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| FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator |
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| jdmoranii:
Hi, Dave. Sorry to resurface a long-dead thread, but… I recently discovered that my FY6600 was dead. The -12V DC supply was being loaded down. I connected a (-) dc supply to that rail, limited current to 1A and cranked up the voltage until 750mA flowed. C81 got toasty hot. So I removed it. Searching this thread for “C81” and “C82”, I found your comment that C81/C82 were 100nf. But they look physically too big, the smaller caps in parallel with them are 100nf. So I removed C82 and measured it. It was 10u. I replaced C81 with a 10u. |
| DaveR:
By chance, I just happened to look in on this thread for the first time in several months! I remember the C82 incident, and have to say that I had no idea what its value was at the time (it blew on 10 Aug 2018, according to my notes!), but 100nF has done the job for the last four years, so it can't be too critical. Physical size is, of course, no indication of value, and C53, 54, 56 and 57, which are all supposed to be 10uF, are massive in comparison to the original C81 and C82 on my PCB (as per some photos I took when did the 3095 opamps upgrade). However, looking again at the photos, it would appear that C81 and C82 were actually different beasts (at least in colour and shape - although you couldn't tell that from the frazzled remains of C82 I removed), so my original assumption that they were the same value may have been incorrect - although why the capacitors on the 4558 VCC+ and VCC- should be different, I have no idea. Thanks for your message, though: if C82 ever blows again I'll consider replacing it with a 10uF (if I can find one with a small enough footprint to fit in its place on the board). Regards, Dave |
| Johnny B Good:
Hi Dave :) If you don't want to clutter your web browser with a tabbed link to a moribund topic thread or have to check your bookmarks' folder every so often just to take look for fresh postings, why not click on the "Notify" button? :) ============================================================================================== [EDIT 2022-09-03] To add to the above advice, that the key benefit to clicking the "Notify" button is that you can delete the tab any time thereafter and de-clutter the web browser. I usually wait a day or three to see how many times the attached images have been viewed before doing that, even longer if I think I may have more to add. If the viewed count rate drops right off after a week or three and I'm still planning on adding another post, I really aught to add it to my bookmarks folder and close the tab but I'm not that organised so just tend to leave the tab open. ::) ============================================================================================== Another trick you can use when trying to resurrect a thread that hasn't seen a new post in several months (or even a year or three!) is to attach an image or three to your post. That way, you can gauge the level of passive interest from the number of views they get even if no one bothers to post a reply. Here's an example of the effectiveness of that trick where the latest post had been two and a half years prior to my own contribution. >:D Sadly, no actual replies but the view count against each attached image does at least reveal a level of interest (the initial 4 views in the space of only 5 minutes strongly hinting at the use of the notification button). https://www.eevblog.com/forum/metrology/i-just-bought-an-efratom-100318/msg4176703/#msg4176703 By way of an on topic update, I'm pleased to able to report that my much modded FY6600-60M is still going strong. Indeed, its upgrade replacement, a Siglent SDG2042X (120MHz version ;)), has effectively been relegated to acting as a support plinth for the 6600, mainly it has to be said, for its inability to offer the advertised 1 microHertz tuning resolution 'feature' beyond 100KHz for an insufficiency of digits in the frequency display :o :( >:( I've attached an image which I think might be of some interest (after all, this is the latest round in my search for a better frequency reference than the 6600 had originally been cursed with). >:D BTW, the gps disciplining wobble accounts for some 6 or 7 ns of the band of persistence recorded in that screen grab. The remaining 29 ns comes from what appears to be a diurnal temperature influence on the ruby's frequency stability (along with a tiny calibration error and a smidgen of ageing drift). |
| DaveR:
