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

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soundtec:
I finally got the 5 volt regulator down to a proper working temperature ,I needed to heatsink the ic's and the bridge. Excess heat is directed into to metal screen between powersupply and signal board .I wound the +/- rails up 13.7 volts for a bit more headroom at high output amplitudes ,where clipping was apparent with the original Feeltech power supply of 11.5-12 volts, and as little as 100mV of DC offset caused hard clipping of the output op amps .

I was hoping I could simply swap over the main board and front panel from 6800 to the powersupply and enclosure of the 6600 with the linear supply ,but the recessed screen on the 6800 makes that impossible .

I'll most likely try a dual switchers one for op amp rails and another for 5volts ,for simplicity and size I might reuse the second Feeltech switcher and maybe try adjusting resistor values to increase the dual rail section while leaving the 5volt unloaded completely tends to raise the other rails to some degree as well ,any ideas on that would be greatly appreciated . I was thinking of trying an expanded aluminium mesh as a RF cage for the powersupply to prevent any Rf gash .

I also noticed on my 6600 with the linear that the negative rail measures just 2.2mV ac, the positive rail measures 103mV ac and the 5 volt measures 80mV ac ,is it because of other supplies being derived from the 5volt and 12 volt + that this extra noise exists?
Exactly the same readings from the unmodified 6800 ,so it has to be coming from the signal board


I decided to try the 6600 (15mhz) front panel on the 6800(60mhz) and vice/versa .
Both machines loaded fine ,appart from the waveforms preview being garbled ,the mhz on the 6600 main board now went up to 60 mhz with the 6800 V3.7 front panel and board of the 6800 only went as far as 15mhz with 6600 front panel . One difference I noticed in the 6800  was now when you change between channels if you were previously on say amplitude on ch 1 if you select ch 2 and go back to ch1 it retains the relevant page on both channels  ,where in the 6600 as soon as you change channels it reverts to frequency adjustment by default ,very anoying , Its a minor detail but it does make it nicer to use .

Scratch.HTF:
Good idea, but the filter should be able to be switched in and out via a DPDT telecom relay (it can be controlled via a mechanical switch).

soundtec:
So I tried using two feeltech switch modes to power the 6800 ,one for 5 volt rail the other for +/- rails .
When I drew no current from the 5 volt rail ,the +/- rails oscillated up and down and were way below the volts they should have been .
I tried adding 40 ohms across the 5 volt rail to draw some current ,and this stabilised the +/- , up around 12 volts but only with a 20 ohm resistor ,it got quite hot . Just goes to show if theres any moments of high current draw on the 5 volt line it can modulate the +/- rails ,not great really .

I guess I could split the 5 volts supply on the main board ,and run some current from both switchers 5 volt lines to stabilise things ,but then my 12 volt rails are too low . Ac milivolts on the supply rails stayed around the same in any case around 100 mV on the positive 12volts around 4 mV on the neg 12 volts line and around 80 mV on the 5 volts rail . The noise must be coming back through the 1117 regulators from somewhere else down the line . Maybe 80-100 mV is nothing to worry about in this situation.

ln the end I ended up reverting to a 2x12volts +  5 volts supply from an old satelite tv box ,bit more juice than the original item .

GregDunn:
I guess we're still using this thread to comment on and possibly offer feedback to the functionality of the FY6600 and FY6800 units?

I've been playing around with my new FY6800 (thanks to precaud!) and it seems to be able to be coerced into doing everything the manual says; bottom line, it's a great value and will get a lot of use on my bench.  But the frequency units display is rather tedious to decode while trying to quickly enter values.  I was trying to generate an AM modulated signal and it took a couple of tries to get carrier and modulation frequencies which were appropriate to generate the display I was looking for because I was trying to parse uHz on one channel and MHz on the other during the setting procedure.

It seems that the units suffix (Hz, MHz, etc.) is usually updated to a more sensible value after you complete entering the frequency and hit OK.  That's good, and desirable; although I've been able to trick it into displaying 100 KHz as either 0.1 MHz or 100000000 uHz depending on the order in which I entered the data and hit OK.  That's not so good, and could be improved if FeelTech is interested. 

What would make sense to me would be if, as you selected the appropriate frequency digit to change, the unit suffix were to change color, or blink, or something, and indicate the range of the decade you were manipulating.  Ex: as you moved into the digit group setting kHz it could blink "kHz", and if you moved past that into the group covering Hz it could blink "Hz" and then return to a steady indication of the appropriate units after you hit OK and the software was able to determine the value of the highest digit.  As it stands, you could be looking at something silly like "uHz" even while you're in the process of setting 10 MHz, or "MHz" while you're trying to set a frequency of 10 Hz.  More mental effort required on what should be a simple setting.

It's kind of like my soldering stations - I have one which is fixed to display in F and another which is only in C. I can do the math in my head while setting values, but it's something which could be made a little easier for the user.  It would be easier still for the FY6800 user if the software dynamically shifted the frequency display left or right and calculated units as you set the digits, but that would take considerably more effort for the coder to implement - I've done such in the past, so I have a hint of the effort.

I don't know if FeelTech would consider a similar change for future revisions, but I think it would substantially improve the usability of what is already a superb value in test equipment.

soundtec:
Hi Greg,
Thats great you managed to pick up an unloved Fy6800 from Precaud. There really isnt much to be said against these units in terms of value for money ,and of course you can do many simple mods ,which make it even better .

On the 6600 the encoder has a push switch button ,this allows you to change the display to  uHz Hz Mhz etc , its the OK button on the 6800 does that ,I wasnt sure from your post if you had figured out how to toggle Mhz/hz in the display or not .
And yes do keep posting your thoughts or possible improvements here .

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