Beachmaster Files

[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

[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]

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]

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

[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]

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]

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

[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?

[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]

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

[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.

Hi
I test it again but:





About 5.5v pk-pk!

[Olly]

Hi,
It just doesn't make sense!
U1 has a 12V supply, but its output at Pin 4 (TP1) only appears to be swinging to 5.5V
The falling edge is also very slow, what kind of scope probe are you using and do you know its impedance?
Also, how confident are you in the accuracy of your scope's calibration? Does it show 12V when hooking up to your 12V power supply?

Did you manage to get a scope trace from U3, Pin 2 to confirm that it's running at 1 kHz and not periodically at a much higher frequency?

Apologies for all the questions but it's very important that each section is working as expected before moving on to the next.

Kind regards

Hi
I test it again but:

[ATTACH]57908[/ATTACH]

[ATTACH]57909[/ATTACH]

About 5.5v pk-pk!

[hamedtaran]

Hi,
It just doesn't make sense!
U1 has a 12V supply, but its output at Pin 4 (TP1) only appears to be swinging to 5.5V
The falling edge is also very slow, what kind of scope probe are you using and do you know its impedance?
Also, how confident are you in the accuracy of your scope's calibration? Does it show 12V when hooking up to your 12V power supply?

Did you manage to get a scope trace from U3, Pin 2 to confirm that it's running at 1 kHz and not periodically at a much higher frequency?

Apologies for all the questions but it's very important that each section is working as expected before moving on to the next.

Kind regards

you're welcome! I have to thank you for giving your design to people for free.
The frequency of U3 pin2 is 1KHz
My scope channels impedance is 1MΩ 25pF and I tested it with 1khz output on the device panel and there is no problem
I will replace the U1 IC again tomorrow, I feel that they are all fake, of course your opinion is important to me.
regards

[Qiaozhi]

I will replace the U1 IC again tomorrow, I feel that they are all fake,

Are the ICs all from the same supplier? If so, you may be replacing a fake with another fake.

[hamedtaran]

Are the ICs all from the same supplier? If so, you may be replacing a fake with another fake.

No! , I want to replace another IC with a different manufacturer