Please help with A/B speaker switch

[jvinhj240]

I have Yamaha AR304. The Speaker A have no output at all, Speaker B working fine. I connect only A no output. Speaker B has OUtput. I put A/b same time still same result.

Please help me basic troubleshoot , where do I start and which point i need to check . thanks

I attached Service manual if anyone can help. Thank you.

 

[chazix]

I have Yamaha AR304. The Speaker A have no output at all, Speaker B working fine. I connect only A no output. Speaker B has OUtput. I put A/b same time still same result.

Please help me basic troubleshoot , where do I start and which point i need to check . thanks

I attached Service manual if anyone can help. Thank you.

I do not think that your attachment is what you think it is.

Also, I am not sure that your equipment is what you think it is. If a Yamaha AR304 exists, the internet does not seem to be aware of it. Kenwood, perhaps?

Regardless, I believe that the most likely reason for the symptoms is that there are two independent relays for speaker A and B, and that the A relay is not operating. A good first step would be to measure the voltage on the coil terminals of the A relay when Speaker A is selected.

Cheers,

chazix

 

[jvinhj240]

I do not think that your attachment is what you think it is.

Also, I am not sure that your equipment is what you think it is. If a Yamaha AR304 exists, the internet does not seem to be aware of it. Kenwood, perhaps?

Regardless, I believe that the most likely reason for the symptoms is that there are two independent relays for speaker A and B, and that the A relay is not operating. A good first step would be to measure the voltage on the coil terminals of the A relay when Speaker A is selected.

Cheers,

chazix

Sorry , its Kenwood AR304
Thanks, when i press A it does click. DO i need to open the relay? and see it really attach on the legs?

 

[chazix]

If you are sure that the A relay is clicking, and if all the connections between that relay and the A speaker terminals look good in a visual inspection or an ohmmeter check, then I think it is reasonable to conclude that the relay itself is defective. I don't think there is much to be gained by opening up the relay (except to satisfy curiosity, which might be a good enough reason).

 

[jvinhj240]

oops, i double check its not clicking. your right. its the relay. I must now check ohmmeter. do i nset to DC voltage? what voltage i am looking for?

 

[chazix]

oops, i double check its not clicking. your right. its the relay. I must now check ohmmeter. do i nset to DC voltage? what voltage i am looking for?

I would suggest setting the meter to measure DC voltage and measuring across the coil terminals of the A relay (equivalently, across the terminals of diode D11). With A Speaker selected, the voltage on the coil should be about 22V. If that voltage is present but the relay does not engage, then the relay is defective.

If the coil voltage is too low, the next logical step would be to measure the voltage on the base terminal of transistor Q29 (with respect to ground - if you don't know how to find a convenient ground point, you can use the emitter terminal of Q29). The base voltage should be about 0.7V when A Speaker is selected. If that voltage is present but the transistor is not delivering the relay coil voltage, then the transistor is defective. In that case, it would be a good idea to also check or replace diode D11, because a defect in that diode may have caused the defect in the transistor.

Please be extremely careful when making measurements with the receiver powered up. While there are probably few points bearing voltages which could harm you, there are many ways that a small slip in positioning test probes can harm the receiver.

 

[jvinhj240]

Thanks so much . I give it a try.

 

[jvinhj240]

so after busy week, I replace both relay but same problem. So I poke around , I found the mosfet pic attach read from left to right

1, 3 and continuity from legs across
2,4 nothing , whatever i poke there are non continuity.

I don't know any thing about it do you think this is my problem? the mosfet are bad?


KENWOOD RECEIVER AR-304

 

[chazix]

I don't know any thing about it do you think this is my problem? the mosfet are bad?

If the receiver works correctly with speaker B, there is no reason to suspect the power amplifier output devices (which are not MOSFETs).

 

[jvinhj240]

If the receiver works correctly with speaker B, there is no reason to suspect the power amplifier output devices (which are not MOSFETs).

Ok thanks, I think this is as far I can go .

 

[elnaldo]

Speaker B working, the amplifier works. You just need to trace the fail in the A relay circuit. Is the voltage present at the IC coil? Compare the behavior with the working B relay.

I have years of experience and I try by all means to avoid poking with my DMM inside a live unit. I always try to clip the probes to the right place with the unit OFF, then power ON to read the DMM without touching anything inside the live unit.

You need to see why the signal is not reaching the output terminals. You need: continuity from the relay to the speaker terminal, continuity from the Power amp output to the relay (you can check this wih the unit OFF AND UNPLUGGED FROM THE WALL). then you need a voltage engaging the relay. If that voltage is not there, time to trace back that circuit. But if the B relay works you have chance of a simple fail like a bad speakers selector switch or even some broken wire or pcb trace.

 

[coonmanx]

Quick thought...

If you are listening to only one set of speakers then there isn't much of a problem just running them on B. If you would like to set up two different sets of speakers and then have the ability to run either one at at time or both at a time then you need to fix the issue. According to Hifi Engine this amp is rated to deliver into a 4 ohm load so if you were interested in running four speakers at once you could just tap them both of of the B connections...

Of course if you are trying to figure out what is actually wrong and learn then disregard everything I just said... elnado gives some good advice.

 

[jvinhj240]

Thanks I can live with only Channel B. Yes I like to learn for simple fix as this receiver cost almost nothing now. I could buy it for $20 working condition same receiver. I only use 1 set of speaker with a sub. The sub is not working due to channel A but I use other output to use as sub it sounds ok. I thought simple fix like relays or something . I guess there more troubleshoot involved in relay continuity ,voltages. etc.....