Update on a KA 701

xpert54

xpert54

Lost in Music
I posted about a KA 701 a while back that I had got in a trade along with some other audio gear. The 701 has a few problems but I was not able to check it out at the time. Well today was the day and it turns out the the KA 701 has 4 bad caps on the preamp board. ELNA 100uf 63V. These have been ordered from Mouser and will be here tomorrow.

While I have it down this will give me the oppertunity to dissamble the power switch and see if it can be repaired as the amplifier is constantly powered on.

As the KA 701 is a 80wpc amplifier I'll be anxious to set it up on my system. My KA 405 is 55wpc and has the most wpc of all the kenwoods I have except for the KA 701. So the KA 701 will be a welcome addition to the stable.

I owe much to redcoats7 and jblcrazy. Thanks Guys for your advice as it was very much needed.
 
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It's always a pleasure to help a bud out. I hope that you can get the power switch fixed- well worth the effort. I recently let one go to my cousin, and he just loves it. Enjoy! :thmbsp:
 
That 701 should be a nice step up in sound quality. The 405 was a price point/wpc targeted amp and the 701 was part of the Kenwood Hi-Speed amps. higher slew rate and all.

Let us know what you think of the sound.
 
What are the other Kenwood amps/tuners from the same era?

I am not very familiar with this series...
 
What are the other Kenwood amps/tuners from the same era?

I am not very familiar with this series...
Click to expand...

KT-515 .. 615 .. 715 .. 815 .. 917
KA-501 .. 601 .. 701 .. 801 .. 907
There are brochures on the TIC site someplace.
Regards, Steve
 
Firby13 said:
KT-515 .. 615 .. 715 .. 815 .. 917
KA-501 .. 601 .. 701 .. 801 .. 907
There are brochures on the TIC site someplace.
Regards, Steve
Click to expand...
Good picks here- if you ever get the chance at a KA-801, grab it. Best preamp section I have ever heard. :thmbsp:
 
A bit more on the KA 701. After letting it run for around 3 hours the right channel started to distort at mid volume. I shut it down and recleaned all the switchs and controls rechecked connections and reset the offset and bias. The offset set at zero both channels.

The bias will not get below 70mv on the left channel and the right had no reading at all. So after another recheck and cleaning of all the connections I was able to adjust the bias on the right channel at 50mv. Neither the left or right will go any lower as both adjustments are at the extreme.

The amp is playing at present and sounding excellent however we'll see in another 3 hours if it does the same thing again. I'm certinly hoping it will be fine except for a bit of high bias.
 
The KA 701 has been rotated to my main system as of today. I ran it for 7 hours after the caps were replaced and a few minor cold solder joints reflowed yesterday. It is working with out issues and has a nice synergy with my main system.

I was a bit concerned about it working with my L-15's (DIY) speakers as My KA 405 simply did not sound good with them although my other Kenwood amps worked quite well with them (KA 6004, KA 5700) The KA 405 sounded a bit flat thru them although it works quite well with my Boston Acustic BA 150's and my Polk Audio M5jrs.

I will be giving it a bit more of a work out tomorrow as it seems the more its working the better it sounds. Does that make any sense??. I don't know how long it sat before I got it but as of right now its as sweet a sounding amplifier as I have. I like it!!.
 
On a quick note I was unable to repair the power switch as its broken inside and permently in the power on position.
 
Glad to hear the 701 is up and running well! My only experience wasn't that good. It ran well, but just didn't sound very good. Very dry, kinda harsh. Now, I'm sure there was plenty of adjusting that could have been done. I was pretty new to vintage audio at the time, and didn't know very much. Recently, I've been curious as to how one would sound properly set up.

So, how is the sound? :D
 
Now that I've had a chance to work the KA 701 for a bit. I find that it does the same as my KA 405 on the L-15 Speakers. At low volume 9:Oclock or below you can hear the bass or keyboard notes but theres no punch to them.

My listening preference is no bass or treble added, loudness off. The KA 701 works very well with the Boston Acustic BA 150's and it does not have the problem with those speakers like it does using the L-15's. I think those speakers (L-15's) are particular as to what amplifier is driving them as my KA 6004 and KA 5700 work quite well with them.

