Author Topic: Re: FeelElec New Arrival FY-6900 Signal Generator  (Read 59284 times)

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Offline davebb

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #425 on: October 29, 2020, 10:36:56 pm »
OK, so I have a question however I cannot seem to find an answer using the search engine....
So, I made a whole host of mods to the FY6900, but essentially apart from the PSU upgrade, ground, fan etc etc all described in this thread, the most important one was upgrading the reference crystal - I replaced it with a VC-TCXO IQD LFTVXO009900BULK with a 0.9ppm accuracy, and indeed the DDS works like a charm, as there’s no more drift. However, I noticed that there’s an offset, that at 10 MHz is about +170 hz, is there any way to calibrate the FY6900 and remove it? It is vary stable and does not drift (too much).
However, I do not yet have a GPSDO, that’s next on my list, so I am relying on the fact that both my counter (a Fluke PM6666) and my DSO 1202x-e roughly agree on this offset.

Eta pictures

 The short answer is "Yes, there is!" (or rather, there certainly is for the FY6600). However, if you use that hidden menu option, your 'magic'  (free of the 4ns jitter) frequencies at 50, 25, 12.5 MHz and so on, will no longer be jitter free. The best way to address this is to calibrate your VCTCXO to a reference traceable to an atomic standard - a GPSDO (or a RFS that's been recently calibrated within the past year or so :) against a traceable frequency standard (eg a GPSDO  >:D).

 I checked out that VCTCXO's datasheet which suggests there's every chance that your Fluke counter is overdue its next re-calibration (don't place too much trust in your DSO's frequency read out) since the tuning range is specified as being a minimum of +/-5ppm over a 2v tuning range centred on 1.85v (+/-50Hz for a 10MHz centre frequency). The actual tuning range could be as much as double that quoted minimum figure but more likely to be around the +/-7ppm mark.

 Assuming the EFC pin is at the 1.85V mark either by design or from a connection to an external trimpot across the 3.3v Vcc rail and ground, preset to its mid point for the time being until you can gain access to a trustworthy frequency reference by which to calibrate your VCTCXO as exactly as you can get it tuned to its specified 10MHz, it may already be within +/-1ppm of 10MHz to start with.

 IOW, there's every chance that it's closer to 10MHz than your DSO and frequency counter are implying. Wait until you have access to a GPSDO or RFS before attempting to recalibrate it, whether you use the software option or do it the right way with a trimpot wired to the EFC pin of that VCTCXO.  :)

John
Hi John
I am just changing my 10mhz ref for the VC-TCXO IQD LFTVXO009900,
what value pot would you suggest to use to do the adjustment,
 Thanks Dave 
 

Offline davebb

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #426 on: October 29, 2020, 11:03:28 pm »
Hi I have just checked and the adjust track and the 3.3v are joined so that is why the frq is high using this tcxo I will have to cut the track ,
Thanks Dave
 

Offline Labrat101

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #427 on: October 30, 2020, 10:19:24 am »
Hi I have just checked and the adjust track and the 3.3v are joined so that is why the frq is high using this tcxo I will have to cut the track ,
Thanks Dave
Hi Dave
there is a 33 \$\Omega\$ from the out on the pcb near the the Fake cyclone . this maybe incorrect for your tcxo
 On one of my previous attempts to get this chip to respond correctly due bad track design I connected directly
to the cyclone pin direct . (Not recommended as the pins & tracks are pore. )
On my attempt I mounted a new resistor vertically and connected that to a short piece of RG3** then to a
TCXO . which was later scraped and used OCXO  20Mhz with a PLL & divider and then to the cyclone .
Due to the fact that the cyclone chip is NOT original the clock correction circuit malfunctions .
 

My FY6*** was scrapped as a AWG  and repurposed as a 40Hz med strobe .

You Might be wise to return the shity tcxo back as it does stay just within the scope rest of the
Bad design layout .   which they tried to correct with a software patch .. Magic Jitter  :-DD
Sorry . I hope I have not up set you .
« Last Edit: October 30, 2020, 10:55:07 am by Labrat101 »
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Offline pizzigri

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #428 on: October 30, 2020, 10:32:59 am »
Yes. As a matter of fact, I have learned all I could from this thing. I spent now about 140 Euro, all included - FY6900 from Amazon, parts, TCXO, time. It works, even if in a crappy way. The FY did improve it a lot, thanks to all the EEVBlog members that helped me!
But, it's limitations are unavoidable, since the flawed Cyclone chip and convolved design.
That is the reason I just calibrated it via SW, and not built the breakout board I intended to... I dont want to spend any more time on it.

I can use it until I score a REAL AWG, but I am only a hobbyist.
 