Hi John, Nice to see you're still active! Thanks for the tips, but, as someone who keeps the most cluttered browser in the universe (three of them, in fact, all multi-windowed and multi-tabbed), I don't intend to spend half of what's left of my life resorting tabs or converting them into bookmarks just to save a few seconds every six months or so :). Some of them are several years old, but I know where they are and I can easily find them thanks to the ColorfulTabs addon. A number are linked to topics on here that I've participated in over the years, and I keep them open because it's an amusing diversion to look in occasionally to see how many more times the wheel has been reinvented since I became a lapsed member of the thread. The FY6600 was a nice project to be involved in, and it eventually evolved to a level of sophistication which more than met my user needs (and many others', it would appear), and your efforts to squeeze even more performance from it have taken it to another level again. It's amazing what can done with a bit of cheap kit and some ingenuity, isn't it? Regards, Dave |
| Johnny B Good:
Hi Dave, I've just edited that post to clarify the benefit of clicking the notify button as per the following. To add to the above advice, that the key benefit to clicking the "Notify" button is that you can delete the tab any time thereafter and de-clutter the web browser. I usually wait a day or three to see how many times the attached images have been viewed before doing that, even longer if I think I may have more to add. If the viewed count rate drops right off after a week or three and I'm still planning on adding another post, I really aught to add it to my bookmarks folder and close the tab but I'm not that organised so just tend to leave the tab open. ::) As for the venerable FY6600, that proved to be a surprisingly excellent performer once you'd voided its warranty with several relatively trivial modifications to fix its seemingly beancounteritus inspired penny pinching induced shortcomings. Sure, the penny pinching did save a few cents on the dollar in production costs but I think the motivation to even risk such a ludicrously foolish penny pinching strategy was more to do with reducing their costs on handling warranty returns down to a nice fat zero by taunting their target market demographic into turning this Sow's Ear into a silken purse at the expense of a voided warranty. I think Feeltech knew their target demographic far better than it knew itself and were maximising the PRC's government subsidies on export shipping costs to make any warranty return attempts a high risk exercise if the AWG had been 'fiddled with' in any way since the return shipping charges would be an upfront cost to the customer, only refunded if Feeltech deemed the warranty hadn't been voided. When I'd offered this hypothesis to the group two or three years ago, it was discounted as just another "conspiracy theory" but the fact that their latest 6900 version has an unpopulated fan cooler aperture moulded into its back panel only lends further credence to this hypothesis imho. The original motivation for such nonsensical penny pinching may well have been simply that of reducing production costs which, after monitoring this topic thread, would have revealed the warranty voiding efforts of its target demographic soon enough that it seems they'd decided to pretend ignorance of the more egregious defects, electing to apply a cack handed half live mains leakage fix in the 6800 (and the 6900!) models and leave the remaining defects unaddressed to ensure a minimum of valid warranty returns where they would not only have had to deal with the expense of any repair (in reality more likely just take another unit from their stock of spares set aside for such warranty replacements) but also that of the customer's warranty return shipping costs. Looking at the way FeelTech have failed to respond to their customers' requests to fix blatant shortcomings, looks very much like a strategy to cut overheads by taking advantage of their customers' propensity to void their warranties (deemed worthless by most anyway) by having a go at fixing the issues for themselves, and thereby reduce the number of warranty returns they would otherwise be obliged to deal with. However, despite what I think of the situation, I'd still be inclined to replace the 6600 with a 6900 should it ever develop an irreparable fault. After all, for the money, it still represents an excellent bargain in AWG technology for what most of us would consider "chump change". It's certainly cheap enough to risk improving to a higher standard with an OCXO lockable to an external 10MHz reference and an upgrade of the 85 ohm attenuator to a real 50 ohm 20 dB resistor network plus replacing the earthing wire link to the PE pin of the C14 socket with a 4.7K resistor to eliminate random dc offsets and noise coming in from the mains earth wiring and, of course, fitting a fan into the case for a modicum of active cooling. Incidentally, the abysmal lack of passive convective cooling airflow proved inspirational in the ventilation arrangements I'd used in my rubidium frequency standard. I needed the cooling fan to be the sole arbiter over the LPRO's base plate temperature so any natural convective flow would have been counterproductive, so it's hats off to FeelTech for a real tour de force lesson on how to achieve virtually zero convective cooling. >:D :-DD :-DD |
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