Kenwood Trio KA6004 power board repair

Well, once again, I am amazed at your skill in locating the problem area. I treated the new Separate/Normal switch with switch cleaner and secured the relay and now have a good signal from both channels. :music: :D I will note that the wiring to and from that switch may need to be replaced if this problem recurs.

The bonus is that the relay seems to be working properly too, so I am set to go.

My sincere thanks for your kindness and help, ecluser. :thmbsp: I hope I can do the same for others as my knowledge grows.

By the way, does your moniker suggest that you have a fondness for ECL82 and ECL86 tubes too?
 
Happy that your amp is running. I'm not a tube man... besides the ones I have in my test equipment.

For the relay, you can clean the contacts with a piece of thick paper (like a business card) saturated with contact cleaner. The clear plastic box is easy to open. But if the contacts are spotted, it's a waste of time.
 
A quick pic to close this thread, for now. The Kenwood Trio KA6004 parked temporarily on top of my Trio W38 tube receiver.
 

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thank you

I just want t thank you all for this thread!

I recently picked up a KA 6004 with KT 6005 tuner and this page gave me the first clues where I needed to clean what in order to hopefully have two functioning channel instead of one with distortion and one clean one...

Because I don't have any deoxit here I cleaned it with 100% ethanol, normally that should also do the trick.

Cleaned the A and B selectors, the NORMAL/SEPERATE switch, the balance and volume regulator, the stereo/left right/rev selector. And I hear the relay pulling when I start it up, so that one should be Okay, but replacing it won't be to hard thanks to you guys!

Now waiting untill all the alcohol has evaporated, but that shouldn't take long, I give it o before I go to bed this evening.

I just have one more little annoying question, how do I get the lightbulbs out? None of them are working, what seems a little strange to me? not even the on/off light.
 
still a bad left channel

I guess I'll have to start measuring out some contact point tomorrow to find why the left channel keeps dropping...

Lucky it is a spacious amplifier with lots of room inside, replacing some components shouldn't be to hard.

If it was the speaker relay, can that also affect just one channel?
There is still a very little bit sound coming out of the left channel, but about 15x more silent than the right channel.
 
Can you get hold of Servisol Super 10, a switch cleaning lubricant? As you will have seen the switches definitely needed cleaning.

I wish I could help you with other diagnostics, but I hardly ever work on solid state units and haven't learned much more since ecluser helped me so superbly.

You might need to describe the problem with your left channel more exactly to try and locate it. e.g. do the preamp outs work well for both channels?
 
melted isolation on wire

Just found that the isolation of the wire connected on point 20 just melted away, over 2cm or more, and as I recall reading this post 20 was the one for the left channel?

Looks like I found something to further investigate tomorrow...

And cleaning contacts is never a waste of time...
 
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And the green resistors 3W5%, 0,47 ohm on the ampboard show signs of leakage, or serious overheating, especially on one side, the other side also but much less severe, seems that those should need to be replaced. I'll post the pics in the morning!
 
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I'm sorry I can't take a look at the boards on my unit to compare what they look like, as it is in storage in another town.

I suggest you start a new thread asking for help with this troubleshooting.

I have definitely found that Trio/Kenwood units (also on the KA2002) had trouble with their slide switches, so cleaning and/or replacing them is worth doing. Even if just to rule out simple issues.

Are you working with a schematic? Those resistors do look like they've been hot. Do they measure correctly now?
 
just found out that the problem is situated in the preamp, I only get sound from the right channel, the left one is completely dead when using the pre out rca's.

But, one positive thing, there is only one lightbulb that doesn't work after replacing a broken fuse...
 
Next step should be testing the power supply transistors on the heatsink, and the output transistors, correct me if I'm wrong?
 
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After leaving it standing in a corner for bad behaviour I decided to give the amp another attempt in order to fix the preamp problem.

The suply was OK, so I decided to take the preamp card off and completly clean it with alcohol and cotton swaps, their was a lot of grud coming of, and after that the kenny performed again like it was meant to. I knew cleaning all contact switches was important, but the effect of cleaning the grud from the solderjoints on the back of the preampcard couldn't be any greater!

So, mission acomplished, the 6004 is up and running again, allready installed in my livingroom
And I couldn't be happier with the result!
 
Long time since you finished this thread, but I’ll give it a go! I purchased a KA-6004 in cosmetic mint condition, however, sadly enough, the 160 mA fuse on the power supply board blows as I push the power button (which doesn’t stay in the "on" position, it comes back out immediately). All the lamps light up if I push the button to its "in" position, but there is no sound. Something is causing the fuse to blow, and according to the trouble shooting-guide in the Service manual this can point to poor connection of the power supply board. Do yuo have any suggestions what to check next? Regards, a very very inexperienced hifi-mechanic...
 
Hi, Looking4lux, welcome to AK. Sorry, I can't advise on this, mainly because I seldom work on solid state gear. But also because my KA-6004 is physically inaccessible to me at present. Here's hoping other Kenwood owners may be able to help. Otherwise post a query in the Kenwood/Trio dedicated section.

Have you visually checked the connections in the power supply board, and also the condition of the power supply caps? It sounds as if there is a short somewhere. You will of course need to sort out the switch too. Sometimes these can be disassembled and repaired. Otherwise you could wire it on, and switch it on and off externally, e.g. via a switched extension cord.

It might be worth checking the history of this fault with the seller.
 
Many thanks for your advice, I will check the connections of the PSB again, and the PS caps. The switch, yes, wouldn’t it be nice to find an original replacement? Too much to hope for, I guess. Again, thanks for your informative reply.

PS. I didn’t know there was a dedicated Kenwood section. Now I do!
 
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