Power Supply Troubleshooting--No Voltage from Secondary Winding - diyAudio
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Old 1st February 2014, 08:10 PM   #1
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Default Power Supply Troubleshooting--No Voltage from Secondary Winding

I built this amplifier last summer, using a modification I saw on Reddit (utilizing both the low mu and high mu units in the 6EM7).

I decided to rebuild the amplifier, using a tube rectifier as called for in the original schematic, and replacing the metal chassis from Mouser with a birch plywood chassis.

However, following the rebuild, I am no longer receiving power from my transformer (an Antek AS-05T240). Both heater wires are producing voltage, but neither the 220 or 240V wire is producing voltage. This also occurs when the transformer is disconnected from the rectifier. I replaced the transformer, and I am still experiencing the same problem. I have performed a continuity test, and have measured the resistance in the winding (13.6 ohms in the heater wires, 165 ohms in both the 220 and 240V wires). Likewise, when powered on, I notice that there is negative voltage between the circuit and the ground (-1.3V).

I am beginning to think there is something wrong with my wiring/construction. Any thoughts?
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Old 1st February 2014, 10:50 PM   #2
sreten is offline sreten  United Kingdom
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Hi,

Your basically saying two transformers don't work
disconnected from the rectifier for no sensible reason.

It doesn't work with a replacement transformer ?
Any idea how to test the transformer you replaced ?

Get a grip, and work it out.

rgds, sreten.
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Old 2nd February 2014, 03:56 AM   #3
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Hi Streten,

Thanks for the reply. I agree, disconnecting the transformer from the rectifier did seem weird, but it was recommended by a user of a different forum as part of a test on the transformer.

The replacement transformer is producing voltage to the two 6.3V heater winding sets, but is not producing voltage to the 240 or 220 windings. This was the identical problem I encountered with the original transformer.

I'll continue researching ways to test the transformer, and the accompanying rectifier circuit.
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Old 20th September 2014, 04:19 PM   #4
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The 240V and 220V are taps. You have take the voltage from the low side and either the 220 or 240, not both, and not between 220 and 240. I have used several of these for projects and had no problems.
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Old 20th September 2014, 05:43 PM   #5
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Quote:
Originally Posted by Vermillionbird View Post
I decided to rebuild the amplifier, using a tube rectifier as called for in the original schematic, and replacing the metal chassis from Mouser with a birch plywood chassis.
could it be that originally the metal chassis was used to distribute ground and now a ground connection is missing somewhere, e.g. the one right at the transformer ?
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Old 20th September 2014, 05:49 PM   #6
rayma is offline rayma  United States
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Quote:
Originally Posted by Vermillionbird View Post

The replacement transformer is producing voltage to the two 6.3V heater winding sets, but is not producing voltage to the 240 or 220 windings. This was the identical problem I encountered with the original transformer.
This must be something simple, post a schematic.
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Old 22nd September 2014, 04:21 AM   #7
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.
It sounds like cohearent has the right idea, or the transformer is otherwise mis-wired, as I've indicated below.

Surely the transformer came with a wiring diagram of some sort?
.
Attached Images
File Type: jpg z_transformer_error.jpg (58.0 KB, 45 views)

Last edited by bentsnake; 22nd September 2014 at 04:25 AM.
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Old 22nd September 2014, 02:38 PM   #8
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AS-05T240 - 50VA 240V Transformer - AnTek Products Corp
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