Kenwood AV Reciever No Audio Output

[Solder Boy]

Hi guys I have a Kenwood VR-5090 A/V reciever on my bench. Unit turns on, display works, function switch works etc but there is no audio output at all.

Obtained the service manual for this thing and looked at it but I didn't see where the output amp chip(s) would be. Client said the unit had been working but the audio was slowly dying and then one day the audio quit.

If this thing does have an output chip I'm suspecting that is the culprit just wondering if any of you have come across this.

Thanks!

[Th3_uN1Qu3]

Re: Kenwood AV Reciever No Audio Output

It doesn't necessary have chips, it may be a discrete design. In which case you will probably have something to do with the output transistors. Pics and a copy of that service manual please.

[Solder Boy]

Re: Kenwood AV Reciever No Audio Output

I will take a pic of the unit and put up a copy of the SM after lunch.

[dood]

Re: Kenwood AV Reciever No Audio Output

Don't forget to check the output delay relay, if it has one. Sometimes they fail and will no longer "click" the output on.

[Solder Boy]

Re: Kenwood AV Reciever No Audio Output

Hi there I took a picture of the unit this morning..

Tried to upload the Service Manual for the Kenwood.. wouldn't let me it's too big for the forum. How do I make it available for you?

Thanks

[Longbow]

Re: Kenwood AV Reciever No Audio Output

The outputs are obviously connected to the heat sink in the rear left corner of the unit. A quick test of E-C resistance should reveal any shorted outputs. If they are not shorted, then confirm that you have B+ B- to the outputs. Measure the d.c. on the output line of each channel, which should be zero. Finally, the audio has to go through the speaker relay which monitors the d.c. output voltage and lastly through the speaker switch. Headphone audio out? Then post results.

[Solder Boy]

Re: Kenwood AV Reciever No Audio Output

Hi Longbow.. just have a question about testing the B+ B- you were talking about.. I've recieved permission to tear this unit down so I can test it but wanted to get a couple of things cleared up before I do.

You mention I should check for B+ but then mention something about measuring DC which should be zero. Is B+ referring to AC?

What did you mean by the output line?

When I used headphones I did not hear any audio at all.

Thanks..

[Longbow]

Re: Kenwood AV Reciever No Audio Output

Start at the heatsink. The output transistors (or maybe output IC) will be bolted to it. With power off, use your ohm meter to check for E-C shorts. That will find blown output transistors. Find your power supply d.c. ground and look at the voltages on the collectors and emitters of the outputs. There will typically be 2 transistors per channel. B+ on one collector should be around +50, B- on the other emitter will typically be about -50 volts. Where the transistors connect you should see 0 vdc. This is your audio output for that channel. 0 volts is needed here. What are the voltages?

[stoyania]

Re: Kenwood AV Reciever No Audio Output

Start at the heatsink. The output transistors (or maybe output IC) will be bolted to it. With power off, use your ohm meter to check for E-C shorts. That will find blown output transistors. Find your power supply d.c. ground and look at the voltages on the collectors and emitters of the outputs. There will typically be 2 transistors per channel. B+ on one collector should be around +50, B- on the other emitter will typically be about -50 volts. Where the transistors connect you should see 0 vdc. This is your audio output for that channel. 0 volts is needed here. What are the voltages?

i have the same no sound issue...has anyone been able to trace it to a bac cap or transistor?