Another KA-5700

[rickl]

I picked up a KA-5700 today.

Seller said it powers up but no sound. Pictures look good and complete.

Pulled the cover and found cracked emitter resistor


and missing fuses


Checked the back and found a missing speaker screw.


This will take more time than my KA3500 but should be a fun project. I have a 5700 (with matching tuner) as my music server in one room so I've spent a lot of time with one.

Once I get it working I'll need to read Spencer's resto thread https://audiokarma.org/forums/index.php?threads/another-kenwood-ka-5700-recap-bom.785133/ for new emitter resistors and caps.

If anyone has an spare speaker screw, let me know. I'll need one.

 

[rickl]

Someone has been in here. Found LED lights for the power meters


I haven't powered it up to see how this looks but I'll try to post a pic when I do.

 

[rickl]

Got the amp working. All batwings tested fine. I'm currently using a .39R/2W emitter resistor for testing. Each channel is balanced with balance centered.


Note the blue LED meter lights.

Now to start the cleaning and re-cap journey.

I still need to make an order for a .33R/3W and any missing caps. If anyone has an emitter resistor recommendation, please let me know. Should I replace all 4 or just the broken one?

 

[gort69]

https://www.mouser.com/ProductDetail/KOA-Speer/BPR58CR33J?qs=/ha2pyFaduhOhYgeJgpNBbtkeiNw5hdSrpD88kFW5cIdazktq634FA==

I'd replace all 4, but your call

 

[dstariha]

I agree with gort69, replace all four. They cannot be that expensive. Why do you suppose it cracked? Any evidence of thermal problems.
Maybe you should measure the voltage drop across them to see if the OEM resistors might be near their limit. I found that sometimes makers push the ratings. My KA-7002 did that with the cap voltages.

Have fun.

Dave

 

[rickl]

https://www.mouser.com/ProductDetail/KOA-Speer/BPR58CR33J?qs=/ha2pyFaduhOhYgeJgpNBbtkeiNw5hdSrpD88kFW5cIdazktq634FA==

Perfect. Thanks gort. If I need to buy one, I'm buying 4.

Why do you suppose it cracked?

I think something spilled in the amp. The transformer is rusty near the emitter resistor too. Who knows the history but it is working and sounds very nice. The glue around the PS caps was difficult to remove but my Harbor Freight interior panel tools and a bit of solvent worked slick.

Got the PS caps, bi-polars and wimas installed.

DC offset: right 38mV , left 4mV. Not sure if I want to mess with Qm8,10.

I do have some 100R pots for bias adjustment. I bought them for my first 5700 but never installed them. I'll check the bias once I get the new emitter resistors installed.

Thanks again for the help.

 

[rickl]

Emitter reisistors arrived and installed. Factory bias is very big range so will within spec.

Cleaned up face plate.



Kenwood is pretty proud of their assembly glue



Removed the old glue and added fresh PS caps.



One of our Kenwood Experts rjsalvi sent a speaker screw set. So that was fixed too. No pics but just imagine how happy I am getting this back together. Thanks again Robert!

_The_Wife_(tm) thought it was a little loud but I wanted to get the amp warmed up and verified bias. Not much bass with the pair of tiny ADS 200s but it sounds great.

Not really sure which I like more the KA-3500 or KA-5700. Meters and speaker relay might take the 5700 to the top but not much different in sound.

 

[rickl]

since everyone love nudies, here are the new emitter resistors for the left channel. I did all 4. Too bad I can't take a good pic. Thanks again gort!

 

[swamppirate]

Very nice!