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FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
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DaveR:
Hi John,

I think the warranty thing is a bit of overthinking by you.  Like all Chinese companies at the lower end of the market, warranty doesn't enter their minds: they just know that they can build something for x dollars and sell it for y dollars, and if (y-x)*n sales is enough to set them on the road to riches then they are happy.  No need to follow international safety standards or awkward things like that, and they write the specs themselves and sometimes even manage to meet them: if they don't, so what?  Caveat emptor!  If they've done a bit of research, they'll know that there's absolutely no chance of getting a faulty item returned to them, because sending it back is likely to cost more than the item is worth, and if, by chance, something is sent back, they can just throw it in the skip and say they never received it!  It's all in the Chinese Business Manual.  That's not to say that they all follow the Manual to the letter, because I've dealt with some really good sellers in the past, who went way beyond expectations to provide a good service, but you just have to weigh the chances of buying a pig in a poke before you part with your money, and be prepared to write it off if the item turns out to be porcine.

As for the actual AWG itself, I knew what I was getting after the FY6600 and bought a 6800 because I saw a good deal from some seller, knowing I could easily upgrade it in a couple of hours - although I stopped after the earthing correction and the TCXO change because the newer firmware meant that I didn't see the need to do anything else to it - and even went on to buy a 6900 a couple of years ago just because curiosity got the better of me.  (I'm actually not that keen on the 6900 because the keypad buttons are too firm, and are a definite downgrade from the 6800.)  Having just looked at the 6900 case, I find that I did actually fit the "missing" fan (I can't remember doing it, but I'll have had one or two suitable ones lying around, no doubt), but that's probably all I've done to it, apart from the obligatory earthing fix.

Out of interest, do you actually NEED a rubidium standard, or is that just another obsession?  (Says I, with two Thunderbolts next to the PC keeping my feet warm, four more GPSDOs in various places, and half a dozen home-made 10MHz OCXOs sitting in a box upstairs!)  :)

Regards,
Dave
Johnny B Good:
Hi Dave.

 Very nicely put. :) That's a less contentious version than mine but the conclusions reached are the same. I knew I was buying a "Pig in a poke" (more accurately, a "Sow's Ear") when I bought mine from a UK based Ebay seller as I mentioned in my very first eevblog post way back mid November 2018 to which my first reply had come from your good self!  :)

https://www.eevblog.com/forum/testgear/feeltech-fy6600-60mhz-2-ch-vco-function-arbitrary-waveform-signal-generator/msg1973777/#msg1973777

 I was interested to note your comments on the 6900's overly stiff buttons. Obviously stiff compared to the 6800 but surely an improvement over those bumps used on the 6600 front panel? These operate actual momentary push switches soldered onto the PCB. Those bumps are the one remaining annoyance only tempered by the fact that it's at least possible to replace any switches that may fail or start behaving erratically.

 Answering your question over my need of a rubidium standard, I have to offer an unqualified yes. I had been tempted to claim you'd answered your own question but although there is an element of want over need, in this case it's a vital tool in assessing other frequency standards (tcxo, ocxo, docxo, gpsdo and so on). In any case, I'll eventually be converting it into a GPSDRO to get rid of its ageing drift.
DaveR:
Hi John,

The buttons on the 6900 are truly awful, at least on the model I bought, although they may have been changed again to something more acceptable on the latest 5v incarnations.  The buttons on mine are soft silicone rubber on a very stiff spring or switch; there is no tactile feedback, and it takes a lot of effort to compress the wobbly blobs enough to move the spring and activate the switches underneath - solid plastic buttons would have been far better.  The membrane buttons on the 6600 are a pleasure to use by comparison - at least you can feel the click when the switch operates.  The 6800 buttons are light touch, and feel just right: I couldn't believe how far backwards Feeltech had gone with the 6900, because you need two hands, or have it braced against something immovable, to use it!

Thanks for that link!  It's almost four years ago now, but reading a few pages from the thread brought it all back to me as if it were just last week.  I see I was stalling on the 6800 opamp upgrade even then, and never did carry it out :).