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Offline davebb

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #429 on: October 30, 2020, 09:36:40 pm »
Hi Thanks for all of the info,
I have fitted the new TCXO and did cut the track between pins 1 and 4 ,and used a r/divider using a 47kohm coming from the 3.3v to a 500K ohm pot to the pin 1 voltage control pin of the tcxo, and now I can set it to 10.000000 and it is very stable without software frq offset adjustment (I just need to get a 10 turn pot)
Thanks Dave 2E0DMB
« Last Edit: October 30, 2020, 11:55:51 pm by davebb »
 

Offline davebb

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #430 on: October 31, 2020, 02:20:42 am »
OK, so I have a question however I cannot seem to find an answer using the search engine....
So, I made a whole host of mods to the FY6900, but essentially apart from the PSU upgrade, ground, fan etc etc all described in this thread, the most important one was upgrading the reference crystal - I replaced it with a VC-TCXO IQD LFTVXO009900BULK with a 0.9ppm accuracy, and indeed the DDS works like a charm, as there’s no more drift. However, I noticed that there’s an offset, that at 10 MHz is about +170 hz, is there any way to calibrate the FY6900 and remove it? It is vary stable and does not drift (too much).
However, I do not yet have a GPSDO, that’s next on my list, so I am relying on the fact that both my counter (a Fluke PM6666) and my DSO 1202x-e roughly agree on this offset.

Eta pictures

 The short answer is "Yes, there is!" (or rather, there certainly is for the FY6600). However, if you use that hidden menu option, your 'magic'  (free of the 4ns jitter) frequencies at 50, 25, 12.5 MHz and so on, will no longer be jitter free. The best way to address this is to calibrate your VCTCXO to a reference traceable to an atomic standard - a GPSDO (or a RFS that's been recently calibrated within the past year or so :) against a traceable frequency standard (eg a GPSDO  >:D).

 I checked out that VCTCXO's datasheet which suggests there's every chance that your Fluke counter is overdue its next re-calibration (don't place too much trust in your DSO's frequency read out) since the tuning range is specified as being a minimum of +/-5ppm over a 2v tuning range centred on 1.85v (+/-50Hz for a 10MHz centre frequency). The actual tuning range could be as much as double that quoted minimum figure but more likely to be around the +/-7ppm mark.

 Assuming the EFC pin is at the 1.85V mark either by design or from a connection to an external trimpot across the 3.3v Vcc rail and ground, preset to its mid point for the time being until you can gain access to a trustworthy frequency reference by which to calibrate your VCTCXO as exactly as you can get it tuned to its specified 10MHz, it may already be within +/-1ppm of 10MHz to start with.

 IOW, there's every chance that it's closer to 10MHz than your DSO and frequency counter are implying. Wait until you have access to a GPSDO or RFS before attempting to recalibrate it, whether you use the software option or do it the right way with a trimpot wired to the EFC pin of that VCTCXO.  :)

John
Hi The offset is due to the EFC/control pin 1 having 3.3v on it , you need to cut the track and supply with the correct voltage then it will set to the correct frq with no software offset
Dave
 

Offline Johnny B Good

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #431 on: October 31, 2020, 02:38:12 am »
Hi Thanks for all of the info,
I have fitted the new TCXO and did cut the track between pins 1 and 4 ,and used a r/divider using a 47kohm coming from the 3.3v to a 500ohm pot to the pin 1 voltage control pin of the tcxo, and now I can set it to 10.000000 and it is very stable without software frq offset adjustment (I just need to get a 10 turn pot)
Thanks Dave 2E0DMB

 IMHO, that's the only sensible method to calibrating the AWG. The secret software calibration option is for the "Rubes" who wouldn't know one end of a soldering iron from the other. >:D Not only will you know exactly how you stand with regard to those "Magical Frequencies" in these Feeltech AWG models, you've also left yourself a simple way to lock that TCXO to an external 10MHz frequency reference using a PLL circuit that allows a glitch free way to make an automatic changeover from internal to external clock sources and back again with no need for a gross mechanical switch alongside of the external reference input socket. >:D

 That circuit will work just fine in your case but most electrically tunable OC and TC XOs will typically arrange for the EFC to float at the mid voltage point with an input impedance somewhere between 68 and 100K which might require a control voltage lower than the mid point, hence the more usual potential divider arrangement of trimpot flanked with padding resistors at each end to limit the tuning range to a more useful 10 to 20% of the full EFC tuning range.

 A typical setup where the the EFC pin has to be pulled lower than its mid point might for example, consist of a 500 ohm multi-turn trimpot connected to gnd via a 2.2K with a 2.7K resistor connecting the other end to the Vcc rail with the wiper contact connected to the Hi-Z EFC pin which will normally be shunted to gnd with a 100 to 10000nF ceramic de-coupling cap to block any HF interference that might be floating around.

 The padding resistors ideally need to be selected so as to get the mid point setting of the trimpot as close to the currently required tuning voltage as possible to preset the XO to its designated frequency. A good idea would be to provide easy access to allow additional shunt resistors to be soldered across either of these padding resistors to allow compensation for ageing of the XO over the next few years of its operational life.

