Kenwood L-05M Vintage Amplifier Review

[ConnorG]

So in the end, the MK1 version will last longer and wont oscillate

The Mk1 can and will oscillate if the ground implementation isn’t taken care of. It’s a very poor connection that suffers fatigue from stress overtime. Both the Mk1 and Mk2 suffer from this same issue sadly.
Here is the original ground connection on the main PCB. As you can see, it is very poorly done. A small terminal post is soldered into the main PCB, with the large copper ground plane sloppily soldered directly to it. This area is very susceptible to cracking due to heat and physical stress overtime.
Here is my fix for the problem. I used solid core copper wire to connect the copper ground plane directly to the PCB. I added a small loop to the wire to allow a small amount of movement if need be.

 

[Waxx]

The Mk1 can and will oscillate if the ground implementation isn’t taken care of. It’s a very poor connection that suffers fatigue from stress overtime. Both the Mk1 and Mk2 suffer from this same issue sadly.
Here is the original ground connection on the main PCB. As you can see, it is very poorly done. A small terminal post is soldered into the main PCB, with the large copper ground plane sloppily soldered directly to it. This area is very susceptible to cracking due to heat and physical stress overtime.
Here is my fix for the problem. I used solid core copper wire to connect the copper ground plane directly to the PCB. I added a small loop to the wire to allow a small amount of movement if need be.

That's how i fixed a broken MKI about 5 years ago. It was given to me by the former owner, and i could sell it if i could fix it for my own profit.

I did replace the whole copper board (that was cracked and oxidated) with a copper ring terminal (the kind you use on car batteries) that i put between the bolt and the nut.. And I connected the pcb ground to that with a stranded 1.4mm OFC wire (the kind i use as speaker wire). The guy who bought it still use it without any issues anymore. Your way is as good off course, and closer to original state.

 

[SirPaulGerman]

Would it be possible to convert the MK1 to a MK2 ? I know the MK2 has different output transistors

If you have to choose between
The 05 vs 07 mk1 ?

Also to take advantage of the MK2 and 05 amps, do I need a preamp with the same frequency response ?