• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Kenwood L-07M Vs L-07MII

It is a lot of work to overtake this Combi. In any case you need a desoldering station because the board of the L-07c is double-sided. What do you want to do with it ??? I completely overhauled an L-07Cii and L-07Mii Combi. Cleaning the switches and potentiometers of the L-07C is also quite a job. Depending on how much you want to do the costs will be high. In any case, I would replace all of the electrolytic capacitors and Zener diodes. With the power amplifiers, the electrolytic capacitors and Zener diodes have to be removed as well as the offset and bias trimmers. I've done a little more and I love this combination, the best I've had so far.
 
Sunnybaker said:
i have a pair of L-07's and a L-07C that i want to restore/update top to bottom- i have never done anything of this caliber - how much tooling would i need? is it cost effective or should i send them to an expert? any advise on who could do it for me? Im up in Burlington Vermont
Click to expand...
It is a very time consuming job. If you don’t have any experience, I suggest bringing them to a professional. The double sided board in the L-07C is a nightmare to work with.
 
Connor G said:
It is a very time consuming job. If you don’t have any experience, I suggest bringing them to a professional. The double sided board in the L-07C is a nightmare to work with.
Click to expand...
Thanks Connor - im ok with the time element - its the skill level i worry about. it seems like this may be the wrong project to cut my teeth on ....
 
I recently bought a pair of L-07Mii.
They arrived last week from Japan, hooked them up with a Accuphase C200 and Yamaha NS1000m, holy cow those things are phenomenal!
Stereo separation, low frequencies, soundstage all amazing.




upload pic

The infamous black flags are present, so I will change them soon.
I will probably recapped the amp board.

Does anyone have a suggestion on the caps to select for the black flag replacement?

have all a great day! (night?)
 
For electrolytics I suggest panasonic FR. They will last longer and take heat better than most.
This is a DC amp. The caps are not in the signal path.
Get the FR caps.
 
Replacing the "black flag" polystyrene caps:

This is indeed mandatory and fortunately has been done in my pair of L-07M II monos.
Richard / Broesel02 has done so many of these Kenwood/Trio monos that I asked him what to use as replacement for the black flags.
He recommended PP caps down to around 33pF. Where PP is unavailable he uses silver mica too.
Polystyrene may be very good soundwise but degrades too fast with the heat inside the device (cracks in the foil, later failing completely).

@cultmax: Congrats on your perfect work. My PCBs are restored to a similar state but somehow do not look as nice as yours ;-)
I started restoring amps in the 1980s. The L-07M and L-07M II have absolut amazing sound quality. Beyond compare.

- Johannes
 
Connor G said:
Silver mica caps will work best IIRC

Congratulations on them by the way. They are fantastic amplifiers.
Click to expand...
I restored three of the MIIs in September that had been sitting in my garage for five years in non-working condition because they would immediately go into the oscillation and not come out of protection because of aging black flags. I replaced the black flags with 30-cent TDK NP0 ceramics and no issues. I also used basically caps I had on hand to do a full recap, and maybe only a handful were actually audio grade caps.

These amps really don't have electrolytics touching the signal path, so capacitor choice is really a lot less crucial than in designs which use a lot of cap coupling.

l07mii-1.jpg l07mii-2.jpg l07mii-3.jpg
 
here is the replacement list for one Power amp board:

upload_2021-1-24_15-1-18.png

n.b: no 1uF caps in Panasonic FR serie, i went to Unisted Chemicon.
n.b.2: I had to increase the max Voltage of some electrotitycs, for instance original was 50V and i will put a 100V.

cheers
 
Poetry2me said:
Replacing the "black flag" polystyrene caps:

This is indeed mandatory and fortunately has been done in my pair of L-07M II monos.
Richard / Broesel02 has done so many of these Kenwood/Trio monos that I asked him what to use as replacement for the black flags.
He recommended PP caps down to around 33pF. Where PP is unavailable he uses silver mica too.
Polystyrene may be very good soundwise but degrades too fast with the heat inside the device (cracks in the foil, later failing completely).

@cultmax: Congrats on your perfect work. My PCBs are restored to a similar state but somehow do not look as nice as yours ;-)
I started restoring amps in the 1980s. The L-07M and L-07M II have absolut amazing sound quality. Beyond compare.

- Johannes
Click to expand...

Thank you for the compliment. You are absolutely right, the L-07M amplifiers are fantastic and special at the same time. I also got tips from Richard / Broesel02 I think hardly anyone knows the L-07 series from Kenwood as well as he does.
 
Yes there is some fine equipment on that photo. I like the look of the L-07MII on the shelf and not on the floor......gives them the respect they deserve! Im looking forward to finally getting around to going through my L-07m's and giving them a listen (they have been sitting in their boxes for afew months now while I finish other projects). Always curious how the L-07m's compare to the L-07mII's and have been watching this thread.
 
Part 2 done!



DSCF4218.jpg


I noticed something unusual on the rebuild.

The 2 monoblocs i have have been serviced before i bought them.

Some electrolytic caps were changed, non of the Black Flag caps where changed though.

However, i noticed that on the 2 boards C26 caps were cut off.



I decided to install them back, and the amps works great.

Anyone has an idea why those 2 caps were cut off?

cheers,

Etienne
 
esteboune said:
Part 2 done!



DSCF4218.jpg


I noticed something unusual on the rebuild.

The 2 monoblocs i have have been serviced before i bought them.

Some electrolytic caps were changed, non of the Black Flag caps where changed though.

However, i noticed that on the 2 boards C26 caps were cut off.



I decided to install them back, and the amps works great.

Anyone has an idea why those 2 caps were cut off?

cheers,

Etienne
Click to expand...
Not all of the boards were fully populated from the factory. This could be one of those cases.
On the other hand, a few L-07M's I have worked on have had caps cut on the main board. Not really sure why.
 
You must log in or register to reply here.
Back
Top Bottom