 A major issue with using trimpots as potentiometers in this way is that of variable resistance between the sliding contact and the track. The higher the impedance of the EFC pin, the lower this small but still significant voltage error you will see resulting from such contact resistance variation. The ultimate in Hi-Z 'zero' loading to reduce this effect to 'zero' is to use a suitable opamp as a simple voltage follower buffer (a cmos RRO opamp with low tempco DC offset being an obvious choice - the DC offset isn't a major issue as long as the tempco is nice and low) to drive the actual EFC pin.

 A 500 ohm trimpot flanked with 2.2ishK padding resistors will typically provide a low enough variation in slider contact resistance induced voltage error when connected to a 70 to 100K impedance EFC as to make the use of a Hi-Z input buffer amp of rather marginal benefit, especially in the case of a TCXO where the classic two resistor and a trimpot (with decoupling cap) arrangement is a more than ample solution.

 A potentiometer arrangement as above (with or without padding resistors) is the best choice of controlling or trimming a control voltage input when the input is a relatively high impedance since it minimises voltage variations induced by slider contact resistance variations, However, there are situations where using a trimpot simply as a variable resistor can be just as effective.

 I have a fine example of this situation in my MK II GPSDO where I've taken advantage of the ready made temperature controlled voltage reference built into the CQE 10MHz VCOCXO (as used in Symmetricom kit) that I'm using to create a stable set of DC offset voltages in 1 volt steps over the 0 to 4 volt range to allow me to monitor the EFC voltage in increments of 0.1mV using just a cheap Mestek "9999 counts" DMM that would otherwise only measure in 1mV steps when measuring the full 2.285V EFC directly.

 Currently, I'm measuring the difference between the 2v DC offset and the 2.2855v EFC voltage - I know the DC offset is a fixed unvarying two volts and the meter has auto-ranged to its 1000mV scale with a difference reading of 285.5mV which is all I really need to see. The accuracy of the two volt DC offset voltage is of secondary importance to that of its stability which is guaranteed in this case by a temperature stabilised voltage reference source second only to an expensive lab reference, courtesy of the one supplied by the OCXO's Vref pin.

 The Vref on these CQE OCXOs (I'd bagged myself a set of seven just over a year ago for just a fiver each) is a nominal 5v (typically around a 100mV or so higher) with an output impedance of just one ohm meaning that the string of five matched 1K resistors plus a 120 ohm padding resistor with its fixed 1mA drain causes a fixed 1mV drop on the original unloaded 5.128v Vref of my chosen OCXO example. This results by design in just over a +1mV error across each of the lowest three best matched resistors.

 I mention the phrase "by design" because I knew I'd have to have some way to trim this source of 1 volt DC offsets as close to exactly 1000mV each as I could achieve. With a 10Mohm input DMM measuring a voltage difference less than 1 volt, the worst case 1.2K impedance at each of these 1v taps on the fixed potentiometer could  only induce a vanishingly small error into my mV readings, leaving me only the small matter of how best to trim the the voltage at the top end of this potentiometer string to exactly 5,000mV (give or take a mV or two to trim out the slighlty less well matched 1K resistors at the top end of this string should a change of OCXO require a 3 or 4 volt DC offset).

 I'd chosen a 120 ohm padding resistor so that I'd only need to increase its ~120mV drop by just another 7mV using a variable resistor to draw the required additional 58uA or so. This corresponds to a shunt resistance value around the 86K mark across the 5K resistor string so I used a 50K pot with a 56 or 68 K resistor - the circuit was such a no-brainer, I didn't bother taking notes ::). In this case, the very low 58uA current through the wiper contact in what was virtually a constant current circuit seemed unlikely to cause any voltage stability issues (and subsequent voltage checks bear this out).

 I had suitable 5v cmos rro opamps to hand and a Vcc of 5.31v to allow the use of one to buffer a well padded out trimpot to completely eliminate the slider contact resistance issue but this seemed a rather unnecessary complication in this case where a 0.5% variation due to slider contact resistance would only result in a ~0.03% change in my DC offset voltages at worst (around a third of a millivolt per volt's worth of DC offset).

 Although the advice to use trimpots as lightly loaded potentiometers in preference to using them as variable resistors is generally sound, there are situations where using them this way can offer a simpler and more optimal solution with my own example above being a case in point.

 Your case, rather fortuitously, is not too far from the 'virtual constant current' situation of the above and, as ageing of the XO tends to reduce its resonant frequency, the EFC voltage adjustment trend with age is a rising one with virtually all EFC XOs, you can simply add a shunt resistor (typically half a M ohm or so in this case), if needed, across your chosen 47K padding resistor to compensate any ageing drift that might eventually take it beyond the trimpot's adjustment range over the next few years.

