gslikker
Super Member
Recently, did get this defective Kenwood 700c pre-amplifier. these seem a bit rare. One switch cover is missing, but I still could not resist buying it after negociating the price.
It appeared to have terrible audible distortion, on both channels, one one channel it went away partly after some time..Only the AUX input was tried. Also the switches seem to have problems.
The schematic is on the internet, but is a little bit hard to understand from it, how everything works together.
To understand it better, I started the easy way and took every easy-to-take-out board and used it as "victims of my soldering hobby".
I use new, salvaged, and NOS components just as I like, a bit unrespectful to "audiophile opinions" and "common knowledge" about types and brands.
Although: I also took the information which knowledgable AK members like Echowars and ConradH did post in many threads.
As an example, while certain transistors are supposed to fail over time, I replaced them as a precaution. I measure and select components going in, it takes time.
This is obviously real quality stuff, the pcb's do NOT fall apart when you point a soldering iron towards it. Also the boards are ready to take film cap replacements for electrolytics. This amp was "made for hobbyists".
There was only minor visible damage inside, some soldering at the power supply wiring, and a few resistors burnt off their painting.
I just finished partly repopulating the "easy" boards, which look more neat than before, partly because the brown capacitors originally used always seem to look dirty even when mounted in a clean, closed amp!
First some pictures, of the missing switch cap and the finished (but not tested) boards.
When finished, I'll put what I did on my internet homepage, for future reference ( if I do not do this, I also forget what I did myself...)
It appeared to have terrible audible distortion, on both channels, one one channel it went away partly after some time..Only the AUX input was tried. Also the switches seem to have problems.
The schematic is on the internet, but is a little bit hard to understand from it, how everything works together.
To understand it better, I started the easy way and took every easy-to-take-out board and used it as "victims of my soldering hobby".
I use new, salvaged, and NOS components just as I like, a bit unrespectful to "audiophile opinions" and "common knowledge" about types and brands.
Although: I also took the information which knowledgable AK members like Echowars and ConradH did post in many threads.
As an example, while certain transistors are supposed to fail over time, I replaced them as a precaution. I measure and select components going in, it takes time.
This is obviously real quality stuff, the pcb's do NOT fall apart when you point a soldering iron towards it. Also the boards are ready to take film cap replacements for electrolytics. This amp was "made for hobbyists".
There was only minor visible damage inside, some soldering at the power supply wiring, and a few resistors burnt off their painting.
I just finished partly repopulating the "easy" boards, which look more neat than before, partly because the brown capacitors originally used always seem to look dirty even when mounted in a clean, closed amp!
First some pictures, of the missing switch cap and the finished (but not tested) boards.
When finished, I'll put what I did on my internet homepage, for future reference ( if I do not do this, I also forget what I did myself...)