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GReg/Electrical Tech Journal

All your geeky questions about electronics, microphones, tape machines, etc.

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Re: GReg/Electrical Tech Journal

Postby drpat on Thu Nov 29, 2018 8:08 am

Are those voltages read off the transformer connected to the circuit, and mic, or lifted from the rest of the power supply?
You're feeding it 220VAC?


Yes, the voltages were read directly off the transformer fully loaded with mic. Being fed from a 220V variac.

With the above conditions:
Node1 measured 217.74VDC (supposed to be 220VDC)
Node4 measured 14.15VDC (supposed to be 14VDC)
Last edited by drpat on Thu Nov 29, 2018 9:50 am, edited 3 times in total.
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Re: GReg/Electrical Tech Journal

Postby drpat on Thu Nov 29, 2018 8:14 am

That was probably a custom toroid transformer that we bought for this purpose.
I've had good luck with the Hammond 262D6 in other PSU projects. It doesn't have a dual primary, which is too bad, but the price is right...


I'll probably end up with a custom part too... I've got a query in to Edcor for a custom EI core jobbie.
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Re: GReg/Electrical Tech Journal

Postby greg on Thu Nov 29, 2018 8:05 pm

drpat wrote:
Are those voltages read off the transformer connected to the circuit, and mic, or lifted from the rest of the power supply?
You're feeding it 220VAC?


Yes, the voltages were read directly off the transformer fully loaded with mic. Being fed from a 220V variac.

With the above conditions:
Node1 measured 217.74VDC (supposed to be 220VDC)
Node4 measured 14.15VDC (supposed to be 14VDC)


That's pretty spot-on for unregulated voltages. The 262D6 won't be a drop-in replacement, I see.
I tend to rebuild supplies when the caps are dead, and make them fully regulated w/ solid state parts.

I'll probably delete these posts to keep the log clean, btw. Feel free to start a new topic on this.
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Re: GReg/Electrical Tech Journal

Postby greg on Tue Dec 04, 2018 2:45 pm

Shure 94A1670 preamplifier, used for our SM98s, but used in many Shure condenser mics-

Busted pin in the mini XLR connector.


Replaced the connector. Part number, in case it helps, Switchcraft TB3M.

Sorting through Sony and Gefell mics and busted capsules...
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