Picked this one up about a year ago with only one channel working. I had a local "tech" here in CT do some work on it and he did get it up and running but I decided to go in myself and put some better quality components in to see how good one of these little amps could sound with a bit of extra attention, and sadly yes money too 
I ordered some Nichicon KZ Muse caps to replace the electrolytics on preamp/tone, main amp and phono boards. These seem to give a nice clean and detailed sound without being too pricey (Partsconnexion) I also upgraded the big power supply cap from 4700uF to a 10000uF 63V Panasonic TSHA from RS. The two output coupling caps went from 2200uF/50V to 4700uF 80V Nichicon Gold Tunes. Also used some Wima and Epcos film caps to replace lower value electrolytics.
Ouput transistors were replaced with ON Semi MJ15032G and all the evil little 2sc458LG were replaced with Fairchild KSC1845. Also all new transistors on the main amp board as per advice I got from tech people online.
Not the easiest amp to work on and I am a relative novice at this stuff. I just took a lot of pictures before and after and built myself a dim bulb tester to limit current when checking the amps functionality after each board was completed. Also cleaned out all pots and switches with Kontakt 60.
Last step has been setting the bias according to service manual. I may still get someone to hook up a scope to adjust for symetrical clipping as well.
End result is very nice! a sweet smooth Marantz sound with clear mids and detailed highs and decent bass extension. I am powering a pair of B&W DM110i. The caps need to burn in apparently but I am quite impressed with this little amp of only 15W per channel. Love to get my hands on a 1060 next but have a Sansui AU-999 on the bench for my next project.
Completed phono board by bregtje_lush, on Flickr
P700 board complete top by bregtje_lush, on Flickr
Output transistors in place by bregtje_lush, on Flickr
Completed and reassembled ready for testing by bregtje_lush, on Flickr
I ordered some Nichicon KZ Muse caps to replace the electrolytics on preamp/tone, main amp and phono boards. These seem to give a nice clean and detailed sound without being too pricey (Partsconnexion) I also upgraded the big power supply cap from 4700uF to a 10000uF 63V Panasonic TSHA from RS. The two output coupling caps went from 2200uF/50V to 4700uF 80V Nichicon Gold Tunes. Also used some Wima and Epcos film caps to replace lower value electrolytics.
Ouput transistors were replaced with ON Semi MJ15032G and all the evil little 2sc458LG were replaced with Fairchild KSC1845. Also all new transistors on the main amp board as per advice I got from tech people online.
Not the easiest amp to work on and I am a relative novice at this stuff. I just took a lot of pictures before and after and built myself a dim bulb tester to limit current when checking the amps functionality after each board was completed. Also cleaned out all pots and switches with Kontakt 60.
Last step has been setting the bias according to service manual. I may still get someone to hook up a scope to adjust for symetrical clipping as well.
End result is very nice! a sweet smooth Marantz sound with clear mids and detailed highs and decent bass extension. I am powering a pair of B&W DM110i. The caps need to burn in apparently but I am quite impressed with this little amp of only 15W per channel. Love to get my hands on a 1060 next but have a Sansui AU-999 on the bench for my next project.
Completed phono board by bregtje_lush, on Flickr
P700 board complete top by bregtje_lush, on Flickr
Output transistors in place by bregtje_lush, on Flickr
Completed and reassembled ready for testing by bregtje_lush, on Flickr