Overall I like the KA 701. Its got plenty of power for me (At present) 80wpc. Working with the BA 150's its as decent a sounding amplifier as I have. I don't find it harsh. Its got good mid range, good lowend and good hi's. So I believe I will keep it in my main system for a pretty good while.

I'll set KA 6004 back up on the L-15's. Theres just a synergy with that amplifier and speakers. I wonder if Kenwood didn't lose something when they designed the Hi Speed amplifiers. I have two of them the KA 405 and the KA 701 and both have the same problem using the L-15s as far as listening at low volume.

Before its mentioned I did try the loudness control with the L-15's and the KA 701. I was disappointed as I thought it muddied the bass at low volume.
 
Hi,

I'm new to the forum and I've just got a KA 701 I'm about to open up and see what's what. Wanted everyone to know I snagged the service manual and just uploaded it to the database. If someone needs it quick, just let me know and I'll send it on.

As for my KA 701, it was a gift from a friend who bought it new in Chicago back in the day. She said it had been "acting up" and she decided it had to go. So far I can report it powers up, inputs seem functional, sound comes out. At the moment I can only say it lacks any real punch, seems pretty weak (volume pot at 12 oclock to get decent volume out of a set of infinity bookshelf speakers - same with headphones).

I'll be getting deoxit to clean up the contacts, but I have a feeling I've got some work to do on the preamp section. Anybody with experience working on it, can help me track down caps and such would be appreciated.

I'll post photos as I go.

Jim
 
Welcome to AK, I have a KA 701 among several others as I'm a kenwood fan. when I got my KA 701 it had several issues that I posted about. I was able to locate and download a Service manual.

what I found was 4 caps were leaking on the control board and several cold solder joints. After replacing the caps and reflowing the cold solder joints the KA 701 has been working very well.

One thing I have found out is that it takes a bit more volume to really make the Kenny sing. A lot of it has to do with the source you are using, tuner, TT, CDP or Cassett deck. Mine gererally works ok around 10:OClock on the volume. Anything lower and it gets a flat. But then again source seems to make a difference.

Be sure and set the DC offset to zero and the bias to 25mv. you can find the DC offset pots on the control board. one is very visable and the other is under it on the bottom of the board but can only be reached from the top. I recommend a non conducting tool to adjust the lower pot as its very close to several componets.

Something you might want to do is clean the bias pots very thourghly before any adjusting. I did mine several times and was finally able to get the bias down to 70mv on one channel and 50mv on the other. I have new pots ordered so I will be able to get the bias set where it needs to be.

The KA 701 is a really nice amp as it has 80wpc so you've got plenty of power. I have found that it can be a bit picky about speakers. Mine is set up on a set of Boston Acustic A-150 series II's and it really sounds nice good lowend, mids and highs.

To me the Kenwood Hi Speed amplifiers seem to work better with the more efficent speakers at low volume. Course that maybe just me. However mine sounds best setup on the BA 150's. Enjoy yours. I sure do mine
 
Xpert54 -

I wasn't sure if it was appropriate to get into detail on my project in your thread, so later this morning I started my own just in case. But wherever I get help is fine by me and that's a lot of great info. you just gave me. Thanks!

I think I'm going to end up down the very same road you are. Without even fully accessing the control board, I've spotted two leaking caps. They're 63V 100f electrolytics, located near top center and not far from the attenuator switch that clearly needs attention too. Two of the caps you replaced? I'm having to bone up on this stuff, so I'd appreciate any info. on what you replaced them with, where you sourced the parts, etc.

So far other than spiders (dead) and some signs of corrosion, all I've spotted that needs replacing besides the caps are the foam cushions around the rocker switches (there's none around the power switch, but gee, there's a piece next to the dead spider).

I'm fairly good with a camera and close-ups, so everything is being well documented. I have to say what I could see with the naked eye was nothing compared to the camera. I wasn't sure about the caps, but the photo says they gotta go.

Any suggestions are appreciated.

Jim
 
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