Products > Test Equipment
FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
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Johnny B Good:

--- Quote from: Cliff Matthews on June 10, 2019, 03:49:15 pm ---
--- Quote from: Johnny B Good on June 10, 2019, 02:53:15 pm ---
--- Quote from: beanflying on June 09, 2019, 11:15:14 am ---You are assuming the big fat Earth pin is connected inside the box  :-DD  :horse:

--- End quote ---
Has anyone managed to get hold of an FY6900 to check this out yet?

--- End quote ---
AFAIK, they're still only pre-booking orders.

--- End quote ---

 I thought this was the case but I wasn't sure so I posed the question anyway.  :-\  :)

JBG
Johnny B Good:

--- Quote from: GerryR on June 10, 2019, 02:59:27 pm ---Hello, new here to this forum.  I had just purchased an FY6800-60M and ended up returning it.  The DC offset was over 35mV when set to 0.  There was a lot of jitter in frequencies above 20 MHz or so.  Amplitudes were way off into a 50 ohm load; there was considerable distortion in the output into a 10 k load.  Square waves started to look more and more like sine waves as frequencies got past 15 MHz.  Etc. Etc. Etc.   I haven't read all the posts in this thread yet, so I don't know if any of these problems have been experienced by others, but I am curious to know what others have found in actual use, i.e. tied to a real circuit and not just an o'scope.  Any input will be appreciated.

--- End quote ---

 Others have already mentioned the jitter and rounded square waves issues so I'll only address the issue of "DC offset error". I've put this in quotes because there's every chance that Feeltech introduced the problem when they upgraded the mains socket to a 3 pole earthed one to address the howls of rage over the half mains live voltage leakage with the FY6600 inevitable with any class II smpsu, courtesy of the 1nF EMC bodge capacitor mandated by EEC regulations, and made the skoolboy howler of hard linking the ground rail to the protective earth instead of using it to suppress the 100 or so volts of 'touch voltage' when powered off a UK/European 240/220 volt supply.

 If they'd inserted a 1K to 10K "drain" resistor between chassis ground and the protective earth tag on the mains socket to load down the touch voltage to either 50mV (1KR) or 500mV (10KR) with such a 'static drain resistor', this would have neatly  attenuated such external galvanic and/or thermo-couple generated DC offset voltages via the unfortunate effect of the mains earthing ground loop circuit whilst attenuating such unwanted effects by some 60 or 80dB, allowing you to actually see the millivolt or so of DC offset produced by the FY6800 itself.

 It's a pity you didn't discover this thread before going to the trouble of shipping your FY6800 back to the vendor. You may have saved yourself the trouble as a previous contributor did some months back when he followed our advice to test with the safety earth disconnected and discovered the true source of his high "DC voltage offset" problem. :)

[Edit]  Found the relevant post here:

https://www.eevblog.com/forum/testgear/feeltech-fy6600-60mhz-2-ch-vco-function-arbitrary-waveform-signal-generator/msg2202948/#msg2202948

JBG
GerryR:
Thank you for finding that; a very interesting read.  With all the free engineering that has been done here for FeelTech, maybe the YF6900 will not have these same issues!  :-//
Johnny B Good:

--- Quote from: GerryR on June 11, 2019, 11:19:48 am ---Thank you for finding that; a very interesting read.  With all the free engineering that has been done here for FeelTech, maybe the YF6900 will not have these same issues!  :-//

--- End quote ---

 It's just possible but looking at the way they implemented the C14 switched socket upgrade on the FY6800, I rather doubt it. In view of my observations on the changes to the Pk - Pk voltage limits shown in the 6900's manual, I'd rather take my chances with a 6800 where I know I won't be swindled out of a 20Vpp capability that goes up to 20MHz rather than with a 6900 model which may or may not suffer from the same (very fixable) ground loop issue but be swindled on the Pk -Pk capabilities in the 10 to 20MHz range (extremely unfixable).

