On Sun, 11 Nov 2018 15:47:48 -0800, Klaus Kragelund wrote:
> On Sunday, November 11, 2018 at 1:29:23 AM UTC+1, Johnny B Good wrote:
>> On Wed, 07 Nov 2018 15:51:00 -0800, Klaus Kragelund wrote:
>>
>> > On Thursday, November 8, 2018 at 12:04:50 AM UTC+1, Johnny B Good
>> > wrote:
>> >> On Fri, 26 Oct 2018 08:21:39 -0700, speff wrote:
>> >>
>> >> > On Friday, 26 October 2018 06:40:37 UTC-4, Clifford Heath wrote:
>> >> >> On 26/10/18 7:42 pm, speff wrote:
>> >> >> > On Thursday, 25 October 2018 17:27:24 UTC-4, John Larkin
>> >> >> > wrote:
>> >> >> >> https://www.amazon.com/Adoner-Precision-Arbitrary-819214bits-
>> >> Modulation/dp/B07BF7Y7TJ/ref=sr_1_3?
>> >> ie=UTF8&qid=1540502597&sr=8-3&keywords=fy6600&dpID=41vbYI%
>> >> 252B7YiL&preST=_SX342_QL70_&dpSrc=srch
>> >> >> >>
>> >> >> >> Other places have this box for $99.
>> >> >> >
>> >> >> > $99 would be a very good price, from what I can see, better
>> >> >> > than China list- looks like a more normal price would be about
>> >> >> > $150-$200 in the US for the 60MHz version. The lower frequency
>> >> >> > versions are significantly cheaper.
>> >> >> >
>> >> >> > It appears to use an Altera Cyclone IV FPGA driving 14-bit DAC.
>> >> >> > 320x240 color TFT. This is NOT your hobbyist DDS chip.
>> >> >>
>> >> >> The prevalence of cloning in this kind of device is usually
>> >> >> because someone published the designs.
>> >> >>
>> >> >> It's often an advanced hobbyist. I have a couple of gadgets like
>> >> >> this;
>> >> >> if you search hard enough you can find the original blog postings
>> >> >> showing where the design was developed. There are plenty of
>> >> >> hobbyists advanced enough to have developed this design.
>> >> >>
>> >> >> I haven't searched, but mere hardware copying wouldn't result in
>> >> >> the plethora of clones; the original software has to be published
>> >> >> somewhere. Otherwise the cloners would have to write it again
>> >> >> (differently) to accommodate any design changes, and that's too
>> >> >> much like hard work; they'd need to understand how what they were
>> >> >> cloning works.
>> >> >
>> >> > Googled it and there's a huge thread at EEVBLOG on this product.
>> >> >
>> >> > https://www.eevblog.com/forum/testgear/feeltech-fy6600-60mhz-2-ch-
>> vco-
>> >> function-arbitrary-waveform-signal-generator/
>> >> >
>> >> >
>> >> Yeah, thanks (I think). I've just spent the last couple of hours
>> >> reading
>> >> that thread and am only on page 8 (after having a quick peek at the
>> >> last 10 pages to see how it petered out)!
>> >>
>> >> My interest is motivated by my purchasing a "fy6600-60m" in the
>> >> small
>> >> hours of this morning for £75.66 from an Ebay trader offering
>> >> free[1] delivery from a UK warehouse (delivery ETA 10th to 12th of
>> >> this month).
====snip====
>> >> At a mere £75.66 postage free delivery within the week, I can
>> >> easily
>> >> forgive its "shortcomings". For the money, it's excellent value,
>> >> "warts 'n' all". That thread in EEVblog seems to offer ways and
>> >> means by which to sandpaper down the more objectionable warts - I
>> >> have yet to finish reading it. Still, it's something to help pass
>> >> the time whilst I wait to take delivery of my 'new toy'. :-)
>> >>
====snip====
>> >>
>> >> Anyway, the EEVblog thread you linked to looks well worth reading,
>> >> especially now that I've paid my money and have an actual
>> >> "fy6600-60m" about to wing its way to me. :-)
>> >>
====snip====
>> > Thanks for the hint
>>
>> I'm not sure whether your thanks were directed to both speff's and my
>> posts combined or just mine alone but, in either case, your thanks are
>> appreciated anyway. :-)
>>
>>
>> > I just bought one also. I have a HP33120 Arb, but it is single
>> > channel, and I need dual channel to do PWM signals for halfbridge
>> > drivers etc
>> >
>> >
>> How recently? Are we talking days or weeks ago? Mine turned up just
>> after 10am Friday morning with the regular mail delivery, just over 50
>> hours after placing my order (it beat the deadline for earliest ETA by
>> two days and RM's tracking by several hours). For anyone interested,
>> it's sporting the 3.3 version of firmware (and the latest revision
>> mainboard as mentioned in the EEVblog).
