Hopefully we'll see a basic teardown soon.
An FPGA and R2R ladder DAC is rather common for the low cost Fgens.
I would consider 4 points for further tests:
1) Noise, e.g. from the SMPS or just from the DAC: So maybe use just a DC or low amplitude sine.
2) DAC linearity: This can usually be seen from a slow triangle / ramp.
3) Output amplifier slew rate: Many similar low cost generator run in to a slew rate limit with full amplitude and high frequency. So usually the maximum amplitude is reduces at the highers frequency.
4) There are 2 relays per output channel. So this could be an output attenuator. This has good sides, but might also limit the Offset range, when using low amplitudes.
The JDS6600 generator family has very similar functionality to the Feeltech FY3200 and the MHS-5200 generators. The JDS6600 even uses the exact same plastic case for the enclosure as the FY3200, MHS-5200. For a comparison of those other generators see:
https://www.eevblog.com/forum/testgear/feeltech-fy3224s-24mhz-2-channel-dds-aw-function-signal-generator/msg697718/#msg697718
From testing the FY3200 myself and reading on the MHS5200 they both are both limited in their output voltage range into 50 Ohm load without clipping or high distortion. So the first test I would suggest is:
1. Set 10 KHz sinewave with 20 Vpp/maximum amplitude on an oscilloscope with 1 Meg impedance. Then add the 50 Ohm termination and see if the output drops to 1/2 or if clipping or distortion starts happening.
On these type generators the output buffer is often slew rate limited which in turn means the output amplitude at higher frequencies is limited. So, the second test I recommend is:
2. Set a 10 Vpp 100 kHz sinewave on the output into oscilloscope with 50 Ohm termination. Then increase the frequency until maximum frequency to see if or at what frequency it starts distorting horribly.
On the FY3200 generator when you change the frequency the output waveform glitches. Ideally one would expect a change in frequency with a sine wave to step change the slope at the frequency change with no step in the actual voltage. Unfortunately the FY3200 has steps in the output because the phase as well as the frequency changes when you change the frequency. So, the third test I would love to see is:
3. Set the generator to 5 Vpp, 10 kHz sine wave and then step change the frequency to 20 kHz. Try to capture on the oscilloscope the moment when the frequency changes. If you have advanced triggering I set trigger width must be < 20 uSec and then set to capture once.
When you use two channels both outputting the same frequency sine wave with the phase 90 Deg apart it would be great to repeat test 3 to insure that both channels change frequency at the same time and with no glitches.
4. Repeat test 3 but with two sine wave channels outputting sine waves with 90 Deg relative phase.
The last requested test is really just a question of functionality. This generator can do frequency sweeps. But, can it do frequency sweeps while outputting two wave forms? Last requested test is:
5. Can you set the generator to output 2 sine waves with 90 Deg relative phase and then sweep the frequency such that both channels sweep in frequency and stay in phase lock?
In advance I thank you for any of the above tests that you could do and report back results.
The triangle waveform looks quite good - better than I remember from the MHS5200. However the scope setting is not that good to tell if the little nonlinearity is from the scope of from the generator. If would need a zoom in on details of the slope and maybe an even lower frequency. Usually a simple R2R DAC would show visible errors near the center or 1/4 of the range. There are 2 pots for each channel so these might be for adjusting at least that largest error.
The picture of the circuit is just to bad in resolution to read the chip numbers. The output amplifiers might be interesting. For the rest I would expect an AD603 or similar for the amplitude adjustment.
Are the USB and TTL I/Os isolated from the normal outputs ? It does not look like.
Here's kind of a youtube video about the signal generator:
https://www.youtube.com/watch?v=Fn76Yp-vATI#t=179.894071
There's no audio - not even a muzak track - but you get a closeup of the face of the unit being manipulated by what I suspect are Chinese hands.
Sure seems to do a lot.
>Charlie
Well, I guess we'll all find out together!
I've ordered it from AliExpress, and they'll be shipping via e-packet. So I should have it in about 3 weeks.
When it shows up, I'll share my experiences here.
Take care, all. Hope this works!
>Charlie
I ordered one of these about 10 days ago. According to Canada Post, they received it a few days ago, but haven't done anything with it.
However, the unit is on sale right now. I paid $136.86 CAD; the current price is $123.50 CAD, so maybe 10% off or so. Or a little more; I think their regular price was $140 CAD, but I got a few bucks off for being a nice guy. Heh, heh. Little do they know.
Anyway, mine hasn't arrived yet, so I can't endorse it. But for any one who was on the fence about ordering one, you can get it for 10% off right now.
Here's a link:
https://www.aliexpress.com/item/RD-JDS6600-Series-25MHZ-Digital-Control-Dual-channel-DDS-Function-Signal-Generator-frequency-meter-Arbitrary-sine/32811781657.html
It's also worth noting that they've introduced several new models; they now claim a new high frequency of 60Mhz on their most expensive model. This is for a sine wave. For square or triangle waves, they claim a maximum of 15Mhz across the board, for all their models.
Here's a link to a page listing all their models:
https://www.aliexpress.com/item/RD-JDS6600-Series-40MHZ-Digital-Control-Dual-channel-DDS-Function-Signal-Generator-frequency-meter-Arbitrary-sine/32814611834.html
I don't believe the 60Mhz claim. I'm sure there's something there, but I'll bet it winds up looking like a weak, wobbly triangle wave than a pure sine.
Anyway, for someone interested in checking it out... there it is.
>Charlie
I bet this device is nearly identical to the MHS-5200A (and higher versions), except that it has the much nicer screen (and perhaps better UI).
Hopefully we'll see a basic teardown soon.