 The rather questionable (have they upgraded the PSU board to one with +/-15v voltage rails?) 24Vpp rating (who would benefit from that?) in the DC to 5MHz range is just a marketing exercise imho to distract their customers from the more serious limitations they've now imposed to disguise the shortcomings of their over-stock of the very shite THS3002i dual opamps they're seemingly determined to use up come Hell or High Water.

 TBH, that downgrade on Pk to Pk voltage capability is such a detriment that even the original FY6600 would be a much better bet as a "Fixer Upper". There, at least, all the shortcomings are fixable. When the 20Vpp frequency range goes up to 20MHz, an opamp upgrade is well worth the effort but when it falls woefully short at just 10MHz, there's very little point in attempting such a marginal improvement. As I said, it looks like they've elected to downgrade the spec rather than upgrade the opamps. What's the betting that this new 6900 abomination will also sport an 85 ohm attenuator to serve the 0 to 500mV output range?  >:D

[EDIT]

 When it comes to the voltage output specifications published in the two FY6600 manuals and the single FY6800 manual, Feeltech (Feelelec) appear to have perpetrated a mistake since they all quote exactly the same levels and frequency limits (excluding the FY6900's 24Vpp upgrade in the 0 to 5MHz frequency range), despite the truth being a 20Vpp limit extending all the way from 0 to 20MHz for the sine and square wave forms at least.

 In this case, the manuals can't be relied on as authoritative guides to their performance and this might well (probably does) apply to the FY6900 as well. Obviously, we won't know until someone finally manages to acquire an FY6900 to test the actual frequency limits that apply to the 20Vpp setting and report their findings here or the other FY6900 thread that was started just two days ago.

 https://www.eevblog.com/forum/testgear/fy6800-vs-fy6900/msg2521413/#msg2521413

JBG
Johnny B Good:

--- Quote from: bdunham7 on June 10, 2019, 02:35:09 pm ---The only differences I see are the increased max Vp-p of 24V and the elimination of the 100uV step in the amplitude setting.  I guess we'll wait for a teardown to see what they've done for the power supply this time--but I'm not expecting much!  Meanwhile, the prices of the FY6600-60MHz have hit $40 on eBay, so if you like the idea of multiple synced units, now is the time to pick some up.

--- End quote ---

 If you ignore the rather questionable 24Vpp "upgrade" for the DC to 5MHz range, it basically amounts to a downgrade on the FY6600, let alone the FY6800 (which is basically just an FY6600 with a C14 switched socket and a revamped front panel with nicer to touch buttons - most likely still using the same SMD momentary action switches underneath though, but at least they can be replaced if any get worn out).

 The 24Vpp rating does suggest the possibility that the PSU board now sports +/-"15v" rails as opposed to the +/-"12 volt" (+/-11.7 volt actual) rails of the earlier models. However, that rather flies in the face of the claim of 5 watts or less consumption when the previous models typically consumed some 7 or 8 watts (un modified) against the previous 10W maximum claim. Does anyone get the feeling that their "Marketing Department" is doing what all marketing departments do as a matter of routine, which is making up their own figures without regard to actual test measurement data?  >:D

 Anyhow, regarding your mention of those forty dollar FY6600s on Ebay, I was intrigued enough to investigate what was on offer for myself. I did check out the prices on the FY6800s btw, before placing an order just half an hour ago on a FY6600-60M from Hong Kong for a mere £40.41p (just over half of the £75.66p I'd paid for my now much modded unit some seven months ago).

 I didn't fancy paying a 30 quid premium just to get a slightly nicer revamped front panel and a big butch switched C14 socket on what is essentially still an FY6600 inside. Besides which, it's a case of "Better the Devil you know." and it makes for a very cheap "Spare". The only concern with these "last available FY6600s" being whether they're unsold stock of all those models which had been afflicted by the version 3.0 firmware bug. :-\ Hopefully not but I should be able to determine that in some two to three week's time.  ;)

JBG
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