Testing power supply

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theojohn4
 
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Testing power supply

Post by theojohn4 »

Hi, I recently purchased a willzyx x0x. I have just soldered in the big caps, the 7805 reg and the two small caps. It says to measure the V across several components.
Across power jack is just over 10V as expected
Across each big cap is 34V (should be 26)
Across 7805 and leftmost pin is just over 10V (should be 5V)

It appears I have done something wrong but I've checked all steps and I don't appear to have missed anything. Can anybody lend help?

I don't want to proceed until I can figure this out.

Thanks a lot

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antto
 
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Re: Testing power supply

Post by antto »

make sure you measure the adapter with the multimeter in "VAC" mode, and the rest of the circuit in "VDC" mode

theojohn4
 
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Re: Testing power supply

Post by theojohn4 »

Ah, great, that seems to have done the trick thank you.

Will the 7805 and small caps have changed the reading over the big caps because they're now reading 15V instead of 26V?

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antto
 
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Re: Testing power supply

Post by antto »

oops, sorry
just checked the instructions again
you're supposed to measure around C3 and C5 in "VAC" mode as well, okay, but from there onwards most things are DC, thus "VDC" mode

here's the quote from the instructions: "Try measuring AC voltage across C3 and C5, it should be about 26VAC."

so, try again and measure the voltage around those and also on the adapter, both in VAC mode
and then again at the 5V regulator, but in VDC mode
also, check the components (diodes / electrolytic caps) for proper orientation

theojohn4
 
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Joined: Sat Jun 14, 2014 2:34 pm

Re: Testing power supply

Post by theojohn4 »

In that case I'm getting about 34VAC across each large cap and about 30VDC across both (neg to pos terminal)
Or just less than 15VDC across both (neg to neg)

I am using a budget analogue multimeter. Could this be the problem?

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antto
 
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Re: Testing power supply

Post by antto »

hm... how about the regulator? do you get 5VDC on it?

theojohn4
 
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Re: Testing power supply

Post by theojohn4 »

Yeah, I get just over 5VDC on the regulator

theojohn4
 
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Re: Testing power supply

Post by theojohn4 »

(I've checked all resistors and trim pots and they all appear to be correct resistance)

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antto
 
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Re: Testing power supply

Post by antto »

okay, good, if you have ~5V on the 5V regulator, and it doesn't get uber hot (put the heatsink on) - then it's all fine, continue with the build

theojohn4
 
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Re: Testing power supply

Post by theojohn4 »

Okidoki, thanks a bunch

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