05-02-2016, 04:16 PM
Hey all, back from an extended recess. I pose a couple of questions for the experts here:
1. I'm aware of all the conversation about the "death cap" on these Ampeg amps. Can I confirm it is NOT required with the later 70's amps that use a three-prong polarized AC plug? My concern is hum and I assume this cap bypasses any AC potential between neutral and ground (although both are common within the chassis itself, seems redundant?)
2. My standby switch failed a while back, replaced it with a stock white rocker from Fliptops. I really prefer the stock look of the new switches although I'm not sure how well the standby switch holds up to the 600VDC it controls. Something inside me cringes every time I switch it on, imagining some level of arcing on the contacts. So here's the question: If I switch on the power long enough to get the tubes good and warm, then turn off the power long enough to turn on the standby with the power off, then immediately turn the power back on with the standby already on (tubes still warm), this will spare the harsh inrush to the contacts on the standby switch. Is there any reason this would not be an acceptable practice?
3. Again regarding hum issues, my amp was rewired at some point in the past using all white wire (nightmare to troubleshoot!). I question if the routing of the chassis wiring is causing some of the hum problems. I'm going back to rewire the chassis wiring again and need to know the best practices for keeping everything tidy and quiet. I've been unable to locate a wiring layout diagram which would be helpful. I will replace the heater wiring with tightly twisted wires observing consistent polarity on the tube heater pins as per the schematic, routing the wire pair as far away from everything else as possible. I was also considering using star grounding with the PS caps, preamp boards, power tubes and everything else with a ground wire going to one central point common with the chassis. Not sure this is worth the effort because the input jacks and pre out/power amp in jacks are all common with the chassis (possible ground loops?). Good idea or not? What other considerations do I need to observe routing the other power tube wires (control grid, screen, cathode and anode) and the HV DC supply wiring? At this point I know enough to interpret the schematic and work around the HV without killing myself; the finer points of induced hum and noise are still a mystery. Thanks in advance to the forum's brain- trustee's assistance, Dan B.
1. I'm aware of all the conversation about the "death cap" on these Ampeg amps. Can I confirm it is NOT required with the later 70's amps that use a three-prong polarized AC plug? My concern is hum and I assume this cap bypasses any AC potential between neutral and ground (although both are common within the chassis itself, seems redundant?)
2. My standby switch failed a while back, replaced it with a stock white rocker from Fliptops. I really prefer the stock look of the new switches although I'm not sure how well the standby switch holds up to the 600VDC it controls. Something inside me cringes every time I switch it on, imagining some level of arcing on the contacts. So here's the question: If I switch on the power long enough to get the tubes good and warm, then turn off the power long enough to turn on the standby with the power off, then immediately turn the power back on with the standby already on (tubes still warm), this will spare the harsh inrush to the contacts on the standby switch. Is there any reason this would not be an acceptable practice?
3. Again regarding hum issues, my amp was rewired at some point in the past using all white wire (nightmare to troubleshoot!). I question if the routing of the chassis wiring is causing some of the hum problems. I'm going back to rewire the chassis wiring again and need to know the best practices for keeping everything tidy and quiet. I've been unable to locate a wiring layout diagram which would be helpful. I will replace the heater wiring with tightly twisted wires observing consistent polarity on the tube heater pins as per the schematic, routing the wire pair as far away from everything else as possible. I was also considering using star grounding with the PS caps, preamp boards, power tubes and everything else with a ground wire going to one central point common with the chassis. Not sure this is worth the effort because the input jacks and pre out/power amp in jacks are all common with the chassis (possible ground loops?). Good idea or not? What other considerations do I need to observe routing the other power tube wires (control grid, screen, cathode and anode) and the HV DC supply wiring? At this point I know enough to interpret the schematic and work around the HV without killing myself; the finer points of induced hum and noise are still a mystery. Thanks in advance to the forum's brain- trustee's assistance, Dan B.