>
> I ordered it on the 7th, seems it will come on the 13th, so effectively
> only 3 business days :-)
Well, seeing as it's now the morning of the 14th (I've been pondering
cost effective ways and means of improving my new toy - rereading the
EEVblog from start to finish... again! - and I had to get up early to put
our wheelie-bin out 'cos I forget to do so last night, therefore my being
up at what I usually regard as "Silly O'clock in the morning.", hence
this delayed response), I suspect you may well have had a chance to gain
some hands on experience by now. :-)
One handy "shortcut setting" that's well worth remembering is the, "One
long press of the "OK" button (the rotary knob) until it beeps", one
which stores the current settings of the two channels (freq/amplitude
etc) to use as subsequent power on defaults. That can be a real time
saver at the start of your next session.
>
>> I've been familiarising myself with its interface and discovering more
>> ways to become confused with my Siglent SDS1202X-E's features as well
>> as those of the FY6600-60M, hence my tardy response, not helped by my
>> plodding through the last dozen or so pages of that EEVblog thread.
One of the things I was having trouble with was my tendency to press the
on screen icons of the soft menu rather than the actual buttons. A
strange affliction considering I had no such problem with the soft menu
buttons on the Siglent 'scope - I guess the tiny screen on the FY6600
must be the main factor in this case.
>>
>> I've added a 47K resistor across the low side resistor in the 10K+10K
>> potential divider network which drives the ref input of the adjustable
>> shunt reference chip which drives the opto-isolator in the PSU to raise
>> the 4.95v on the +5V line to 5.49v primarily so as to raise the +/-12v
>> rails by another volt to get them to circa 12.7v (+ & - rails) rather
>> than circa 11.7 volt.
>>
>> It seemed a reasonable first mod to do since it was just a case of
>> soldering a pin through hole 1/8th watt resistor onto the underside of
>> the PSU board to bring the + & - 12v rails onto the better side of the
>> tolerance range (normally +/-10%). Total power consumption went up by
>> less than half a watt on its idling consumption of 5W ("Powered Down"
>> using its front panel "On/Off" button).
One of my "cost effective mods" I've researched since then has been
going through my collection of scrapped smpsu parts, notably the high
speed low Vf rectifier diodes as replacements of the mis-identified by
ebel0410 "LT7506"s which are actually FR107s, a cheap high speed version
of the classic 1N4007 1A rectifier diode. His replacements, 1N5819s, were
hardly any improvement despite being high speed 3A rated diodes.
I picked out all the likely candidate shotky rectifier diodes from my
collection and checked them out on my DVM's diode/continuity buzzer
setting. this passes a constant 1mA test current through the DUT and
shows a reading corresponding to the diode's Vf in millivolts. Standard
silicon diodes show, as one might well expect, values of 550 to 600,
depending on their current ratings.
My candidate diodes ranged from a low of 141 (ESAD83-004R) to a high of
247 with one of a candidate pair (MBR3045CT) at 201. The FR107s I'd
removed from the PSU board measured a whopping 518/520 on my DVM. Looking
at all the diode data sheets I downloaded, I thought I might see an extra
half volt improvement by shoehorning a couple of these TO220 dual diodes
onto the PSU's circuit board but I got a little more than I bargained for
with the positive rail going up again from the previously boosted 12.78
to 13.8 volts with the slightly less loaded negative rail going up by a
similar amount to just over 14 volts.
>>
>> Even at maximum output with both channels driving 50 ohm dummy loads
>> at
>> 10MHz 20v p2p square wave, it draws just under 9W maximum off the mains
>> supply. Actually, after testing with and without the 50 ohm
>> termination, it looks like the output Z is more like 79 ohms than the
>> claimed 50 ohms (a claim also backed up by the pairs of 100 ohm
>> resistors discovered by DerKammi's reverse engineering of the circuit
>> boards).
Subsequent testing after the diode upgrade revealed a very slight but
definite reduction in this maximum power consumption (about a 100mW's
worth) which is a rather reassuring result after applying such a
modification to an SMPSU. :-)
>>
>> Open circuit versus 50 ohm loading of a 50 ohm impedance source should
>> only result in a drop down to 50% of the open circuit voltage, not a
>> drop down to 37.1% as I've just discovered. I've a sneaking suspicion
>> that all those 100 ohm resistors may turn out to be 150 ohm as per the
>> TI reference 150 ohm units of loading mentioned in their data sheets.
