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JunTek PSG9080 Programmable Signal Generator (80 MHz - 300 MSa/s - 14-bit)

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torch:
Are those images of one of the channel outputs, or the strange output from the rear connector?

radiolistener:

--- Quote from: torch on April 21, 2021, 03:12:42 pm ---Are those images of one of the channel outputs, or the strange output from the rear connector?

--- End quote ---

pictures above are taken from the output channel. It was captured with a high speed/high dynamic range ADC to show signal purity details.

Here is rear pannel SYNC OUT connector output waves (yellow = CH1 output, magenta = rear panel SYNC OUT output).
First two pictures in normal mode square wave 20 MHz.
Pictures 3 is for a sweep mode from 10 to 30 MHz with 1 sec.

radiolistener:
Does anyone tried to write custom opensource bare metal firmware for PSG9080?

I can try, but I'm afraid of losing the original firmware :)
Any idea on how to save it?

May be there is a sense to identify where FPGA firmware is stored, backup it and then try to desolder original STM32, replace it with a new one for experiments. And in case of needs just solder original STM32 and restore FPGA firmware. Or maybe just use custom STM32 devkit board instead of original front panel?

Neper:
Just a short report from someone who's had his PSG9080 in the Joy-IT incarnation for a few weeks now...

I've been used to mostly surplus Eastern European lab gear of which ginormous quantities swamped the West German market after the fall of the Berlin wall. Now, that was 30 years ago and although all that stuff is still working fine (all of it is built like the proverbial battleship) I thought it might be time for something a little more modern, so I got hold of a PSG 9080 to replace a Soviet G4-102-A RF generator and an East German Praecitronic GF22 AF generator, both sinewave only.

The PSG9080 is giving me quite some brain gymnastics. I was used to my older AF generator that (a) is calibrated in Vrms and that (b) will output the voltage you set it to, no matter the load. You practically have to short-circuit it to make the output voltage drop below the set level. All my docs and instructions for the audio equipment that I work with ask for levels in Vrms. So, with the PSG9080 I find myself having to do a lot of mental acrobatics to convert forth and back between Vpp and Vrms and on top of that have to factor in the load resistance. Guess I'll keep my trusted old AF millivoltmeter connected in permanence to the PSG9080's output and set output levels watching the meter.

But the real prob I'm having with the PSG9080 is its noise, supposedly from the built-in SMPS. Not only on the output signal but also backwards via the mains into all the other equipment of my workshop. So, I replaced the original mains socket of the PSG9080 with one with a built-in mains filter. That got rid of some of the noise coming out at the mains side only to add more of it to the output signal. Running the PSG9080 from a linear (i.e. non-switching) 5 V power supply cured most of that. But I'm still somewhat shocked about how noisy that thing is. How are other people coping with this?

Oh, and I'm still looking for a way to get rid of those stupid ears without breaking the rest. They appear to be glued solidly to the housing. Not for cosmetic reasons, mind you, but to be able to fit in where I want it to go.

And I'll certainly be keeping my old friends from the East. :-)

Ralf

radiolistener:
yeah, it's a little bit noisy due to switching mode power supply, but I didn't note noise interference for mains. May be because I plug it into power strip which has mains filter. You can power off it with mains switch on the rear panel.

Does anybody tried to replace switching mode PSU with linear bipolar PSU? I think it's very possible, but there is needs to research power and DC/DC circuit schematics on the analog frontend board to find where is analog ±voltage needs to be applied and where is digital voltage. When you power it from external 5V PSU, it still use DC/DC switching mode converters to produce ±voltage for analog amplifiers. I think with linear PSU it will be much better.

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