| Products > Test Equipment |
| RD JDS6600 25MHz 2-Channel DDS AW Function Signal Generator |
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| jdev99:
Here is a pic of an earlier model, maybe same IC's. https://www.eevblog.com/forum/testgear/anybody-know-anything-about-this-signal-generator/ |
| bugi:
Interesting, quite big changes between those versions. Mine is somewhere between and the changes compared to the 1.0 were minor, I had to really look for them. Especially, on that v1.5, more heatsinks/components under heatsink... and can you spot any adjustable components (v1.0 has 2 per channel)? |
| Johnny B Good:
@ jdev99 Shit, isn't it, compared to the FY6600 and FY6800 models? :) I've just read the whole of this thread (didn't take very long) to try and track down a video, which I've not been able to relocate again, that showed the artefacts you'd expect to see on the 20vp-p sine and triangle waveforms from the use of an R2R network made up from 1 or even 0.1% tolerance smd resistors. As bad as the FY6600 might have seemed (unjustly in view of its very low price point compared to even a Siglent function generator), this JDS6600 is just a "Poor Man's" version of the FY6600 it's aping. For anyone still looking for something a lot better for similar money who is still unable to justify spending some 5 to 7 hundred dollars/euros/pounds, the FY6800 is the obvious contender. Feeltech responded to the criticism of the half mains live touch voltage issue that afflicts the unmodified FY6600 by replacing the IEC C8 figure of eight mains socket with an IEC C13/14 earthed mains socket on their improved version, the FY6800. Unfortunately, they did the absolute minimum they possibly could to link the Protective Earth pin to the ground rail by simply snipping one of the two ground returns at the main board end of the ribbon cable that links to the PSU board simply because that left them with a flylead just long enough to divert to the earth pin of the mains connector. Unfortunately, this compromised the connection between the PSU and the main board ground rails and worse, introduced a new problem that had never existed before with the FY6600, the issue of ground loop induced interference from galvanic and thermocouple induced dc offsets in the mains earth wiring and the more usual mains hum and random noise induction so familiar a problem to vintage audio enthusiasts. For anyone working at millivolt levels, this cure was worse than the disease. Luckily, the solution to this problem, without compromising the half live mains touch voltage fix, is simply to wire a 1 or 10 K resistor in series with the wire connected to the mains socket earth pin (the PSU is still the original class II double insulated PSU it's always been so no electrical safety issues involved in this case). Using a 10K resistor attenuates the 90 odd volts on a 220/240v supply to a mere half volt (50mV using a 1K resistor) and attenuates unwanted earth loop effects by some 60 to 80dB (40 to 60dB in the case of a 1K resistor). At least, in the case of the FY6800, Feeltech have already done the hard work for you by fitting an earthed mains socket, all you have to do, compared to owners of the FY6600 doing their own conversions from the C8 mains inlet socket to a C6 clover leaf or C13/14 socket, is add a 1 or 2.2 or 10K resistor in series with the earthing wire, preferably a replacement wire soldered onto a convenient ground point on the main board so you can rejoin that borrowed ground return to the ribbon cable plug to uncompromise the ground return circuit. Easy peasy! :) Thereafter, it's just a question of which of the many improvements that have been described in the 74 page long FY6600 thread that you'd like to apply to your recently acquired FY6800 (which is essentially just an enhanced version of the FY6600). However, do make sure there are no pre-existing faults before you embark on any such warranty voiding modifications. You can make up an external mains extension lead incorporating this resistor in the earth circuit by way of a temporary external modification and use a small desk fan to mitigate the high internal temperatures due to ventilation slots unsympathetic to the requirements of passive cooling (an effect actually made worse when it's propped up on its kick stand). If nothing else, adding a small 12v cooling fan driven off the 5v rail will have a dramatic effect on the internal temperatures for virtually no additional noise. I know it might seem a bit off topic to be "selling" the FY6800 like this but, quite frankly, the DJS6600 is such a pile of excrement, I suspect, given the dearth of posts in this thread, that most of its contributors may have already sold or even given away their JDS6600s in favour of something a little better, perhaps even an FY6600, or more recently, an FY6800 (if not a Siglent or better). I was just posting to set the record straight and offer any cash strapped hold outs a better and more cost effective alternative to consider. HTH & HAND :) JBG |
| sv2hqx:
hi to all iam loocking for a dds like this but have a question its possible to adjust frequency on real time via knob like analog generators or need to set every time new frequency ? thanks |
| Johnny B Good:
--- Quote from: sv2hqx on April 23, 2019, 09:31:16 pm ---hi to all iam loocking for a dds like this but have a question its possible to adjust frequency on real time via knob like analog generators or need to set every time new frequency ? thanks --- End quote --- They tune in real time. However, you need to pick which digit you want to base your incremental steps on, 1Hz or 10Hz and so on. If you have 10MHz dialled in and you want to go up and down in 1Hz steps, you'll have to select the 1Hz digit before rotating the tuning knob. if you keep rotating it clockwise the units digit will roll back to zero and generate a carry into the tens digit just like you see on a vehicle's trip odometer, except you can go down as well as up in frequency in whatever step size you care to select (tens of MHz right down to microHertz). If you want to dial in a spot frequency such as 2182KHz, it's probably easier to select the MHz step, wind it backwards to zero all the digits then dial it to 2MHz, drop to the 100KHz digit and dial in 200KHz so you're tuned to 2.2MHz, then select the 1KHz digit and wind it back down to till you get your target frequency of 2182KHz showing on the frequency read out. You could simply step to each digit and set them individually but this usually takes longer to input the frequency than a bit of clever manipulation to reach your target as per the example above. HTH & HAND :) JBG |
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