FeelTech FY3224S 24MHz 2-Channel DDS AW Function Signal Generator

[Aldo22]

I did some further testing and have come to the conclusion that the problem is not due to the signal generator. With one of my oscilloscopes (Owon VDS1022i) I did a scope and probe calibration and now the Vpp I measure stays at 5Vpp through the entire frequency range up to 21MHz. 

However, you should not expect the amplitude to be held until the end.
The specified limit is usually -3dB. This means that if you have 0.707V from 1V at 24MHz, this still meets the specifications (or 3.6V from 5V)

I have run my script on the DSO2000 to show how this looks for the FY3224s.
That should be roughly correct (Right scale is irrelevant).

[nikbry]

Thanks Aldo,

I'm aware of the -3dB spec and was expecting the signal attenuation at the end of the bandwidth spectrum as you nicely show in the graph.
From what I could observe today, the attenuation for the sine wave became obvious at around 20-21 MHz, which roughly matches your data.

It's been an unfortunate sequence of events, that have led me to wrong conlusions all along. The very first checks of the generator I did the very first day with the Owon scope were fine, and I did not see the strange attenuation effect. A few days later I tried with the Zotek and saw strange things happening even in the KHz range. Checked again with the Owon and the signal looked attenuated too, so I started suspecting the generator. I believe the Owon must have lost calibration and the Zotek's probe is probably not reliable.
I'm glad the generator is working as it should, and the Owon when calibrated can be relied upon.
I have a work trip coming up and wont be able to "play" some more with the Feeltech for the next days, also need to look into the Zotek probe issue when I get back.

Cheers!

[BrokeEngineering]

Can someone give me the spacing for the PCB mounting holes on the OEM power supply? I am going to be making a PSU module for it and mine has not arrived yet

[Aldo22]

Can someone give me the spacing for the PCB mounting holes on the OEM power supply? I am going to be making a PSU module for it and mine has not arrived yet

As this is probably a general-purpose housing, there is some kind of hole pattern (Attached is a picture of the top, it is the same with the bottom).
I measure 6cm x 3.8cm (or 3.75cm) without guarantee.

[BrokeEngineering]

Thank you very much, is that hole to hole or to the end of the stubs? Looks like M3 size to me

[Aldo22]

Thank you very much, is that hole to hole or to the end of the stubs? Looks like M3 size to me

Hole to hole, of course.
M3: This has no thread, you simply choke a wood screw into it.

[BrokeEngineering]

I was thinking single 2 tap 12V 5W transformer that goes into the PCB into a full wave bridge rectifier (With proper caps ofc). The +12/-12 can be from the LDO's direct, and for the 5V I will make a high efficacy, low EMI buck down to around 6.5V for the 5V LDO. Will be quite cheap, probes BOM + single PCB around 10USD. I can filter the output of the BUCK for even less EMI, it wont be much added cost. I wonder if 5W will be enough.

[BrokeEngineering]

Thank you very much, is that hole to hole or to the end of the stubs? Looks like M3 size to me

Hole to hole, of course.
M3: This has no thread, you simply choke a wood screw into it.

I got M3 brass inserts, if the hole is M3 I can just melt some in the plastic so its a better fit/ M2 outer brass diamater needs to be between 2.8 and 3mm, for m4 I think it was around 4mm. Too much trouble to check the hole diameter please?

[Aldo22]

Don't you think you're exaggerating a bit?
The FY3200 is OK as it is for the price, but I wouldn't invest much time in “improving” it.

Too much trouble to check the hole diameter please?

I have taken a photo (top view) for you.
You know that the longer hole spacing is 600mm, so you can calculate everything else from the photo.
I think it's about 2.2mm (from the photo).
I can't measure it to the micrometer anyway.

[BrokeEngineering]

Don't you think you're exaggerating a bit?
The FY3200 is OK as it is for the price, but I wouldn't invest much time in “improving” it.

Too much trouble to check the hole diameter please?