John
« Last Edit: October 31, 2020, 11:37:31 pm by Johnny B Good »
 
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Offline davebb

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #432 on: October 31, 2020, 04:36:58 am »
Hi John
This is brilliant info Thanks
I have ordered a multi turn trim pot to replace the 40 year old carbon pot I bogged in for testing , this new tcxo is very stable with this old pot ,
I mainly use the awg on the sine wave setting,
Thanks Dave 2E0DMB
 

Offline Trader

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #433 on: October 31, 2020, 06:50:17 am »
 

Offline pizzigri

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #434 on: November 01, 2020, 10:51:13 pm »
IMHO, that's the only sensible method to calibrating the AWG. The secret software calibration option is for the "Rubes" who wouldn't know one end of a soldering iron from the other. >:D

Ouch that hurt.... although I cannot deny being a "Rube" as you say since I am not a EE but just a newb hobbyist playing around. Audio, HAM Radio and electronics always fascinated me so if I have a little time to spare I study and try to learn. My specialization is product and industrial design, so I'm a bit more at home with SolidWorks than LTSPice - although my daytime job is in journalism.

However, the reason I'm demoralized is the fact that the FY6900 allegedly uses a counterfeit Cyclone IV chip. I believe you cant squeeze blood from a turnip, and there's a law of diminishing returns, over a certain point IMHO it makes little sense to try to improve the FY, the effort may not be worth it. This said, I also believe that I fu*ed up at the very beginning, after improving the PSU (thank you for your great help with that, BTW!), when I replaced the TXCO.... as has been said in this thread, that may have already broken the Magic Pulse s*it from FY and reintroduced the jitter. It did help immensely with the stability however.
So I'm not really sure if it makes sense forme to break open again the bugger and build all the described circuitry, unless there's a way to reinstate the sw patch for the 4ns jitter?
IE, "updating" the firmware from the PC software?
And, I got a used ooold HP33120A to play with, so I can compare and see how it goes. It was a decent deal on ebay, for much less that 200$ and I couldnt resist - if nothing else, to play with it.
 

Offline Labrat101

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #435 on: November 01, 2020, 11:42:04 pm »
IMHO, that's the only sensible method to calibrating the AWG. The secret software calibration option is for the "Rubes" who wouldn't know one end of a soldering iron from the other. >:D

Ouch that hurt.... although I cannot deny being a "Rube" as you say since I am not a EE but just a newb hobbyist playing around. Audio, HAM Radio and electronics always fascinated me so if I have a little time to spare I study and try to learn. My specialization is product and industrial design, so I'm a bit more at home with SolidWorks than LTSPice - although my daytime job is in journalism.

However, the reason I'm demoralized is the fact that the FY6900 allegedly uses a counterfeit Cyclone IV chip. I believe you cant squeeze blood from a turnip, and there's a law of diminishing returns, over a certain point IMHO it makes little sense to try to improve the FY, the effort may not be worth it. This said, I also believe that I fu*ed up at the very beginning, after improving the PSU (thank you for your great help with that, BTW!), when I replaced the TXCO.... as has been said in this thread, that may have already broken the Magic Pulse s*it from FY and reintroduced the jitter. It did help immensely with the stability however.
So I'm not really sure if it makes sense forme to break open again the bugger and build all the described circuitry, unless there's a way to reinstate the sw patch for the 4ns jitter?
IE, "updating" the firmware from the PC software?
And, I got a used ooold HP33120A to play with, so I can compare and see how it goes. It was a decent deal on ebay, for much less that 200$ and I couldnt resist - if nothing else, to play with it.
just out of interest set the FY to 11Mhz square wave . with a 200mhz probe @ x10
 so you have about 3 cycles showing .
Set the persistent at 1ns do you get a double vertical on the rise and double fall .
 If yes zoom in and you will see its a complete over lay ie the first wave is lagging about 4ns
 behind the first ..   just curious .

HP33120A  Nice find
« Last Edit: November 01, 2020, 11:57:50 pm by Labrat101 »
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Offline pizzigri

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #436 on: November 02, 2020, 08:13:36 am »
This is what  I get....
did it this morning before goi g to work so I did not do any fancy stuff
 

Offline Labrat101

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #437 on: November 02, 2020, 09:51:02 am »
Ok Thanks ..
I just wanted to know if they had made any hardware changes ..
 They haven't . This is due to the Cyclone chip timing comparator . it should take
 if I remember correctly about  5 counts of clock cycles and ignore the errors.
  this was a hardwired in feature . To reduce jitter to less than 1ns .

  It seems that there early version ie Fy66  was made with better quality parts.
 and there profit markup was too low as the cyclone cost About $35 on its own .
 PCB & etc.etc screen panel ,Box . all for around $80 . is a close cut.

 Thanks it was just curiosity
 
 I move over to the UTG962 really very happy with it . I can not get it to reproduce a jitter
 or any other weird stuff that the FY6*** do .
 
