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FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator

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Noy:
You don't need the powerpad.
I also used them. But now i have some overshoots  with square Signal...

masterx81:
One more reason to remain on classic 3091 😅

bdivi:
PowerPad thermal relieve is not required for the FY6600 output power. The original heat sink on top is more than enough.
The PCB is silkscreened bellow the ICs so no issues with shorting anything.

I have perfect square waves here - no overshoots whatsoever with sub 5ns rise and fall times.

Miti:
Look what I found in the dumpster at work today... among other goodies. GPS modules, brand new 7" LCDs 800x480, RF cables, pressure sensors, small screws, etc.

Fully isolated +/- 15V and 5V power modules. The first thought was... replacement for my FY6600 power supply. With a Mean Well 24V/15W (or even a decent 24V wall adapter from a thrift store) and two of these power modules, plus double LC filtering, I think I can get a pretty decent and quiet power supply with a small footprint. What do you think?

Johnny B Good:

--- Quote from: Miti on February 21, 2020, 01:27:08 am ---Look what I found in the dumpster at work today... among other goodies. GPS modules, brand new 7" LCDs 800x480, RF cables, pressure sensors, small screws, etc.

Fully isolated +/- 15V and 5V power modules. The first thought was... replacement for my FY6600 power supply. With a Mean Well 24V/15W (or even a decent 24V wall adapter from a thrift store) and two of these power modules, plus double LC filtering, I think I can get a pretty decent and quiet power supply with a small footprint. What do you think?

--- End quote ---

 You lucky B'stard you! :)

 I don't usually bother downloading these "Show 'n' Tell" photos but since I wanted to invert the 2nd one to check out those GPS modules, I made an exception. They, and the inverted copy, are now in a folder in the Feeltech signal generators folder in the test equipment folder which I named "Miti's dumpster find (2020-02-21)" for future reference.

 I'd suggest using one of those 'R' cored mains transformers rather than replace one smpsu (the original bare board unit) with another (that Meanwell one you mentioned) to supply the required nominal 20vdc input to those dc-dc converter modules.

 There's no guarantee that even a a metal cased mains smpsu will do much better in preventing the high voltage switching spikes from escaping onto its low voltage output rails than the existing smpsu board. Using a conventional high quality mains transformer with capacitor smoothed full wave rectification of its low voltage secondary(ies) to feed those modules guarantees elimination of such a troublesome switching noise source from your proposed psu solution.

 The biggest downside with the classic conventional analogue mains psu arises from the waste heat of analogue voltage regulators (intelligent resistive droppers being a better description of your classic 7805, 7812 and 7912 voltage regulator).

 Using switching regulators in place of analogue regulators deals rather nicely with this waste heat issue although they may suffer some low level of switching ripple and noise on their output rails (but only extremely low levels of directly radiated or conducted switching noise in the case of competently designed switching regulator modules).

 At least you won't have to suffer the issues of high voltage switching transients being coupled onto the output rails via the inter-winding capacitance of a cheap commodity unshielded high voltage isolating/step down transformer so commonly used in your typical smpsu whether nicely encased in a metal "screening box"  like that Meanwell or just a tiny circuit board mounted in a lump of plastic directly plugged into a wall outlet.

 When you see claims of "Low noise and ripple" for the better quality smpsu, it's worth reminding yourself that that's just a relative term for the switching class of psu - even the 'low noise' types can still negate the benefit of all those low noise dc-dc converter modules you've lucked out on.

 Judging from the photos you posted, those modules appear to be good quality items, well worthy of such a project. I think it would be a big mistake to power them off yet another mains voltage smpsu whilst there's ample room to include a 15 to 25 VA R type mains transformer and a bridge rectifier and smoothing cap (along with a cheap 10MHz OCXO driving an NB3N502 programmed as a 5 times multiplier sat where the crappy smd XO used to be). A 15VA transformer is sufficient if you're not planning on upgrading to an OCXO but you might want the extra margin of an additional 5 to 10 VA to cater for any possible future OCXO upgrade.

 It looks like the left hand column is displaying the 5v modules and the middle column the +/-15v modules. It also looks like they're all blessed with heavy duty LDO post dc-dc converter voltage regulators intended to attenuate residual ripple and switching noise - they need to be special LDO chips with a much higher frequency psrr performance (100s of KHz versus the typical 10KHz max of an LM1117 LDO regulator) in order to achieve this hoped for reduction in output ripple and noise.

 Are the output rails really fully isolated from their input connections? Also, did you manage to track down any datasheet information on them? It looks like you've managed to capture a few of the "Unicorn Parts" I've been searching for on ebay this past year or so, you lucky B'stard.  ;)

 One final question (idle curiosity really) in regard of those GPS boards. Do you have any information of the actual gps modules themselves? I suspect they're most likely timing modules rather than cheap commodity navigation modules - u-blox maybe?

JBG

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