Yamaha RX-V375

[Captain Blu Ballz]

Recently the power went out at my house. Well I thought it went out, but I noticed some weird behavior from a few electronic devices I own. My radio was off but buzzing. I quickly grabbed my multimeter to check the power at the outlet to discover only 20v a/c. Just as I discovered this my girlfriend tells me that the surround sound receiver was clicking, trying to come on. She unplugged the receiver and TV. After the power was restored the radio would turn on but still had a buzzing sound coming out of the speakers and the receiver would not turn on. Apparently the receiver has a protection built into it that will disable the unit after 5 unsuccessful attempts to power up do to a low voltage condition. I am very thankful that my Samsung TV was not damaged too because it was connected to the receiver along with two game consoles.

Any help resetting the receiver would be greatly appreciated. Thank You,
Captain Blu Ballz

[sam_sam_sam]

Re: Yamaha RX-V375

Do you know how to use a meter
Do you have a ESR cap meter

Can post some photos of the power supply section of surround sound receiver

Your radio may have the same problem

[Captain Blu Ballz]

Re: Yamaha RX-V375

I do have a meter. I don't have an ESR cap meter. I'll post pictures of the power section in a minute. Thanks for your help.

[Captain Blu Ballz]

Re: Yamaha RX-V375

Here are the pictures.

[sam_sam_sam]

Re: Yamaha RX-V375

The first thing I would do check the big main transformer
This is the way I would do it

Make sure that take a photo of each connector of the transformer windings before you removed them so you where they went

Disconnect all winding wires to all boards and find the main power in winding wires and check for any resistance and all other windings make sure that you do not have any open windings

If you get resistance on each set of winding -----> and you feel comfortable doing this you can do this test to see if you can get any voltage on all winding make sure that no winding wires are touching each other report the results ***** Please be careful when doing this test ****

*****You will be working with live 120 volts AC so be careful ******


I would also check the small transformer on the small board

I would take photos of the connectors before you remove them unless the connectors are different and can not be plugged in any where else

I would also take all boards out of the unit and look for any other fuses and check them

I would also look at all components and see if you find any burnt or any discoloration on all components

I would check all diodes and all bridge rectifiers on all boards for open or shorts

What brand are the caps

What component is the one that has a row of caps in front of it that is mounted to the case of the unit

Please post all results and we will go from there

Thanks for the good photos

I hope this helps

[Captain Blu Ballz]

Re: Yamaha RX-V375

I'm not by any means an expert but I would guess that the board with the caps in a row on top would be the pre amp. I am probably wrong but like I said, I'm guessing. One thing I did notice when observing the boards for defective components (visually, haven't taken measurements yet) is that there is a note on the board with the caps in a row that says "when replacing the fusible resistor, replace with the same type and size". I know a little bit about electronics and know what a resistor looks like and the two resistors they are referring to look like normal old old-school resistors (they are not surface mount). I'm assuming by the name "fusible" that it's possible that the resistor could blow Or open like a fuse.

I will update my findings hopefully by later this evening. I am at the Vet because my dog is having emergency surgery. I figured it was time to clear the bank anyway. I am in the wrong profession.

[budm]

Re: Yamaha RX-V375

The standby power supply board with small transformer and a black power relay, do you hear that relay click on when you hit the power switch?
That power relay supplies 120VAC to the primary winding of that large power transformer.
BTW, did you read the user manual to see if it can be reset?
Service manual:

[Captain Blu Ballz]

Re: Yamaha RX-V375

Ohm'ed out the windings on the large transformer. There were no open or grounded windings. As far as the clicking from the relay when you hit the power button, there is no clicking. There is nothing. No display, noise, smell, but there is voltage present. Here's my readings.....

Ohms starting with the two pin connector next to the mains on the small board. 2.4 ohms. That's with all the wires unplugged from the transformer (the big transformer).
The next plug is the one coming off the transformer that the two pin plug is located. I'm going to list the wires starting with the first red one being "1", second red "2"........

