Tweet
I have a 6505+ I'm puttin on the bench tonight. Everything sounds perfect except the presence, on both channels, squeals like a banshee when the presence control is around 2-3:00 and beyond. Anybody have a clue as to what is going on? Happens even at bedroom volumes. Thanks for looking.
-
-
Phase splitter tube microphonic?My band:- http://www.youtube.com/user/RedwingBand -
Nah. I replaced all 6L6's and 12AX7's. still does it. I turned it on for a short period without a speaker on it ( I know you're not supposed to do that) and the squeal can be heard without the speaker. It's resonating from the circuit somewhere. It also changes audible frequencies as you turn the presence knob. WTF?? I thought it could be a cap but it's happening on both channels.Comment
-
Try removing pre-amp tubes to see which is the first one in the signal chain that will make it stop, ie start with V1.
Have you got a schematic, or is http://www.webphix.com/schematic%20h...ey_evh5150.pdf accurate?My band:- http://www.youtube.com/user/RedwingBandComment
-
Was someone else in there mucking around?
Can't seem to find the schematic
What are the chances that the output transformer primary is incorrect?
Maybe what you are seeing is "positive" feedback.
I think the squealing that you heard, when the speaker was not connected (bad boy!), was the output transformer "singing".Comment
-
It's a 5150-2.Education is what you're left with after you have forgotten what you have learned.Comment
-
Well, thanks for all your replies. I gave it a thorough cleaning, (the top of the chassis was tan with dust) and reflowing the solder on the pre-amp board, it has stopped. That was really weird.Comment
-
Can't tell you how many amps that where fixed by resoldering.Comment
Comment