Need help with Yamaha R9 Receiver issue PLEASE?

C

Confusilated

Enthusiast
Hi, so I know very little about repairing gear, but I'm willing to attempt a repair if anyone has an idea what may be a likely culprit for the problem that just manifested.
I have the Yamaha R9, and I had speakers hooked up to A and C speaker inputs. The right output on the B speaker never worked, so I didn't use it. Into the C input I had a Niles Audio SPS4 speaker switch box which had 4 inputs. I had 3 sets of speakers hooked up to that box, and on the 4th input, I went to test an M-Audio DX4 powered speaker, which promptly blew the Yamaha receiver. No power or anything now to the receiver.

Here's what I've done thusfar. I have no speakers or ANYTHING connected to the receiver, just power cord. I only see one fuse, a 250V, 10 amp, which although is a Littelfuse, I replaced with a Buss fastblow 250v 10amp. It blows instantly when powering up. My questions are as follows...

Is there something about the Littelfuse that makes a difference? It looks like ceramic or paper wrapped perhaps (it's white), as opposed to clear glass like the Buss. Is there a difference and do I need the Littelfuse? I can't get it locally but can buy on ebay I suppose. Could it be something as simple as that?

Is there another fuse somewhere that I am missing?

If not, Is there a likely culprit for what caused the issue by hooking up the M-Audio DX4? If it blew the power supply, then I guess it's a cool looking paperweight now. But I'd really like to get it working again. Any ideas?

As I stated, I know little about gear repair, so if please reply if you seriously are interested in helping, as it would be greatly appreciated.

Thanks in advance : )
 
R

roadrune

Audioholic
You say the new fuse is called fastblow, i believe you would need a slow fuse for the startup current.
 
TLS Guy

TLS Guy

Seriously, I have no life.
A blown fuse is always bad news.

I suspect that you blew one or more of the power transistors on that channel.

You need to observe the power draw to that channel as you slowly increase the power to the unit with a Variac.

Most likely the power transistors on that channel need replacement. The driver transistors and some diodes may also. The driver stage may be an IC.

However the real issue is that it is usually impossible to service a unit without a service manual and good test gear. Th biggest problem is that companies refuse to issue a service manual which is a disgrace.
 
C

Confusilated

Enthusiast
Thanks for the replies so far. TLS, is that true regarding fast blow fuses like what Roadrune is suggesting? Does the paper wrapped or ceramic looking aspect indicate its a slow blow? Also, I have a variac in storage. I can get it, but its a little bit of a hassle to get to. If its hooked up to the variac, are you saying that with minimal power draw, it shouldn't blow when I power on? Thanks again
 
TLS Guy

TLS Guy

Seriously, I have no life.
Thanks for the replies so far. TLS, is that true regarding fast blow fuses like what Roadrune is suggesting? Does the paper wrapped or ceramic looking aspect indicate its a slow blow? Also, I have a variac in storage. I can get it, but its a little bit of a hassle to get to. If its hooked up to the variac, are you saying that with minimal power draw, it shouldn't blow when I power on? Thanks again
Thanks for the replies so far. TLS, is that true regarding fast blow fuses like what Roadrune is suggesting? Does the paper wrapped or ceramic looking aspect indicate its a slow blow? Also, I have a variac in storage. I can get it, but its a little bit of a hassle to get to. If its hooked up to the variac, are you saying that with minimal power draw, it shouldn't blow when I power on? Thanks again
Well a blown fuse is almost always bad news.

You will need slow blow fuses. Replace the fuse once and power it up. If the fuse blows which it probably will, replace it again, but do not power up. Disconnect the rail voltage to the bad channel. If you have no service manual that tells you the correct voltages, then you need to study a working channel. Now carefully measure the voltages around the driver stage and output stage with a high impedance amplified FET or tube VOM. Do not use a standard multimeter, or you will do a lot of damage. When you think you understand it, then put in the Variac and study the bad channel as you power it up. See if you can determine the high current draw from voltage drop. It is hard to measure current directly.

Now replace what you think are the bad components. Now repower slowly and see if the problem is solved. Now connect a signal generator and look at the signal on an o-scope and compare it to a good channel. Use power resistors on the speaker terminals of appropriate impedance.

If a power transistor is blown you may well have to replace both with a matched pair.

I have no service manual so I have no idea if bias has to be instrument set.

These sort of repairs really should not be done without a service manual.

Unless you have some experience this is not something you should likely attempt.
 

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