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Acurite Digital Readout Power Supply

Acurite Digital Readout Power Supply
Hope someone can help.

ANSWERS:

"Hi @jwa2 ,

I assume that the faulty transformer is connected to the J4 connector on the board in image 3, is this correct?

Long shot maybe but try gently removing the insulation covering the windings on the transformer as some transformers have a cutout thermal fuse inserted in the transformer. Not sure if it is on the primary or the secondary or even if it is buried within the windings and not on the top under the insulation, but maybe worth a look.

If there is one there and it is blown you could try replacing it (hopefully its rating is stamped on it) and then check if the primary winding is OK and if so connect power to it and measure the output voltage on the secondary. You may have to be quick in case the fuse blows again due to an internal fault in the transformer

Knowing the output voltage is one thing as you still need to know the secondary output current required as well so that you can get the correct replacement or a suitable alternate supply.

The input voltage and current for the device is shown in the specs in the user manual (see Sect 5-1)

Update (03/08/2022)

Hi @jwa2 ,

Did you check all the primary windings, you never said?

Here’s an image to show how you might be able to still use it perhaps.

(click on image to enlarge)

If it tests open circuit between terminals A - E as shown in the image try between B - E, C - E and D - E and check if there is a reading at all.

If there is no continuity between D - E then unfortunately the main part of the primary winding is open circuit so it can’t be used but if it is only open between A - B or A - C or A - D, you can use the other windings as the primary input e.g. B - E, C - E or D - E

The specs in the user manual list 4 AC input values so presumably they connect 240VAC across A - E, 220VAC across B - E, 120VAC across C - E & 100VAC across D - E so depending where the problem is in the primary winding you may be able to supply the appropriate AC input voltage across the working section of the primary.

If the transformer can’t be used, I would try connecting 10V AC first and check if the device functions normally and is still accurate,"

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