Kenwood L-07 repairs needed

curtpenn

Member
Two of the four L-07 amps I have are no longer working. The symptoms seem to relate to the delay/protection at start-up when the amps are powered on. They took longer and longer to start until finally they just don't. Is this an easy fix? Anyone have any suggestions for a possible service tech in the Dallas, TX area?

Seems I spoke to someone locally a few years back who quoted me $200 + per amp to troubleshoot and possibly fix. Almost doesn't seem worth it since I think these tend to sell for around that when they come up. Thoughts?

Thanks
 
Tying the worth of a unit only to what it might sell for can be a trap of sorts. Bottom-of-the-line units might certainly sell for a low price, but some really well-built pieces that are seemingly undiscovered by the audio community also tend to sell for bargain-basement prices. The L-07M and L-07MII fall into that category, at least here in early 2015. And you are also discounting the personal worth of a well-functioning unit (as a rebuilder/restorer, it's not terribly uncommon for someone to request a rebuild of a unit that might, on a good day, sell for maybe $75 on eBay).

I've not had the opportunity to open up a first-gen '07M. Seems that all of this style of amp that I've come across were the '07mII variety, so I cannot say with any authority whether the '07m suffers from the same 'Black Flag' capacitor disease as the '07mII.

Link 1: http://www.audiokarma.org/forums/showthread.php?t=97091
Link 2: http://www.audiokarma.org/forums/showpost.php?p=5303574&postcount=4
Link 3: http://conradhoffman.com/BF_caps.htm

So you can see the '07MII has some issues, and the '07M probably suffers from the same issues. That being the case, you'd have to decide if you'd simply like to see only your immediate issue addressed, or whether you'd like to have the unit restored to the point where reliability is guaranteed (as much as is possible).

With regard to the specific issue you are experiencing (the protection relay refusing to close), there's two possibilities: Either the unit has some excessive DC offset that is triggering the protection circuit, or the protection circuit itself has problems. In the first instance, there's a long list of possible issues. In the second, chances are good that there's a few old, dried-up electrolytic caps and perhaps a few weak driver transistors that are keeping the relay from closing. All in all, the odds favor a simple-to-repair issue with the protection circuit.
 
Back
Top Bottom