Kicking It with a Kenwood KA-2000!

[jmccanna]

Well I'll Be Darned

I am not 100% sure anyone cares but I got her fixed. I pulled the preboard all the way out and just cleaned up all solder joints and pulled the 4 2SC458s and replaced them with 4 KSC1845s I had left over from my Adcom repair.

Phono sounds great now as does Aux/Tuner channels. Thanks.

Now what do I do? Wait, going go watch the Warriors kick the Spurs hiney!

James

"Just because you are paranoid doesn't mean they are not out to get you."

 

[irext]

Regarding the black oxide on small signal transistor legs, I have seen leakage caused by this with a device (can't remember what transistor it was but it was in an audio amp preamp stage) under test on a Tektronix curve tracer. The HFE traces were all merging and heading upwards after a certain VCE was reached indicating leakage. A sort of Zener effect. I then scraped the encapsulation in between the legs with a scalpel and the leakage was gone. I still threw it out but it was interesting nevertheless. Whenever I see that black oxide on the legs I become suspicious.

 

[latala]

Well done
This amp is a design classic I used to sell them here in the Uk about £39 in the early 70,s I have always liked them I think I have 6 or seven in my collection Well worth doing up
To me they were a little bright but in a nice and cheerful way
Best regards Trev

 

[jmccanna]

Thanks

Since I successfully fixed the preboard I went ahead and changed out the 3 transistors (2sc458) that remained on the main board too with the KSC1845s. After a bit of fiddling I got it to work.

I remain impressed that something as old and simple as this sounds as robust and full as it does. I have it set up now with a B & O Beogram 3404 turntable to a Nikko Beta II preamp to a 31 analog EQ to an electronic crossover crossed at 850Hz to a Nikko NA-850 and the rest to the little Kenwood. They are playing on speakers I built that were inspired by Siegfried Linkwitz's LXMini setup.

Sounds good - way better than it should.

I have had my hands in everything above except the crossover and EQ.

Too fun.

Thanks,

James

 

[jmccanna]

This forum

Hi Trev,

I love that this forum is international and people connect over this stuff. One challenge I had initially was finding a schematic for the one sold in the US. There two phono inputs that actually link to the same circuit. This is a bit different than the English version.

I put in a bigger main power filter cap 3300uf vs. 2000uf and it is a beefier.

Nice little thing actually. Made when I was a freshman in high school. Lots has happened since then!

Best Regards from the Pacific NW!

James

“Just because you're paranoid doesn't mean they aren't after you.”
― Joseph Heller, Catch-22

Well done
This amp is a design classic I used to sell them here in the Uk about £39 in the early 70,s I have always liked them I think I have 6 or seven in my collection Well worth doing up
To me they were a little bright but in a nice and cheerful way
Best regards Trev

 

[latala]

Hi Trev,

I love that this forum is international and people connect over this stuff. One challenge I had initially was finding a schematic for the one sold in the US. There two phono inputs that actually link to the same circuit. This is a bit different than the English version.

I put in a bigger main power filter cap 3300uf vs. 2000uf and it is a beefier.

Nice little thing actually. Made when I was a freshman in high school. Lots has happened since then!

Best Regards from the Pacific NW!

In the Uk they were sold under the trio banner as the Kenwood label was already taken by a company that sold food proccessors. There were two models the earlier brown faced model the KA2000 and the later silver faced model the KA2000A
I really loved those amplifiers because of their reliability The engish equivalents while sounding ok did not have the build quality or reliability
I knew when I sold a Trio that would be the last that time i it
After many years i had to change a few output transistors these being not unlike a TO66 package but even they were on plug in bases so it was a doddle to repair no soldering required
All the best from sunny Stoke on Trent

Trev

James

“Just because you're paranoid doesn't mean they aren't after you.”
― Joseph Heller, Catch-22