Responses from hifigeek1

AR SP9 MKlll
Replace the relay... 
Scott 340A Repair help
I may be able to help. Email me. 
ARC D-115 use half of tubes
Same goes for the D115.... 
ARC D-115 use half of tubes
Use all the tubes in your D70mk2. 
Tube dampeners on ARC gear ... FREE TWEAK
Those dampers are suppose to be put in that position normally. They do not belong over the plate structure of the tube. 
Refurbish a Dynaco St70
And before Electronic Industries, Bill Johnson's company was known as Peplo. I don't know why or the significance of the name. 
Surge Protection for ARC Tube Amps
I don't believe Audio Research recommends any power conditioners at this time. I might suggest you contact Kalvin in Customer Service at Audio Research and ask him directly. 
Quad ESL-63 and low-powered amps; Sun Audio, Atma
Three watts is insufficient to drive the Quads. I do not know if an OTL amp would work with the Quads. 
New KT150 tubes?
There are a quite a few ARC amps where the tubes will not clear the top cover. Be advised. 
winged c 6550c is not good for ref 5se??
The issue isn't with the Preamp, it's with the Winged C 6550. Don't use them! The last of those tubes that came from the factory before the plant burned down were awful tubes. Use a 6550WE. That is what ARC is using now. 
Audio Research M100 Thumping
Yup I have an ARC SP-10 that's been modified and the work was simply awful. It's taken me forever to find all the problems wrong with it but I think I'm finally in the home stretch. 
Audio Research M100 Thumping
Not really...Looking at it on a scope but it could also be a faulty filter cap as well. I would suggest having a tech you trust look at it. If that preamp has a tube rectifier in it, make sure the tube is functioning and if need be replace it. 
Audio Research M100 Thumping
You may have a bad Hexfred in the power supply. 
Audio Research M100 Thumping
The only other thing it may be is the coupling caps in the C/J are leaking DC voltage causing it to destabilize the M100's. It's also possible a regulated power supply in the C/J or caps in the C/J are defective. How old is your C/J preamp?? 
Audio Research M100 Thumping
Run the amp without turning the C/J on, but leave it connected to the amp, and see if it motorboats. If after the 15-20 mins. the amp remains fine, it's not the amp.