 The Only mode required for the UTG962 is to dust it off once in awhile  :)
 
 
« Last Edit: November 02, 2020, 09:53:13 am by Labrat101 »
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Offline battlecoder

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #438 on: November 02, 2020, 11:55:20 pm »
I was actually playing with my FY-6600 yesterday and ran into the jitter issue.
So here's my 4 cents of jitter evidence:
[attachimg=1]

I really like all the features they managed to package in the device, especially considering its price. But it's exactly this kind of stuff what makes me want to get a better frequency generator. Inconsistencies and glitches can have you hunting problems that are not really in your circuit, but in your gear.
 
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Offline Labrat101

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #439 on: November 03, 2020, 08:26:45 am »
@ battlecoder

This might interest you this link.
Its a comparison of several AWG and the UTG962 & Tek & Rigol etc .
Its Long and full.

https://www.element14.com/community/groups/roadtest/blog/2020/05/17/tektronix-afg31052-verification-tests
« Last Edit: November 03, 2020, 09:19:32 am by Labrat101 »
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Offline battlecoder

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #440 on: November 03, 2020, 04:28:10 pm »
@ battlecoder

This might interest you this link.
Its a comparison of several AWG and the UTG962 & Tek & Rigol etc .
Its Long and full.

https://www.element14.com/community/groups/roadtest/blog/2020/05/17/tektronix-afg31052-verification-tests
That's a pretty thorough comparison. Would have loved to see how the DG800 compared to the models tested, but this is already pretty good information to pick a device, thanks!
 

Offline Johnny B Good

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #441 on: November 03, 2020, 05:36:01 pm »
@battlecoder

 That 4ns jitter in the FY66/6800 AWGs is "by design". However, if you just need a fast pulse with low jitter for a stable triggering source, take a look at the Sinc pulse.

 Just like the sine waveform, it's free of this 4ns DAC clock jitter, leaving just the matter of some 300ps Pk-Pk of noise jitter (just over one third of what you see in the SDG1032X AWG ::)). This is good up to 12MHz (the Nyquist limit for this flavour of Sinc Pulse, 10 squiggles per cycle, being at 12.5MHz).

 You don't start seeing the 4ns clock jitter until you go beyond the Nyquist limit. At 20MHz, the 4ns jitter becomes very evident again but if you're after a low jitter pulse waveform around the 10MHz mark, this is your best choice. Not only do you get a low jitter pulse, you also get a very distinctive narrow pulse shape that distinguishes it from the more anonymous sine and square wave shapes making it easy to keep track of the direction of drift at mHz frequency offsets when you might only be glancing at the 'scope trace just once every few minutes. :)

 Of course, you'd only likely to be running such frequency comparisons after upgrading the internal clock reference to a 10MHz OCXO with a 3N502 clock multiplier to recreate the 50MHz clock feed to the FPGA chip. :) Incidentally, it's worth keeping in mind that this 4ns DAC clock jitter issue also afflicts massively more expensive DDS based AWGs - it's only the square and pulse waves that get the special low jitter treatment in Siglent's AWG models. Any awfms with a sharp transition suffer this DAC clock jitter effect (6.7ns in the case of the 150MHz clocked DAC in the SDG1000X series and 3.3ns in the case of the 300MHz clocked DAC used in the SDG2000X series to generate awfms),

 It came as rather a disappointment to discover that the SDG2000X's Sinc pulse with its 20 squiggles and 300MHz clock whilst looking perfect at its 10MHz 'magic frequency' (exactly 30 clock cycles' worth) turned to shit with just a tiny 1mHz offset. The Nyquist limit in this case being a mere 7.5MHz (and half that for the SDG1000X).

 This had only been of importance to me with the FY6600 due to it's excellent low jitter performance as a 10MHz reference signal for testing my DIY GPSDO projects against. It wasn't until rf-loop had given an excellent explanation for this apparent shortcoming of an AWG costing seven times what I'd paid for the FY6600 two years ago and the reliance on the Sinc pulse as an only source of low jitter timing pulse being rendered redundant now that I had a generator that could supply low jitter square and variable duty cycle pulse waveforms up to 25MHz for this task that stopped me from returning it as "Unfit for Purpose".

 Now you might think that's the end of the disappointments in the SDG versus the FY AWG comparisons but sadly no. It might surprise you to know that, aside from the crappy dimple operated front panel switches of the FY6600 model range, the FY series has a much more user friendly UI than that of the SDGs which can best be described as "User Hostile".

 I know, I know, who would have imagined that, aside from the obvious shortcomings of the FY AWGs, it had so many good features as to outclass the best efforts of Siglent (and naturally, Rigol) and much of the A brand offerings? Who knew? I didn't until I actually got my hands on first an SDG1032X, swiftly followed by the SDG2042X (now hacked to the 120MHz - sine wave only- specification) in my possession.

 Obviously, with the SDG2000X series, you get a 16 bit 1.2GSa/s generator (but only 300MSA/s for DDS generated awfms - not a lot better than the FY's 250MSa/s specification) along with a high quality all metal cased construction containing high quality components and a larger feature set (unfortunately cursed by what can only be described as a "Shit UI").