1-2 = 1.3
1-3 = .7
1-4 = .7
1-5 = 1.0
1-6 = .5
2-3 = .7
2-4 = .7
2-5 = 1.0
2-6 = .5
3-4 = .1
3-5 = .4
3-6 = .4
4-5 = .4
4-6 = ..4
5-6 = .7

With the transformer unplugged I wanted to see what voltage I would get at the two pin connector with no load on it and it had 120v ac. After I plugged in the two pin connector to it I was getting 154mV ac at the two pin connector. With my meter connected to the two pin connector still I plugged in the other plug on the same side as he two pin plug and my meter dropped to 87mV ac. The last plug resulted in dropping the meter to 57mV ac.

The manual does not list a way to reset the receiver. It said that you have to take it to an authorized repair facility to have it reset.

I am a little confused why I would have power going to the transformer when the unit wasn't turned on. Then once I plugged the connectors in one by one the voltage basically went to nil.

[Captain Blu Ballz]

Re: Yamaha RX-V375

Ohm'ed out the windings on the large transformer. There were no open or grounded windings. As far as the clicking from the relay when you hit the power button, there is no clicking. There is nothing. No display, noise, smell, but there is voltage present. Here's my readings.....

Ohms starting with the two pin connector next to the mains on the small board. 2.4 ohms. That's with all the wires unplugged from the transformer (the big transformer).
The next plug is the one coming off the transformer that the two pin plug is located. I'm going to list the wires starting with the first red one being "1", second red "2"........

1-2 = 1.3
1-3 = .7
1-4 = .7
1-5 = 1.0
1-6 = .5
2-3 = .7
2-4 = .7
2-5 = 1.0
2-6 = .5
3-4 = .1
3-5 = .4
3-6 = .4
4-5 = .4
4-6 = ..4
5-6 = .7

With the transformer unplugged I wanted to see what voltage I would get at the two pin connector with no load on it and it had 120v ac. After I plugged in the two pin connector to it I was getting 154mV ac at the two pin connector. With my meter connected to the two pin connector still I plugged in the other plug on the same side as he two pin plug and my meter dropped to 87mV ac. The last plug resulted in dropping the meter to 57mV ac.

The manual does not list a way to reset the receiver. It said that you have to take it to an authorized repair facility to have it reset.

I am a little confused why I would have power going to the transformer when the unit wasn't turned on. Then once I plugged the connectors in one by one the voltage basically went to nil.

[budm]

Re: Yamaha RX-V375

If that power relay is not being turned on the there will be no main AC applied to the main winding of that power transformer so do not wasting time checking the power transformer until you find out why that power relay is not turned on.
The mV AC you are getting is just stray AC reading.
Look at the service manual to see how the relay coil is driven, see if you do have DCV between the two legs of the relay coil or not, or the power supply on that standby power supply board is OK or not. You do know how to read the diagram, right?
Also do the research to see if there is reset procedure on the web some where, I am sure you are not the only one with the this problem.

[Captain Blu Ballz]

Re: Yamaha RX-V375

Yes, I can read a schematic. I thought that most components on the board couldn't be tested unless removed from the circuit. I have looked online but unfortunately the owners manual doesn't get into circuitry, only basic operation instructions. I couldn't even find a tech manual anywhere. I'm probably not looking in the right spot.

Back to the drawing board. Thanks for your help.

I want to take the receiver to the power company and have them fix the thing but you know that ain't gonna happen.

[budm]

Re: Yamaha RX-V375

So you did not download the service manual that I searched for you in post 7?

[Captain Blu Ballz]

Re: Yamaha RX-V375

Sorry, thought that was a link to owners manual. Thank You
I'll have a look. Got a lot going on.

[Captain Blu Ballz]

Re: Yamaha RX-V375

I just wanted to say thank you to everybody that offered help. I checked out the service manual and sure enough the instructions for resetting the system were in there. It's fixed! ! I've got another issue now though. While the receiver was out of commission the two negative terminals for the main front speakers were snapped off. These are the screw in type that will also work with banana plugs. They threaded posts were sheared off. I'm gonna try to tackle that tomorrow.. Once again, thank you for your help.

[budm]

Re: Yamaha RX-V375

Glad to hear the service manual helps you solve the problem.

[Captain Blu Ballz]

Re: Yamaha RX-V375

Everything is fixed now and it is up and running. This forum is awesome. Happy camper.

[budm]

Re: Yamaha RX-V375

Thanks for the follow-up.