Kenwood ka3500 distortion both channels

An o'scope can tell you frequency of the ripple on the capacitors, if 120Hz the capacitor is bad if 60Hz the rectifier is bad.

Craig
 
Ok

Replaced the bridge rectifier no go same readings.
I did remove de2 and seam to test fine.

My meter won't test 6800uf on the cap but removed ce29 and will test.

Any other thoughts?
 
I thought the two 6800 uf caps are the filter caps we already tested correct?
Are they tested in dc not ac?
 
So,

Pulled both 6800 uf caps and just tested resistance.

C30 was 0.000 ohms
C29 was 2.9 m ohms

I will search for replacements.
Assuming the above indicates a problem.

Nichicon gold FW 6800uf 63v or ?


Thanks again to All getting closer.......
 
Match the diameter of the original 6800 UF caps with something that fits. 63 volts is fine. I'd be ordering new caps for the entire board as well as new diodes. Do a visual check for anything that looks heat stressed and the foil side for thinning joints. Providing photos sure wouldn't hurt. Help us help you.
 
Wow, it was the cap. It's rather unbelievable the main fuse didn't blow. Check what value fuse was in there.

0 ohms is a dead short, but all caps will start out as a 'short' until they charge. You are using a DMM on the ohms scale- maybe the 2.9M cap is actually open circuit, but that doesn't explain the low rail.

Check that fuse rating- a shorted cap will blow a fuse instantly.
 
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So I had a pair of 4700 63 v sitting around.

Don't know their health but hooked up and bulb tested 100 watt bulb.

The bulbs glowed not bright but not dim may be 15 watts.

The voltages on both caps were like 18v

At least they were equal not sure on the bulb glow....

Used the dbt on my sa6700 and no glow at all.

Used it on the kenwood 3500 before I pulled the caps and got a dull glow. But 25v still on the suspect cap and 39v on the other.

Not reduced voltage like the substitutes at 18v each but no bright bulb either.

The ka3500 says max power consumption at 280w so don't know what idle is.

Should the bulb be glowing?
 
Ok,

Checked the dbt on two
others amps and I'm thinking the test capacitors had a problem since the bulb glowed very dim with the originals in place.

That being said if it was a wrong fuse( forgot to check) it should have not passed the bulb test if there was a short.

At this point hoping that c29 is still the issue.
When I put in the test caps (that created a bulb test fail) the voltages matched c29 18v c30 18v showing the rectifier was working.

I did this for seconds only with the probe clip hooks as I was not wanting to damage anything.
It's my understanding that during bulb test that voltages won't be accurate but as stated before with old caps under bulb test I got 39v and 25v on c30 and c29.

This shows a change not sure positive but hoping :)


Ordered two 6800 63v nichicon kg
Will get some diodes local and test the ones that are installed now or just replace they are cheap after all.

Also wanted to state my appreciation to all.
The forum members are very helpful and have given insight to many besides myself resulting in amplifiers world wide working again!
 
Ok,

It was c29 cap she sings like a bird!

I will now replace the other caps and diodes since its on the bench.

One channel is 60 mv bias and the other 5mv

This is non adjustable how would I go about dropping it down to 5mv like the other channel?

It does sound pretty good right now.
 
One issue came up.

When I press the phone button no turntable hooked up I get low 60 Hz hum?

When I shut the amp off the hum increases until psu is depleted.

This does not happen on other inputs just phono.
 
Will try.
I know that makes a difference on one of my turntables if it's flipped but this is amp only no turntable plugged in and just switching to phono with nothing plugged in all other inputs silent just phono hum. Must be in the phono pre amp area?
 
I did deoxit all the switches when I started the repairs.
Will check solder joints.
Tried jumper to rca phono ground there was no change.

Just wondering if there was a section to look at.
 
Have you recapped the power supply yet? You haven't updated us.
If not, It could be the issue, and if turns out to be something else at least you've eliminated it as a culprit.
 
I have not replaced the other caps in power supply yet. 330uf 35v. Have been getting together a list for the pre amp etc to get rid of the phono noise. I will try to replace the 330 uf first.

Is there a certain type these need to be or does it matter?

Audio grade or? I put nichicon kg gold fw for the 6800uf at 63v.

Amp sounds great right now aux but phono is a no go.

Thanks again for direction!
 
No I was thinking there was a broken ground at rca so just grounded the jack to see if there was any change.

I will look for panasonic fc for the 330 uf caps.
I bought some KME 330 uf caps local but not sure on them. I assume that since the other sources are 0k no noise that it's something in the phono stage. Unless this amp would make noise when no phono is selected with no turntable plugged in? My other amps don't do this so I assume it's not correct.
Tested the 6800uf caps that I replaced, one was 7100 uf the other c29 did not read was not a direct short but toast never the less.

Is there an affordable esr meter out there to test on circuit?

Also there is one transistor on the psu(black legs bent over from heat?) that I want to replace. What would be a good match? Have a cheap hfe meter should it read lower or higher for its application?
I was going to order a bunch of transistor of numerous types as I have a few amplifiers to work on after I get this 3500 in shape.


I have a Ka6000 I picked up many years ago with tuner with a smoked cap at psu.
Have read they have a ton of noise transistors in them.
 
Does it hum WITH a turntable connected, you may be chasing nothing. Hum on both channels? Does it vary with the volume control?

Craig
 
IIwhtt,

You are correct once the turntable was connected so hum.

Don't know if that is a ghost but will not chase further.

3500 is working well.

Thanks to all who helped me!
 
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