I have taken a photo (top view) for you.
You know that the longer hole spacing is 600mm, so you can calculate everything else from the photo.
I think it's about 2.2mm (from the photo).
I can't measure it to the micrometer anyway.

I am not trying to improve it, I am trying to make it safe, I live in Eastern Europe and Earth is tied to neutral. So running a wire to the plug earth does nothing. Using a Linear AC transformer with LDO's is the only real way to get no leakage voltage on the BNC's

[BrokeEngineering]

Hmm I wonder if the + and -12V rails are accurate enough on this

[BrokeEngineering]

Welp I finished the PSU,

Here it is if anyone has anything to comment/improve before I order it:

Schematic


Pcb View


3D Top


3D Bottom

[tautech]

Welp I finished the PSU,

Here it is if anyone has anything to comment/improve before I order it:

Consider changing the layout in some areas to make the PCB more friendly to repair/rework hand soldering.

[BrokeEngineering]

Welp I finished the PSU,

Here it is if anyone has anything to comment/improve before I order it:

Consider changing the layout in some areas to make the PCB more friendly to repair/rework hand soldering.

I am using 0805, that's as friendly as I can make it haha. I normally use 0402.

Also just did BOM cost. Its 10 USD BOM

And PCB is 2 layer less then 100*100 so each PCB comes to around 1.2 USD.

So call the entire board less then 12USD.

Which part do you think its not easy to repair?

All parts are over-specced by a minimum a factor of 2 so there should be no need to repair lol.

[tautech]

Welp I finished the PSU,

Here it is if anyone has anything to comment/improve before I order it:

Consider changing the layout in some areas to make the PCB more friendly to repair/rework hand soldering.

Which part do you think its not easy to repair?

L3 = rotate
R2&3 = move

[BrokeEngineering]

Welp I finished the PSU,

Here it is if anyone has anything to comment/improve before I order it:

Consider changing the layout in some areas to make the PCB more friendly to repair/rework hand soldering.

Which part do you think its not easy to repair?

L3 = rotate
R2&3 = move

R2 and 3 are feedback resistors that need to be placed close as possible to feedback pin in order to have correct and stable feedback.

L3 is a filter inductor and moving it anywhere will increase ground loop of other components.

Thanks for the suggestion though. I will post the project files and gerbers so you can fork it and make the mods if you think its hard to solder

[tautech]

Welp I finished the PSU,

Here it is if anyone has anything to comment/improve before I order it:

Consider changing the layout in some areas to make the PCB more friendly to repair/rework hand soldering.

Which part do you think its not easy to repair?

L3 = rotate
R2&3 = move

R2 and 3 are feedback resistors that need to be placed close as possible to feedback pin in order to have correct and stable feedback.

L3 is a filter inductor and moving it anywhere will increase ground loop of other components.

Thanks for the suggestion though. I will post the project files and gerbers so you can fork it and make the mods if you think its hard to solder

Then consider moving the other components that restrict access to R2/3.

[BrokeEngineering]

Welp I finished the PSU,

Here it is if anyone has anything to comment/improve before I order it:

Consider changing the layout in some areas to make the PCB more friendly to repair/rework hand soldering.

Which part do you think its not easy to repair?

L3 = rotate
R2&3 = move

R2 and 3 are feedback resistors that need to be placed close as possible to feedback pin in order to have correct and stable feedback.

L3 is a filter inductor and moving it anywhere will increase ground loop of other components.

Thanks for the suggestion though. I will post the project files and gerbers so you can fork it and make the mods if you think its hard to solder

Then consider moving the other components that restrict access to R2/3.

Better?

[BrokeEngineering]

Made a version with Earth Connection between 2 Y capacitors after the CM Choke and a bit more safety aspects.

This is mainly for the people that already have an 3 pin earthed connector fitted.

There is a few more changes, its a bit bigger but based on the pic and some image measuring software it should still fit

[BrokeEngineering]

After a bunch more tweaking, I think its ready.

Fixed some routing, added a filter for the +12V rail and added an Parallel damped filters to all the LDO inputs where there was a bit of a peak at around 20khz due to the filter: