Kenwood KR-2400 fuse blows at power on

[iamthejeff]

Those readings were using pin 6. Using pin 3 I get 18V and -11V

 

[petehall347]

is the preamp chip in a socket ? if so pull it out and measure voltages again .

i do think its a grounding problem though ...

are the rca jacks grounded well ?

 

[iamthejeff]

the pre-amp looks like this, can't be removed

I can try reflowing around it, but I hope it's not dead because it looks impossible to replace.

 

[petehall347]

just check all grounding point for now ...they should all read 0 ohms between any of them ..
or to be more accurate the same ohms as touching your meter leads together .
pins 3 6 and 9 power board
pins 12 4 3 and 11 amp board
pins 36 37 and 38 vol balance board ..i am assuming it is a board

both pin threes push switch .
pre board 36 33 31 32 34 ..

rca shells ...

so to explain better pick a number stick one meter lead on and work your way through the other numbers with other lead ...

 

[iamthejeff]

3, 6 and 9 on the power board give all different values, none are zero ohm.

 

[iamthejeff]

Oddly enough, it works again. There's gotta be a loose connection somewhere.

 

[petehall347]

there is a bad connection/s then ..just a matter of finding it / them...

 

[iamthejeff]

Some progress... if I leave the chassis ground screw removed from the power board, everything works.

If I screw it in, everything goes dead.

With the screw removed, I can press down on the ground post and it works without a problem. So the screw is causing the problem somehow.

 

[petehall347]

maybe shorting something somehow .. seems to be getting close now

 

[iamthejeff]

I reflowed the connections on the ground post, screwed it back in, and everything seems to work. Seems too good to be true. I will continue to monitor the situation.

 

[petehall347]

excellent news ...lets hope it keeps stable ...
so i take it bias and offset are good now ?

 

[iamthejeff]

I was able to set the bias properly yes. so far so good

 

[petehall347]

great news ... :thmbsp:
i cant even remember the original fault ...

 

[iamthejeff]

Yeah no kidding.

One of the output transistors was toast, and also two diodes on the power supply. I replaced all of those and then began this cat and mouse game, trying to find out why I was getting weird voltages all over the place.

 

[iamthejeff]

I recapped the amp and power board. Made sure all the ground connections were solid, and everything sounds perfect. I can't believe it was a grounding issue this whole time!

Thank you so much for your help and patience helping a newbie through this!

 

[Texas Audiot]

Congratulations Jeff....

Guess you can't really call yourself a NEWBIE any more! Survived a trial by fire...

Great Job!!

 

[iamthejeff]

Thanks! One last issue remains, the tuner pointer light doesn't come on all the time. I think it's an LED because there's a resistor wired along with it. Other than that, everything else is holding up!

 

[petehall347]

all lamps in there are incandescent .no led ones .
resistor is to drop voltage as its a 5v bulb .
again look for a bad connection .
it grounds through the selector switch .so does the meter lamp .if the meter lamp is staying on ok its not the switch

 

[iamthejeff]

It ended up being the pin connector for the lamps. There was some oxidation buildup. For good measure, I gave all of the pin connectors a good cleaning with deoxit.

It's been a long time coming, but finally... she lives:

 

[gwestwood]

Hey I sold you the receiver and amp.Glad to here you figured it out.Kinda wish I had the knowledge to try to repair it.Hopefully you figure the akai out.