>>
>>
> I will test mine, when it arrives, and write back
I've since done some more testing and it seems the output Z is close to
the 50 ohm mark after all. The big problem here is the use of a dual high
voltage CFB opamp (THS3002I which Texas Instruments refused to
acknowledge the existence of the variant used by Feeltech!) which might
have been fine in the first 15MHz model but which has now been pushed to
its limits and way beyond with the 25, 30 and 60MHz models.
The presence of unpopulated chip locations (U21 and U22) indicates that
Feeltech must have considered their frequency upgrade options and the
need to upgrade that dual high voltage CFB opamp to a higher performance
pair of single opamp chips, notably the THS3001 or THS3095 (or, now that
TI have produced an even higher spec version of the 3095, the THS3491).
The PSU mod is all well and good (any mod that improves an SMPSU's
efficiency can only be "A Good Thing"(tm) imo) but in this case, it's
rather wasted on the THS3002I dual opamp chip that Feeltech neglected to
upgrade to match the ever increasing demands of the later -25MHz to
-60MHz models.
The next obvious no-brainer modification (after all, you did choose a
60MHz model to at least provide 40 to 60 MHz 20V pk2pk *sine* waves...
didn't you?) is to replace that dual opamp chip with a pair of THS3001s
(or THS3095s or even THS3495s). Unfortunately, unlike the PSU diodes mod,
this one is unlikely to be satisfied by a change of BoMs using recycled
parts and will cost anywhere from £17.68 (a pair of THS3095DDAR from
China) and upwards to 40 quid or so in an order for a pair of opamp chips
from Digikey or Mouser.
A pair of 3091s will do nicely (the 3495s are a little OTT for 60MHz 20v
Pk2Pk sine wave duty and have the same minor issue of dealing with the
surplus to requirements Vref and /PD pins which also curse the 3095 chip).
Either of those three chip options will provide a much overdue
performance upgrade but try as I might, I can't see me satisfying my
requirement for under 33 quid which represents an extra 43.62% of the
price I'd paid for the FY6600 in the first place. I think that's one mod
best left on hold for the time being (at least until I've exhausted all
other possibly cheaper alternatives that might become available with a
little more research).
=====snip=====
>>
>> Adding a 47Kohm resistor to the PSU is a simple and easy to reverse
>> mod
>> to correct for the voltages being on the wrong side of the tolerance
>> range. In this case, a little more voltage is "A Good Thing" in that it
>> gives the amps that extra margin against clipping.
>>
>> I wouldn't bother about the other suggested mods to the PSU since the
>> 10μF 450v HT smoothing cap is fine as it stands without replacing it
>> with a 68μF 400v one. After looking at several 'scrapped for spares'
>> 'Universal' 100-240vac smpsus that I had to hand, the design rule
>> appears to be "Specify 1μF per watt of rated output power and no more"
>> (and this is for 'universal' smpsus designed to work off as low a mains
>> voltage as 90vac rms!). For those of us blessed with 200 volt plus
>> mains supplies, the need to 'upgrade' that ht smoothing cap simply
>> doesn't exist. :-).
>>
>> Replacing 220μF 16v caps on the 12v lines with 25v versions is just
>> pointless. A much better option would have been to use 16v 470μF caps
>> instead if you'd really thought some improvement had been required
>> (that should half the 300mV or so of HF ripple I saw when I looked at
>> the 12v rails with my 'scope probes - the 16v rating simply isn't an
>> issue, not even if you push the rails to 15v!).
>>
>>
> A lot of good info, must dig deeper into it. I guess I will only really
> do what is nessesary, is busy at work, so cannot spend much time on
> instrument tweeking
>
>> For the money, I think these signal generators are exceptional value,
>> warts and all. The nearest competing products by Siglent are five times
>> the price and more (and Siglent are at the cheap end of this market).
>> Most of the perceived shortcomings can be overcome using relatively
>> inexpensive mods.
>>
>> However, the one shortcoming highlighted in the EEVblog forum that was
>> deemed the most seriously difficult to deal with was the matter of
>> timing jitter (in this case, a mere +/- 4ns). Right now, I'm looking at
>> the example traces in Siglent's features pdf of their sdg1000 series
>> generators showing how they've overcome this issue of jitter with their
>> 'innovative EasyPulse Technology' and it seems to me that all they've
>> done is sacrifice 8ns of resolution by averaging two or three clocks'
>> worth of sampling to smear out that 8ns rise time over a nicely
>> displayed 16 to 24 ns slope.
>>
>>
> Just today I was doing a test on the HP 33120A, and it has 25ns rise
> time, so couldn't complete my test. The FY6600 is about 7ns, so a lot
> better, 10 times cheaper :-)
>
And there you've discovered its attraction to the cost conscious
purchaser. A better performing (with some caveats) and cheaper version of
all those hideously expensive mainstream contenders. :-)
--
Johnny B Good