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

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bitseeker:
I've heard about the differences in terminators due to geometry, but it's neat to see it.

maxwell3e10:
It would be good to start a thread on passive RF hardware: cables, attenuators, terminators, etc. At work I have a pile of cheap BNC cables and a pile of double-shielded Pasternack cables. For a critical signal its amazing how much difference a good BNC cable can make.

rhb:
I've been playing with my new toy some more.  It is beginning to appear that there is more variation in the Chinese stuff I'm using than in  the preceding thru vs tee & terminator comparison.  I can radically deform the trace by mashing on the male part of the connectors.

It's amazingly difficult to figure out how to get valid comparisons.  To really do it right I'd need a pair of BNC-F  1 M ohm input active probes with  50 ohm SMA-M outputs which went to 20 GHz.  That would let me look at what the scope would see.  My LeCroy DDS-125 goes to 1.5 GHz, but it's got 20% overshoot on a step which makes tests like this impossible.


https://www.eevblog.com/forum/rf-microwave/testing-rf-connectors-and-cables/msg2640531/#msg2640531

Dbldutch:
A while ago I decided to upgrade and tune my rather old (30MHz Version 2.9) because I wanted to have a higher precision counter function.
After reading this enormous number of postings, with some very good information (thank you guys), I decided on three items.
The power supply, the oscillator and the driver opamps for the waveforms.
The latter two are easy and have been described various times.

The power supply has been talked about many times, with several options, but there are only a few examples for a replacement.
I decided to design a completely new supply, that would let me adjust the +/- 12V outputs to +/-15V as well.
Going through my parts collection, I picked a 24VA block transformer that I could mount on a protoboard. The transformer is a little heavy with 2 seperate windings of 12VA each, and an output of 15VAC. Both secondary windings are fused with 0.8AT PTC fuses. The primary has two seperate 115V windings. 

I decided to use simple LM317 and LM337 voltage regulators for both analog supplies. The only specialty is the circuit around the trimmers, because they are China quality, and therefore cannot really be relied upon. The worst case is when the runner looses contact, creating a much higher output voltage then you intended, and this could potentially blow up the FY6600.
For the digital voltages, I selected a simple DC-DC Buck convertor because doing that with normal regulators would create too much heat. I specifically did not want a fan, with all it's generated noise inside the box. I also used some parts from the old supply, specifically the line filter and the 5V choke.

My unit is intentionally still floating. This can be fixed easily with a BNC/USB connection to another instrument.

To reduce some heat hot-spots from the three on-board regulators, I added some sticky heat-sinks to them.

More information can be found on my blog: http://www.paulvdiyblogs.net/2019/09/upgrading-tuning-my-fy6600-waveform.html

Enjoy!

StillTrying:

--- Quote from: Dbldutch on September 01, 2019, 11:04:14 am ---The transformer is a little heavy with 2 seperate windings of 12VA each, and an output of 15VAC.
--- End quote ---

Why did you use 2 bridge rectifiers, with 2 matched secondaries I'd have made a center tap using just one BR.

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