help with audio resesrch d76

Thanks HifiGeek!! I have never looked at the schematic for the original D90. Clearly shows matched GE6550s. I was fooled by the http://www.arcdb.ws/D90/D90.html website. Has a picture of D90 with GE6l6s in it. must be D90Revised...oh those ARC guys. When I talked to Mr. Johnson he said there was a heated debate between himself and his "engineers" between the 6550 and 6l6, but I did not realize they produced a 6550 version. Mr. Johnson seemed pleased he produced an amp using 6l6s. Also, I have an amp stamped on the back with D90-B and it does not have the servo in it. Leonard at ARC finally told me that it was at a dealer and was sent back for the B update and they took a little short cut... ;) Thanks again for the audio trivia. Larry

Larry, hopefully it doesn't have the white relay in it either. That can become problematic.

Hifigeek1 I need your help. What was the purpose of the "Servo" circuit? in the ARC 90B? Also, is the white/gray relay located down in between the large grey tall power supply caps? where the 6550 power supply tube was located in the 90? I do not have one in mine. The reason I am asking is that all of a sudden my 90B(ish) upon start up, the output tubes glow orange after about 30 seconds and then the fuse blows. Techs look at my 90B and say it does not match the ARC schematic for 90B?? Again ARC said it started out as a 90?? or 90Revised. Very confused. Thanks Larry

Larry, In the D90, V19 is the 6550 regulator. In the D90B the regulator consists of a 12BH7 V15, and a 12AT7 V16. The B version does not use a 6550 for voltage regulation. It is possible the unit started out as a D90 and got updated to D90B. I have seen updates like this before. You unit needs to be serviced by someone who knows ARC products. I would be happy to take care of it for you if you do not wish to ship it back to ARC. The servo was used to illuminate coupling caps.

HiFigeek1 you have sent myself and my fellow audio buddies on a wild goose chase.....for several days...we just thought we were dumb and didn't know how to ask you...Illuminate coupling caps???? We thought you knew an audio term we did not know....WELL DID YOU MEAN ELIMINATE coupling caps...??? Larry ;)