 You might wonder then, why I didn't reject this outright as "Unfit for Purpose" but the plain truth is that all of these shortcomings could be sorted by a 4 years long overdue (but quite do-able) firmware update to totally revamp the UI and fix all the other irritations such as polluting a perfectly good lab reference distribution with its rather lacklustre internal 10MHz clock reference whenever it's switched from the external clock back to the internal clock reference.

 Simply put, there's a missing user option to disable the "export the internal clock" part of this switching between internal and external clock references. The option to export its internal clock onto a distribution cable can still be useful when no existing lab reference is available to synchronise other test and measuring kit, hence my suggestion to allow the user to configure it to suit their circumstances rather than remove it completely from the clock source choice option.

 I had hoped I could retire my much modified FY6600 when I'd acquired the SDG2000X but this hasn't proved to be the case, admittedly largely due to all my modifications to improve its functionality. It still remains a very useful item of test gear in spite of the addition of the generally better Siglent AWG to my stock of T&M kit.

 The main annoyance I have with the FY6600's UI is that of the stiff front panel dimple operated pcb mounted switches of rather inconsistent quality making operation of some functions a rather hit and miss affair. I'd speculatively invested some £2.73 in a bag of 100 such switches from Bang Good almost a year ago in the hope I could use them to replace the existing switches and improve the situation but I still haven't gotten around to dismantling the front panel again to verify whether these switches can be used to replace the originals. Assuming the switches do prove to be suitable, there's still no guarantee of gaining a worthwhile improvement.

 Ideally, I'd upgrade to the rubber key operated panel switch arrangement as used on the later models but there's no cost effective way to achieve this, hence this rather more pragmatic approach to the problem. A significant factor could simply be due to the plastic dimples themselves which would limit the effectiveness of a switch upgrade. However, I'll be able to get a feel for this (literally!) once I've pulled the front panel apart. Basically, it's a journey into the unknown but, considering the potential payoff, it's a journey I think will be worth embarking upon... when I do eventually get a round tuit. :)

John
 
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Offline battlecoder

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #442 on: November 03, 2020, 07:03:37 pm »
Of course, you'd only likely to be running such frequency comparisons after upgrading the internal clock reference to a 10MHz OCXO with a 3N502 clock multiplier to recreate the 50MHz clock feed to the FPGA chip. :) Incidentally, it's worth keeping in mind that this 4ns DAC clock jitter issue also afflicts massively more expensive DDS based AWGs - it's only the square and pulse waves that get the special low jitter treatment in Siglent's AWG models. Any awfms with a sharp transition suffer this DAC clock jitter effect (6.7ns in the case of the 150MHz clocked DAC in the SDG1000X series and 3.3ns in the case of the 300MHz clocked DAC used in the SDG2000X series to generate awfms),

Thanks for the detailed reply, John. As I'm a complete ignorant regarding the specifics of these devices, I have two questions for you, if you don't mind:
1.- In your opinion, s it worth upgrading from the FY-6600 to the FY-6900?
2.- If I were to replace the 50Mhz clock inside my FY-6600, what would work best: A 50Mhz OCXO? A 10Mhz OCXO with a clock multiplier? (Even more: Is it possible to use an external 10Mhz signal instead?)

Thanks
 

Offline Johnny B Good

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #443 on: November 04, 2020, 02:22:51 pm »
Of course, you'd only likely to be running such frequency comparisons after upgrading the internal clock reference to a 10MHz OCXO with a 3N502 clock multiplier to recreate the 50MHz clock feed to the FPGA chip. :) Incidentally, it's worth keeping in mind that this 4ns DAC clock jitter issue also afflicts massively more expensive DDS based AWGs - it's only the square and pulse waves that get the special low jitter treatment in Siglent's AWG models. Any awfms with a sharp transition suffer this DAC clock jitter effect (6.7ns in the case of the 150MHz clocked DAC in the SDG1000X series and 3.3ns in the case of the 300MHz clocked DAC used in the SDG2000X series to generate awfms),

Thanks for the detailed reply, John. As I'm a complete ignorant regarding the specifics of these devices, I have two questions for you, if you don't mind:
1.- In your opinion, s it worth upgrading from the FY-6600 to the FY-6900?
2.- If I were to replace the 50Mhz clock inside my FY-6600, what would work best: A 50Mhz OCXO? A 10Mhz OCXO with a clock multiplier? (Even more: Is it possible to use an external 10Mhz signal instead?)

Thanks

 Regarding question 1, I can't really say whether the FY6900 is a safe alternative in view of Labrat101's experience with the cheap FPGA clone in his FY6800 which may possibly have been more to do with his example simply suffering from a faulty clone chip rather than just that it was a cheap cloned FPGA.

 It occurs to me that Feeltech may well have been using cloned FPGAs from day one with the FY6600 rather than switching production over to a cheaper cloned chip option for the later FY68/6900 models. Until Labrat101 had discovered the use of a cloned FPGA in his FY6800, no one, as far as I know, had even questioned whether the FPGA was the real deal or not. Until someone examines the FPGA as closely as Labrat101 did in their FY6600 or FY6900 AWGs, we can only speculate over how far back the use of this 'cheap cloned FPGA' issue extends.

