Quick Question - Resistance values

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Ravi Miranda

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Feb 15, 2021, 5:07:27 PMFeb 15
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Hi,

I have just connected up my board to the Raspberry Pi and IC203, IC401
and U! seemed to get very hot

I temporarily removed R201 120R to check for shorts. However, checking
voltages on IC204 i am getting 3.3V on the tab (Pin4) of IC204 and
this tab is showing continuity to tab (Pin4) of IC203

Have I fried my ICs?
Are there any resistance checks that someone has for the beta4 board?
Any help will be appreciated.

Best 73,

Ravi/M0RVI

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I'm here to add more value to the world than I'm using up.

Radioberry

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Feb 16, 2021, 7:04:50 AMFeb 16
to Radioberry

Ravi

That does not sound good.

Please do not remove R201 when powering the board. This resistor is to get the 1V2.

The voltage you are measuring is wrong.... the scheme is showing the right values.

If you cut the 2V5 trace at the bottom side of the PCB you can see if the 2V5 chip is working? 


You  can supply 5V to the CN302 header pin and waching the current.... (exclude the RPI)


Hope this gives some ideas to find your problem?

73 Johan
PA3GSB












Op maandag 15 februari 2021 om 23:07:27 UTC+1 schreef ravim...@gmail.com:

Ravi Miranda

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Feb 16, 2021, 8:33:01 AMFeb 16
to Radioberry
Hi Johan,

Thank you for the message.

I have excluded the RPi - Current draw little over 900mA

Cutting the 2V5 trace under the board, I still get 2.5V on the input
pin of IC204 and 3V on the output side on IC204. The current draw is
around 1A

Best 73,

Ravi. M0RVI
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Radioberry

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Feb 16, 2021, 9:26:43 AMFeb 16
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Ravi

Your current is way to high!

You need 1V2 for IC204 can you apply 3V3 after the cutting of the trace 2V5 (not applying other voltages) and look for the outpur of IC204; must be 1V2.

There must be a short ... 

73 Johan
PA3GSB

Op dinsdag 16 februari 2021 om 14:33:01 UTC+1 schreef ravim...@gmail.com:

Ravi Miranda

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Feb 16, 2021, 9:46:37 AMFeb 16
to Radioberry
Hi Johan

Here are my observations with the trace cut

Applied 3V3, Current draw 400mA - output of IC204 is at approx. 3V (2.96V)

Yes, looks like there is a short, but I;ve cleaned and inspected the board.

Many Thanks.

Best 73,

Ravi, M0RVI
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