Regards,
Dave
Johnny B Good:
 Hi Dave,

 Thanks for giving me a "heads up" on the overly stiff buttons used by the (hopefully) early versions of the 6900. If they're so stiff as to make those used in the 6600 models a joy to use by comparison, they must be very stiff indeed (BTW "a joy to use" isn't a phrase that immediately springs to mind when using the 6600 buttons).

 If I ever need to replace the 6600 with another cheap AWG capable of 1uHz resolution from DC to 60 or 100MHz and lower sine wave jitter than that of an SDG2000X model, the latest 6900 models look (stiff button issues aside) to be an ideal replacement since most of the hard work, with the exception of replacing the resistors in the 85 ohm 20 dB attenuator, has already been done.

 They carried on using those cheap dual opamps but doubled them up to reduce sine wave distortion at the 20v pk-pk and 20MHz limits when driving 50 ohm loads. The improvement falls a little short of the opamp upgrade in the 6600 and 6800 models but still sufficient to make the expense of a pair of THS3091s or whatever, questionable so I'd be inclined not to bother.

 The current models using a single rail smpsu board makes for a simpler upgrade to a quieter 5v psu (it also simplifies the battery powered test setup somewhat to check whether such an upgrade is even worth the trouble of purchasing or making up a replacement psu).

 The change from a 50MHz XO to a 10MHz XO eliminates any need to add a 3N502 clock multiplier chip onto the OCXO upgrade's BOM list, saving both time and costs all of which make for a relatively easier DIY upgrade path. What's not to like (stiff buttons aside)? ;D

 With regard to unused component purchases (that still to be done opamp upgrade you mentioned), that's not so unusual with DIY projects. The simplified battery power test I mentioned was prompted by the fact that the two 6v lantern batteries I'd purchased almost three years ago now, are still gathering dust on a shelf. I never did get around to testing whether a psu upgrade would be worth the effort. :palm:  :)

 I think the reason for putting this "battery test" exercise off indefinitely was due to having an epiphany involving the use of an HF transceiver with a short wire aerial to monitor the quality of the AWG's output into a metre or so of wire plugged into its BNC socket and being left a little bit bemused by the apparent high levels of mains frequency sideband noise which would vary in strength depending on how I laid out the AWG's transmitting antenna.

 Suspecting that the mains wiring was re-radiating the 10MHz test signal and mains current was modulating this re-radiated signal via some non-linearity mechanism (the "rusty bolt" effect), I connected the transceiver directly to the AWG through a 2 metre BNC patch lead and an SO239(?) adaptor, having already enabled its built in 20dB front end attenuator (no pre-amp required for the HF bands - just a bandpass filter feeding the 1st mixer directly). Lo and behold! A nice clean carrier sans the mains frequency harmonics. It turns out that relying on an "over - the - air" link path with an HF receiver to monitor the signal quality is not really a good idea (it's a quick and (very) dirty test with the "quick" of that description being its only redeeming quality).

 After belatedly running a proper test, I realised that what I'd initially concluded to be a psu noise issue was in fact just the result of a badly organised test that had allowed a polluted version of the test signal to be re-radiated from the mains wiring. :palm: The "psu noise issue" had proved to be nowhere near as bad as I'd assumed and quite possibly not even an issue at all so my planned battery test lost all sense of urgency and was literally left to gather dust.

 I might eventually get round to running this battery test, most likely when I get round to adding more padding to the trimpot on the OCXO board to make it less 'touchy' to adjust. The main impediment to running the battery test had been the lack of a suitable 6 pin connector to plug into the main board power socket. However, since I'd now like to be able to switch between battery and mains power at the flick of a switch to run the comparison as a "Blink Test", I'll probably just (temporarily) solder the wires straight onto the cct board (psu or main). One additional 'complication' in my case being the need to include the OCXO's 12v rail in this scheme since it's powered independently from its own smpsu (another possible noise source) regardless of the rear panel on/off switch state.
tzok:
Any chance that the Front Panel firmware will be finished, or at least it will reach full functionality, like ability to turn the device off ;)
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