| Author | Message | ||
     jamie danter |
HD130R-2275- Experiencing intermittant distortion- Makes no difference with Master/Chan Vol settings, or Low/High Power settings. Changed driver tubes w/no change in problem. Distortion still comes and goes. Pwr Supply caps replaced, new tubes, bias set, cleaned pots and tube sockets. Dirty 1/4" sockets? Dirty IC sockets? Bad resistor? | ||
| Terry |
HAVE YOU LOOK AT THE LM307H IC? MOVE EACH ONE DOWN ONE STEP.YOU MAY HAVE A BAD ONE.  | ||
| Daniel |
I have that problem on my 212HD-130 as well. I went to a guy who could repair it, but in one month he hasn't solved the problem. What can it be besides the IC? | ||
| Terry |
Jamie & Daniel Is there any difference in CH1 or CH2? Take the first two LM307H IC out. They are for CH1. Rotate them in with the other five, looking for a bad one. If this makes no difference, I would say the IC's are OK. Do you have all IC's that say LM307H ? Next, when I rebulid a amp, I take out the 50V-150 Caps. (all five) Put in new Sprague, then go to the brown PVC 6147, 600V-.047 replace them. Now on two power tubes. Take out the brown PVC 2000V-.001, Pin 1 to Pin 3. Replace them with Ceramic Disk 3000V-470. This is straight from Tom Walker himself. Check the resistor to see that the values are close. They take a beating from all the heat of the tubes. Also check the diodes. This is all just good maintenance and should be done to your amp . If this does not fix the problem, I would start looking at the solder joints and checking the resistor values. This is a good start to correcting the problem. It may or may not fix the amp. Good Luck. Terry. | ||
| Jim Harper |
My HD150 plays fine for a while and then starts humming. You can turn to standby and then back to Hi and it quits for a while. I checked the bias cross the 3.9 ohm resistors, it measured 90mv on both resistors. This amp looks like nothing has ever been replaced in it. It uses the BB3 driver board. Any suggestions? | ||
| Steve Kennedy |
Does anything get hot (like glowing output tube plates)? Excess current drain from a power supply will cause hum. Also, your filter caps might not be doing their job all the time. Most people do not replace their caps UNTIL they have a hum problem. | ||
| jim harper |
I set the bias to 25mv across the driver emitter resistors and that fixed the problem. Thanks for responding anyway. | ||
| Tom Laskow |
I have a 212 65 with 1 12AX7 and 2 EL34's. The amp is breaking up (overdrive sound) at any volume in channel 1 on both the solid state and tube sides, and sounds a little better on channel 2. It also seems to be getting a bit warm and a really slight burning odor. The amp sat for about a month (which is a sin) then when I went to play it, I had this problem. Anybody have any ideas? Thank you for any help/suggestions in advance. | ||
| Steve Kennedy |
First, all channels go through a solid-state preamp and a tube output stage. The 12AX7 is a phase splitter for the output tubes, not a preamp tube. You symptom could be a phase splitter tube failure, a shorted output tube, a loss of a power supply rail or a preamp section problem. In other words.. almost anything! Your amp needs to visit a qualified tech if simply replacing the tubes doesn't do it for you. Just don't leave the amp on for any great length of time while playing around trying to fix it and FIRST verify whether or not you tubes are glowing abnormally or not at all! |