Question about Electro-Harmonix 12ay7 Tube Microphone Preamp
You must be on 50Hz power. You don't really need a schematic to repair the unit. Since the hum is twice power line frequency, the likely cause is the electrolytic filter cap for the high voltage has failed. The cap should be obvious in the unit. It will be near rectifier diodes and have a voltage rating above 50 volts. To test, bridge the one in there with another cap observing the correct polarity. If hum changes, replace the original cap.
Posted on May 25, 2011
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
Posted on Jan 02, 2017
Tips for a great answer:
Feb 17, 2016 | Marshall Music
Sep 18, 2014 | Music
Mar 04, 2011 | SWR Music
Feb 16, 2011 | Music
Feb 06, 2011 | Fender Custom Vibrolux Reverb Tube...
Jan 06, 2011 | Music
Jan 01, 2011 | Marshall Mg50dfx 50-Watt Combo Guitar...
Feb 11, 2009 | Yamaha Electric Guitar
98 people viewed this question
Usually answered in minutes!
Step 2: Please assign your manual to a product: