Beachmaster Files

[hamedtaran]

Hmm, U3 may be running periodically in self-oscillation mode now, what does a scope trace at U3 Pin 2 look like ?
Also are you getting 12V pk-pk at TP1, (you previously had 5V). The full 12V swing is needed for the emitter-follower Mosfet driver Q1 and Q2 to work properly.

Ok, I will check all the points you said, thank you for your time

[Olly]

Hmm, U3 may be running periodically in self-oscillation mode now, what does a scope trace at U3 Pin 2 look like ?
Also are you getting 12V pk-pk at TP1, (you previously had 5V). The full 12V swing is needed for the emitter-follower Mosfet driver Q1 and Q2 to work properly.

Hi, I checked all the parts and they were all correct, I made the following changes and the circuit worked correctly:
C12=680pf
R21=10k

[ATTACH]57900[/ATTACH]

[ATTACH]57901[/ATTACH]

Of course, I saw the value of C12 in the schematic and decided to test it instead of 0 ohm resistor
What do you think? Did I do the right thing?

[hamedtaran]

Actually most of your soldering looks very good , just one or two joints looked a bit suspect...

The pk-pk at TP1 should be pretty close to U1 supply voltage (around 12V). If you measure across pins 7 and 14 of U1 what voltage do you get? (It should be around 12V) and comes directly from your power supply through the switch. You've bridged the switch out so it should be direct.

Hi, I checked all the parts and they were all correct, I made the following changes and the circuit worked correctly:
C12=680pf
R21=10k





Of course, I saw the value of C12 in the schematic and decided to test it instead of 0 ohm resistor
What do you think? Did I do the right thing?

[hamedtaran]

Actually most of your soldering looks very good , just one or two joints looked a bit suspect...

The pk-pk at TP1 should be pretty close to U1 supply voltage (around 12V). If you measure across pins 7 and 14 of U1 what voltage do you get? (It should be around 12V) and comes directly from your power supply through the switch. You've bridged the switch out so it should be direct.

Yes I use a piece of wire instead of power switch, Tomorrow I will replace the u1 and test again, I will also implement the tips you said. thank you for your attention

[Olly]

Actually most of your soldering looks very good , just one or two joints looked a bit suspect...

The pk-pk at TP1 should be pretty close to U1 supply voltage (around 12V). If you measure across pins 7 and 14 of U1 what voltage do you get? (It should be around 12V) and comes directly from your power supply through the switch. You've bridged the switch out so it should be direct.

The soldering is not as bad as it looks in the photo, the photography light caused it, but I will check again that everything is correct, the pk-pk voltage in tp1 is about 5V, is it correct?
Excuse me for bad english

[hamedtaran]

One more general comment; The joints on some of your resistors don't appear to have flowed 100% properly (e.g. the 10K base resistor R20).
Perhaps just re-solder any suspicious joints - I find that a good liquid flux is invaluable here.
You need to be very careful if you ever remove and re-use these SMD resistors as the end plating gets damaged very easily and they cease to have the correct resistance.

Kind regards

The soldering is not as bad as it looks in the photo, the photography light caused it, but I will check again that everything is correct, the pk-pk voltage in tp1 is about 5V, is it correct?
Excuse me for bad english

[Olly]

One more general comment; The joints on some of your resistors don't appear to have flowed 100% properly (e.g. the 10K base resistor R20).
Perhaps just re-solder any suspicious joints - I find that a good liquid flux is invaluable here.
You need to be very careful if you ever remove and re-use these SMD resistors as the end plating gets damaged very easily and they cease to have the correct resistance.

Kind regards

[Olly]

If all your parts are correct, then try removing C13 and checking whether you then get a proper 12V pk-pk square wave at U3, Pin 2.

[Olly]

Double-check your R21 - see above reply.
I'd be surpised if U1 was defective, although anything is of course possible.

I checked all the parts, I used two 10k resistors instead of R21, the value of c3 is correct, about 91nf, do you think U1 could be defective?

[Olly]

Zoomed in on the photo of the bottom of your board and you have two resistors in series for R21, they appear to be marked '010' which is 1 Ohm... R21 needs to be 20K.
Unless the marking is 01C, which then is actually 10K (EIA-96 markings)

Regards

[hamedtaran]

Firstly, your TP1 has quite a slow falling edge and I can't make out what the voltage scale is.

I checked all the parts, I used two 10k resistors instead of R21, the value of c3 is correct, about 91nf, do you think U1 could be defective?

[Olly]

Hi,

Your traces seem somewhat odd!

Firstly, your TP1 has quite a slow falling edge and I can't make out what the voltage scale is.
It should look something like this: -


As you can see, the pulse amplitude is up to 12V with a nice fast falling edge.
Double-check all your solder connections on U1, especially its GND at Pin 7 and the decoupling cap C3.

Your signal at Pin 7 of U3 also has a really slow rising edge, this is what mine looks like: -


Again, a nice clean signal with fast edges. The voltage only goes up to a bit over 2V.
Double check that the value of R21 is 20K.

Finally, the output at Pin 2 of U3 should be a good 12V pk/pk square wave as follows: -


All of these traces should be measured with the scope GND lead attached to TP6.

Hi

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[ATTACH]57879[/ATTACH]

[ATTACH]57880[/ATTACH]

[ATTACH]57881[/ATTACH]

[ATTACH]57882[/ATTACH]

[ATTACH]57883[/ATTACH]

[ATTACH]57884[/ATTACH]

[ATTACH]57885[/ATTACH]

Thanks

[hamedtaran]

Hi,

I can't quite make out the ploarity of the diodes from your photo. Check that D4 and D5 are fitted correctly and also check capacitor polarity (C13 & C14).
I presume that C12 has been replaced with a 0R resistor as per the text.
Could you send a scope trace of U3 Pin 2 and then also one from TP5.

Kind regards

Hi

















Thanks

[hamedtaran]

One other thing, I see you have a power supply connector fitted.
Make sure that its voltage is 12V.

Hi, I checked all the parts you said, they are all correct, the supply voltage is 12V, tomorrow I will show you pin2 and tp5 on the oscilloscope.

[Olly]

One other thing, I see you have a power supply connector fitted.
Make sure that its voltage is 12V.

Hi,

I can't quite make out the ploarity of the diodes from your photo. Check that D4 and D5 are fitted correctly and also check capacitor polarity (C13 & C14).
I presume that C12 has been replaced with a 0R resistor as per the text.
Could you send a scope trace of U3 Pin 2 and then also one from TP5.

Kind regards