Need a good reputation repair shop for Mitsubishi DA-P20 preamp.

My suggestion would be to buy something new or at least newer. There have been some major improvements in audio electronics since that unit was made. You can easily get something for the cost of repairing the Mitsubishi. Seriously, For a couple hundred dollars you could buy something used! Others may have ideas, best wishes.

I have thought about that approach, I like the dual mono design and phono MM/MC included in the DA-P20. With so many newer options I get lost as to what might be a better preamp. 

I would get that unit fixed,I treasure mine and have the entire tower full so would preserve the set(DA-P20,DA-F20 tuner,DP-EC1 TT,DT-40S cassette,DA-A15 amp/with meters)driving a set of EPI100 and a set of Allison Acoustic 6 speakers,very fine sounding old equipment that is hard to find,well worth the expanse of repair

or just leave it on,don't shut it off

I am in New Jersey if I can be of service.

Bad experience with audio techs, I work on my own gear most of the time. Lazy about tube HK, Get the PS section redone. Been sick, check out the repair water. 

Techs wanted 3k, says amps are great were built well BS... Needs to be stripped and rebuilt blah blah. 

Told me they have to accept the job. Like some type of lotto. 2 of them said same thing!

I told them, I was being lazy, worked on tube amps for 20 years, you need to strip the amp completely to change PS filter caps? 

Avoid CA lol.