Yamaha CA-1010:fuse blown in Class A

[triodo]

Hi guys,

My Yamaha blows one of the fuses installed after the transfomers : it happens when I switch in Class A mode.
This doesn't happen all the times that I use the class A mode.
See the red square in the the wiring diagram : is one of the two fuses on the lines OR-OR-->fuse values are T6.3A-250V

Do you have suggestion?
Could be the relay the problem?

No problems in class B .
Power supply in my home is 235V so the voltage selector is on 240V.

Thanks in advance for your help.

bye

Yari

 

[Dr. Ear]

please see this thread:
http://audiokarma.org/forums/showthread.php?t=166535

 

[triodo]

thanks Dr Ear to remember me my previous post on a similar problem occurred two years ago.

In that case , checking the relay as suggested, I found the fuse blown.
I replaced the fuse and the problem is never occurred until now.

Therefore,
Do you think that it's time to replace the relay?

Thanks

Yari

 

[OvenMaster]

Hi, Yari! :wave:

I do not think that the relay is the cause of the problem. A fuse opens because too much current flows through it. The relay is only a switch. I think that perhaps you have a faulty (short circuited) component in the box marked "Electrolytic Capacitor C. Board" or the "Main Circuit Board L" or "R".

Does the same fuse fail every time?

Tom

 

[triodo]

Hi Tom,

nice to read you....

No, the fuse doesn't fail avery time.
In 15 days of running, every day for 2 hours , 3 fuses burnt. The fuse burnt is always the same.
See the yellow target on picture enclosed.



Uploaded with ImageShack.us

I'm not an expert....but if there is a short circuit ,the fuse should fault every time..... I think...(?).
I think...also:
The relay is the first component on the fuse line : it could have a discontinued contact in one of two relay section..... maybe Could this problem does "stress" on the fuse?

The problem of the discontinued contact is already occurred on same relay type installed on speakers output .I already replaced it myself.

The amp has been checked in laboratory some months ago : bias values were ok.

I hope to solve the problem myself....if possible.

Thanks :thmbsp:

Yari

 

[OvenMaster]

Yari:

1. That relay -- "the first component on the fuse line" -- is the relay that controls "Class A" or "Normal" operation. If the fuse only blows in class A, then I still say that there's something that's drawing too much current on that little board or elsewhere -- a faulty component -- and that it's not the relay that's at fault.

2. If you have replaced that relay and the problem keeps happening, then the relay is not the problem.

3. You're right. If there was a short circuit, the fuse would blow every time.

 

[triodo]

Thanks Tom,

Your suggestions are always appreciated by me!!

I agree with you that the problem could be not the relay.

As wrote , the relay replaced is on speaker output, so...
as first step :
1)I will replace in any case the relay for operation Class A (it is 30 yeards old at least!!)
2)I will replace the six small capacitors on the electrolituc capacity board


I will let you know

Thanks

Yari