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Kenwood L-07M Vs L-07MII

I have rebuilded both types, the L-07M & the L-07MII. In my opinion the MK II version is a improvement. Both are very good amps, and the MK II version is IMHO the better one. Rebuidling them is for me: change all Z- diodes, all Resistors, all Condensators, many of the transistors, all Relays and much more.
Richard
 
Broesel02 said:
I have rebuilded both types, the L-07M & the L-07MII. In my opinion the MK II version is a improvement. Both are very good amps, and the MK II version is IMHO the better one. Rebuidling them is for me: change all Z- diodes, all Resistors, all Condensators, many of the transistors, all Relays and much more.
Richard
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That's totally unnecessary to replace every diode & resistor in these amps, why? Zener diodes don't age, most resistors stay in tolerance too, you are just doing a lot of unessesary work. I have 5 of these that are all totally recapped, replaced a couple power resistors that were too close to the board & used 24vdc protection relays wirh a change of R17 on protection board.
 
All the transistors too?? Wow, talk about unnecessary work & expense, but whatever makes you happy.
 
I have rebuilt until now more than 20 of the L- 07 M II Amps. And I don’t like to see them again o_O. Often i had found faults in the Zener Diodes. These parts are not expansive so it is easier to change them and have later on no faults because a zener Diode is dead. Very often the Diodes for the reference Voltage of the Super-Regulator broke down. In this Case you have the Voltage supply of the Voltage amplification stage to high - and the transistors there may get damaged.

It is your own decision what you will do and change when you fix up a L-07 M II. My decision is: To have one of the best amplifier of the World in an old Case. I you just want to have a fine amplifier working there is no need to do so much work as i do.

But if you want to play at the cutting edge you have to do more.

A long time i did not change the transistors of the second and third differential stage. But if you find the amp oscillating, the bias is to high, the temperature will increase to high an much more faults – it is just easier to bring new transistors in.The amp just will work safe and right and that is what i want

But as I sad: it is your own decision

Richard
 
I can confirm what Richard found out about many of the parts in these amps, like in other amps the same age. Just keep in mind that L-07M / L-07M II are around 40 years old. If you would have asked the engineers back then in Japan, what lifespan would they have foreseen? Certainly not 40 years.

Before getting into the HiFi classics restauration hobby myself, I would never have suspected Zener diodes to be instable over the years. Same is true for ceramic capacitors BTW. Or polystyrene caps if under heat stress.
Today, I see it like Richard. I just don't want my friends and family to come back with the amps.
- Johannes
 
Broesel02 said:
View attachment 1466878

Thats the way i do it
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I've used those exact speaker connectors in the picture on a KA-6100, & a 7100, they work great for bananna connection but try to use the wire or fork connection option on them with the slightest bit of torque of a screwdriver, they crack, you can't get enough torque to hold the wires securely with your fingers.
 
Trio L07MkII are Great Amps
Luckily grabed a unrestored pair of this wonderful Amps for a good price in Japan the weakest point of the deal are the shipping cost via airmail cause Japanese auction house dont send anymore goods via seamail to Germany which is frustrating
All i can say the Amps are untouched inside after finishing OPI
So decided doin a testrun pair with JBLs and Sansui BA-606 and all i can say after 2hrs listing session this Amps are worth every single Euro
Guess there is no need for restoration in the moment
Cheers
:beerchug:
IMG_20201214_184414.jpg
Nice chimneys:thumbsup:
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Wally1955 said:
Guess there is no need for restoration in the moment
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You absolutely need to restore these amplifiers and make certain to change out the “Black Flag” capacitors on the driver board. They will send the amplifier into oscillation and you won’t even know it until it’s too late. Save yourself the heartache of having the outputs blow up. Change the black flags out, as well as all of the other electrolytics, clean and remove corrosive glue and reflow all solder joints on the PCBs.

See here for more information on the “Black Flag” capacitors found inside of the L-07Mii, as well as many other “high speed” amplifiers of the day

There are a total of 9 black flag capacitors on each of the driver boards. You can see many of them in this photo I took of one L-07Mii driver card.

B412C826-0317-4EFE-9DDF-B5ADC7333B68.jpeg
 
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Yes, they are top quality amps. Some of the best available back then. Refreshed they can still hold their own against most Solid State Amps. They are something special.
 
