| Author | Message | ||
| Lou Bintz (vanderpol2) Username: vanderpol2 Registered: 02-2012 |
Hello all, Could use some advice: musicman 210 HD130 (12AX7 splitter) that I bought in 1978 and kept! Only played occasionally for fun and it still had its original tubes, till very recently Anyway I have an issue in the last Lm307H, signal gets to the inverting input but the out is zero, it also is warm to the touch. I suspect the non inverting input but haven't traced the issue & could use some help. I can hear "scratchiness" in the master but again no signal on the Deep switch or master. I have a function generator and an old Heathkit IO-12 oscillicope DMM ,, Thanks in Advance Lou P.S,Just replaced the original 6AC7 tubes and the Lm307H replaced the 50uf 50V -15V supply cap as it was mushroomed and am getting to the others.. Bias is set pretty hot from the factory at .6V on the power tubes (original Sylvania) heaters work etc.. | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Yeah, you're going tohave to scope it and trace through it. I suspect that op amp went up in smoke. I assume that you have + and - voltage present since you say it gets warm. You might check first so see if you have both before you start tracking the signal. It just sounds like the finals are working but no gozinta. |
Tue, 03/25/2014 - 09:52
#1