AC/DC & POWERSTATION KIT BUILD THREAD

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Joe Malone
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Re: AC/DC & POWERSTATION KIT BUILD THREAD

Postby Joe Malone » Fri Apr 05, 2019 3:16 pm

Miko wrote:Hey Joe. Kinda stumped. I'm hoping you can help. I'm trying to setup my V5. I have 30VAC unregulated, no CT coming off my power transformer. I set the doubler to D, and jumped C1 and C2 to drop the 48V to 24V as recommended in a previous post. When I connect one secondary to AC and the other to 0V it blows mains fuses. When I connect both secondaries to AC it doesn't blow fuses but of course doesn't produce the -voltages. I checked all component orientations, placements, and solder joints. Any ideas? Thanks!


HI Miko

Email me or attach up there some top and bottom photos of the built kit and wiring so I can check them over.

30vac is very high as it will give 42vdc unreg to each + and - reg but it should be fine except for heat under load.
Joe :-)
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Re: AC/DC & POWERSTATION KIT BUILD THREAD

Postby cabbagerock » Thu Oct 31, 2019 2:42 pm

Hi Joe, Here is my sad tale: I built a v3 AC/DC with 48v and +/- 28v and it worked great for many months powering a DIY mic pre. Then one day it blew a mains fuse, I disconnected from the mic pre, replaced the fuse, and 48v had turned into 5v. I then replaced R7 because it was blown up and D10 because it looked possibly blown up, tested on the bench and 48v was back (yay). I repaired what I thought was a culprit short in the mic pre, powered back up and the fuse blew again because I had not actually fixed the short in the mic pre. Anyway, I replaced both R7 and D10 again and now instead of 48v I'm getting 68v. I replaced R2 because it looked a little stressed but still am getting 68v instead of 48v (+/- 28v still look good). Any advice on how to proceed would be greatly appreciated, thanks you!

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Re: AC/DC & POWERSTATION KIT BUILD THREAD

Postby Joe Malone » Thu Oct 31, 2019 3:03 pm

cabbagerock wrote:Hi Joe, Here is my sad tale: I built a v3 AC/DC with 48v and +/- 28v and it worked great for many months powering a DIY mic pre. Then one day it blew a mains fuse, I disconnected from the mic pre, replaced the fuse, and 48v had turned into 5v. I then replaced R7 because it was blown up and D10 because it looked possibly blown up, tested on the bench and 48v was back (yay). I repaired what I thought was a culprit short in the mic pre, powered back up and the fuse blew again because I had not actually fixed the short in the mic pre. Anyway, I replaced both R7 and D10 again and now instead of 48v I'm getting 68v. I replaced R2 because it looked a little stressed but still am getting 68v instead of 48v (+/- 28v still look good). Any advice on how to proceed would be greatly appreciated, thanks you!


If 48v LM317 is stuck at 68v then usually it will be the reg is short if the trimpot is not open circuit. If you mic pre 48v is likely to go short again add a tiny inline fuse between the 48v rail to the mic pre or a small value poly switch. Usually a 48v phantom rail will only draw 10 to 20mA per channel.
Joe :-)

JLM Audio

Capturing Audio without Injury

cabbagerock
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Re: AC/DC & POWERSTATION KIT BUILD THREAD

Postby cabbagerock » Thu Oct 31, 2019 4:15 pm

Joe Malone wrote:
cabbagerock wrote:Hi Joe, Here is my sad tale: I built a v3 AC/DC with 48v and +/- 28v and it worked great for many months powering a DIY mic pre. Then one day it blew a mains fuse, I disconnected from the mic pre, replaced the fuse, and 48v had turned into 5v. I then replaced R7 because it was blown up and D10 because it looked possibly blown up, tested on the bench and 48v was back (yay). I repaired what I thought was a culprit short in the mic pre, powered back up and the fuse blew again because I had not actually fixed the short in the mic pre. Anyway, I replaced both R7 and D10 again and now instead of 48v I'm getting 68v. I replaced R2 because it looked a little stressed but still am getting 68v instead of 48v (+/- 28v still look good). Any advice on how to proceed would be greatly appreciated, thanks you!


If 48v LM317 is stuck at 68v then usually it will be the reg is short if the trimpot is not open circuit. If you mic pre 48v is likely to go short again add a tiny inline fuse between the 48v rail to the mic pre or a small value poly switch. Usually a 48v phantom rail will only draw 10 to 20mA per channel.


Thanks Joe! I have ordered some LM317, in the meantime I have both an LM7805CT and NTE958 lying around, are either of these a suitable replacement?

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Re: AC/DC & POWERSTATION KIT BUILD THREAD

Postby Joe Malone » Thu Oct 31, 2019 9:52 pm

cabbagerock wrote:
Joe Malone wrote:
cabbagerock wrote:Hi Joe, Here is my sad tale: I built a v3 AC/DC with 48v and +/- 28v and it worked great for many months powering a DIY mic pre. Then one day it blew a mains fuse, I disconnected from the mic pre, replaced the fuse, and 48v had turned into 5v. I then replaced R7 because it was blown up and D10 because it looked possibly blown up, tested on the bench and 48v was back (yay). I repaired what I thought was a culprit short in the mic pre, powered back up and the fuse blew again because I had not actually fixed the short in the mic pre. Anyway, I replaced both R7 and D10 again and now instead of 48v I'm getting 68v. I replaced R2 because it looked a little stressed but still am getting 68v instead of 48v (+/- 28v still look good). Any advice on how to proceed would be greatly appreciated, thanks you!


If 48v LM317 is stuck at 68v then usually it will be the reg is short if the trimpot is not open circuit. If you mic pre 48v is likely to go short again add a tiny inline fuse between the 48v rail to the mic pre or a small value poly switch. Usually a 48v phantom rail will only draw 10 to 20mA per channel.


Thanks Joe! I have ordered some LM317, in the meantime I have both an LM7805CT and NTE958 lying around, are either of these a suitable replacement?

No it needs to be a LM317 to work
Joe :-)

JLM Audio

Capturing Audio without Injury

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