Adam Smith
Well-known member
- Joined
- Dec 26, 2010
- Messages
- 58
My Am pex MX-10 developed a severe 60 cycle hum recently. I went through it with my scope and found lots of AC on DC the power rails. Star ground was good and the power transformer checked out. I replaced the selenium rectifier with diodes and I replaced the diodes on the high power portion of the PSU, I also replaced the most likely smoothing caps and checked what resistors I could in the power filter section. It didn't settle down, so I went back and checked my work and found I had damaged some of the diodes when replacing them.
I'm a novice at dealing with tube electronics and I have never dealt with point to point wiring before. I understand the basics of doing this sort of thing safely. However, working on P2P stuff is a total pain in the ass. Troubleshooting is especially hard, as it seems easy to damage components when disconnecting them to troubleshoot other components.
So, I decided to make a PCB for the power supply in my mixer. The idea is to make it much easier to troubleshoot problems and swap out components when they fail. I am trying to stick to the original design so I can use the stock power transformer, also I like the sound of the thing, so I'm not looking to change it much.
I have the PCB broken up into two parts, the HV rectifier circuit and the filter/voltage divider circuit. I haven't decided how I want to work out the heater supply. I'm thinking it would be best to keep it off of the boards.
This is my first attempt at laying out a high voltage PCB, I would appreciate any feedback on any mistakes I am making. I kept the traces at 3mm and kept the distance between traces at 3mm. This was an arbitrary decision, but I figured it couldn't hurt.
Here is the schematic I'm working from.
Here is the schematic I drew up in Eagle
rectifier
filter
Here are the PCB layouts
rectifier
filter
I'm a novice at dealing with tube electronics and I have never dealt with point to point wiring before. I understand the basics of doing this sort of thing safely. However, working on P2P stuff is a total pain in the ass. Troubleshooting is especially hard, as it seems easy to damage components when disconnecting them to troubleshoot other components.
So, I decided to make a PCB for the power supply in my mixer. The idea is to make it much easier to troubleshoot problems and swap out components when they fail. I am trying to stick to the original design so I can use the stock power transformer, also I like the sound of the thing, so I'm not looking to change it much.
I have the PCB broken up into two parts, the HV rectifier circuit and the filter/voltage divider circuit. I haven't decided how I want to work out the heater supply. I'm thinking it would be best to keep it off of the boards.
This is my first attempt at laying out a high voltage PCB, I would appreciate any feedback on any mistakes I am making. I kept the traces at 3mm and kept the distance between traces at 3mm. This was an arbitrary decision, but I figured it couldn't hurt.
Here is the schematic I'm working from.
Here is the schematic I drew up in Eagle
rectifier
filter
Here are the PCB layouts
rectifier
filter