Kenwood KR-3400 - DOA?

[Calder]

Hi folks, I'm brand new here and am thoroughly humbled by this forum's wealth of knowledge and kind spirit.

I'm not by any means an audiophile, nor do I have a huge desire to dive very deep on fixing this unit. BUT, I do have a masochistic tendency to not throw anything away, and I really enjoy keeping old things functioning.

After doing a little research I landed on this website being my best bet for help. So, here I am, asking for help!

This KR-3400 came to me by way of an abandoned storage unit cleanout (among LOTS of other items in similar condition). I have a set of speakers that have been taking up space and I'd love to get this tuner (amplifier?) up and running for them.

This unit has clearly been opened before as it's missing the cover's "top" screws. I gently blew out the dust with compressed air. If it has a chance at rising from the ashes, I'll go much deeper on the cleaning by following proper techniques. I have no illusions of this ever being a museum piece, but I've read quite a few user reviews and think it's worth a little time (and possible a little $).

I have downloaded a copy of the service manual. The troubleshooting section doesn't seem to cover the "doesn't work at all" scenario. Honestly, I've learned over the years to seek help from those with experience prior to jumping in and making a bad situation worse.

Facts:

• When plugged in there are no signs of life. Pressing the power button yields no sound other than the click of the switch. I have an 80s or 90s Kenwood and I'm used to it making an electrical "clunk" sound after it's power button is pressed (it died a couple years back, but that's another project/post...).
• Power is getting to the inside of the unit - tested with multimeter.
• The power switch is at least somewhat functional - the switched AC outlet functions as it should.
• It's dirty.

The attached photos hopefully help to shed light on the unit's status. The close-up photo shows what could be bent pins? I put a little pressure on these in an attempt to straighten them, but they seem to quite like being in that position - so I didn't force them. Are they bent, should they be straight?

Thank you for looking, reading, and hopefully offering some advice!
- Calder

 

[Punker X]

I've going to guess that this not actually tuner or radio related. So going to move this over to the Kenwood forum where you will get wider exposure.

 

[rschweitzer]

Welcome! There is a wealth of excellent engineering knowledge on this site.

To start, you should have a dim bulb tester (DBT) when powering up and unknown amp/reciever. You can build one easily out of components you can readily purchase at your local home center. For this reciever, suggest a 60 watt bulb, incandescent. It should flash dimly on power up and turn off or barely glow. If it powers up bright and stays bright, there is a short.

As for it not powering up, check the fuse on the power supply. But....don't just replace it. Use the DBT. That way you can avoid smoke and other issues.

The pins from the transformer, straighten them out. Looks like the red wire pin is touching the yellow wire pin and blue wire pin touching the white wire pin. Not good.

Hopefully this will get you started.....

 

[rickl]

The pins from the transformer, straighten them out.

straighten these out:

 

[rickl]

i checked the schematic and didn't see any speaker protection circuit (relay, transistor driver, delay cap, ...). I'd hold off on connecting speakers until we know the health of the device.

Using common sense, I'd measure the voltage at pin 15 and pin 16 (power off, attach red lead to 15, black lead to ground, power back on).




you should be measuring about 10mV (+-40mv). post results. if they measure B+ or B-, your outputs failed and will need to be replaced.

 

[petes'picks]

And check that fuse by the bent pins with a multimeter for continuity.