The L-07M ii are really great power amplifiers. I was also lucky and found 2 original ones after a year of searching. Then I completely restored them from the ground up and now they play indescribably well together with an L-07C ii also completely restored that is a league of its own ...
 
@cultmax, thanks for sharing pics of your gear. I'm amazed how many of these lab series amps are showing up lately.

And welcome to AK!
 
Thanks for the images of the boards. I don't recall looking at the protection boards (lower boards with edge connectors). I'll crack my 07Ms open again in January (2 year checkup) and update those boards with the 100/10 NP and 470/100 axials.

mine are kind of beat up (and probably over paid) but I really like them.
 
These amplifiers are never overpaid once you've heard them. Unfortunately, there aren't that many that are still in their original condition, the Black Flags have unfortunately destroyed many of them and especially the original NEC outputs are now almost impossible to get ...
If you completely restore them, they work perfectly. Mine don't even get lukewarm in normal operation, but in between they can show what they can do ... :)
 
Aloha
the Trio L-07MkII since 96hrs on fire now and paired with the JBL 4311Bs are the most satisfying results from all the different setups all over the years since im into the wonderful hobby again its really good now in my ears its sounding in the moment kind better then the pair Yamaha B-3s in BTL
well later i will check again the B-3 setup for direct shotout need to kill time during lockdown here in Germany
Cheers and happy holidays stay safe
:beerchug:
IMG_20201220_172739.jpg
2x Yamaha B-3 neighborhood
16084827916895086419714366449870.jpg
 
Wally1955 said:
Aloha
the Trio L-07MkII since 96hrs on fire now and paired with the JBL 4311Bs are the most satisfying results from all the different setups all over the years since im into the wonderful hobby again its really good now in my ears its sounding in the moment kind better then the pair Yamaha B-3s in BTL
well later i will check again the B-3 setup for direct shotout need to kill time during lockdown here in Germany
Cheers and happy holidays stay safe
:beerchug:
View attachment 2071651
2x Yamaha B-3 neighborhood
View attachment 2071655
Click to expand...

Greetings, Wally! I have the smaller brothers Trio L-05Ms and the Trio L-07CII preamp (all on 100V). I was unable to find enough time to listen to this combination (with my YAMAHA NS-1000M speakers) to have a final and clear verdict. I have listened like 4 year ago to Trio L-05Ms and YAMAHA CX-1000 preamp and I can say that this is a wonderful combination.

These are good stuff, as you say, but now YAMAHA B-3s are on my top preference. Perhaps you should listen to your B-3s in BTL mode on these NS-1000 speakers as they were made for each other.

Curiously, back in 1979 one YAMAHA B-3 costed the same as two Trio L-07Ms or one Accuphase P-260 power amplifier (200000 Yen), therefore Kenwood-Trio was a strong competitor to any of the big Japanese companies on this power amplifier market.
IMG_20160718_201305_HDR.jpg
 
Cosmin2000 said:
Greetings, Wally! I have the smaller brothers Trio L-05Ms and the Trio L-07CII preamp (all on 100V). I was unable to find enough time to listen to this combination (with my YAMAHA NS-1000M speakers) to have a final and clear verdict. I have listened like 4 year ago to Trio L-05Ms and YAMAHA CX-1000 preamp and I can say that this is a wonderful combination.

These are good stuff, as you say, but now YAMAHA B-3s are on my top preference. Perhaps you should listen to your B-3s in BTL mode on these NS-1000 speakers as they were made for each other.

Curiously, back in 1979 one YAMAHA B-3 costed the same as two Trio L-07Ms or one Accuphase P-260 power amplifier (200000 Yen), therefore Kenwood-Trio was a strong competitor to any of the big Japanese companies on this power amplifier market.
View attachment 2080384
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Aloha Cosmin
My brother visited me for a Soundcheck this evening
Honestly in his and my ears L-07ms + B-3s with Sony TA-8450 sounds unbelievable good
Cosmin have a try with your L-05s and pair them in 1 setup with the B-3s its worth in my ears
Cheers and stay safe
:beerchug:
IMG_20201229_154550.jpg
ps.are the Yamaha Ns-1000 good for biamp configuration?
 
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
 
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