcohol.

If I remove from the power supply the CD system, the display blinks, also the temperature of the zenner decreases.

But no sure from where to start, if it's a main cd changer circuit problem or a power supply issue.

Here is the service manual, and one image of the power supply and audio board.

If some one could give a hand would appreciate

[ex250]

Re: JVC XL-EX70 no power on stanby

The voltages from the power supply seems ok, but I don't know why with the cd drive disconnected the frontal screen blinks with some text, a short on the drive? there are 2 voltages on the cd drive circuit 8v and 5v, it's safe to inject some voltage to see if there is anything hot?

[ex250]

Re: JVC XL-EX70 no power on stanby

Just checked the feed to the screen and controls, there are some discrepances from my view

on the CN820, from power supply, the pin 7 is 16v not 10v as the scheme, a typo?

on the CN 821 F1 and F2 lines are -29,97v, where should be -25,7v
pins 3 and 4 are 0v and 0,01v and pin 5 is 8.33v

On the feed to the controls, there are 14pin CN802
these are unconnected and with control connected, note the cd player circuit is disconnected and the screen blinks quickly
1 - 0v // 0
2- 4,89v // 3,99v
3- 4,91v // 4,01v
4 - 0v // 0,12
5- 2,46v ?? should not be 0v? // 0,8-0,9
6- 0 // 1,4v oscillating
7- 0 // 0,3v oscillating
8- 0 // 0,6v oscillating
9- 0 // 1,8v oscillating
10-0 //0
11- -30,01 // -29v
12- 4,91 // 4,01v
13- -30,01 // -29v
14- -30,01 // -31,8v

any clues on this??

[R_J]

Re: JVC XL-EX70 no power on stanby

I would replace C101 or at least bridge it with about a 2200µf cap, see if that stabilizes the voltage. The schematic is misleading, on the line it says 13.0, at the plug it says +10v. The line is unregulated but 16v seems a bit high but not likely the problem.
F1 and F2 are the filament lines for the display, the voltage is fine, I suspect your a/c line voltage may be a bit higher than normal, that would explain the slightly higher secondary voltages.

The zener diode D132 is ok, it sets the -30 voltage for the display, There are many small caps (C132,C133 etc.) that bay be weak due to age, this is where a scope becomes useful.

[ex250]

Re: JVC XL-EX70 no power on stanby

Will check the caps, I have no scope.
The C101 states 16v 6800uf, reading around 7400uf on the meter, seems healthy, not?

many thanks!

[R_J]

Re: JVC XL-EX70 no power on stanby

Sometimes bad capacitors read high, especially in circuit, try soldering another cap across it (1000~2200µf) and see what the voltage measures, Like I said this not likely the problem, there are other low voltage regulators with small filter caps that may cause problems.

[stj]

Re: JVC XL-EX70 no power on stanby

changers are a pain in the ass.
dont be too surprised if somebody moved it with the discs inside and one came out of the transport and jammed it all up!

[redwire]

Re: JVC XL-EX70 no power on stanby

I find it's always mechanical problems, especially brushed motors failing and overloading the H-bridge driving it.
It might have shorted when OP ejected the tray.

[ex250]

Re: JVC XL-EX70 no power on stanby

Sometimes bad capacitors read high, especially in circuit, try soldering another cap across it (1000~2200µf) and see what the voltage measures, Like I said this not likely the problem, there are other low voltage regulators with small filter caps that may cause problems.

Soldered one 1000uf cap and same voltages, unsoldered many of the smaller ones and all are in spec.

[ex250]

Re: JVC XL-EX70 no power on stanby

I find it's always mechanical problems, especially brushed motors failing and overloading the H-bridge driving it.
It might have shorted when OP ejected the tray.

Tried to move both motors with a 1.5v feed and they move slowly, but moves.
I can't guess where is the fault, why the screen flickers with the circuit of the cd disconnected, and there should be some short or high drain because when I connect it screen goes out.