Yamaha CR-620 Dead Tuner

N

nongrata

Member
I am restoring a Yamaha CD-620 and got the amp section running again.
It is amazing how much details I can hear in the music.
The tuner however seems completely dead.

No sound, no noise, no signal on the meter, nothing.
AM and FM are completely dead.

If I turn up the volume up to the max i hear some 50 Hz Hum.
I can not hear it in AUX.

Thought maybe some voltage was gone.
There is 30v (26V if I measure) and 12V and - 12V.

All (glass) fuses are fine.

Anyone had such issue before with a CR-620 or CR-820 ?
 
I had a dead tuner on a CR-420.
There was a dead IC.
Can you get to the tuner transistors and check voltages?
 
Checked already (however in circuit) the transistors on the tuner board, they all look ok to me.
Also checked diodes.
No visible damage on resistors or capacitors.
 
nongrata said:
Checked already (however in circuit) the transistors on the tuner board, they all look ok to me.
Also checked diodes.
No visible damage on resistors or capacitors.
Click to expand...

They "look" OK or they measure OK?

You would have to measure voltages on the transistor legs in circuit with the unit powered up.
 
avionic said:
Are you getting any red LED's illuminating?
Click to expand...

Very good question, stupid I did not think about that myself.
Only the power led lights up. If I switch to Tuner no FM or AM light at the right, also not when I push the Tuner button to select AM or FM.

Indeed I just measured with an ohm meter (system switched off) , so not the voltages.
It indeed just give an indication.
 
Last edited:
nongrata said:
Very good question, stupid I did not think about that myself.
Only the power led lights up. If I switch to Tuner no FM or AM light at the right, also not when I push the Tuner button to select AM or FM.
Click to expand...

Are you sure the 12 volt power supply(s) are working ? And getting to there proper destinations on the tuner circuit.
 
avionic said:
Are you sure the 12 volt power supply(s) are working ? And getting to there proper destinations on the tuner circuit.
Click to expand...

There are wires going from the amp and power supply board to the tuner board.
I measured on the soldered jumpers (J) near the cables the voltages, 12V, -12V and 26V on the tuner board.
So thought voltages are there but.....

On the amp board there are pins with - 12 V ---> indeed - 14 V (violet)
+ 12 V----> no voltage (Orange)
12 M ---> + 12V (brown)

The orange cable ( + 12V ) goes to the tuner board so 0 V is a little strange.
 
The orange cable ( + 12V ) goes to the tuner board so 0 V is a little strange
Click to expand...

Well.. We need to find out why. Look over solder connections or for circuit board cracks.
 
Last edited:
Suspect C806 47µf/25v , C825 10µf/16v
Check the voltage at the base of TR804 ( looking for roughly 13 vdc )
 
Going back to the schematics and hope i find a clue.
Also will check your suggestion and try to follow the pad and look for a break in the circuit.
Was temped to connect the 12M with +12 V see if that would give juice to the tuner but presume that is not a good idea as they did not separate them in a 12V and 12M cable for nothing.
 
nongrata said:
Going back to the schematics and hope i find a clue.
Also will check your suggestion and try to follow the pad and look for a break in the circuit.
Was temped to connect the 12M with +12 V see if that would give juice to the tuner but presume that is not a good idea as they did not separate them in a 12V and 12M cable for nothing.
Click to expand...

Lets t-shoot the +12v and leave 12M alone.:thmbsp:
 
Thanks will check the components you suggested.
Yamaha does not print all the components numbers on the boards.
Good sounding amps but the layout of the board and printing is not as good as the Sansui's I have.
If there is no reply or comment here in te coming hours it is because my wife is urging me to go to friends now and enjoy the sun (maybe one of the last times this summer here).
 
Repaired.

TR803 did not have a 12 V out.
Also a 2SD400.
I had a 2SD439 (also used as driver) which has only 0,7 A collector current instead of 1 A but it did the trick.
FM led works. Got stereo reception on a wire.
Now only need to get the bulbs (LED's) working tomorrow.
Thanks for your great help you all and especially Avionic who pointed me to the component that caused the failure.
 
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