Yamaha CA-610 Protection relay not engaging

[MathiasNuyts]

Hello everyone from Belgium, i'm new here and after reading allot of the threads i still can't get the protection relay to work on my Yamaha CA-610 amplifier.

So the problem lies somewhere around the relay. When i force the relay to close (i.e. with a clamp) the sound comes thru and the amp works perfectly, apart from the malfunctioning relay. So now i am trying to fix the problem.
No previous repairs where done.
And for story, this amplifier was used at a party when my dad was young (around 25 years ago) and they overheated (that's what he says) the amp by placing the record player on top when blasting it full volume. That is the last memory my dad has from this amplifier.

The first test i conducted was to check if the relay even works at all. A small 12V supply to the coil and voila, the relay closes. So i think this isn't the culprit.
Next i tested the idling current and adjusted it. Results:
TP1 and TP2 : -10,5mV (+ on TP1 and - on TP2)
TP3 and TP4: -10,8mV
TP2 to E: 28mV
TP4 to E: 14mV

Then i closed the relay with a clamp and tested the DC offset i think for the Lo and Ro
This gave a reading of 20,8mV. I think this is way too high as the service manual states 0V. I also think this is the problem as why the protection relay isn't closing but how can i fix this?

Then i tested the transistors around the relay.
TR429
19 / 33,2 / 18,5
TR428
18 / 31,9 / 15,5
TR427
0 / 0,4 / 0,4 (This is'n right i think)
TR426
1 / 0,4 / 0,4

I also tested the capacitors with a multimeter by checking for resistance at they all climbed in resistance value like i think they should.

Someone here with some information would be deeply appreciated

 

[avionic]

Welcome aboard Mathias.
Check FR403 10Ω fusible resistor. It is the15v power supply for the protect circuit.

 

[MathiasNuyts]

Welcome aboard Mathias.
Check FR403 10Ω fusible resistor. It is the15v power supply for the protect circuit.

Thx!
Checked the fused resistor and it reads exactly 10.6 Ohm
So this one is still working i guess

 

[avionic]

Do the meter lamps illuminate ?

 

[MathiasNuyts]

Do the meter lamps illuminate ?

Yes one is working and i desoldered the other one because it was broken. But i assumed that because the meter lamp works fine, the circuit had the 12v working fine

 

[avionic]

Hmm... Kind of looks like a bad solder connection. Do you measure any DC voltage on either end of FR403 ?

 

[MathiasNuyts]

Hmm... Kind of looks like a bad solder connection. Do you measure any DC voltage on either end of FR403 ?

Nope, no voltage across the fr, and no voltage from either side to ground. So this means that the fr is not getting any power?
Checked the big capacitors again and they hold 39,4 Vdc and 86 Vac (don’t know which one is relevant). The smaller one next to it holds 78,6 Vdc and 0 Vac.

 

[avionic]

Do you have a schematic ?

 

[MathiasNuyts]

Yes, the capacitors i mean are in following schematic
Capacitor C462 and C463
39,4Vdc ; 86Vac

Capacitor C428
78,6Vdc ; 0Vac

i'm using the Yamaha CA-610 Service manual

 

[avionic]

The area in concern is the path from cathode of D415 to FR403. If C466 is shorted. It would ground out your supply voltage to the protect circuit.

Do you have 12-15vdc at the cathode of D415 ?

 

[MathiasNuyts]

I measured from the cathode of D415 to ground
18,98 Vdc
The anode side reads 0 Vdc
This anode side of D415 is directly connected to the relay on the PCB

Capacitor C466 has 18,98 Vdc over its pins.
The upper pin of C466 shorts to ground but this seems normal from the schematic.


So if i'm understanding this correctly, i have a fault in D415. Or is C466 damaged?

 

[avionic]

The anode side reads 0 Vdc

Anode side is AC...

 

[avionic]

So if i'm understanding this correctly, i have a fault in D415. Or is C466 damaged?

No....You have a bad connection -- broken solder trace -- bad solder connection-- broken solder pad.. etc. Between D415 and FR403.

 

[MathiasNuyts]

Ok, so i got the first part wrong. I measured the wrong resistor but got the right one now. (the small white resistor next to C462)
Voltage at FR403: (R=FR403 ; E=ground)
Before R to E -> 19V
After R to E -> 0,48V
Over R -> 18,6 V

When i measure resistance over FR403 the multimeter reads OpenLine and not 10 Ohm.
This doesn't seem right i guess

 

[avionic]

FR403 the multimeter reads OpenLine and not 10 Ohm.

Its a fusible resistor -- it is " open" ie. bad....

 

[avionic]

Need a 10 Ω , 1/4 watt , with flameproof coating.. This is a safety component replace with nothing larger than a 1/4 watt flame proof/flame resist resistor.

 

[MathiasNuyts]

Need a 10 Ω , 1/4 watt , with flameproof coating.. This is a safety component replace with nothing larger than a 1/4 watt flame proof/flame resist resistor.

Thx!
I removed the resistor FR403 from the board and it does in fact not have any resistance reading.
I'll be ordering a new one with these specs. (This one FRN25J10R, or a variant)
I will post when i replaced the FR. Hopefully it works
Anyway, thank you for the help! Much appreciated

 

[avionic]

That will work..

 

[MathiasNuyts]

Parts arrived and soldered the FR in. Relay clicks from the moment you turn it on. Audio works perfectly, i consider this one fixed (for now ).
U sir are a legend! Thank you for the information!