Kr-4200

[niejls]

Kr-4200 - Cardboard?

Hi,

I've recently bought a Kenwood KR-4200 that I'm planning to repair. Does anyone have a service manual for this?

More specific, I'm looking for the idling current adjustment and some good schematics. I can only find a real poor scan of this.

Thanks in advance,
Niels

 

[ecluser]

This schematic is not so bad:

http://elektrotanya.com/kenwood_kr-4200_sch.pdf/download.html

The bias current recommended by Kenwood for the KR-4200 is 20mA. Adjust the bias trim pot for 10mV across each 0.47 Ohm emitter resistor at the output transistors.

 

[niejls]

Thanks for the bias info. This scheme indeed isnt that bad, once printed...

I've just opened it up and found this:




Some orange greasy stuff on the pots.
Anyone seen this before?
Just clean it off? Or is there a cause/reason for this?

The rest of the inside seems ok at first sight.

 

[niejls]

I cleaned of the orange stuff off and cleaned the contacts if the pots with deoxit. They look a lot better...
The entire PCB wa soaked with grease. So it got a good clean as well.



When pulling back the tone-PCB I noticed there was some sort of cardboard behind it. Again, soaked with grease.





Does it serve any purpose? Can it be replaced with ordenary cardboard, it looks/feels like it? Or is it something else?

Thanks!

 

[petehall347]

that looks like it has been stored somewhere really damp .

 

[niejls]

It's been more than a year since I've had the time to work on my KR-4200, but now I'm planning to finish it...

I'm currently looking to order the replacement caps. But I need some help on finding a replacement for the largest ELNA caps.

There are two ELNA CE-W 3300µF 35V caps in this unit. What would be a good replacement?

It would also be nice if the diameter of the new cap would be about 25mm, so it would fit the mounting claps (see picture).

Thanks!

 

[EchoWars]

I'd use these: http://www.digikey.com/product-detail/en/LAO-50V472MPDS2A#/604-1095-ND/2171146

You'll need some small ring terminals to crimp and solder to the snap-in lugs to give you a wire attachment point. Digikey #A28269-ND should do.

 

[niejls]

Thanks, EchoWars.

I've noticed that both the capacitance and voltage of this cap exceed the values of the original. I can understand that the voltage isn't a problem. But should the capacitance not be the same?

The datasheet of the series shows that 3300µF, 35V caps exist, but these aren't available on Digikey.

 

[EchoWars]

The small bump in capacitance isn't a problem. Run with it.

 

[shair00]

I am trying to repair a Kenwood KR-4200. It locks onto a frequency but has no output.

 

[roger2]

Welcome to AK shair00

You will probably have better luck if you start your own thread instead of attaching your project onto an old thread.