 Since nobody else has reported the issues Labrat101 had suffered and his discovery that the FY6800 had been cursed by the presence of a cloned FPGA (probably simply because nobody else had taken the trouble to "Look this particular Gift Horse so closely in its mouth"), it's quite possible that the FY6900 may prove to be no less reliable than its predecessors if Labrat101's findings had been simply the result of a faulty cloned FPGA.

 In other words, if we assume that Labrat101 had simply suffered the misfortune of getting a unit that happened to have a faulty cloned FPGA rather than the FPGA being a low quality clone, the FY6900 would seem to be the obvious choice to go for, since not only is it enhanced by the "Magic Pulse" feature to eliminate the 4ns clock jitter issue, it also provides an easy way to install a cooling fan and, like the 6800 models, improves on the front panel buttons used by the 6600.

 However, you're talking about upgrading from the 6600 to the 6900 rather than making a first time choice over which of these two models to purchase. Unless you're expecting to be able to sell your 6600 to partially finance the 6900 acquisition, you'd be doubling up your total expenditure for just a relatively modest upgrade.

 Since you already possess an FY6600, which I presume is working as good as its design limitations allow, it may be better to stick with it on the basis of "Better the Devil You Know" and put up with the stiff dimple operated front panel switches until you can afford to buy a significantly better AWG like an SDG1000X or SDG2000X for example.

 Regarding question 2, I think a 10MHz OCXO with multiplier chip would be a better alternative to a 50MHz OCXO unless you discover a really cheap source of 50MHz OCXOs on account of its non-standard frequency. The 10MHz OCXO is the safer bet despite the additional cost of a clock multiplier chip, since it has a much wider range of applications should the FY6600 let out all of its magic smoke, leaving you with a spare OCXO to add to your collection of salvaged components. Also of course, it can be used as a direct replacement for the 10MHz XO chip used in the FY6900 model.

 Regarding the addition of an external 10MHz reference socket, either frequency option (10 or 50MHz, including a 20MHz OCXO option) is amenable to being locked to such an external 10MHz clock source using a simple PLL circuit which will allow an automatic glitchless change-over between the internal and external reference clock options.

 Using a PLL (or in my case, injection locking) allows an automatic glitchless change-over between internal and external clock sources without any need for a separate mechanical change-over switch such as the one suggested by forum member "Arthur Dent" some two years ago in the FY6600 topic thread.

 When I designed my own injection locking circuit, I'd been so concerned about eliminating the risk of upsetting the FPGA from interruptions to its 50MHz clock feed via a simple change-over switch that I became rather fixated on the frequency injection locking technique, overlooking the more obvious PLL option (an OCXO with an EFC pin fed from a calibration trimpot that I'd forgotten could just as easily be driven by a PLL :palm:).

John
 
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Offline Labrat101

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #444 on: November 05, 2020, 07:07:51 pm »
Hi Johnny . And All ..
Guess what someone just loaded up a photo of their new FY6900 .
 They Have renamed the cyclone to it's  Correct Name .
  Sorry if any one is  |O    But it looks like the Cat is out of the bag .
    The True colours just shine though .

https://www.eevblog.com/forum/testgear/feeltech-fy6600-60mhz-2-ch-vco-function-arbitrary-waveform-signal-generator/msg3312048/#msg3312048

I just want to cut the lid off this puppy  ..
« Last Edit: November 05, 2020, 07:28:54 pm by Labrat101 »
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Offline Adrian_Arg.

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #445 on: November 05, 2020, 10:20:48 pm »
Labrat101, how to know when an FPGA is original or fake? :-//
 

Offline Labrat101

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #446 on: November 06, 2020, 12:40:12 am »
Labrat101, how to know when an FPGA is original or fake? :-//
Hi the first is the marking and the package. Looked good at first glance
The label should not wash off with a mixture of IPA  & Acetone. . ( use with care very strong solvent)
Some Clones have the wrong size pins . The Top Could have a flow over and lazer print
and only the texture is wrong . Example Intel has a small 'R' inside the O very small and hard to see .
 (Not on all versions change with year or batch.The newer versions has a different plate )
 
I work for Intel for 10yrs . The are a lot of documents on this chip. The main thing that this chip
has is a very low jitter of less than a ns . All intel chips are tested at die level before being enclosed.
 all bad or out of spec chips are destroyed . The cyclone 4 has a very good responses and also
 has , and can run @100Mhz as per the Spec sheet . It also has several inputs for different xtals .
 There are a few test pins that are not normally used . These when I tested were not connected.
 Also on my cyclone the label rubbed of with just plain 90% alcohol  :wtf:

There were other thing as well . FY68 did not respond to a better OCXO 2ppm . Made things worse
this when I realized that the fault was with the FPGA  was something else.
 And been chasing a rabbit down a hole. There is a mile of info that has been done on these units
 and yes we all missed the obvious .  |O .
  If you search the other 500 pages under several heading going back I believe nearly 3 yrs
I am sure some will correct me on that . Yes I have read every one .
 Some people seemed Happy with these Units so their must be a difference between
 the chip quality ( luck of the draw)
 
 In a nut shell it is very hard to spot some of the Fake chips now .
Some of the clones are very good and will work fine . At a lower spec or out of spec .
 
