Problem with power supply testing (with SMR-4 v0.7.)

Hi everyone,
I’m building the filter SMR-4 and I arrived at step 4.
But when I test the power supply voltage (following your instructions), I have only a 0 or -0 voltage.
I don’t now what happened.
Maybe an IC1 problem? or something else?
Let me know
Thanks in advance.


Have you soldered the little “bridge” over the pads labelled “SW”?

What is the voltage and polarity of your power supply?

yes, the bridge is soldered and I use a power supply with an output of 12VDC and positive polarity (If I check it with the tester it works)
thanks for your fast answer.

What is the voltage:

  • at the pads labelled “SW”?
  • at pin 8 of IC1?
  • at the pin labelled I on the 7805

When I put the COM probe to GND hole (on the far left) and other to SW or pin 8 of IC1 or pin I on the 7805 I have always 0 voltage.
What is the problem? I don’t understand.

First, check if there is no short between those points and GND.

If there is no short, it might be that the connector of your power supply does not fit well in the connector J3.

That or your meter or power supply are not working…

I tested again the power supply and it seems to have some fitting problem (maybe it was dirty inside)…
Now every points has the correct voltage.
Anyway many thanks for your help :slight_smile:

Another question is…I have build also the control board (until step 11). How could I check if it works? I don’t have much clear that passage. (what power supply voltage I need?)
Sorry for my stupid question but I don’t want to burn something :wink:
Thanks a lot again.

It is not recommended to test the control board with another +5V power supply than that from the filter board.

So your options are:

  • Build the full SMR4 board fully, then the digital board, then get back to tuning the SMR4 board.
  • Build the power supply of the SMR4 board (up to step 5) ; then the digital board ; then finish the filter board.

I have a similar problem with batch 9

  • switch is soldered, polarity is center pin positive 12 v DC
  • Voltage at sw is 12.16V
  • pin 8 11.72V [correct orientation]
  • 11.72V at pin I on 7805

All components are fitted however only IC1 is in its holder. all other IC’s are empty

Any thoughts on whats going on? I’m somewhat at a loss as there are no obvious problems, all capacitors are correct orientation diodes the right way round optional c31 also correct

So you have 11.7V at pin I of 7805 but nothing at the output? It might be that the ground pin of the 7805 (labelled “-”) is incorrectly soldered (or worse, there’s a short between the ground and output pins).

flipped it over and taking measurements from the solder side taking ground as the reference ground on j3 rather than off of the power cable directly.

Now getting jack all anywhere so i’m going to try and find a different power supply that fits properly.
Do you know what power supply you’re using? Or where you bought it from?
Having a power supply i know works giving me a firm contact might help me error check. Failing that i’ll go into uni labs and hook up a bench power supply to the input pins of j3.

My soldering is all good there are no bridged joints, so i’m hoping that it’s just the power supply now.

s. thanks for your help so far!

Sadly, the power supplies I shipped with the kits are no longer sold by Farnell, so I am currently hunting for another supplier.

do you know what size the connector is?

It is listed as 2.1mm

I have 6 of these - supersmall, versatile and stable.

I have these

Voltcraft - the Brand Richard Wagner would have chosen ™

Hi again, so i’ve connected my bench power supply DC 9 Volts to the possitive pin of the input [connected to the switch jumper] and grounded it against the input ground.

IT WORKS :smiley: [and i suspect must have been working all along as i’ve changed nothing else]

Now i just need to find an actual DC plug supply rather than my bench supply.

Thanks for your help guys!