They assume the the average hobbyist won't notice . But when some one spends weeks building
 there new little project followed all the instructions starts running some test and all the scope
reading are nothing like  what they should be . They assume they wired it up wrong etc.
 Chances are it is Ok .  . Making a new Project for the Novice a heart breaker .
From all the feed back And what I have seen these units don't come close to CE standards.
 My AWG most of the ARB waves were so far off spec made them useless .
 ( FY   Now Replaced with a uni-t  99% within all Specs  @ $20 more)

  If it works and seems to be within your usage . Be Happy .
 But always double check if there is an error.
 you could be checking a good circuit and getting bad results .
Been there . spent 3 days looking for a fault that wasn't there .   |O |O |O

Edit update ..
If you want to know more about these FPGA . There is plenty of Info.
https://en.wikipedia.org/wiki/Field-programmable_gate_array
Also Just Google  FPGA
« Last Edit: November 06, 2020, 10:50:33 am by Labrat101 »
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Offline Adrian_Arg.

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #447 on: November 06, 2020, 04:19:46 pm »
Bad_Driver, the 5.6K resistor that you connected to the ground and that connects with the screw, is empty since the screw does not make ground with the plate, the screws are isolated from the ground of the plate and the source, what is its usefulness ??? I mean the green and yellow wire

in spanish
Bad_Driver, la resistencia de 5,6K que conectaste a la tierra y  que conecta con  en el tornillo, esta al vacio ya que el tornillo no hace masa con la placa, los tornillos estan aislado de la tierra de la placa y de la fuente, cual es su utilidad??? me refiero al cable verde y amarillo
« Last Edit: November 06, 2020, 04:22:48 pm by Adrian_Arg. »
 

Offline battlecoder

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #448 on: November 08, 2020, 07:06:44 am »
@John, again, thanks for your reply. I have a couple more comments/questions, if you don't mind.

Since you already possess an FY6600, which I presume is working as good as its design limitations allow, it may be better to stick with it on the basis of "Better the Devil You Know" and put up with the stiff dimple operated front panel switches until you can afford to buy a significantly better AWG like an SDG1000X or SDG2000X for example.
It's firmware 3.1 so considering all the people I've seen recommending to stay away from a v3.0 or 3.1 device...should I look into replacing the firmware?

Regarding question 2, I think a 10MHz OCXO with multiplier chip would be a better alternative to a 50MHz OCXO unless you discover a really cheap source of 50MHz OCXOs on account of its non-standard frequency. The 10MHz OCXO is the safer bet despite the additional cost of a clock multiplier chip, since it has a much wider range of applications should the FY6600 let out all of its magic smoke, leaving you with a spare OCXO to add to your collection of salvaged components. Also of course, it can be used as a direct replacement for the 10MHz XO chip used in the FY6900 model.

 Regarding the addition of an external 10MHz reference socket, either frequency option (10 or 50MHz, including a 20MHz OCXO option) is amenable to being locked to such an external 10MHz clock source using a simple PLL circuit which will allow an automatic glitchless change-over between the internal and external reference clock options.

I'm on the fence regarding the mods (because I actually intend to purchase a better instrument, so not sure if worth my time?), but considering I still think the FY6600 is NOT a bad frequency generator, and has a lot of really cool features and capabilities (I'm really impressed by the amount of modulation types that can actually accept an external signal), there's a chance I'll give the hacks a go. *IF* I do, I'll probably be using a 10Mhz OCXO plus the 5x multiplier as per your recommendation, with a PLL circuit to switch between internal and external source (Will need to do some research to design that, though. PLLs are unknown territory for me), and *maybe* a better supply (for some reason my supply doesn't measure the terrible leakage voltage ... or I've been measuring it wrong), but I feel inclined to increase the positive and negative 12V rails to something like 15V. I think I read somewhere that it helps with the awful distortion in 20V p-p sine waves. If that's not the case then I be damned, I would love to have better looking waves at those voltages.

Any other mod I should consider doing to it?

 

Offline Labrat101

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Re: FeelElec New Arrival FY-6900 Signal Generator
« Reply #449 on: November 08, 2020, 11:50:36 am »
@ battlecoder
I would not take the voltage up to 15+_ as the output ops are rated for 30v duel voltage MAX . Nom 28v.
 also take into account the working voltages of some of the caps .
I would not take the voltage above 12.5_+ . duel voltage 25v .
 I think JBG will agree . As we both have been to see Alice .  :)
 
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